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Magmatic relationships between depleted mantle harzburgites, boniniticcumulate gabbros and subduction-related tholeiitic basalts in the Puerto Plataophiolitic complex, Dominican Republic: Implications for the birth of theCaribbean island-arc

Javier Escuder-Viruete, Mercedes Castillo-Carrion, Andres Perez-Estaun

PII: S0024-4937(14)00096-6DOI: doi: 10.1016/j.lithos.2014.03.013Reference: LITHOS 3229

To appear in: LITHOS

Received date: 23 December 2013Revised date: 11 March 2014Accepted date: 12 March 2014

Please cite this article as: Escuder-Viruete, Javier, Castillo-Carrion, Mercedes, Perez-Estaun, Andres, Magmatic relationships between depleted mantle harzburgites, boniniticcumulate gabbros and subduction-related tholeiitic basalts in the Puerto Plata ophioliticcomplex, Dominican Republic: Implications for the birth of the Caribbean island-arc,LITHOS (2014), doi: 10.1016/j.lithos.2014.03.013

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http://dx.doi.org/10.1016/j.lithos.2014.03.013

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ACCEPTED MANUSCRIPTpp. 1

Magmatic relationships between depleted mantle harzburgites, boninitic cumulate gabbros

and subduction-related tholeiitic basalts in the Puerto Plata ophiolitic complex,

Dominican Republic: Implications for the birth of the Caribbean island-arc

Javier Escuder-Viruete a,*

, Mercedes Castillo-Carrión a, Andrés Pérez-Estaún

b

a Instituto Geológico y Minero de España, La Calera 1, 28760 Tres Cantos, Madrid, Spain

b Instituto Ciencias Tierra Jaume Almera-CSIC, Lluís Solé Sabarís s/n, 08028 Barcelona, Spain

Abstract

The Lower Cretaceous Puerto Plata ophiolitic complex (PPC) occurs west of the main collisional

suture between the Caribbean and North America plates in northern Dominican Republic, and

imposes important constraints on the geochemical and tectonic processes associated with the birth of

the Caribbean island-arc. The PPC exposes a tectonically dismembered 3.0-km-thick section of

upper mantle harzburgites, lower crustal cumulate gabbroic rocks and upper crustal basaltic pillow

lavas, volcanic breccias and pelagic sediments. The harzburgites exhibit a highly depleted signature

in terms of their modal compositions, mineral chemistry and whole rock major and trace element

contents, suggesting that they are residues after high-degrees of partial melting. Melt modeling

suggests that they were similar in trace-element characteristics to a boninite. In the crustal sequence,

three magmatic episodes have been recognized based on field, mineral and geochemical data. The

first phase is composed of the lower layered gabbronorites, which are variably deformed and

recrystallized at high-temperature conditions. Trace element modeling suggests that the

gabbronorites crystallized from LREE-depleted island-arc tholeiitic (IAT) melts. The second phase is

composed of the intermediate layered troctolites (126 Ma), which are undeformed and preserve

igneous cumulate textures. Modeling indicates that the troctolites crystallized from boninitic melts.

The gabronorite-troctolite substrate was intruded by a third, supra-subduction zone tholeiitic

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magmatic phase at <126 Ma, which formed the upper olivine gabbros and gabbronorites. These

gabbroic rocks formed from melts similar in composition to the IAT basalts and basaltic andesites of

the overlying Los Caños Fm. Contemporaneous Aptian to lower Albian mafic volcanic rocks of the

Los Ranchos Fm and Cacheal complex have comparable IAT geochemical and isotopic signatures,

suggesting that all of them may have erupted over a single piece of the Caribbean oceanic

lithosphere.

The Lower Cretaceous PPC is interpreted to have formed during initiation of W/SW-directed

subduction in an intra-oceanic island-arc setting. Fast rollback of the subducting slab would have

induced extension in the Caribbean upper plate, and upwelling of mantle already depleted by the

generation of oceanic crust. Aided by fluid expelled from the downgoing plate, the decompression

melting of this previously depleted mantle at shallow levels yielded boninitic melts. The supra-

subduction zone tholeiite sequence would have formed from ascending fertile mantle fluxed with

subduction-related fluids as rollback continued. This model constrains the initiation and early

evolution of a SW-dipping subduction zone that was responsible for the formation of the primitive

Caribbean island-arc/back-arc system currently preserved in several locations in the Greater Antilles.

Keywords: ophiolite; suprasubduction zone; boninite; gabbroic cumulate; geochemistry; Caribbean

plate

(*) Corresponding author: Javier Escuder-Viruete. Instituto Geológico y Minero de España, C. La Calera 1, 28760 Tres

Cantos, Madrid. Spain. Tel.: +34 917287242

E-mail addresses: [email protected] (Javier Escuder-Viruete), [email protected] (M. Castillo-Carrión),

[email protected] (Andrés Pérez-Estaún)

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1. Introduction

Ophiolites are relics of oceanic lithosphere that commonly delineate suture zones between former

oceanic or continental terranes. Their origin and tectonic evolution thus impose important constraints

on geotectonic reconstructions of orogenic belts. The Greater Antilles orogenic belt results from the

late Cretaceous-late Eocene closure of the proto-Caribbean oceanic domain, which led to the

assembly of the North America plate with a number of collided intra-oceanic arcs, oceanic plateaus,

oceanic basins and microcontinents (Escuder-Viruete et al., 2008, 2011c, 2013b; García-Casco et al.,

2008; Hastie et al., 2009; Iturralde-Vinent, 1996; Kerr et al., 2003; Mann et al., 1991; Neill et al.,

2010, 2012, 2013; Pindell and Kennan, 2009; