Lithos 125 (2011) 190–210

Contents lists available at ScienceDirect

Lithos

j ourna l homepage: www.e lsev ie r.com/ locate / l i thos

Tectonometamorphic evolution of the Samaná complex, northern Hispaniola:Implications for the burial and exhumation of high-pressure rocks in a collisionalaccretionary wedge

Javier Escuder-Viruete a,⁎, Andrés Pérez-Estaún b, Guillermo Booth-Rea c, Pablo Valverde-Vaquero a

a Instituto Geológico y Minero de España, C. La Calera 1, 28760 Tres Cantos, Madrid, Spainb Instituto Ciencias Tierra Jaume Almera-CSIC, Lluís Solé Sabarís s/n, 08028 Barcelona, Spainc Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, 18071 Granada, Spain

⁎ Corresponding author.E-mail addresses: j.escuder@igme.es (J. Escuder-Viru

(A. Pérez-Estaún), gbooth@ugr.es (G. Booth-Rea), p.valv(P. Valverde-Vaquero).

0024-4937/$ – see front matter © 2011 Elsevier B.V. Adoi:10.1016/j.lithos.2011.02.006

a b s t r a c t

a r t i c l e i n f o

Article history:Received 28 October 2010Accepted 14 February 2011Available online 21 February 2011

Keywords:Collisional accretionary wedgeHigh-pressure metamorphismDuctile thrustingMetamorphic P–T pathsCaribbean plate

The Samaná complex exposes a segment of a high-P metasedimentary collisional accretionary wedge, builtduring Caribbean island arc-North America continental margin convergence. Combined detailed mapping,metamorphic mineral assemblages, multi-equilibrium calculations and thermodynamical modelling of garnetzoning, together with isotopic ages, allow proposing a tectonothermal evolution of the complex involvingthree major stages (M1 to M3). M1 metamorphism was characterised by a prograde P–T path towards thepressure-peak in the lawsonite-blueschists (Santa Bárbara Schists and Rincón Marbles lower structuralnappes) and garnet-blueschists to eclogite-facies conditions (Punta Balandra upper nappe). This high-Pmetamorphism and related D1 deformation took place from the Eocene to Late Oligocene, when the differentnappes were buried along a cold subduction-zone gradient. Contemporary to the D2 deformation, M2retrograde metamorphism was associated in all nappes with substantial decompression under nearlyisothermal or cooling conditions to the epidote-blueschists and greenchists facies conditions. D2 deformationproduced ENE-directed folding, thrusting and nappe stacking in the complex, when nappes went sequentiallyincorporated to a growing collisional accretionary complex between the Late Eocene and the earliest Miocene.D2 deformation is thus responsible for much of the exhumation of the subducted rocks and for the thinning ofthe nappe pile. As the continuity of the P–T conditions within the accreted metasedimentary material were inthis case preserved, the exhumation mechanisms for Samaná complex high-P rocks was most probably drivenby underthrusting/underplating and erosion. Non-penetrative fabrics associated with D3 and D4 latedeformations indicate M3 cooling in the greenschists and subgreenchists-facies conditions. D5 sinistral strike-slip brittle faults cut and laterally displaced the whole nappe pile of the Samaná complex from the LowerMiocene to the Present.

ete), andres@ija.csic.eserde@igme.es

ll rights reserved.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

Accretionary wedges (or complexes) are formed in front of oceanicand continental arcs. They develop by the transfer of materialdecoupled in the lower down-going plate and accreted to the upperplate from an early intra-oceanic subduction stage to a latecontinental collision stage. Geophysical and petrological studiesindicate that during the pre-collisional evolution of a subductionzone the oceanic crust and the overlying sediments are dragged atdepth along the subduction plane into the so-called subductionchannel (Cloos and Shreve, 1988), and experienced high-pressure (P)metamorphism. The pre-collisional evolution finishes when a large

continental piece (i.e., a passive margin or an isolated block) entersthe subduction zone. This down-going continental crust may bedragged down by ‘continental subduction’, but generally only during arestricted period of time (c. 10 Ma; Chopin, 2003), after whichcollision develops. The introduction of the low-density continentalmaterial is often responsible for the choking of the subduction, whichthen stops or jumps outboard of the accreted continental block (e.g.Stern, 2004). Subsequent shortening is accommodated by theincorporation of continental margin rocks to the collisional accre-tionary wedge, and results in the progressive migration of thedeformative front towards the foreland.

As a result, subduction channels and accretionary wedges are twoenvironments where high-P metamorphism takes place in a subduc-tion to collision zone setting. However, the exhumed metamorphiccomplexes derived from these two environments present three majordifferences: the nature of constituent lithologies, the large-scalestructure, and the metamorphic evolution followed during the

191J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

exhumation of the subducted rocks (Agard et al., 2009). Thesubduction channel environment is dominated by blueschist andeclogite mafic bodies embedded in a mechanically weak, shearedserpentinite matrix with the characteristics of a tectonic mélange.These mafic blocks record different P–T metamorphic conditions andusually crop out in an internal structural position with respect to thelater accretedmaterials (Maruyama et al., 1996; Tsujimori et al., 2006;Krebs et al., 2008). By contrast, the high-P rocks in the accretionarywedge environment are mainly derived from the sedimentary coverof the down-going oceanic crust and/or the passive continentalmargin. They form usually an imbricate stack of slices of hectometricto kilometric thickness, where higher pressure slices thrust over thelower pressure ones and the continuity of P–T conditions is oftenpreserved (Agard et al., 2009). The type of driving forces for theexhumation of the high-P subducted rocks also seems to be differentin the subduction channel and in the accretionary wedge (Jolivet et al.,2003; Guillot et al., 2009). Underthrusting, detachment faulting anderosion are the main driving exhumation mechanisms for thesediments in the accretionary wedge (Platt, 1993; Ring and Layer,2003). While in the subduction channel, the exhumation of maficoceanic rocks takes place by return flow facilitated by their associationwith serpentinites, which would counterbalance their negativebuoyancy and enhance mechanical decoupling (Hermann et al.,2000; Gerya et al., 2002; Guillot et al., 2009).

The inliers of igneous and metamorphic rocks cropping out innorthern Hispaniola constitute part of a subduction complex formedduringMesozoic to Cenozoic convergence, and final collision betweenthe Caribbean island-arc and the southern continental margin ofNorth America (Draper et al., 1994). In this tectonic context, the high-P metamorphic rocks exposed as a nappe stack on Samaná Penínsulaare a prime example of a sedimentary-rich paleo-accretionary wedgeformed in a subduction/collision zone (Escuder-Viruete, 2008a).Therefore, the metamorphic lithologies that form the Samanácomplex allow the examination of the metamorphic and deformationprocesses that control the burial and exhumation of rocks in acollisional accretionary wedge. In this study, we have reconstructedthe metamorphic evolution of each nappe of the Samaná complex inthe form of P–T paths and their links to the structural evolution, whichhas been recently established by Escuder-Viruete et al. (2011). Themetamorphic P–T paths were obtained using equilibrium mineralassemblages, thermobarometric calculations using multi-equilibriumtechniques, and thermodynamical modelling. The tectonometa-morphic history that we have unravelled provides a new outlook onthe tectonic setting of the Samaná complex within the framework ofnorthern Caribbean tectonics, and the mechanisms at play in theexhumation of high-P metasediments in accretionary wedges.

2. Regional setting

Located on the northern margin of the Caribbean plate, the Islandof Hispaniola is a tectonic collage produced by the convergence of theCaribbean island-arc system with the North American plate whichbegan in the Cretaceous (Draper et al., 1994). The arc-related rocks areregionally overlain by Paleocene/Lower Eocene to Holocene siliciclas-tic and carbonate sedimentary rocks that post-date the volcanicactivity. This cover records the oblique arc-continent collision inthe northern Hispaniola area, as well as the intra-arc strike-slipdeformation, and retroarc basin development in the central andsouthern areas of the island. Today, the oblique convergence betweenthe Caribbean and North American plates in Hispaniola is partitionedbetween plate-boundary-parallel motion on the Septentrional andEnriquillo strike-slip faults in the overriding plate, and normal motionat the plate interface in the offshore low-angle subduction thrustsof the northern Hispaniola fault and Los Muertos trench (Fig. 1; Mannet al., 2002; Manaker et al., 2008).

In northern Hispaniola, the Septentrional Cordillera-SamanáPeninsula geological domain is composed of arc- and ocean-derivedunits formed during arc-continent convergence. The accreted unitsform several inliers, termed El Cacheal, Palma Picada, Pedro García,Puerto Plata, Río San Juan and Samaná complexes, which constitutethe pre-Eocene igneous and metamorphic substratum of the Septen-trional Cordillera (Draper and Lewis, 1991). These six complexesinclude metasedimentary rocks of the subducted continental marginof North America, serpentinite-matrix mélanges containing blocks ofblueschists and eclogites, ophiolitic fragments of the proto-Caribbeanlithosphere, plutonic and volcanic rocks related to the CretaceousCaribbean island-arc, and non-metamorphic rocks deposited in pre-collisional forearc sedimentary basins (Escuder-Viruete, 2008a,b). Inthe Puerto Plata and Río San Juan complexes, the first forelanddeposits with a record of the collisional process are the Paleocene?/Lower Eocene olistostromes of the Imbert Fm (Draper et al., 1994),which contain clastic elements derived from the Cretaceous volcanicarc, the metamorphosed ophiolites and, in minor amounts, the high-Pmetasediments derived from the subducted continental margin.

The Samaná complex (Fig. 1b) contains metamorphosed pelitic,carbonate and mafic rocks, alternating in variable relative amounts.Joyce (1991) recognised a sequence of three metamorphic mineralzones, ranging from lawsonite-bearing schists in the NE to eclogitesand garnet-blueschists in the SW. Rocks preserving relict primarystructures and recrystallised to lawsonite+albite-bearing assem-blages characterise Zone I (Santa Barbara unit; De Zoeten et al., 1991).The narrow, 1 to 2 km wide, intermediate Zone II is defined bylawsonite+glaucophane+albite assemblages in mafic rocks. Zone III(Punta Balandra unit) is characterised by mafic lenses with garnet+omphacite+phengite and garnet+clinozoisite+glaucophane-bearing assemblages intercalated within micaschists and marbles.The metamorphic sequence was generated during SW-dippingCretaceous–Eocene subduction (Joyce, 1991). Minimum P–T condi-tions achieved were about 13±2 kbar and 450±70 °C in the PuntaBalandra unit, and 7.5±2 kbar and 320±80 °C in the Santa Bárbaraunit (Joyce, 1991; Gonçalves et al., 2000). Structural data and thepressure gap between them permitted Gonçalves et al. (2000) todeduce that the Punta Balandra unit is thrust over the Santa Bárbaraunit, and to interpret the metamorphic nappe stack of Samanácomplex as a fragment of an accretionary wedge thrust onto the NorthAmerican continental shelf. The mafic eclogite lenses present in thePunta Balandra unit have been the subject of numerous petrologicaland geochemical studies (Perfit et al., 1982; Giaramita and Sorensen,1994; Sorensen et al., 1997; Catlos and Sorensen, 2003; Zack et al.,2004; Escuder-Viruete and Pérez-Estaún, 2006), but their structuralposition is often ambiguous. In the metasediments of the PuntaBalandra unit (calcschists, micaschists and marbles), eclogite faciesassemblages are more difficult to identify because they are moreretrogressed. However, for suitable compositions, the blueschist toeclogite transitional facies assemblages are locally preserved andcomposed of phengite, garnet and rutile, with or without paragonite,chloritoid and porphyroblastic lawsonite, mostly replaced by para-gonite and epidote/clinozoisite pseudomorphs (see below).

3. Geology of Samaná Peninsula

3.1. The metamorphic complex

The general geology of the Samaná Peninsula consists of threeelements (Joyce, 1991; Escuder-Viruete, 2008a; Fig. 1b): (1) ametamorphic complex whose internal structure is an imbricatestack of discrete high-P nappes; (2) a group of Middle/Late Miocenecoarse-grained siliciclastic rocks that are both in fault contact andunconformably overlie the metamorphic complex along the southcoast; and (3) a second unconformable cover of subhorizontal LateMiocene to Pleistocene limestone strata. The whole Samaná Peninsula

a

b

c

d

192 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

193J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

is deformed by a system of sinistral strike-slip and reverse faultsassociated with the (at least) earliest Miocene (~24 Ma) to Presentmovement along the Septentrional fault zone (Mann et al., 2002). Thislarge-scale, subvertical fault zone occurs onshore just south of thecomplex.

The nappe stack of the Samaná complex is essentially composed ofhigh-P Mesozoic platform to pelagic metasediments. In ascendingorder, the major tectonic nappes are (Escuder-Viruete et al., 2011):Playa Colorado Phyllite, Rincón Marbles, Santa Bárbara Schists, PuntaBalandra nappe, and Majagual-Los Cacaos Marbles. This nappe pile isdescribed in Appendix 1. The cross-sections and the structural data(Fig. 1c) show that the nappe pile dips to the S-SSW. At the top of thepile, the Majagual-Los Cacaos basal out-of-sequence thrust cuts thePunta Balandra basal thrust and localises across a jump in the P–Tmetamorphic conditions (see below). The Punta Balandra nappecontains a relatively coherent metasedimentary sequence metamor-phosed under upper blueschist- and eclogite-facies conditions. Maficeclogites and garnet-bearing blueschists occur as spatially restrictedlenses, boudins or layers within metasedimentary and/or Mg-richmafic lithologies that display similar or slightly lower P–T mineralassemblages (Escuder-Viruete and Pérez-Estaún, 2006). Block sizesrange from a few centimetres to about 25 m. The unit also includes inthe uppermost structural levels a b35 m-thick, mélange-like sub-unitcomposed of meta-ophiolitic mafic to ultramafic blocks in a stronglysheared and retrogressed metapelitic and serpentinitic matrix. Mg-rich rinds enveloping blocks composed of chlorite, tremolite andfuchsite are common here. Serpentinized peridotites and serpentinitelenses also occur against the northern boundary of the Septentrionalfault zone, tectonically interleaved with Tertiary rocks.

3.2. Deformation history

The structural evolution of the Samaná complex is characterised byfive deformational events (D1 to D5; Escuder-Viruete et al., 2011),which are briefly described in Appendix 2. D2 is the dominant ductiledeformation in the complex. Earlier D1 structures and fabrics havebeen substantially modified and transposed and therefore only littleinformation about the D1 deformation is preserved. D3 to D5deformations are discontinuous and much less penetrative, recordingthe evolution from ductile to brittle deformation conditions.

3.2.1. D1 deformationThe first recognisable deformation, D1, is characterised by

mesoscopic rootless isoclinal and intrafolial fold hinges. D1 deformedprimary sedimentary fabrics S0, e.g. marble-calcschist alternations,and led to the formation of earlymetamorphic veins or segregations ofquartz and calcite, which can contain fibres of Fe–Mg carpholite ortheir pseudomorphs. The D2 event has obscured or entirely destroyedmost of the D1 folds, and transposed the S1 foliation. D2 is particularlyintense in the upper structural nappes of the Samaná complex. In thelower structural nappes, where D2 structures are less penetrative, thedominant foliation in the marbles of the Rincón nappe is S1. In thePunta Balandra nappe, most mafic eclogites still preserve a relictplanar–linear (S1–L1) eclogitic fabric in the core of the lenses,characterised by coarse-grained omphacite-rich domains that alter-nate with garnet-rich ones.

Fig. 1. (a) Map of the northeastern Caribbean plate margin. Box shows location of Samancomplex modified from Escuder-Viruete (2008a) and Joyce (1991), showing major rock urepresentative structural attitudes of rocks. The different nappes are described in Appendix 1nappe. The Majagual-Los cacaos basal thrust is a late-D2 structure reworked as a D4 mid- toearlier ductile contacts. The Samaná Conglomerate fills a Neogene pull-apart basin. I–I′: Possection. (d) Simplified metamorphic map of the Samaná complex showing the distributioMineral abbreviations after Bucher and Frey (2002), except for Car, Fe–Mg carpholite; Ctd,

On a microscopic scale, most of the metapelites and calcschists ofthe Santa Bárbara, Rincón and Playa Colorada nappes have a folded S1foliation within S2 microlithons. S1 is defined by a mineralassemblage composed of chlorite, phengite and quartz, with orwithout Fe–Mg carpholite, chloritoid, paragonite and albite in Al-richmetapelites, by lawsonite, chlorite, phengite, quartz and calcite, withor without paragonite in Ca-rich schists, and by pumpellyte, lawsoniteor glaucophane-bearing assemblages in metabasites. In the PuntaBalandra nappe, the metapelites and calcschists have idioblasticgarnets (up to 5 mm diameter) showing cores with sigmoidal andsnow-ball inclusion trails of S1 Qtz, Lw, Ctd, Rut and Grap that aresurrounded by clinozoisite-bearing rims. Fine-grained clusters of Clzand Pg (±Phg) form rectangular pseudomorphs after S1 Lw in thecore and inner rim of those garnets, which exhibit an inclusion-poorouter rim. In the mafic eclogites two main textural types have beendistinguished: non-foliated granoblastic eclogite, and foliated blas-tomylonitic eclogite. Both types contain a pressure peak assemblage(22–24 kbar at 610–630 °C) composed of garnet, omphacite, phen-gite, quartz and rutile. Just like the garnets from the surroundingmetasediments, garnet porphyroblasts in the mafic eclogites show aMn-rich core with sigmoidal inclusions of S1 Lw and Omp, and a Fe-rich inner rim with Ep/Clz pseudomorphs after Lw that grades to aninclusion-free outer rim (Escuder-Viruete and Pérez-Estaún, 2006).

3.2.2. D2 deformationThe D2 deformation led the development of tight to isoclinal folds

and thrusts. In the lower structural levels of the Samaná complex, theRincón Marbles nappe is internally folded by large-scale D2 folds.Macroscopically visible S2 schistosity is well-developed in the hingezones of these folds and the associated ductile thrust surfaces. Towardupper structural levels the strain of the D2 folding and shearingincreases. The previous S1 fabric is transposed by S2, which becomesthe main penetrative fabric in almost all lithologies and on all scales.In the Santa Bárbara Schist and Punta Balandra nappes, D2 foldsdeform S1 planes and are intrafolial with respect to the S2. Theintercalated eclogite lenses often present a rim characterised by astrong syn-D2 fabric, defined by S2 Phg, Ep and elongated L2 Glnassemblages, which is subparallel to the S2 in the enclosingmetasediments. The epidote-blueschist facies S2 foliation is subpar-allel, or cuts at a high-angle the relict S1 eclogitic foliation. Kinematicindicators associated with S2 indicate a top-to-the-NE and E shearsense during D2.

In the lower Playa Colorada and Rincón Marbles nappes, the S2 isvery fine-grained and comprises combinations of aligned S2 phengite,chlorite, lawsonite, quartz, calcite, albite, titanite and rutile. Lawsoniteporphyroclasts and albite often occur as late-D2 poikiloblasts thatpreserve inclusions trails of S1 phengite, titanite and graphite. In themetapelites and calcschists of the Santa Bárbara nappe, the S2foliation is coarser relative to Rincón Marbles metapelites, anddefined by the oriented growth of chlorite, phengite, paragonite andquartz, with or without calcite/dolomite, albite, biotite, glaucophane,actinolite, rutile and titanite, or by a differentiated layering of quartzand sheet silicates on a 0.1–2.5 mm scale. Elongated Qtz aggregatesand rods, oriented Phg flakes and Phg±Pg+Chl associationsreplacing Car crystals mark L2. Asymmetric strain shadows developedaround syn-D2 Lw, Ep and Ttn. Rarely, small (b200 μm) chloritoidcrystals appear to have formed directly from chlorite. In the

á Peninsula in northern Hispaniola area. (b) Simplified geological map of the Samanánits, thrusts and faults (with barbs and ticks on the hanging wall sides), as well as. The D2 Punta Balandra basal thrust brings the nappe on top of the Santa Bárbara Schistslow-angle extensional fault. Numerous strike-slip and normal D5 faults overprinted allition of cross-section (below); s: serpentinized peridotite lenses. (c) Geological cross-n of high-P metamorphic index minerals, mineral assemblages and relevant isograds.chloritoid; Grap, graphite; and KWM, potassic white-mica.

194 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

uppermost structural levels of the Santa Bárbara nappe, there is a late-D2 blastesis of elongate albite poikiloblasts, with inclusion trails of S2Phg, Pg, Gln, Chl, Qtz and graphite, with or without Bt and Clz. Furtherup, in the higher structural levels of the complex, the metapelites ofthe Punta Balandra nappe contain quartz, clinozoisite, and garnetporphyroblasts surrounded by an S2 association of phengite, para-gonite, chlorite, rutile, titanite and calcite, with Clz-Pg rhombohedralpseudomorphs after Lw. Lawsonite is only preserved as armouredrelicts inside garnet. All these microstructures point to decreasinghigh-P metamorphic conditions during D2 (from M1 eclogite andupper blueschist to M2 blueschist and greenschist facies). In theuppermost Majagual-Los Cacaos nappe, the S2–L2 planar–linearfoliation in impure calcitic marbles contains phengite, chlorite, quartz,calcite and opaques.

3.2.3. Late deformations (D3, D4 and D5)The D3 deformation is less penetrative than the previous D2. In

thin section, phengite and chlorite deformed by D3 are bent with orwithout minor recrystallisation in the fold hinges. Fe–Mg silicateswere partially replaced by chlorite, indicating that D3 took placeduring retrogression under greenschist-facies conditions. Fabricsassociated with D4 are only locally developed. In thin section, theolder S2 mica foliation is kinked by D4. Irregular solution-transferseams marked by concentration of opaques, sericite and chlorite forma spaced S4 cleavage. D4 and D5 late deformations produced brittlestructures in marbles of all nappes.

4. High-P metamorphism

4.1. Regional distribution of the high-P metamorphism

About 350 samples were collected from outcrops throughout theSamaná complex to describe the different parageneses present inmetasediments, and to characterise the regional distribution of thehigh-P metamorphism. Fig. 1 shows the occurrences of the indexminerals and the mineral assemblages. The high-P metamorphicconditions in the Samaná complex are indicated by the presence oflawsonite in Ca-rich metapelites and calc-schists, and Fe–Mgcarpholite in Al-rich metapelites, marbles, albite-free pelitic schists,and quartz or calcite veins, which are index minerals in lawsoniteblueschist facies metapelites (e.g. Vidal et al., 1992; Bousquet et al.,2002). The spatial distribution of the maximum P–T metamorphicconditions throughout the Samaná complex reveal, from bottom totop, upper greenschist transitional to lower greenschist facies in thePlaya Colorado Phyllites, blueschist and upper greenschist facies inthe El Rincón Marbles, blueschist to upper blueschist facies in theSanta Bárbara Schists, eclogite and upper blueschist facies in thePunta Balandra, and lower blueschist to upper greenschist facies inthe Majagual-Los Cacaos Marbles. The maximum Si4+-content inearly (pre-D2) phengite obtained from microprobe analyses alsoincreases from the lower to the upper structural nappes (Fig. 1d),indicating a progressive increase of the P–T conditions structurallyupward.

4.2. Metamorphic evolution

The spatial distribution of the metamorphic grade and the relativetime of crystallisation of the metapelite mineral assemblages withrespect to the deformation fabrics allow the general evolution in P–Tconditions of the complex to be established. This evolution ischaracterised by three metamorphic stages (M1 to M3). As will beshown quantitatively below, pressure peak mineral assemblages inthe Samaná complex developed during D1, and therefore arereferred to as M1. The associated Chl+Phg±Pg S1 foliation inmetapelites and calcschists was porphyroblastically overgrown byLw, rare Ctd and Gln during a syn- to late-D1 growth event under

lawsonite-blueschist facies conditions (Fig. 2e). Other occurrences orrelics of the M1 high-P mineral assemblage Car+Chl+Phg+Qtz arefound within quartz- and calcite-bearing veins apparently only at thelower structural levels of the Santa Bárbara Schists and RincónMarbles nappes (Fig. 2g, h). The fibrous mesoscopic appearance andthe characteristic light green silvery colour of such metamorphicveins resemble the typical Fe–Mg carpholite pseudomorphs de-scribed in the literature (Goffé and Bousquet, 1997). In the PuntaBalandra nappe metapelites and calcschists, S1 Lw, Ctd, Pg and highSi4+-content Phg are included in Grt porphyroblasts and grew duringM1 (Figs. 2 and 3).

During the D2 deformation, the M1 high-P assemblages in theSamaná complex were replaced by M2 blueschist and uppergreenschist-facies assemblages (Fig. 3). Most metasediments showretrogressed M2 mineral assemblages composed of Phg+Chl±Pg+Qtz±Cal/Dol. The retrograde and decompressive evolution path isconstrained by the lower Si4+-content in S2 Phg and the decay of Fe–Mg Car to Chl+Phg, forming pseudomorphs. Both M2 characteristicsindicate decompression under isothermal, or cooling conditions, afterthe M1 high-P stage (e.g., Bousquet et al., 2002). In the uppermoststructural levels of the Santa Bárbara Schists nappe, Lw is replaced bypseudomorphic Clz and Pg±Phg, with or without Gln, whichcorresponds to the transition between lawsonite-blueschist andepidote-blueschists facies. In calcschists and metapelites of theselevels, M2 was characterised by the prograde formation of epidote,glaucophane, winchite and biotite. Therefore, maximum temperaturewas reached during the D2 deformation, and thus the upperblueschist-facies event is regarded here as M2. In the Punta Balandrametasediments, early syn-D2 garnet crystallisation with lawsonite orclinozoisite indicates a further increase in temperature reachingupper blueschist and eclogite facies conditions. However, in theenclosed mafic lenses, the late M2 evolution is characterised byepidote-blueschist and upper greenschist facies assemblages devel-oped in the S2 foliated rim that wrap around the eclogite cores, wherea strong syn-D2 amphibole zonation is recorded fromMg-Gln cores toGln and Fe-Gln or Mg-Rbk rims (Fig. 3e).

The subsequent greenschist-facies metamorphic event (M3) wasmainly recorded by the retrograde formation of actinolite, chlorite,epidote andwhitemica inmetabasites of the Punta Balandra nappe. Inthe metasediments, M3 crystallisation was limited to Phg laths with alow Si4+-content. Escuder-Viruete and Pérez Estaún (2006) estimatedconditions of 5–8 kbar and 300–400 °C for the M3 event, whichoccurred during further decompression and cooling.

5. Mineral chemistry

Chemical compositions of minerals from 24 selected samplesrepresentative of Rincón Marbles (4), Santa Bárbara Schists (14;lower, upper and uppermost structural levels), Punta Balandra (4)and Majagual-Los Cacaos Marbles (2) nappes were studied in detail.Chemical analyses were performed with a JEOL Superprobe JXA-8900M instrument at the Universidad Complutense of Madrid.Analytical conditions for spot analyses were 15 kV acceleratingpotential, 20 nA specimen current and 1–5 μm beam diameter. Theminerals show evidence of chemical zoning under themicroscope andin back-scattered electron (BSE) images. In order to quantify thiszonation, garnet porphyroblasts with the largest diameter (between2.0 and 8.2 mm) were analysed along rim–core–rim traverses atregular intervals (40–100 μm depending on the size); phengite andchlorite of different textural generations were examined in core–rimtraverses at 2–10 evenly spaced spot analyses; and lawsonite orparagonite were analysed at 2–5 spots per grain (see below).Representative mineral analyses, particularly those used in themulti-equilibrium calculations, are given in Tables 1–5. The completedataset for all samples used in this study and their geographicallocation are included in Appendices 3 and 4.

a b

c d

e f

g h

Ep/Clz

Ep/Clz

Phg+Pg+Chl

Qtz+Cal+Phg+Chl

S2

S2

S2

S2

Gln

Gln

Chl

Lw

Lw

Lw

Lw

Rut/Ttn

Lw

Lw

(Lw)

CarCar

Car

Qtz+CalQtz+Cal

Phg+Chl

Fig. 2.Microphotographs of textures of metasediments. (a) Idioblastic garnet (3.5 mm in diameter) zoned with respect to mineral inclusions, showing sigmoidal inclusions trails ofS1 Qtz, Lw, Ctd, Rut and Grap in the cores, enclosed by an inclusion-poor outer rim. Garnet porphyroblasts is enveloped by S2 Phg, Pg, Chl, Ep/Clz, Rut, Ttn and Cal. Calcschists of thePunta Balandra nappe. PPL, WF=5 mm; (b) garnet porphyroblast with Lw inclusions in the core and Ep+Pg rhomboidal pseudomorphs after Lw in the rim and S2 matrix. Peliticschists of the Punta Balandra nappe. CPL, WF=5 mm; (c) aspect of S2 foliation in garnet-glaucophane-clinozoisite schist. Note late-D2 replacement of Grt by Chl in the pressureshadows. Punta Balandra nappe. PPL, WF=5 mm; (d) coarse-grained Gln elongated with Phg, Ep/Clz, Cal and Qtz defining the S2 foliation. Calcschists of the uppermost SantaBárbara Schists nappe PPL, WF=3 mm; (e) idioblastic Lw porphyroblasts in quartz–calcite schists. Santa Bárbara Schists nappe. CPL, WF=1.2 mm; (f) lawsonite porphyroclastswith asymmetrical pressure shadows aligned to S2 foliation in quartz–phengite–chlorite schists. Santa Bárbara Schists nappe. PPL, WF=1.2 mm; (g) quartz-hosted carpholite hair-like fibres (arrows). Lower structural levels of Santa Bárbara nappe. PPL; and (h) quartz–calcite schist showing euhedral Car acicular crystals in amatrix partially altered to Chl+Phg.Lower structural levels of Santa Bárbara nappe. PPL, WF=1.2 mm. PPL and CPL = plane and crossed polarised light, respectively. WF = width of field.

195J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

5.1. Fe–Mg carpholite

Following Vidal et al. (1992), the Fe–Mg carpholite structuralformula [(Fe,Mn,Mg) Al2Si2O6(OH,F)4] was calculated on the basisof 5 cations for the estimation of Si and 3 cations for Al, Fe, Mnand Mg, to account for the contribution of surrounding quartz

when analysing acicular crystals smaller than the microprobebeam diameter. Analyses showing an oxide sum b85 wt.% orN90 wt.% were rejected. In the Rincón Marbles and Santa BárbaraSchists nappes, the XMg values [XMg=Mg/(Mg+Fe2++Mn)] incarpholite range between 0.43 and 0.52, with an extremely lowMnO content (XMnb0.01; Table 1).

CC

S

ENE WSWa b

c d

e f

g

hP

hg

+Pg

+Ch

l

Ph

g+P

g+C

hl

Phg+Chl

Phg+Chl

Phg+Chlafter CarPhg+Chlafter Car

CtdCtd

Grt Grt

Lw

Lw

Lw

Lw

Lw

Lw

S2

S2

S2

S2

Mg-Gln

Gln

Fe-Gln/Mg-Rbk

Ttn

S1

S1

S1

S2

Fig. 3.Microphotographs of textures of metasediments. (a) BSE image of S2 foliation and related retrograde shear-bands deforming Qtz–Cal aggregates in calc-schist of theMajagual-Los Cacaos nappe; (b) polycrystalline calcite aggregate dynamically recrystallised during D2 deformation. Elongate grains of calcite define an oblique shape fabric respect to thePhg+Chl alignment (S2 foliation; arrows), indicating a top-to-the-ENE sense of shear. Majagual-Los Cacaos Marbles nappe. PPL, WF=1.2 mm; (c) BSE image of folded S1 foliationdefined by elongated Qtz–Ctd–Phg–Lw inclusions in a garnet porphyroblast. Pelitic schists of the Punta Balandra nappe; (d) garnet porphyroblasts with lawsonite inclusions thatdefine a folded internal S1 foliation, discontinuous with the external S2 defined by Phg, Chl and Pg. Pelitic schists of the Punta Balandra nappe. PPL, WF=3.5 mm; (e) BSE image ofretrograde amphibole aggregates in mafic eclogites. Amphibole is strongly zoned, with Mg-Gln cores and Gln, Fe-Gln and/or Mg-Rbk rims; (f) BSE image of a poorly differentiatedS2 crenulation cleavage deforming a finely spaced Phg–Chl previous cleavage (S1). Note syn-D2 growth of Ttn porphyroblasts. Micaschists of the Santa Bárbara Schists nappe;(g) idioblastic lawsonite porphyroblasts in a less-deformed quartz-rich lense surrounded by the S2 foliation. Santa Bárbara Schists nappe; and (h) BSE image of very fined-grainedPhg–Chl aggregates forming pseudomorphs after carpholite. Lower structural levels of Santa Bárbara nappe. PPL. BSE; back-scattered electron image.

196 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

5.2. Chloritoid

The chloritoid formula [(Fe,Mn,Mg)2Al4Si2O10(OH)4] was calculatedon the basis of 12 oxygens. Analyses showing an oxide sum b90 wt.%or N94 wt.% were rejected. The chloritoid prisms from the upper

structural levels of the Santa Bárbara Schists nappe show XMg values[XMg=Mg/(Mg+Fe2++Mn)] between 0.12 and 0.24 (Table 2). In thePunta Balandra nappe metasediments, the chloritoid inclusions ingarnet porphyroblasts have similar values with XMg between 0.16 and0.23. In all samples, the Mn-content is very low (XMnb0.01).

Table 1Representative analyses of Fe–Mg carpholite from veins and metasediments.

Nappe SBS SBS SBS SBS SBS

Sample 2JE54 2JE54 2JE54 2JE54 2JE53

Texture v iq iq ic v

Analyses 181 185 185B 187 192

SiO2 38.80 38.63 38.54 38.30 40.60TiO2 0.04 0.00 0.00 0.00 0.06Al2O3 30.89 29.50 31.24 31.55 33.02FeO 9.89 12.60 12.10 11.25 9.58MnO 0.09 0.16 0.15 0.03 0.10MgO 5.57 5.00 5.40 4.73 5.26Cr2O3 0.07 0.08 0.09 0.04 0.03Total 85.35 85.97 87.52 85.90 88.65Si 2.08 2.09 2.05 2.06 2.09Ti 0.00 0.00 0.00 0.00 0.00Al 1.96 1.88 1.95 2.00 2.00Fe3+ 0.04 0.12 0.05 0.00 0.00Fe2+ 0.40 0.46 0.49 0.50 0.41Mn 0.00 0.01 0.01 0.00 0.00Mg 0.45 0.40 0.43 0.38 0.40XMg 0.52 0.47 0.46 0.43 0.49

Fe3+ (=2-Al) and Fe2+ contents are calculated after Goffé and Bousquet (1997).v, syn-metamorphic vein; iq: inclusion in quartz; ic, inclusion in calcite.Nappes: MC, Majagual-Los Cacaos Marbles; PB, Punta Balandra; SBS, Santa BárbaraSchists; RM, Rincón Marbles; PCP, Playa Colorada Phyllite (from Escuder-Viruete et al.,2011, 2011).

197J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

5.3. Phyllosilicates

Structural formulae are calculated on the basis of 14 oxygens forchlorite and 11 for white mica. Only analyses with an oxide sumN83.0 wt.% and b89.5 wt.% for chlorite and N92.0 wt.% and b97.0 wt.%for white mica were considered. Chlorite analyses showing (Na2O+K2O+CaO)N0.5 wt.% and/or K2ON0.1 wt.% were also rejected, as wellas white mica analyses showing (MnO+TiO2+Cl)N0.15 wt.%. Formulti-equilibrium calculations, we only considered compositionsthat could be expressed as linear combinations of the end-membersclinochlore (Clin), daphnite (Daph), Fe- and Mg-amesite (FeAm andMgAm), andMg-sudoite (Sud) for chlorites (Vidal et al., 2001), as well

Table 2Representative analyses of chloritoid from metasediments.

Nappe SBS SBS SBS SBS SBS SB

Sample JE8070b JE8070b 4JE143 4JE143 JE8139 JE8

Texture S1 S1 S1 S1 m m

Analyses 92 94 32 33 48 11

SiO2 24.3 24.26 24.74 24.32 24.26 24TiO2 0.10 0.04 0.02 0.04 0.02 0Al2O3 39.88 39.22 39.96 40.3 39.46 40FeO 23.4 24.1 26.30 24.38 22.86 21MnO 0.38 0.34 0.22 0.56 0.42 0MgO 3.02 3.04 1.88 2.26 4.02 3CaO 0.03 0.02 0.01 0.01 0.01 0Na2O 0.02 0.00 0.02 0.02 0.00 0K2O 0.01 0.00 0.02 0.01 0.00 0Total 91.14 91.02 93.17 91.90 91.05 89Si 2.03 2.04 2.04 2.02 2.02 2Ti 0.01 0.00 0.00 0.00 0.00 0Al 3.92 3.88 3.89 3.95 3.88 4Fe3+ 0.08 0.12 0.11 0.05 0.12 0Fe2+ 1.56 1.57 1.71 1.65 1.48 1Mn 0.03 0.02 0.02 0.04 0.03 0Mg 0.38 0.38 0.23 0.28 0.50 0Ca 0.00 0.00 0.00 0.00 0.00 0Na 0.00 0.00 0.00 0.00 0.00 0K 0.00 0.00 0.00 0.00 0.00 0XMg 0.19 0.19 0.12 0.15 0.24 0

Fe3+/Fe2+ ratio (Fe3+=4-Al) is calculated after Goffé and Bousquet (1997).S1, D1 syn-kinematic growth; m: matrix; ig, garnet inclusion.

as Fe- and Mg-celadonite (Cel), muscovite (Mus), paragonite (Pg),pyrophyllite (Prl), phlogopite (Phl), and annite (An) for phengites(Parra et al., 2002). Mineral compositions should also meet the sixchemical criteria reported by Vidal and Parra (2000). Furthermore,the evaluation of the amount of Fe3+ in phyllosilicates was addressedfollowing Vidal et al. (2001, 2006), because the presence of Fe3+ willaffect the activity of end-members particularly in chlorite. Conse-quently, P–T conditions were estimated using recalculated chloriteand phengite compositions both with and without Fe3+. Errors in P–Testimates introduced with the assumption of Fe2+=Fetotal werereduced using samples that contain graphite (Vidal and Parra, 2000).Following Vidal et al. (2006), the simultaneous estimation of Fe3+ inchlorite and the equilibrium temperature for the Chl–Qtz–H2Oassemblage was done for a given pressure (10 kbar and aH2O=1),using a criterion based on the convergence of the equilibriuminvolving Daph, Clin, FeAm and MgAm end-members, and theindependent equilibrium Clin+Sud=MgAm+Qtz+H2O. In general,adding ~10–20% of Fe3+ is sufficient for the convergence of bothequilibria (within ±50 °C), although the added quantity can exceedup to 50%. The resulting values of XFe3+ [Fe3+/(Fe3++Fe2+)] varyamong nappes and textural positions (Table 3). In chlorites from theRincón Marbles and the Santa Bárbara Schists nappes, XFe3+ rangesfrom 0.05 to 0.35, while in the chlorites from the Majagual-Los CacaosMarbles nappe it varies between 0.18 and 0.30. The chlorites from thePunta Balandra nappe have XFe3+b0.05. In general, the lowest XFe3+

values occur in the chlorites that define the S1 foliation, preserved inthe pre-S2 quartz-rich domains. The amount of Fe3+ in phengite wasestimated using the empirical KdFe–Mg between mica and chlorite atthe temperatures determined from Chl+Qtz equilibria (Vidal andParra, 2000). In contrast to chlorite, the Fe3+ amount in phengite has aminor influence on the P–T estimates (see below).

5.3.1. Tri-octahedral chlorite and sudoite compositionsVariations of chlorite compositions are mainly due to the FeMg−1

substitution (FM), the Tschermak substitution (TK) between Chl-Daph and Am [AlIVAlVISi−1(Mg,Fe)−1], and the di/trioctahedralsubstitution (DT) between Chl-Daph and Sud [(Mg,Fe)3V−1Al−2; Vstands for vacancy] (Vidal and Parra, 2000). The extent of the

S PB PB PB PB PB PB

140 2JE79 2JE79 2JE79 2JE79 2JE122B 2JE122B

ig ig ig ig ig ig

4 5 6 10 112 113

.22 24.85 24.82 24.86 24.96 24.33 24.35

.05 0.10 0.00 0.00 0.02 0.00 0.03

.68 39.80 41.00 41.00 40.79 42.22 42.13

.34 25.52 22.01 21.76 21.37 21.47 22.15

.05 0.27 0.09 0.00 0.01 0.19 0.23

.45 2.50 3.30 3.16 3.43 2.63 2.69

.03 0.01 0.02 0.01 0.03 0.03 0.02

.07 0.05 0.00 0.00 0.00 0.04 0.00

.00 0.02 0.00 0.01 0.00 0.00 0.00

.88 93.12 91.24 90.82 90.63 90.90 91.59

.02 2.05 2.05 2.06 2.06 2.01 2.00

.00 0.01 0.00 0.00 0.00 0.00 0.00

.01 3.87 3.98 4.00 3.98 4.11 4.08

.00 0.13 0.02 0.00 0.02 0.00 0.00

.49 1.63 1.50 1.50 1.45 1.48 1.52

.00 0.02 0.01 0.00 0.00 0.01 0.02

.43 0.31 0.41 0.39 0.42 0.32 0.33

.00 0.00 0.00 0.00 0.00 0.00 0.00

.01 0.01 0.00 0.00 0.00 0.01 0.00

.00 0.00 0.00 0.00 0.00 0.00 0.00

.22 0.16 0.21 0.21 0.23 0.18 0.18

Table 3Representative analyses of chlorite from Samaná complex metasediments.

Nappe RM SBS SBS SBS SBS SBS SBS SBS SBS SBS PB PB PB PB PB MCM MCM

Sample 2JE66 2JE53 2JE53 4JE109 4JE109 5JE128 5JE128 JE8066 2JE65 5JE116B 2JE72 2JE72 2JE79 2JE79 2JE122B JE9049B JE9049B

Texture m S1 S2 S1 S1 S1 S2 S1 S2 S1 S1 S1 S1 S2 m S2 S1

Analyses 17 24 179 29 31 13 15 27 140 5 31 32 14 15 160 164 171

SiO2 26.95 25.78 25.62 26.38 25.81 26.05 25.37 27.28 26.52 25.13 27.57 27.00 27.35 27.29 26.42 25.80 26.56TiO2 0.04 0.07 0.01 0.06 0.07 0.09 0.03 0.00 0.00 0.02 0.07 0.02 0.09 0.06 0.04 0.04 0.06Al2O3 23.83 22.22 22.37 22.18 21.18 22.39 22.89 20.14 22.01 22.42 21.63 21.30 20.69 20.54 21.45 21.34 20.81FeO 19.03 24.83 26.50 20.09 21.16 25.20 26.11 20.50 23.34 26.03 19.59 19.90 19.79 19.25 21.46 23.00 20.40MnO 0.10 0.43 0.33 0.04 0.08 0.39 0.28 0.20 0.93 0.23 0.24 0.20 0.36 0.39 0.07 0.29 0.28MgO 18.03 12.51 12.68 17.38 16.74 13.01 12.44 17.12 14.61 13.11 19.27 18.13 18.11 18.09 17.21 14.19 16.52CaO 0.01 0.03 0.06 0.08 0.02 0.06 0.00 0.03 0.01 0.04 0.00 0.02 0.04 0.03 0.03 0.05 0.03Na2O 0.01 0.02 0.04 0.00 0.02 0.03 0.01 0.00 0.02 0.01 0.02 0.01 0.01 0.00 0.00 0.00 0.01K2O 0.01 0.00 0.04 0.01 0.01 0.02 0.01 0.00 0.02 0.01 0.03 0.00 0.01 0.02 0.00 0.00 0.00Total 88.01 85.88 87.65 86.22 85.10 87.24 87.14 85.26 87.46 87.00 88.41 86.59 86.45 85.66 86.67 84.71 84.67Si 2.69 2.74 2.69 2.72 2.72 2.74 2.68 2.85 2.75 2.61 2.72 2.74 2.82 2.83 2.74 2.76 2.80Ti 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00Al 2.80 2.78 2.77 2.70 2.63 2.77 2.85 2.48 2.69 2.75 2.52 2.55 2.52 2.51 2.62 2.69 2.58AlIV 1.31 1.26 1.31 1.27 1.27 1.26 1.32 1.15 1.25 1.39 1.27 1.26 1.17 1.16 1.26 1.24 1.20AlVI 1.50 1.53 1.46 1.42 1.36 1.52 1.54 1.33 1.44 1.36 1.25 1.29 1.34 1.35 1.37 1.45 1.39Fe2+ 1.35 1.99 2.09 1.56 1.68 2.10 2.19 1.61 1.82 1.58 1.05 1.18 1.62 1.59 1.77 1.85 1.62Fe3+ 0.24 0.22 0.23 0.17 0.19 0.11 0.12 0.18 0.20 0.68 0.57 0.51 0.09 0.08 0.09 0.21 0.18Mn 0.01 0.04 0.03 0.00 0.01 0.03 0.03 0.02 0.08 0.02 0.02 0.02 0.03 0.03 0.01 0.03 0.03Mg 2.68 1.98 1.98 2.67 2.63 2.04 1.96 2.67 2.26 2.03 2.84 2.74 2.78 2.80 2.66 2.26 2.60Ca 0.00 0.00 0.01 0.01 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00Na 0.00 0.00 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00K 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00XFe3+ 0.15 0.10 0.10 0.10 0.10 0.05 0.05 0.10 0.10 0.30 0.35 0.30 0.05 0.05 0.05 0.10 0.10XMg 0.66 0.49 0.48 0.63 0.61 0.49 0.47 0.62 0.54 0.56 0.73 0.70 0.63 0.63 0.60 0.55 0.61

Fe3+ estimates sensu method of Vidal et al. (2001, 2005, 2006).S1, D1 syn-kinematic growth; S2, Id. D2; m, matrix.

198 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

substitutions depends on the metamorphic P–T conditions and thebulk-rock chemistry (Vidal et al., 2001). The chlorite and sudoiteanalyses obtained on samples from the different nappes of the

Table 4Representative analyses of white mica from Samaná complex metasediments.

Nappe RM Lower SBS Lower SBS Upper SBS Upper SBS Upper SBS Upper SBS

Sample 2JE68 2JE53 2JE54 JE8066 4JE109 4JE143 JE8070

Texture S2 S1 S2 LwPh S1 S1 S2

Mineral Phg WM WM Phg Pg Phg Phg

Analyses 122 27 183 29 32 52 49

SiO2 47.22 49.86 47.48 47.64 45.28 53.09 47.36TiO2 0.18 0.09 0.08 0.11 0.06 0.12 0.14Al2O3 34.05 28.49 31.48 27.64 37.31 26.39 27.80FeOt 2.79 2.06 3.83 4.41 2.15 1.87 3.75MnO 0.00 0.07 0.12 0.07 0.00 0.07 0.01MgO 1.65 2.37 1.97 4.13 0.76 3.83 4.63CaO 0.19 0.04 0.08 0.08 0.11 0.24 0.07Na2O 3.26 0.30 1.60 0.16 5.64 0.18 0.14K2O 4.67 8.86 6.74 8.26 1.76 8.55 7.79Cr2O3 0.00 0.00 0.07 0.00 0.04 0.06 0.00NiO 0.00 0.00 0.01 0.00 0.00 0.00 0.00BaO 0.00 0.00 0.00 0.00 0.00 0.00 0.04Total 94.02 92.13 93.46 92.50 93.11 94.38 91.71Si 3.13 3.39 3.20 3.28 2.99 3.51 3.27Ti 0.01 0.00 0.00 0.01 0.00 0.01 0.01Al 2.66 2.29 2.50 2.24 2.91 2.06 2.26AlIV 0.87 0.60 0.79 0.72 1.00 0.48 0.73AlVI 1.79 1.68 1.71 1.52 1.91 1.57 1.53Fe2+ 0.14 0.11 0.19 0.23 0.11 0.09 0.19Fe3+ 0.02 0.01 0.02 0.03 0.01 0.01 0.02Mn 0.00 0.00 0.01 0.00 0.00 0.00 0.00Mg 0.16 0.24 0.20 0.42 0.07 0.38 0.48Ca 0.01 0.00 0.01 0.01 0.01 0.02 0.00Na 0.42 0.04 0.21 0.02 0.72 0.02 0.02K 0.39 0.77 0.58 0.73 0.15 0.72 0.69XMg 0.54 0.69 0.50 0.65 0.41 0.80 0.71

Fe3+ estimates sensu method of Vidal et al. (2006).S1, D1 syn-kinematic growth; S2, Id. D2; LwPh, lawsonite pseudomorph; iGrt, inclusion in

Samaná complex are plotted in (Chl+Daph)-Am-Sud ternary and theSi-content (p.f.u.; cations per formula unit) versus XMg [XMg=Mg/(Mg+Fe2++Mn)] diagrams, which describe the extent of the TK, DT

cto-SBS cto-SBS PB PB PB PB PB PB MCM MCM

2JE65 2JE65 2JE72 2JE72 2JE72 2JE72 2JE79 2JE79 JE9049B JE9049B

S1 S2 S2 S2 S1 iGrt S2 S1 S1 S2

Phg Phg Phg Pg Phg Phg Pg Phg Phg Phg

142 139 168 30 33 99 29 35 165 166

51.02 48.55 49.21 47.22 50.75 50.67 47.69 51.45 51.03 49.930.21 0.13 0.13 0.05 0.19 0.28 0.03 0.29 0.20 0.12

26.85 28.99 28.52 39.67 27.38 27.31 39.93 27.42 28.26 30.202.62 3.92 1.89 0.21 2.06 2.01 0.34 1.58 2.09 2.110.05 0.12 0.00 0.00 0.02 0.00 0.00 0.03 0.06 0.003.17 3.55 2.96 0.09 3.29 2.62 0.18 3.30 2.74 2.440.04 0.02 0.01 0.13 0.02 0.01 0.09 0.02 0.03 0.050.22 0.30 0.30 7.32 0.60 0.53 7.30 0.52 0.38 0.299.85 7.94 8.80 0.36 9.30 9.22 0.46 8.68 9.22 9.170.04 0.00 0.02 0.03 0.00 0.00 0.00 0.00 0.00 0.000.00 0.03 0.03 0.00 0.05 0.00 0.00 0.00 0.00 0.020.00 0.00 0.52 0.00 0.00 0.00 0.00 0.00 0.00 0.00

94.07 93.54 92.37 95.08 93.66 92.66 96.02 93.29 94.11 94.403.43 3.28 3.36 3.01 3.42 3.44 3.01 3.45 3.41 3.330.01 0.01 0.01 0.00 0.01 0.01 0.00 0.01 0.01 0.012.13 2.31 2.30 2.98 2.17 2.18 2.97 2.16 2.23 2.370.56 0.71 0.63 0.99 0.58 0.55 0.98 0.54 0.58 0.671.57 1.60 1.66 2.00 1.60 1.64 1.99 1.63 1.65 1.700.13 0.20 0.10 0.01 0.10 0.10 0.02 0.08 0.11 0.110.01 0.02 0.01 0.00 0.01 0.01 0.00 0.01 0.01 0.010.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000.32 0.36 0.30 0.01 0.33 0.27 0.02 0.33 0.27 0.240.00 0.00 0.00 0.01 0.00 0.00 0.01 0.00 0.00 0.000.03 0.04 0.04 0.91 0.08 0.07 0.89 0.07 0.05 0.040.85 0.68 0.77 0.03 0.80 0.80 0.04 0.74 0.79 0.780.71 0.64 0.76 0.46 0.76 0.72 0.51 0.81 0.72 0.70

garnet.

Table 5Representative analyses of garnet from Samaná complex metasediments.

Nappe PB PB PB PB PB PB PB PB

Sample 2JE72 2JE72 2JE75 2JE79 2JE79 2JE122B 2JE122B 2JE122B

Mineral Core Rim Core Rim Core Rim Interm Core

Analyses 111 124 77 40 67 56 81 107

SiO2 37.47 38.15 38.00 37.98 37.19 38.21 37.99 37.33TiO2 0.15 0.17 0.07 0.08 0.09 0.02 0.11 0.16Al2O3 21.23 21.54 21.27 21.76 21.60 22.31 21.97 22.03Cr2O3 0.00 0.04 0.02 0.08 0.00 0.00 0.00 0.00FeO 29.59 29.04 28.14 30.40 31.40 30.35 29.60 29.44MgO 0.82 1.24 1.20 2.59 2.27 2.10 1.66 1.42MnO 2.64 0.41 3.16 0.28 0.33 0.31 0.94 2.29CaO 8.04 9.53 7.94 6.75 6.32 7.01 7.32 6.87Na2O 0.02 0.09 0.02 0.01 0.07 0.01 0.02 0.15K2O 0.01 0.03 0.00 0.00 0.00 0.01 0.00 0.00Total 99.96 100.23 99.80 99.92 99.26 100.34 99.62 99.69Si 6.01 6.04 6.07 6.02 5.99 6.03 6.04 5.98AlIV 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00AlVI 4.02 4.02 4.00 4.06 4.09 4.15 4.12 4.15Ti 0.02 0.02 0.01 0.01 0.01 0.00 0.01 0.02Cr 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00Fe2+ 3.97 3.85 3.76 4.03 4.22 4.00 3.94 3.94Fe3+ 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00Mg 0.20 0.29 0.29 0.61 0.54 0.49 0.39 0.34Mn 0.36 0.06 0.43 0.04 0.05 0.04 0.13 0.31Ca 1.38 1.62 1.36 1.15 1.09 1.18 1.25 1.18Na 0.01 0.03 0.01 0.00 0.02 0.00 0.01 0.05K 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00XAlm 0.67 0.66 0.64 0.69 0.72 0.70 0.69 0.68XGrs 0.23 0.28 0.23 0.20 0.18 0.21 0.22 0.20XSps 0.06 0.01 0.07 0.01 0.01 0.01 0.02 0.05XPrp 0.03 0.05 0.05 0.10 0.09 0.09 0.07 0.06XFe 95.32 92.93 92.94 86.83 88.56 89.00 90.91 92.11

20 80

(Mg,Fe)-Amesite

Clinochlore/Daphnite

(Mg,Fe)-Am

(Mg,Fe)-Sud

Mg-Sud

Fe-SudDaph2 3

Clin+Daph

TK

TK

DT

FM

Mg-Am

Fe-Am

XMg

Sia.p.f.u.

(Mg,Fe)-Sudoite80

80

60

60

60 40

40

40

20

20

0,3

0,4

0,5

0,6

0,7

0,8

0,9

2,5 2,6 2,7 2,8 2,9 3,0 3,0 3,1 3,2

XMg

Sip.f.u. Sip.f.u.

Mg-SudClin

Fe-SudDaph

RincónMarbles

lowerS.Bárbara

upperS.Bárbara

contactS.Bárbara

P.Balandra

Majagual-Cacaosa b

c

d

Fig. 4. Chemical variability of chlorite and sudoite from the Samaná complex nappescaused by (a, b) the TK and DT substitutions and (c, d) TK and FM substitutions (TK,Tschermak substitution; DT, di-trioctahedral substitution; FM, FeMg−1 substitution).

199J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

and FM substitutions (Fig. 4). Chlorites from the Samaná complexhave a composition lying between the Am and the Chl-Daph end-members, with a Sud content ranging between 5 and 25 mol%, exceptfor some analyses that reach ~45 mol%. In general, chlorites withlower Sud content belong to the Punta Balandra and upper structurallevels of the Santa Bárbara nappes, which is consistent with a highertemperature of formation. In Fig. 6c, the XMg ratio ranges between0.42 and 0.72 for Si4+ contents between 2.60 and 2.85 p.f.u. Thegeneral increase in Si4+-content and XMg values in chlorites from thelower to the upper structural nappes of the complex is also consistentwith progressively higher P–T conditions of metamorphism. Sudoiteoccurs in the Rincón Marble, lower Santa Bárbara Schists andMajagual-Los Cacaos nappes. It has an Si4+-content between 3.0and 3.2 p.f.u. and an XMg ratio between 0.7 and 0.8 (Fig. 4d).

5.3.2. White mica and pyrophyllite compositionsThe variation of white mica composition is essentially a function of

the FeMg−1 substitution (FM), the Tschermak substitution (TK)between Mus and Cel [AlIVAlVISi−1(Mg,Fe)−1], the pyrophyllitesubstitution (P) between Mus and Prl (KAlSi−1V−1), and theparagonite substitution (Pa) between Mus and Pg (NaK−1) (Vidaland Parra, 2000). The extent of these substitutions in white mica alsodepends on the P–T conditions, as well as the whole-rock chemistry(Parra et al., 2002). In the Samaná complex, two compositions ofwhite mica have been recognised: phengite and paragonite. Mostwhite mica in the micaschists and calcschists is phengite, butparagonite coexists with phengite in the foliated matrix, as inclusionsin garnet and forming pseudomorphs after lawsonite. Analyses ofwhite mica in samples from different nappes are plotted in Mus–Cel–Prl and Prl–Pg–Mus ternary diagrams, which describe the extent ofthe TK, P and Pa substitutions (Fig. 5). These diagrams show that thepyrophyllite-content in white mica is generally lower than ~30 mol%,but can reach high values (up to ~40 mol%) in some grains from theupper Santa Bárbara Schists and Punta Balandra nappes, while the

celadonite-content ranges between 20 and 40 mol%. The paragonitecontent in phengite is generally low (b10 mol%), showing withparagonite two clear populations of white mica, but it presents agreater variability in the samples from the lower structural levels ofSanta Bárbara Schists and Rincón Marbles nappes (Fig. 7b). In theRincón and Majagual-Los Cacaos Marbles nappes, some white micasare low in paragonite and high in pyrophyllite.

The chemical variations of phengite from the different nappes ofthe Samaná complex show diverse generations of phengite formedduring successive deformation events. Fig. 1d shows the spatialdistribution of the maximum Si4+-content, which is controlled by thepressure-sensitive TK substitution (Parra et al., 2002). Four maintextural and compositional varieties of phengite have been observedin the metasediments: large relic syn-D1 phengite (Phg1), randomgrains in pseudomorphs after lawsonite, very fined-grained retro-grade grains replacing carpholite, andmatrix lepidoblasts sub-parallelto S2 (Phg2). These different phengite generations are used toconstrain the evolution of pressure conditions. The maximum Si4+-content (p.f.u.) in Phg1 increases upward in the structural sequence,showing a range of 3.35–3.22 in the Rincón Marbles nappe, 3.37–3.30in the lower levels to 3.54–3.30 in the upper levels of the SantaBárbara Schist nappe, and 3.45–3.39 at the contact below the PuntaBalandra basal thrust. In the Punta Balandra nappe metasediments,Phg with a high Si4+-content occurs as S1 inclusions within garnet(3.44–3.22 p.f.u.) or as pre-S2 lepidoblasts (3.46–3.43 p.f.u.). Thesecontents are similar to those of the eclogitic stage Phg inside the

2.85

2.95

3.05

3.15

3.25

3.35

3.45

3.55

XNa=Na/(Na+K)

Si c

aton

s pe

r 11

oxy

gens

0.0 0.2 0.4 0.6 0.8 1.0

paragoniteineclogites

phengitesineclogites

pre-eclogiticphengites

retrogradephengites

20

20

80

80

Pyrophyllite

Pyrophyllite

(Mg,Fe)-Celadonite

Paragonite

Muscovite

Muscovite

80

80

80

80

60

60

60

60

60

60

40

40

40

40

40

40

20

20

20

20

a

c

b

Ms

Prl

(Mg,Fe)-Cel

TK P

Ms

Prl

PgPa

P

Rincón Marbles

lower S.Bárbara

upper S.Bárbara

contact S.Bárbara

Punta Balandra

Majagual-Cacaos

RincónMarbles

lowerS.Bárbara

upperS.Bárbara

contactS.Bárbara

P.Balandra

Majagual-Cacaos

Fig. 5. Ternary diagrams showing the systematic Tschermak (TK), pyrophyllite (P) andparagonite (Pa) substitutions in K- and Na-white micas from the Samaná complexnappes [Prl, pyrophyllite; Ms, muscovite; (Mg–Fe)-Cel, celadonite; Pg, paragonite].Compositional variability of K-white micas (phengite) caused by the (a) TK and Psubstitutions and (b) the P and Pa substitutions. (c) Composition of the white micasfrom metasediments and mafic eclogites plotted in terms of the number of Si cationsper 11 oxygens versus XNa=Na/(Na+Ca).

200 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

metamafic blocks (Fig. 5c; Escuder-Viruete and Pérez-Estaún, 2006).In the Majagual-Los Cacaos Marbles nappe, the Si4+-content in Phg1ranges from 3.20 to 3.18 p.f.u., and there is Phg forming pseudo-morphs after Lw with a range of Si4+-content between 3.30 and 3.26p.f.u. Retrograde Phg replacing Car cluster around 3.20 or 3.10 p.f.u.after correction for the pyrophyllite component. In the Rincón

Marbles nappe, the syn-D2 Phg2 ranges in Si4+-content (p.f.u.)between 3.22 and 3.06. In the Santa Bárbara Schists nappe, Phg variesfrom 3.34–3.11 p.f.u. in the lower structural levels to 3.36–3.15 p.f.u.in the upper structural levels. The compositional range in theuppermost contact zone (3.40–3.28 p.f.u.) is similar to that of S2Phg in the Punta Balandra nappe (3.40–3.32 p.f.u.), as well as the Si4+-content variation in retrograde S2 grains of mafic eclogites andblueschists (Fig. 7c). The lowermost Si4+-content appears in the S2Phg of the Majagual-Los Cacaos Marbles nappe (3.32–3.12 p.f.u.).Paragonite in the micaschist has a restricted Si4+-content between3.01 and 3.06 p.f.u.

5.4. Garnet

Garnet occurs in the micaschists and calcschists of the PuntaBalandra nappe. The chemical zoning of garnet (Fig. 6) displays ageneral symmetric core-to-rim decrease of XSps and XFe (from 0.08 tob0.01 and from 0.94 to 0.86, respectively), an increase in XGrs and XPrp

(from 0.18 to 0.32 and from 0.03 to 0.10, respectively), and a smoothundulatory trend or decrease in XAlm (from 0.70 to 0.58). This zoningcontinues in the inclusion-poor rim. These trends are typical ofprograde growth zoning (Spear, 1993) and took place during the interD1–D2 to syn-D2 deformative stages. Garnet shows variable corecompositions, both between andwithin samples, because thin sectionsprobably do not cut the true core of thesemm-size crystals, but the rimcompositions are relatively uniform within samples. The overallzoning patterns appear to be unaltered by post-growth diffusion,except in crystal truncations at the garnet rim (2JE79; Fig. 6) andaround phengite inclusions, due to the reversal of the chemical trendsof XPrp and XAlm in the outer 50–150 μm by retrograde Fe–Mgexchange reactions. This limited diffusional retrograde effect in zoningis consistent with the Tb600–625 °C for the thermal peak (see below)and the timescale of exhumation for these rocks.

6. Estimates of P–T points and P–T paths

6.1. TWEEQU multi-equilibrium calculations

Multi-equilibrium calculations and equilibrium phase diagrams,including isopleth mapping for selected mineral end-members, werethe methods employed to estimate P–T conditions of specificmetamorphic stages. These estimates have allowed the reconstructionof metamorphic P–T paths and the evolution of mineral compositionswith respect to changing P and T. The multi-equilibrium calculationmethod allows simultaneous estimates of P and T to be obtained usinga small number of phases present at the thin-section scale and alsoprovides a check for equilibrium (Berman, 1991). The method uses allpossible equilibrium reactions (TER, Total Equilibrium Reactions)calculated with the end-members (EM) used to describe thecomposition of selected phases. Increasing the number of EM toexpress the compositional variability of chlorite, phengite and otherassociated minerals allows an increase in the number of TER that canbe computed for a givenmineral assemblage involving theseminerals,and, therefore, the number of linearly independent equilibriumreactions (IER).

The thermodynamic data and solid-solution properties used in themulti-equilibrium calculations are included in the TWEEQU softwareof Berman (1991, version 2.02) and its associated updated databaseJUN92. Additional, external data were included for the followingminerals (details in Appendix 5): chlorite (Vidal et al., 2001), Mg-sudoite (Vidal et al., 1992), white mica (Parra et al., 2002), Fe–Mgcarpholite (Vidal et al., 1992), and chloritoid (Vidal et al., 1994). Themineral assemblages used to perform the calculations were selectedusing microtextural and chemical criteria indicative of equilibriumstate. As a general criterion, the assemblage-formingmineralsmust bepart of the same microstructure (e.g. in the S2 planes) and be devoid

XPrp

XAlm

XGrs

XSps

XFeinclusion-free rim

retrogradediffusion

reabsorbedrim reabsorbed rim

reabsorbedrim

inclusion-freerim

retrograde rim retrograde rimretrograde rim

thin retrograderim

inclusionfree rim

Phgpseudomorph Phg

inclusion

S1 inclusion-rich core

(Lw preserved)

early D2 growth

core with Lwinclusions

S1 inclusion-rich core

syn-D2 growth

syn-D2 growth

Distance (µm) Distance (µm)

0.6

0.6 0.6

0.6

0.8

0.8 0.8

0.8

1.0

1.0 1.0

1.0

0 400 900 14000.0

0.0 0.0

0.0

0.2

0.3

0.40.4

0.2 0.2

0.2

0.10.1

0 500 1000 1500 2000 2500 0 1260 2660 4060 5460

stable rim

late-D2 growth Lw and Cldinclusions

Lw and Ctdeinclusions

S1 inclusion-rich corewith sigmoidal pattern

0 2000 4000 6000 8000

2JE72

2JE75

2JE122B

2JE79

a

b

c

d

Fig. 6. Representative zoning profiles of garnet from high-P micaschists of the Punta Balandra nappe.

201J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

of retrogressive features. A major problem is the assumption of localchemical equilibrium (Berman, 1991), particularly for micas. Thecompositional homogenization of mica minerals involves the removalor addition of matter by grain boundary diffusion or advection, as wellas chemical changes within grains by recrystallisation or volumediffusion. It has been shown that volume diffusion in chorite andwhite micas is not significant at Tb550 °C, a temperature that has notbeen exceeded in the Samaná complex. The equilibration of mineralcomposition is mainly controlled by crystallisation and re-crystal-lisation processes (Vidal et al., 2006). This is compatible with the largecompositional variations observed in micas at the thin-section scale,and the correlation of mica composition and microstructural position.Therefore, crystallisation and re-crystallisation of new chlorite andwhite mica seems to be the main processes that act to maintain localequilibrium during metamorphic evolution. As consequence, recordsof compositions of each stage are in part preserved.

P–T conditions were estimated using five different mineralassemblages: Chl+Phg+Qtz, Fe–MgCar+Chl+Phg+Qtz, Ctd+Chl+Phg+Qtz, Grt+Ctd+Chl+Phg+Qtz and Grt+Chl+Phg+Pg+Qtz. Assuming that the standard-state thermodynamic data andthe activity–composition relationships are well calibrated, all reac-tions computed for a given mineral assemblage should theoreticallyintersect at a single point in the P–T field, if equilibrium was achieved

(Berman, 1991). However, disequilibrium between the differentphase compositions and the cumulated errors for each equilibriumreaction can result in a scatter of intersection points. The INTERSXprogramme included in the TWEEQU software allows the calculationof P, T and the scatter between intersections (σT and σP). Theminerals are considered to be in equilibrium if the first values of σP orσT computed by INTERSX are b10% of the P and T estimates,respectively.

6.2. Calculated equilibrium phase diagrams

Equilibrium phase diagrams display the univariant reactions andmultivariant mineral assemblages that are encountered by a partic-ular rock composition. They are appropriate for assessing changingmineral parageneses in rock types that contain high-variance mineralassemblages, and are useful in tracking the P–T evolution of a rockwith the aid of inclusion assemblages. With this goal, equilibriumphase diagrams for representative metapelites from the PuntaBalandra nappe were calculated with the computer code THERIAK–DOMINO (De Capitani, 1994) and the database of Berman (1988,update 1992), which calculates equilibrium phase assemblages byminimization of total Gibbs free energy (ΔG) in a given P–T space. Theextent and absolute positions of the computed stability fields are

2

4

6

8

10

12

14

16

18

20

6 PrPhg + 4 Dhl5 FeAm + 26 aQtz + 2 W

3 AlCe

ghPrP2+l

4C

hl+

5F

eAm

4D

hl+

5A

mV

ghPrP6+lhC4 W2+div-mA5+ztQ6211

Qtz+ PhPhg +

2 MsPhg + 2 W

12

6 PrPhg + 4 Dph

5 FeAm + 26 aQtz

+ 2 W

7

8

14

4 Chl + 6 PrPhg

26 aQtz + 5 W2+VmA

TER = 45; IER = 4P= 15438 bar (±160.7 bar)T = 359.5 oC (±16.7 oC)

Upper Santa Bárbara Schists

5JE128-3Chlorite-Phengite-Quartz

TER = 45; IER = 4P= 12343.2 bar (±7.7 bar)T = 424.8 oC (±0.5 oC)

4JE109-3

S2 foliation

S1 foliation

2

4

6

8

10

12

14

16

18

20

1 3

5

6 PrPhg + 4 Dph

5 FeAm + 26 aQtz + 2W

911

13

15

16

19

20

24

27

28 29

32

35

38

39

KFMASH systemTER = 79; IER = 5P= 11838.5 bar (±6.8 bar)T = 390 oC (±0.6 oC)

Santa Bárbara Schists

5JE116B-1Chlorite-Phengite-Quartz

S2 foliation

KFMASH systemTER = 14; IER = 3P= 20022.2 bar (±123.9 bar)T = 499.1 oC (±1.0 oC)

Punta Balandra SchistsGrt rim-Chl-Cde-Pg-

2JE122B-3aPhg-Qtz

6

8

10

12

14

16

18

20

22

24

65CtdV+28Dph+25W

35FeAm+13Chl+10PrPg

2

3

4

7Atd+13CtdV+5W

4Chl+7MsPg+2PrPg

6

7

8

9

10

11

12

13

14

S2 foliation

2

4

6

8

10

12

14

16

18

20

2

3

4

5

6

71

8

KFMASH systemTER = 43; IER = 4P= 7623.2 bar (±8.4 bar)T = 320.3 oC (±0.1 oC)

Majagual-Los Cacaos unit

5JE144DChlorite-Phengite-Quartz

S2 foliation

KFMASH systemTER = 40; IER = 4P= 11751 bar (±3.4 bar)T = 322.1 oC (±0.1 oC)

Rincón Marbles

JE66-6Chlorite-Phengite-Quartz

2

2

4

6

8

10

12

14

16

18

20

FeAm + FTdhpD+ghpsM35

aQz

+20

Msp

hg+

6C

hl+

4D

ph+

20W

35aQ

tz+

6C

hl +

20F

eAm

+20

W

15sud

+16

Dph

15su

d+

20FT

d

15su

d+

16FT

d

35aQ

z+

16M

sphg

+

6C

hl+

4Fe

Am

+20

W

S1 foliation

2

4

6

8

10

12

14

16

18

20

1

2Prphg+AmV+2W

2sud+4Qz

4Dph+6Prphg26Qz+5FeAm+2W

5

6

4 Chl +

6 Prphg

26 aQz +

5 AmV+2 W

8

4Chl

+5F

eAm

4Dph

+5A

mV

KFMASH systemTER = 146; IER = 5P= 13085 bar (±240 bar)T = 312.2 oC (±11.5 oC)

Lower Santa Bárbara unit

5JE128-1 (Fe3+)Chlorite-Phengite-Quartz

S1 foliation

TWEEQU calculationsSamaná Complex

300 300400 400500 500600 600700 700

Temperature (oC) Temperature (oC)

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

a b

c

e

d

f

Fig. 7. P–T diagrams showing the plot of all equilibrium reactions computed with TWEEQU for mineral assemblages from the different structural nappes of the Samaná complex. Forthese examples, calculations were made in the KFMASH (K2O–FeO–MgO–Al2O3–SiO2–H2O) system. P–T estimates and the scatters between intersections (σT and σP) reported oneach diagram are calculated with the INTERSX programme (Berman, 1991). TER, number of total equilibrium reactions; IER, number of independent equilibrium reactions. Legend ofequilibrium reactions is included in Appendix 5.

202 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

203J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

dependent on the solutionmodel for eachmulticomponent phase andthe bulk composition given in the input. Details of the usedthermodynamic data and solution models are included in Appendix 5.The main input of DOMINO consists of a simplified bulk compositionin the NCKFMASH model system estimated from modal (volume)proportions from thin sections and microprobe analyses of the mainphases. Minor components such as Mn and Ti are not taken intoaccount because these elements are not included in the solutionmodels. The pure phases Qtz and H2O are added in excess to ensuretheir presence in all computations, because Qtz and several majorhydrous phases (Chl, Lws, Ep/Clz, Phg or Pg) form part of all themetamorphic stages, including the pressure-peak (see below). Arelatively high aH2O is also consistent with the phase relations andwater contents in dehydrated subducting metasediments, as exper-imentally shown by Schmidt and Poli (1998). The input used in thiswork is a combination of adjacent phase rim compositions formed atthe metamorphic thermal peak, taking into account possible compo-sitional changes by exchange or net-transfer retrograde reactions.With this selection, the local equilibrium of an observed assemblagerestricted to a small closed system is thus computed.

7. Interpretations and discussion

7.1. P–T path reconstruction

Multi-equilibrium calculations were performed on samples col-lected in the different nappes of the Samaná complex. Typicalexamples of TWEEQU calculations and P–T estimates with INTERSXare presented in Fig. 7 (see also Appendix 6). All results aresummarised in Fig. 8 (see also Appendix 7), which also includes asreference a petrogenetic grid for metapelites in the KFMASH (K2O–FeO–MgO–Al2O3–SiO2–H2O) and CFMASH (CaO–FeO–MgO–Al2O3–

SiO2–H2O) systems, where the mineral assemblages are stronglytemperature-controlled (after Spear, 1993). These P–T estimates andthe observed microtextural relations were used to reconstruct thegeneral P–T paths followed by the rocks of the Samaná complex. TheseP–T paths are similar in all nappes and are characterised by threeevolving stages correlated with specific deformation and metamor-phic events.

Maximum pressure conditions under relatively low temperaturesare recorded by the M1 mineral assemblages of the first stage de-veloped during the D1 deformation (Fig. 8). The highest pressureswere obtained from the Chl1+Phg1+Qtz±Lw and Car+Chl1+Phg1+Qtz±Pg1 assemblages that define relics of an S1 foliation inmetapelites and calcschists of the Rincón Marbles and Santa BárbaraSchists nappes. The array of P–T points obtained from Chl1+Phg1±Car equilibria can be interpreted as the successive generations ofminerals crystallised along a prograde P–T path in the lawsonitestability field (Fig. 8e). Carpholite was rarely used in the P–Tcalculations because of analyses contaminated by white mica owingto its very small crystal size. In the upper structural levels of theSanta Bárbara and Punta Balandra nappes, the syn- to late-D1 growthof chloritoid and garnet porphyroblasts suggests a further increaseof temperature upwards. The estimates for maximum pressuresprogressively increase from the Rincón Marble (~10–12 kbar) to theSanta Bárbara Schists nappes (~12–16 kbar, lower structural levels;15–17 kbar, upper structural levels), and reach their maximum in thePunta Balandra nappe (19–21 kbar). Therefore, the pressure-peakconditions increase across higher structural levels in the nappe pile.A pronounced metamorphic break (up to 10 kbar) occurs towardslower pressures and temperatures above the Punta Balandra nappe,where maximum pressures in the Majagual-Los Cacaos Marble nappeare ~9–11 kbar.

The second stage is characterised by a pressure decrease undernear-isothermal or cooling conditions during the D2 deformation. TheP–T conditions for this stage were estimated from retrograde M2

mineral assemblages composed of syn-S2 Chl2+Phg2+Qtz±Pg2. Inthe Rincón Marbles and Santa Bárbara Schists nappes, the retrogradesyn-D2 P–T path is constrained by the retrogression of Fe–Mgcarpholite to form pseudomorphs of Chl2+Phg2, following thereaction Car→Chl+Phg (Fig. 8) indicative of decompression after ahigh-P stage (e.g. Bousquet et al., 2002). In these structural levels,pressure-peak conditionswere established very close to but below thetemperature of the reaction Car→Ctd+Qtz, as is suggested by theapparent absence of chloritoid formed by the breakdown of carpholitealong the prograde path (i.e. during the M1 high-P stage) in theSamaná complex. Maximum temperature in the uppermost structurallevels of the Santa Bárbara Schists and Punta Balandra nappesoccurred during the D2 deformation and therefore the upperblueschists-facies event is regarded here as M2. In both nappes, themicaschists and calcschists show M2 characterised by the progradeformation of syn-S2 epidote/clinozoisite prisms parallel to S2 planes,and the formation of rectangular pseudomorphs of fine-grained Ep+Pg2±Phg2 after S1 lawsonite. These microstructures imply decom-pression from the lawsonite to the epidote/clinozoisite stability fieldsduring the D2 deformation (Fig. 10). This P–T evolution is particularlywell-constrained by the P–T vectors obtained linking the equilibriumconditions for the garnet cores and rims (from 19–21 kbar/425–450 °C to 15–16 kbar/500–550 °C, respectively).

The third late greenschist-facies metamorphic stage is character-ised by further decompression and cooling. This is the less constrainedpart of the P–T path, with few computed equilibria for Chl–Phg pairs(often IER=2). These phengites and chlorites are located in late-S2fabrics, where titanite, Fe-rich epidote and sudoite are stable. Inmetabasites of the Punta Balandra nappe, M3 is recorded by theretrograde formation of actinolite, chlorite, epidote andwhite mica, inthe P–T range of 5–8 kbar and 300–400 °C (Escuder-Viruete and PérezEstaún, 2006).

For all nappes of the Samaná complex, the P–T estimates outlinedabove indicate clockwise P–T paths with a prograde evolutiontoward a pressure-peak, followed by decompression and cooling,locally with a minor temperature increase. The results indicate onearray of M1 P–T conditions from 300–325 °C and 10–11 kbar in thelower Rincón Marbles nappe to 500–535 °C and 19–21 kbar in thePunta Balandra nappe in the upper levels of the nappe stack. Theprograde P–T conditions recorded by S1 inclusion assemblageswithin garnets in the Punta Balandra nappe cannot be preciselyestimated, as a consequence of Fe/Mg exchange reactions operatingduring retrogression. For this reason, equilibrium phase diagramswere used to model the prograde history of the Punta Balandranappe, based on interpretations of evolving mineral assemblages inmetasediments.

7.2. Modelling the P–T path in the NCKFMASH system

The equilibrium phase diagram calculated for micaschist 2JE79 ofthe Punta Balandra nappe (Fig. 9a) shows restricted stability fields inthe 450–525 °C and 10–18 kbar range for the assemblages (+Chl+Qtz+H2O): Grt+Phg+Pg+Lw+Cld (divariant field; horizontallyruled area), Grt+Phg+Pg (tetravariant; grey-dotted area), and Grt+Phg+Pg+Cld (trivariant; grey-shaded area). The Grt+Phg+Pg+Cld mineral assemblage was formed during the M1 pressure-peakand its stability field is separated from the stable omphacite region athigh temperature (N500–530 °C) by reactions of the type Pg→Omp+H2O(+Ky) (Wei and Powell, 2006). In the modelled composition,the appearance of omphacite is also controlled at PN18–20 kbar bythe trivariant field Grt+Phg+Omp+Cld+Chl+Qtz. Therefore,the absence of omphacite in the Punta Balandra nappe metapelitesindicates maximum pressures below 20 kbar. The diagram shows alarge stability field of lawsonite that is subdivided into a broad garnet-absent (Lw-blueschist facies) and a narrow garnet-bearing (Grt+Lw-blueschists) region at low and high temperature, respectively. The

22

24

3.50

0.30.4

0.2

3.40

3.30

3.20

3.10

3.05

ChlKln

Car Qtz

Chl Prl

Kln

Qtz

Prl

Prl

Ky

Qtz Ctd

Ky

Chl

St

Ctd

Grt

Ky

Grt K

y

And

St

Ky

Chl P

rl

PrlAnd

Qtz

D3

Ctd

D1

D1

Punta Balandrametasediments

TWEEQU results

2JE79

Chl2+Phg2+Qtz(+Ep)

2JE122B

2JE122B

2JE72

2JE72

2JE79

Grt(core)+Chl1+Phg1±Cde+Qtz

Grt(rim)+Chl2+Phg2±Pg2+Qtz

(Fe3+)

S1 fabricrelics

Grt-core+Cld+Lw

Grt-rim

Ep/Clz(Lw pseudomorphs)

S2-planes

2

Car

3.50

0.4 0.3

0.40.5 0.2

3.30

3.20

3.10

3.05

Chl KlnChl Prl

Prl

Prl

Ky

Qtz C

tdK

yC

hlS

t

Ctd

Ctd

Grt

Ky

Grt K

y

And

Grt

St

St

Ky

Chl P

rlC

td

PrlAnd

Qtz

0.6 0.1

Late-S2

D1

D2

D3

Ctd

Qtz

S1 fabricrelics

Carpholitepseudomorphsand chloritoid

S2 fabric

Syn-S2shear bands

2

4

6

8

10

12

14

16

18

20

Car

Ctd

Qtz

Car

Chl+Phg

[R1]

[R1]

[R4]

[R4]

[R4]

[R4]

[R2]

[R2]

[R3]

[R3]

[R3]

[R3]

3.50

0.4 0.3

0.40.5 0.2

3.40

3.30

3.20

3.10

ChlKln

Chl Prl

Kln

Qtz

Prl

Prl

Ky

Qtz C

tdK

yC

hlS

t

Ctd

Ctd

yKtr

G

Grt K

y

Sil

And

Grt

St

St

Ky

Ky

Chl P

rlC

td

PrlAnd

Qtz

0.6 0.1

Majagual-Los CacaosTWEEQU results

JE9049B (Fe3+)

JE9049B (Fe3+)

Chl2+Phg2+Qtz

5JE144D

Chl1+Phg1±Car+Qtz

D2

D1

S2foliation

S1fabric

300 400 500 600 700

2

4

6

8

10

12

14

16

18

20

D3

D2

Car

Ctd

Qtz

3.50

0.4 0.3

0.40.5 0.2

3.40

3.30

3.10

3.05

ChlKln

Car

Qtz

Prl

Prl

Ky

Qtz C

tdK

yC

hlS

t

Ctd

Grt

Ky

AndKy

PrlAnd

Qtz

0.6 0.1

Ep/

Clz

Lw

D1

Santa Bárbara nappelower structural levels

TWEEQU results

2JE53

2JE53

Chl2+Phg2+Qtz

2JE54

5JE128

5JE128

2JE53

2JE54

Chl1+Phg1±Car+Qtz

(Fe3+)

(Fe3+)

2JE54

S1 fabricrelics

Carpholitepseudomorphs

Syn-S2titanite

Late-S2sudoite

S2 fabric

2

4

6

8

10

12

14

16

18

20

3.50

0.4

0.4

0.5

0.2

0.3

3.40

3.30

3.20

3.10

3.05

CtdChl+Phg

ChlKln

Car Qtz

Chl Prl

Prl

Ctd

Ky

Chl

St

Ctd G

rt Ky

Sil

And

Grt

St

St

Ky

Ky

PrlAnd

Qtz

0.6

0.1

Santa Bárbara nappeuppermost contactTWEEQU results

5JE118

JE8347

2JE65

2JE116B

Chl2+Phg2±Pg+Qtz

(Fe3+)

D1

D2

D2

D3

syn-S2Ep/Czo

albitepoikiloblasts

phogopite

late-S2shear bands

[R1]

[R2]

D2

[R1]

Santa Bárbara nappeupper structural levels

TWEEQU results

Chl2+Phg2+Qtz

JE8066

JE8066

5JE128

5JE128

4JE109

4JE143

Chl1+Phg1+Qtz

±Pg

300 400 500 600 700

Car

3.50

0.4

0.5

3.40

3.30

3.20

3.05

CtdChl+Phg

Chl KlnChl

Prl

Kln

Qtz

Prl

Prl

Ky

Qtz C

tdK

yC

hlS

t

Ctd

Grt K

y

Sil

And

Grt

St

St

Ky

Ky

PrlAnd

Qtz

0.6

Ep/

Clz

Lw

Rincón Marble nappeTWEEQU results

2JE66

Chl2+Phg2+Qtz

2JE68

2JE66

2JE68

Chl1+Phg1±Car+Qtz

D2

D1

S1 fabricrelics

Ctd

Qtz

Carpholitepseudomorphs

S2 fabric

Syn-S2titanite

Late-S2sudoite

TWEEQUMulti - equilibriumCalculationsSamanáComplex

a

b

c

e

d

fXin

Mg Carpholite

XinMg

Garnet

XinMg

Chloritoid

Sip4+

fu.inPhengiteLawsonitestabilityfield(CFMASHsystem)

Metapelite isopleths(KFMASH system):

[R1]

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

Temperature(°C) Temperature(°C)

204 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

STAGESD1

Phg+Omp+Chl+Ctd+Lw

GRT+Phg+Pg+Omp

Phg+Pg+Chl+Ctd+Lw

GRT+Phg+Pg+OMP+Chl

GRT+Phg+Pg+Ep+Gln

GRT+FSP+

(2)WM+Chl

GRT+FSP(2)WM

GRT+FSP+WM+Chl

GRT+FSPWM

Phg+Pg+Chl+Lw

Phg+Pg+Chl+Ep

+Lw

Phg+Pg+Chl+Ep

FSP+Phg+Pg+Chl

+Ep FSP+WM+Chl+Ep

FSP+WM+Chl

a

d

cg

e

f

b

0

5

10

15

20

2

2

D3

D2

D2

300 400 500 600 700

2

2

D1

D3

D2

D2

0.92

0.91

0.90

0.89

0.88

0.87

0.86

0

5

10

15

20

300 400 500 600 700

2

2

D1

D3

D2

D2

0.16

0.180.22

0.260.30

0.08

0.04

0.10

0.14

2

2

D1

D3

D2

D2

3.4

3.35

3.40

3.35

3.30 3.25

3.30

3.25

3.2

3.15

3.45

3.43

3.5

3.553.63.73.65

0

5

10

15

20

2

D1

D3

D2

0.03

0.05

0.120.10

XPrp

XAlm

XGrsXSi

XFe

Grt

Grt

GrtPhg

Ctd

2

2

D1

D3

D2

D2

peakpressure

inclusions peak-temperature

+Qtz+H2O

2D2

0.820.84

0.74

0.70

0.700.68

0.62

0.72

0.72

0.68

0.70

0.72

0.720.66

0.64

phengiteinclusions

garnet

omphacite

lawsonite

plagioclase

epidote

chloritoid epidote/clinozoisite

retrograderecrystalization

D1

a b

c

e

d

f

Temperature (°C) Temperature (°C)

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

Pre

ssur

e (k

bar)

Fig. 9. Equilibriumphase diagram(a) and isopleths for garnet (XPrp,XGrs andXAlm; b, d and f), phengite (XSip.f.u.; c) and chloritoid (XFe; e) computed for sample 2JE79of high-Pmicaschist ofthe Punta Balandra nappe, Samaná complex. The diagrams are calculated for a modelled bulk-rock chemistry [SiO2/Al2O3/FeO/MgO/CaO/Na2O/K2O=3.8:1.5:0.65:0.2:0.05:0.16:0.3]derived from the modes and electron microprobe analyses of the main phases and with H2O in excess, with the software Theriak–Domino (De Capitani, 1994). See text for explanation.

Fig. 8. Generalised P–T paths for the different metamorphic nappes in the Samaná complex deduced from multi-equilibrium calculations (see Appendix 7). Encircled numberscorrespond with metamorphic events described in the text. The figure also includes as reference a petrogenetic grid for metapelites for a temperature range from 250 to 750 °C in theKFMASH (K2O–FeO–MgO–Al2O3–SiO2–H2O) system, where the mineral assemblages are strongly temperature-controlled. The appearance of high-P assemblages with Fe–Mgcarpholite or chloritoid delimits the low-T domain from the middle-T one at around 400 °C. The exact temperature limit depends on rock and mineral chemistry. In the CFMASH(CaO–FeO–MgO–Al2O3–SiO2–H2O) system, lawsonite is the main stable mineral under low-T conditions, sometimes coexisting with Fe–Mg carpholite. Grids drawn after Bousquet etal. (2002), Spear (1993) and Vidal and Parra (2000), as well as own calculations of mineral isopleths using the Theriak–Domino software. Nappes: RM=RincónMarbles; SBS= SantaBárbara Schists; PB = Punta Balandra (non-mélange and mélange parts); and MCM = Majagual-Los Cacaos Marble.

205J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

206 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

reaction that produces garnet takes place between 450 and 475 °C atPN10 kbar and has a steep negative slope in the P–T diagram (Fig. 9b).This reaction corresponds with the “garnet-in” isograd described inmany high-P blueschist terranes (Evans, 1990). Fig. 9 shows theinferred P–T path (arrow) followed formetapelite 2JE79. Between Lw-blueschist facies assemblages and omphacite-bearing metapelites,several narrow subvertical fields occur at T=450–475 °C, thatrepresent the resorption of lawsonite and chloritoid and thediscontinuous growth of paragonite and epidote/clinozoisite duringincreasing T. The pseudomorphs of Pg+Ep/Clz±Qtz after Lwincluded in garnets suggest that these stability fields were crossedduring the prograde evolution through the reaction Lws→Pg+Clz(+Phg)+Qtz+H2O. The lawsonite and chloritoid inclusions ingarnets are relicts of the Lw-blueschist facies assemblages Phg+Pg+Lw and Phg+Pg+Ctd+Lw (+Chl+Qtz+H2O), whose stabilityfields were crossed during the M1 prograde evolution (Fig. 9a). TheM2 metamorphic conditions produced syn-D2 assemblages withepidote/clinozoisite and titanite, without stable lawsonite, as well aslate-D2 poikilitic albite. TheseM2 assemblages constrain the retrogradeP–T evolution at Tb500 °C outside the garnet stability field, in thesuccessive fields Phg+Pg+Ep/Clz, Ab+Phg+Pg+Ep/Clz and Ab+Phg+Ep/Clz (+Chl+Qtz). Crossingduringdecompressionof a narrowtrivariant field with the stable assemblage Grt+Phg+Pg+Chl+Ep/Clz+Qtz (vertically ruled area) can explain the observed clinozoisiteinclusions at the outermost garnet rim.

The computed isopleths for end-members of garnet (XPrp, XAlm andXGrs), chloritoid (XFe) and phengite (XSi) allow precise thermobaro-metric calculations of specific metamorphic stages (Fig. 9b–f). Formetapelite 2JE79, the pressure-peak M1 assemblage Grt+Phg+Pg+Chl+Ctd is stable within a restricted P–T field, in which all phasecomponents of Grt, Ctd and Phg display a narrow spread of isopleths,consistent with these three phases having undergone significantcompositional changes. The white circle in Fig. 9 represents themodelled conditions for re-equilibration during pressure peakconditions, a region where the intersection of the isopleths is inagreement with the real measurements. The P–T conditions obtainedare 485 °C and 19 kbar for the phase compositions XPrp=0.07–0.09,XAlm=0.72–0.74, and XGrs=0.14–0.18 for Grt cores, XFe=0.78–0.80for Ctd, and XSi=3.45–3.50 for Phg. The modelled composition of Grtwithin the stability field of the assemblage Grt+Phg+Pg+Chl isalmost constant, because all of the components of this phase displayisopleths widely spread over a large P–T range, and have a steepnegative slope in the diagram (Fig. 11). This is consistent with thesmooth garnet zoning and the syn-D2 decompressive P–T path, whichis sub-parallel to the isopleths. Analogously, the estimated P–Tequilibrium conditions for the garnet rim are of ~500 °C and14.5 kbar (XPrp=0.04–0.05, XAlm=0.68–0.70, XGrs=0.20–0.24;and XSi=3.40–3.42, black circle). This estimate is consistentwith the real smooth decrease of XFe from garnet core to rim.The modelled P–T segment records a minor temperature risetoward the thermal peak (14–15 kbar at 500 °C). The modelledtrends for XGrs, XAlm and XPrp are consistent with the measuredcompositional profiles in garnets, away from the retrogressedouter rims.

The occurrence of relict inclusions of S1 minerals in the garnetallows the calculation of P–T points relative to the syn-D1 evolution,assuming that Phg+Pg+Lw and Phg+Pg+Lw+Ctd were pro-grade stable assemblages, as is the case in the structurallyunderlying Santa Bárbara nappe. The P–T points obtained forthese assemblages with Phg (XSi=3.43–3.45) and Ctd (XFe=0.84–0.88) record a prograde P–T segment of M1 in the Lw-blueschistfacies (Fig. 11). Along the retrograde P–T path, phengite adapts itscomposition continuously to the changing equilibrium conditions,which causes a broad range of Si4+-content in separate S2 Phggrains. This pressure (and temperature) dependence of Phgcomposition can be used to calculate P–T estimates; the modelled

isopleths of XSi are plotted in Fig. 9c. In the case of sample 2JE79, theXSi values measured in syn-S2 phengites range from 3.45 to 3.18 p.f.u., which reflect a pressure decrease from about 16 to 6 kbar at 425–500 °C. Therefore, the derived syn-D2 P–T path indicates a strongdecompression without any late heating, which explains the lack ofstaurolite and kyanite assemblages in Punta Balandra metasedi-ments. It should be noted that the lowest T part of this retrogradeP–T path (Pb6–8 kbar) is constrained by the late growth of albiteand biotite, as well as the late development of greenschist-facies S2shear fabrics.

7.3. Tectonothermal evolution of the Samaná complex

The nappe pile of the Samaná complex has been recentlyinterpreted as a paleo-accretionary wedge, built on the Caribbeanupper plate as a result of Cretaceous to Cenozoic SW-directedoblique subduction of the proto-Caribbean Ocean and collision ofthe southern continental margin of North America (Escuder-Viruete et al., 2011). The age of the youngest meta-sediments inthe accretionary wedge is Campanian–Maastrichtian (Weaver etal., 1976). In the Samaná complex, the remains of the subductedocean are only preserved in the uppermost mélange of the PuntaBalandra nappe, as blocks of (ophiolitic) serpentinized peridotites,serpentinitic schists and mafic eclogites. These mafic eclogiteshave N-MORB to IAT geochemical signatures, and are interpretedto have formed in a mid-oceanic rift to island-arc setting (Perfit etal., 1982; Joyce, 1991; Sorensen et al., 1997; Escuder-Viruete,2008b).

Three major stages were recognised in the tectonothermalevolution of the Samaná complex (M1 to M3), based on themetamorphic P–T paths (this study) and the structural andgeochronological data included in Escuder-Viruete et al. (2011).The M1 high-P metamorphism is characterised by a syn-D1prograde P–T path in the carpholite and lawsonite stability fields,from 300–350 °C and 10–12 kbar to the pressure peak in thelawsonite-blueschist facies (Rincón Marbles, Santa Bárbara Schistsand Majagual-Los Cacaos nappes) and garnet-blueschist transition-al to eclogite-facies conditions (non-mélange part of the PuntaBalandra nappe). In uppermost mélange mafic eclogite blocksenclosed in the metasediments record a pressure-peak at 22–24 kbar and 610–630 °C (Escuder-Viruete and Pérez-Estaún, 2006).The 40Ar/39Ar plateau ages on phengite and the T–t/P–t estimates,coupled with other regional geochronological data, reveal asequence of Eocene to Late Oligocene ages for high-P metamor-phism (Fig. 10). This shift in age of peak metamorphism is theresult of the progressive incorporation of the different nappes intothe accretionary wedge.

The M2 retrograde metamorphism took place during the D2deformation and nappe stacking in the complex. This M2 stage wasassociated with substantial exhumation of the blueschist- andeclogite-facies rocks. The M2 mineral assemblages, multi-equilibriumcalculations and thermodynamical modelling of P–T paths indicatedecompression under nearly isothermal, or cooling, conditions duringD2 in all nappes. In the Punta Balandra nappe, the rocks passed fromeclogite conditions to epidote-blueschists (8–12 kbar at 400–500 °C)and greenchists facies conditions (4–8 kbar at 400–350 °C). In theother nappes, rocks evolve from carpholite and lawsonite-blueschiststo upper greenchists facies conditions during M2. The 10 Ma timeinterval obtained from 35 to 25 Ma 40Ar/39Ar plateau ages on S2phengite, and the T–t/P–t relationships reveal Late Eocene toearliest Miocene retrograde M2 metamorphism in the differentnappes.

The late, syn-D3 and D4 segment of the retrograde P–T path (Pb4–5 kbar) is characterised by M3 cooling at low-P, and is coeval with thedevelopment of the greenschist to subgreenschist facies S3 planes andS4 shear fabrics. Afterwards, from Lower Miocene to Present (Mann

300 400 500 600 700

2

4

6

8

10

12

14

22

16

24

18

20

Ctd

Ky

Chl

St

Ctd

Ctd

Grt

Ky

Grt K

y

wet

mel

ting

curv

e

Sil

Grt

St

St

Ky

LwE

p/C

lz

eclogiticpeak inmaficblocks(*)

lawsoniteeclogitefield *

lawsoniteeclogitefield *

lawsoniteblueschistslawsonite

blueschistsD1

D1

D1

D1

RM2

cont.SBS

Ctd

Qtz

Car

MCM

lowerSBS

upperSBS

non-mél.PB

uppermostmélange

PB

M2. Exhumation-relatedretrograde evolution

M3. Cooling at low-Pretrograde evolution

M1. Subduction-relatedprograde evolution

Santa BárbaraSchists (SBS)

Jagua Clara(+Arroyo Sabana)serpentinitic-matrix mélange(JCM)

Samaná complexRío San Juan complex

Punta Balandra,non-mélange(non-mél PB)

Punta Balandra,mélange (PB)

Rincón (RM)and Majagual(MCM) Marbles

incorporationof mafic blocks

onset ofcollisionincorporation to

accretionary wedgeSamaná complex

protoliths

D1

D1

D2

D2

Exhumationvelocities(km/Ma)

1

3

5

10

Lawsonite stability inthe CFMASH system

Mineral reactionsin the KFMASHsystem

Samaná ComplexP-T and P-t Paths

D2

D2

D2

D2

D2

D2

D3

D3

D4

0 20 40 60 80 100

Time (Ma)

U-Pb, Zr

Interpreted P-t point

Geochronologicaldata

Sm-Nd, WR-Grt-Omp

Rb-Sr, WR-Phg-Amp

Ar-Ar, Gln

Ar-Ar, Phg

Error bars on age dates(age scale from Gradstein et al., 2004)

exhumationin the

subductionchannel

Punta Balandramélange

mafic eclogites JCMPunta Balandranon-mélange

metasediments

RincónMarblesnappe

Santa BárbaraSchists nappe

continentalexhumation

continentalsubduction

Temperature(°C)

Pre

ssur

e (k

bar)

Fig. 10. P–T and P–t paths derived from petrological and geochronological data of the Samaná complex nappes, as well as Jagua Clara serpentinite-matrix mélange of theneighbouring Río San Juan complex (Krebs et al., 2008). The P–T path for the uppermost mélange part of the Punta Balandra nappe was deduced from mafic eclogite blocks byEscuder-Viruete and Pérez-Estaún (2006), which cross the lawsonite-eclogite field (*) defined for these mafic compositions. See Escuder-Viruete et al. (2011) for construction of themodel paths and inferred exhumation rates, particularly for the exotic mafic eclogite blocks enclosed in the uppermost mélange of the Punta Balandra nappe. Note the diachronousP–t paths for the Jagua Claramélange and Samaná complex nappes, which include the syn-oceanic exhumation for oceanic rocks, onset of arc-continent collision, continental-marginsubduction and continental exhumation stages. In the lower part of the figure, the time interval for high-P accretionary complex development, onset of arc-continental collision, therecord of Bahamas passive margin sedimentation, syn-orogenic turbiditic sedimentation in the Setentrional Cordillera of Hispaniola and final subaereal exposure of the Samanámetamorphic complex are also included.

207J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

et al., 2002), the nappe pile was cut and laterally displaced by a D5system of regional-scale, sinistral strike-slip and reverse brittle faultsassociated with the Septentrional fault zone.

7.4. Structural setting for exhumation of high-P rocks

The D1 deformationwas accompanied and followed by a growth ofprograde high-P mineral assemblages. The P–T estimates areindicative of a progressive subduction path along a cold thermalgradient of ~7 °C/km, like that found in Cenozoic to present-daysubduction zones (Agard et al., 2009). The depth reached duringsubduction increases structurally upwards in the complex from thePlaya Colorada and Rincón Marbles nappes to the Punta Balandranappe, as shown by maximum pressure estimates in each nappe. Inthis sense, the Majagual-Los Cacaos nappe basal contact is interpretedas an out-of-sequence thrust. The kinematic data for D2 ductiledeformation in the metamorphic complex provide a regional-scale,consistent, top-to-the-NE/E sense of shear. In general, the shape of theM2 retrograde P–T path is similar for all nappes, and implies cooling

and decompression under blueschist-facies conditions during the D2deformation. Therefore, D2 deformation is considered responsible formuch of the exhumation of the subducted rocks and for the thinningof the nappe pile. At present, ~6–8 km crop out across the S2 foliationbetween the Rincón Marbles and Majagual-Los Cacaos basal thrust,versus ~24 km at maximum depths (ca. 8 kbar). Escuder-Viruete et al.(2011) have interpreted this syn-D2 tectono-metamorphicevolution as the accretion of a series of subducted nappes into anevolving collision accretionary wedge. The incorporation of eachnappe to the overriding plate implies a jump of the basal thrusttowards the foreland. As a consequence of this process, the fossilaccretionary wedge that represents the Samaná complexwas growingwith the metasediments detached from the crust of the down-goingplate during subduction and collision of the Bahamas Platform. Thisinterpretation is favoured by the 35–25 Ma interval of 40Ar–39Arplateau ages obtained on S2 phengite from the different nappes. Thesephengite ages record the Late Eocene to earliest Miocene retrogrademetamorphism during the diachronous D2 nappe stacking, top-to-the-ENE tectonic transport toward the foreland, and a general

Temperature

M1

M2

erusserP

Caribbean island-arcvolcanism

upper crust

andlithospheric

mantle(proto-Caribbean)

lower crust

oceanic crust

releasedfluids

partial meltingof the mantlewedge

onset of nappe acretion

serpentinitechannelformation

JCM

JCM

SB

RM

JCM

JCM

JCM

PC

Late-Cretaceous intra-oceanic subduction

D1: Late Paleocene/Eocene collision,high-P M1 metamorphism

Bahamian oceanic/plateau crust

PB

SB

RM

subduction channel(40-100 km depths)

SB = Santa Bárbara Schists nappe

JCM = Jagua Clara serpentinitic-matrix mélange

Samaná complex

Río San Juan complex

PB = Punta Balandra nappe

RM = Rincón/Majagual Marbles nappe

PC = Playa Colorada Phyllite nappe

trench axis

serpentiniticolisthostromes

onset of syn-orogenicsedimentation

syn-orogenic turbiditic basins

northeastwardpropagationof deformation

uplift and erosion of the forearc basin

serpentinitemelange wedge

extinted arc volcanismand erosion

coolinghangingwall

mantle wedge

flow

inth

e

subduction channel

pelagic sedimentsand seamounts ontop oceanic plate

forearc basin(Las Guayabas Fm.)

arc crust

proto-Caribbeansubducted oceanic crust

exotic blocksincorporation to theuppermost PuntaBalandra mélange

serpentinitic-matrix mélangewith early exhumed blocks ofeclogitized oceanic crust

PB

NESW

Temperature

erusserP

uplift

nappe stacking,decompressionand thrusting of>P on <P units

sequentialexhumationof high-Pslabs

PB SB RM

PC

D2: Eocene/oligocene exhumationby nappe stacking, retrograde M2metamorphism

PB

PB

SB

SBRM

Fig. 11. Schematic model for the structural and metamorphic evolution of the Samanácomplex, showing the key processes controlling the exhumation of high-P rocks in anaccretionary wedge formed from intra-oceanic subduction to arc-continent collision.The Late Cretaceous intra-oceanic subduction stage is based on Krebs et al. (2008).Afterward, two main stages can be distinguished: D1, prograde high-P metamorphismjust before the nappe accretion to the wedge; and D2, nappe stacking, decompression,retrograde metamorphism, and thrusting of higher-P onto lower-P structural nappes.The effects of post-D3 out-of-sequence thrusting of Majagual-Los Cacaos basal thrustand D5 sinistral strike-slip brittle fault tectonics have been omitted for clarity.

208 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

northeastward progradation of deformation in the northern Caribbe-an convergence zone.

A schematic model for the structural and metamorphic evolutionof the Samaná complex, showing the key processes controlling theexhumation of high-P rocks in an accretionary wedge formed duringarc-collision, is depicted in Fig. 11. Note that an accretionary wedgeand a serpentinite subduction channel existed in the same northernCaribbean subduction zone, but at different times. The Jagua Claraserpentinite-matrix mélange of the Río San Juan complex representsthe deep subduction channel during the intra-oceanic subductionstage and the Samaná complex represents the accreted metasedi-ments to the growing wedge during the collision stage. This tectonicinterpretation is consistent with the internal structural position of theJagua Clara mélange (Escuder-Viruete, 2009) and the Campanian–Maastrichtian older age for the exhumation of eclogites and blues-chists (Krebs et al., 2008; Escuder-Viruete et al., 2009) in thepreviously accreted mélange.

7.5. Mechanisms of exhumation of high-P rocks in accretionary wedges

A number of models have been proposed to explain theexhumation mechanisms of high-P rocks. These include buoyancyuplift, two-way street, extensional tectonics, erosional exhumation,wedge extrusion, channel flow or classic flow-mélange (Platt, 1993;Maruyama et al., 1996; Agard et al., 2009). For the Samaná complexthere are several basic conditions that need to be fulfilled by anymodel regarding the exhumation mechanism: (1) the complex is anappe pile made of platform to pelagic metasediments, withoutsignificant amounts of serpentinites (with the exception of the thinmélange-like uppermost Punta Balandra nappe); (2) D2 ductilestructures and gradients are related to the nappe contacts; (3) P–Tconditions increase toward the upper structural levels (except theMajagual-Los Cacaos nappe, see below), indicating a joint evolution ofthe whole complex duringmuch of its history; (4) the absence of largepressure gaps across the D2 ductile thrusts suggests that the relative,post-D2 displacements were limited and that the nappe pile waslargely assembled prior to D3/M3 (i.e. it formed during D1 and D2deformations); (5) exhumationwas active during D2 deformation at arelatively early stage in the formation of the complex, i.e. duringongoing compression and subduction that includes nappe-stackingassociated with thrusting of high-P units onto lower-P units; (6) theD2 structures formed diachronously and sequentially in the differenttectonic nappes from the Lower Eocene to the earliest Oligocene,predating the subaereal exhumation and erosion of the Samanácomplex in the Middle/Late Miocene, which is typical for tectonics ofaccretionary wedges; and (7) the overall spatial relationshipsbetween the former paleogeographic domains need to be preservedduring the exhumation stage, since internal units were thrust ontoexternal ones. These conditions are satisfied by models that postulateascent by extrusion within, and parallel to, a subduction channel byactive, forced extrusion (Gerya et al., 2002), promoted by slabextraction and/or buoyant ascent (Froitzheim et al., 2003), but notby models that invoke extension in the accretionary wedge such asthose suggested by Platt (1993) for the Franciscan complex. Thus, theexhumation mechanisms in the Samaná complex are probably thoseof a collision accretionary wedge driven by underthrusting/under-plating and erosion, which would preserve the continuity of the P–Tconditions within the accreted metasedimentary units, as in this case.

Similar scenarios for exhumation of high-P rocks during nappestacking were described in theWestern Alps by Bousquet et al. (2002)and in the Sambagawa belt by Aoki et al. (2007), where the upperboundary of the wedge is a low-angle normal fault and the base of thewedge is a subduction thrust. An extrusion wedge configuration canexplain the large-scale structural and thermal features of the Samanácomplex nappe stack. In this sense, the contact between theMajagual-Los CacaosMarbles and the Punta Balandra nappes is a good candidate

209J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

to be a normal fault since it coincides with an important pressure gap,equivalent to 30–40 km of overburden. Mapping indicates that the S2fabrics and the basal thrust of the Majagual-Los Cacaos Marble nappeare cut by WNW-striking strike-slip faults associated with theSeptentrional Fault zone; however, the vertical displacement relatedto this fault system cannot be evaluated. By other hand, there is nodefinite evidence for Eocene to earliest Oligocene normal faulting inthe upper structural units of the complex, or in the Río San Juan andPuerto Plata complexes, which probably overly the Samaná complex-like rocks in the western Septentrional Cordillera (Escuder-Viruete,2009).

Finally, there remains to be explained the absence of collision-related, intermediate-P Barrovian-type metamorphism in the Samanácomplex, which is characteristic of a second thermal peak during thelate stage of the exhumation of high-P rocks – often under quasi-staticconditions – as it is the case of Central Alps (Wiederkehr et al., 2008),the Cycladic Massif (Jolivet et al., 2003), or theWestern Betics (Booth-Rea et al., 2003). In these areas, the Barrow-type overprint representsa separated heating pulse that clearly post-dates isothermal decom-pression after the early high-P stage. This heating pulse is probablyrelated to the accretion/underthrusting of large volumes of continen-tal crust with a high production of radiogenic heat, whichwould causethe intermediate-P metamorphism. In the case of the Samanácomplex, such absence can be explained by the nature of thebasement under the Bahamas Platform, which is a carbonate platformon thinner continental and oceanic crust (for geophysical evidence ofthe different nature of Bahamas basement see discussion in Pindellet al., 2005), and the oblique character of the arc-continent collision(Mann et al., 2002). Thin continental crust occurs beneath the north-western portion Grand Banks, while oceanic or plateau-type crustoccupies the south-eastern portion, from Caicos to Inagua and furthereast. This suggests that the Caribbean island-arc collided diachro-nously with a thinned Yucatán-Bahamian continental crust in the NW,forming the Cuban allochthonous thrust-belts and the para-allochtho-nous Remedios-Placetas belts in northwestern and central Cuba(García-Casco et al., 2008), respectively; and with a thick carbonateplatform overlying oceanic crust in the SE, forming the eastern Cubaand northern Hispaniola accreted terranes, such the Samaná complex.This interpretation explains the partial preservation of the large-scalestructure of the Samaná complex accretionary wedge, the nonexis-tence in the thrust nappes of North American continental basement,and the absence of a late heating event producing a Barrovianmetamorphic overprint. This implies that the metasediments of theSamaná complex were detached from their basement during theaccretion processes, and the underlying oceanic crust was burieddown to mantle depths along the subduction channel and never cameback to the surface.

8. Conclusions

The new metamorphic field and chemical mineral data presentedin this study allow to model the tectonothermal evolution of the high-P metasedimentary nappes of the Samaná complex, which hassignificant implications for the understanding of the evolution ofcollisional accretionary wedges and, in particular, the mechanism forthe exhumation of high-P rocks in this tectonic setting. Three majorstages of tectonothermal evolution were recognised (M1 to M3). M1metamorphism produced a prograde P–T path with pressure peak inthe lawsonite-blueschist facies (Majagual-Los Cacaos, Santa BárbaraSchists and Rincón Marbles nappes) and transitional garnet-blues-chist and eclogite-facies conditions (non-mélange part of the PuntaBalandra nappe). This high-P metamorphism and related early D1deformation took place during the Eocene to Late Oligocene, when thedifferent nappes were buried along a cold subduction-zone gradient.M2 retrograde metamorphism was contemporary to the D2 defor-mation, and associated with substantial decompression under nearly

isothermal or cooling conditions to epidote-blueschist and greens-chist-facies conditions in all nappes. D2 deformation produces ENE-directed folding, thrusting and nappe-stacking in the complex. Thedifferent nappes were sequentially incorporated into a growingcollisional accretionary wedge in the Late Eocene–earliest Miocene.D2 deformation is thus responsible for much of the exhumation of thesubducted rocks and for the thinning of the nappe pile. Non-penetrative fabrics associated with late D3 and D4 late deformationsindicate M3 cooling in greenschist and subgreenschist-facies condi-tions. Final D5, sinistral, strike-slip brittle faults cut and displace thewhole nappe pile of the Samaná complex laterally from the LowerMiocene to the Present.

Supplementarymaterials related to this article can be found onlineat doi:10.1016/j.lithos.2011.02.006.

Acknowledgements

The authors thank G. Draper for field introduction and discussionson the metamorphic rocks in the Dominican Republic. DirecciónGeneral de Minería of the Dominican Government is also thanked forassistance. Constructive criticism byW.V. Maresch and an anonymousreviewer, as well as editorial comments by I. Buick are acknowledged.Funding by the Spanish Ministerio Ciencia e Innovación projectCGL2009-08674/BTE is gratefully acknowledged. This work is acontribution to IGCP-546 “Subduction zones of the Caribbean” andTopo-Iberia Consolider-Ingenio (2010 CSD2006-00041).

References

Agard, P., Yamato, P., Jolivet, L., Burov, E., 2009. Exhumation of oceanic blueschists andeclogites in subduction zones: timing and mechanisms. Earth Science Reviews 92,53–79.

Aoki, K., Itaya, T., Shibuya, T., Masago, H., Kon, Y., Terabayashi, M., Kaneko, Y., Kawai, T.,Maruyama, S., 2007. The youngest blueschist belt in SW Japan: implication for theexhumation of the Cretaceous Sanbagawa high-P⁄T metamorphic belt. Journal ofMetamorphic Geology 26, 583–602.

Berman, R.G., 1988. Internally-consistent thermodynamic data for minerals in thesystem Na2O–K2O–CaO–MgO–FeO–Fe2O3–Al2O3–SiO2–TiO2–H2O–CO2. Journal ofPetrology 29, 445–522.

Berman, R.G., 1991. Thermobarometry using multi-equilibrium calculations: a newtechnique, with petrological applications. Canadian Mineralogist 29, 833–855.

Bousquet, R., Goffé, B., Vidal, O., Patriat, M., Oberhänsli, R., 2002. The tectonometa-morphic history of the Valaisan domain from the Western to the Central Alps: newconstraints for the evolution of the Alps. Geological Society American Bulletin 114,207–225.

Bucher, K., Frey, M., 2002. Petrogenesis of Metamorphic Rocks, 7th edition. Springer,Berlin. 341 pp.

Booth-Rea, G., Azañón, J.M., García-Dueñas, V., Augier, R., Sánchez-Gómez, M., 2003. A“core-complex-type structure” formed by superposed ductile and brittle extensionfollowed by folding and high-angle normal faulting. The Santi Petri dome (westernBetics, Spain). Comptes Rendus Geoscience 335, 265–274.

Catlos, E.J., Sorensen, S.S., 2003. Phengite-based chronology of K- and Na-rich fluid flowin two paleosubduction zones. Science 299, 92–95.

Cloos, M., Shreve, R.L., 1988. Subduction-channel model of prism accretion, melangeformation, sediment subduction, and subduction erosion at convergent platemargins: 1. Background and description. Pure and Applied Geophysics 128,455–499.

Chopin, C., 2003. Ultrahigh-pressure metamorphism: tracing continental crust into themantle. Earth and Planet Science Letters 212, 1–14.

De Capitani, C., 1994. Gleichgewichts-Phasendiagramme: Theorie und Software.Beihefte zum European Journal of Mineralogy, 72. Jauhrestagung der DeutschenMineralogischen Gesellschaft, 6, 48.

De Zoeten, R., Draper, G., Mann, P., 1991. Geological map of the northern DominicanRepublic. In: Mann, P., Draper, G., Lewis, J.F. (Eds.), Geologic and TectonicDevelopment of the North America–Caribbean Plate Boundary in Española:Geological Society of America Special Paper, 262. Plate 1.

Draper, G., Lewis, J.F., 1991. Geologic map of the central Dominican Republic(1:150,000). Geological and Tectonic Development of the North American–Caribbean Plate Boundary in Hispaniola: In: Mann, P., Draper, G., Lewis, J.F.(Eds.), Geological Society America Special Paper, 262. plates.

Draper, G., Mann, P., Lewis, J.F., 1994. Hispaniola. In: Donovan, S.K., Jackson, T.A. (Eds.),Caribbean Geology: An Introduction. University of the West Indies PublishersAssociation, Kingston, Jamaica, pp. 129–150.

Escuder-Viruete, J., 2008a. Mapa Geológico de la República Dominicana E. 1:50.000,Santa Bárbara de Samaná (6373-IV). Dirección General Minería, Santo Domingo.197 pp.

210 J. Escuder-Viruete et al. / Lithos 125 (2011) 190–210

Escuder-Viruete, J., 2008b. Petrología y Geoquímica de Rocas Ígneas y Metamórficas:Hojas de Las Galeras, Santa Bárbara de Samaná y Sánchez. Informe Complementarioal Mapa Geológico de la República Dominicana a E. 1:50.000. IGME-BRGM, SantoDomingo. 79 pp.

Escuder-Viruete, J., 2009. Mapa Geológico de la República Dominicana E. 1:50.000, RíoSan Juan (6174-I). Dirección General de Minería, Santo Domingo. 223 pp.

Escuder-Viruete, J., Pérez-Estaún, A., 2006. Subduction-related P–T path for eclogitesand garnet glaucophanites from the Samaná Peninsula basement complex,northern Hispaniola. International Journal of Earth Sciences 95, 995–1017.

Escuder-Viruete, J., Friedman, R., Pérez-Estaún, A., Joubert, M., Weis, D., 2009. U–Pbconstraints on the timing of igneous and metamorphic events in the Rio San Juancomplex, northern Hispaniola. VII Congreso Cubano Geología. Workshop IGCP-544.

Escuder-Viruete, J., Pérez-Estaún, A., Gabites, A., Suárez-Rodríguez, A., 2011. StructuralDevelopment Of A High-Pressure Collisional Accretionary Wedge: The SamanáComplex, Northern Hispaniola. Journal of Structural Geology 33, 928–950.

Evans, B.W., 1990. Phase relations of epidote-blueschists. Lithos 25, 3–23.Froitzheim, N., Pleuger, J., Roller, S., Nagel, T., 2003. Exhumation of high- and ultrahigh-

pressure metamorphic rocks by slab extraction. Geology 31, 925–928.García-Casco, A., Iturralde-Vinent, M.A., Pindell, J., 2008. Latest Cretaceous collision/

accretion between the Caribbean Plate and Caribeana: origin of metamorphicterranes in the Greater Antilles. International Geological Review 50, 781–809.

Gerya, T.V., Stoeckhert, B., Perchuk, A.L., 2002. Exhumation of high-pressuremetamorphicrocks in a subduction channel — a numerical simulation. Tectonics 21 6–1–6–19.

Giaramita, M.J., Sorensen, S.S., 1994. Primary fluids in low temperature eclogites —

evidence from 2 subduction complexes (Dominican Republic, and California, USA).Contributions to Mineralogy and Petrology 117, 279–292.

Goffé, B., Bousquet, R., 1997. Ferrocarpholite, chloritoïde et lawsonite dans lesmétapelites des unités du Versoyen et du Petit St Bernard (zone valaisanne,Alpes occidentales). Schweizerische Mineralogische und Petrographische Mittei-lungen 77, 137–147.

Gonçalves, Ph., Guillot, S., Lardeaux, J.M., Nicollet, C., Mercier de Lépinay, B., 2000.Thrusting and sinistral wrenching in a pre-Eocene HP-LT Caribbean accretionarywedge (Samaná Peninsula, Dominican Republic). Geodinamica Acta 13, 119–132.

Guillot, S., Hattori, K., Agard, P., Schwartz, S., Vidal, O., 2009. Exhumation processes inoceanic and continental subduction contexts: a review. In: Lallemand, S., Funiciello,F. (Eds.), Subduction Zone Geodynamics. Springer-Verlag, Berlin Heidelberg.doi:10.1007/978-3-540-87974-9. 175–205 pp.

Hermann, J., Müntener, O., Scambelluri, M., 2000. The importance of serpentinitemylonites for subduction and exhumation of oceanic crust. Tectonophysics 327,225–238.

Jolivet, L., Faccenna, C., Goffé, B., Burov, E., Agard, P., 2003. Subduction tectonics andexhumation of high-pressure metamorphic rocks in the Mediterranean orogens.American Journal of Science 303, 353–409.

Joyce, J., 1991. Blueschist metamorphism and deformation on the Samaná Peninsula: arecord of subduction and collision in the Greater Antilles. In: Mann, P., Draper, G.,Lewis, J. (Eds.), TectonicDevelopment of theNorth America-CaribbeanPlate BoundaryZone in Hispaniola: Geological Society America Special Paper, 262, pp. 47–75.

Krebs, M., Maresch, W.V., Schertl, H.-P., Baumann, A., Draper, G., Idleman, B., Münker, C.,Trapp, E., 2008. The dynamics of intra-oceanic subduction zones: a direct comparisonbetween fossil petrological evidence (Rio San JuanComplex,DominicanRepublic) andnumerical simulation. Lithos 103, 106–137. doi:10.1016/j.lithos.2007.09.003.

Manaker, D.M., Calais, E., Freed, A.M., Ali, S.T., Przybylski, P.,Mattioli, G., Jansma, P., Prépetit,C., de Chabalier, J.B., 2008. Interseismic Plate coupling and strain partitioning inthe Northeastern Caribbean. Geophysical Journal International 174, 889–903.doi:10.1111/j.1365-246X.2008.03819.x.

Mann, P., Calais, E., Ruegg, J.C., DeMets, C., Jansma, P.E., Mattioli, G.S., 2002. Obliquecollision in the northeastern Caribbean from GPS measurements and geologicalobservations. Tectonics 21, 1057–1082.

Maruyama, S., Liou, J.G., Terabayashi, M., 1996. Blueschists and eclogites of the worldand their exhumation. International Geology Review 38, 485–594.

Parra, T., Vidal, O., Agard, P., 2002. A thermodynamic model for Fe–Mg dioctahedral Kwhite micas using data from phase-equilibrium experiments and natural peliticassemblages. Contributions to Mineralogy and Petrology 143, 706–732.

Perfit, M.R., Nagle, F., Bowin, C.O., 1982. Petrology and geochemistry of eclogites andblueschists from Hispaniola. 1st International Eclogite Conference, Clermont-Ferrand, France, p. 20.

Pindell, J.L., Kennan, L., Maresch, W.V., Stanek, K.P., Draper, G., Higgs, R., 2005. Plate-kinematics and crustal dynamics of circum-Caribbean arc-continent interactions:tectonic controls on basin development in Proto-Caribbean margins. Caribbean–South American Plate Interactions: In: Lallemant, A., Sisson, V.B. (Eds.), GeologicalSociety of America Special Paper, 394, pp. 7–52.

Platt, J.P., 1993. Exhumation of high-pressure rocks: a review of concepts and processes.Terra Nova 5, 119–133.

Ring, U., Layer, P.W., 2003. High-pressure metamorphism in the Aegean, easternMediterranean: underplating and exhumation from the Late Cretaceous until theMiocene to Recent above the retreating Hellenic subduction zone. Tectonics 2,1022.

Schmidt, M.W., Poli, S., 1998. Experimentally based water budgets for dehydrating slabsand consequences for arc magma generation. Earth Planet Science Letters 163,361–379.

Sorensen, S.S., Grossman, J.N., Perfit, M.R., 1997. Phengite-hosted LILE enrichment ineclogite and related rocks: implications for fluid-mediated mass transfer insubduction zones and arc magma genesis. Journal of Petrology 38, 3–34.

Spear, F.S., 1993. Metamorphic Phase Equilibria and Pressure–Temperature–TimePaths. Mineral Society of America Monograph, Washington DC.

Stern, R.J., 2004. Subduction initiation: spontaneous and induced. Earth and PlanetaryScience Letters 226, 275–292.

Tsujimori, T., Matsumoto, K., Wakabayashi, J., Liou, J.G., 2006. Franciscan eclogiterevisited: reevaluation of the P–T evolution of tectonic blocks from TiburonPeninsula, California, USA. Mineralogy and Petrology 88, 243–267.

Vidal, O., Goffé, B., Theye, T., 1992. Experimental study of the stability of sudoite andmagnesiocarpholite and calculation of a new petrogenetic grid for the system FeO–MgO–Al2O3–SiO2–H2O. Journal of Metamorphic Geology 10, 603–614.

Vidal, O., Theye, T., Chopin, C., 1994. Experimental study of chloritoid stability at highpressure and various fO2 conditions. Contributions to Mineralogy and Petrology118, 256–270.

Vidal, O., Parra, T., 2000. Exhumation paths of high pressure metapelites obtained fromlocal equilibria for chlorite–phengite assemblages. Geological Journal 35, 139–161.

Vidal, O., Parra, T., Trotet, F., 2001. A thermodynamicmodel for Fe–Mg aluminous chloriteusing data from phase equilibrium experiments and natural pelitic assemblages inthe 100–600 °C, 1–25 kbar range. American Journal of Science 6, 557–592.

Vidal, O., De Andrade, V., Lewin, E., Munoz, M., Parra, T., Pascarelli, S., 2006. P–T-deformation-Fe3+/Fe2+ mapping at the thin section scale and comparison withXANES mapping. Application to a garnet bearing metapelite from the Sambagawametamorphic belt. Journal of Metamorphic Geology 24, 669–683.

Weaver, J.D., Panella, G., Llinas-Castellan, 1976. Preliminary Sketch of the TectonicHistory of the Samaná Peninsula, Dominican Republic, Presented at 3rd CongressoLatino–Americano de Geologia, Mexico.

Wei, C.J., Powell, R., 2006. Calculated phase relations in the system NCKFMASH (Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O) for high-pressure metapelites. Journal ofPetrology 47, 385–408.

Wiederkehr, M., Bousquet, R., Schmid, S.M., Berger, A., 2008. From subduction tocollision: thermal overprint of HP/LT meta-sediments in the north-easternLepontine Dome (Swiss Alps) and consequences regarding the tectono-metamor-phic evolution of the Alpine orogenic wedge. In: Froitzheim, N., Schmid, S.M. (Eds.),Orogenic Processes in the Alpine Collision Zone: Swiss Journal of Geosciences, 101(Suppl), pp. S127–S155.

Zack, T., Rivers, T., Brumm, R., Kronz, A., 2004. Cold subduction of oceanic crust:implications from a lawsonite eclogite from the Dominican Republic. EuropeanJournal of Mineralogy 16, 909–916.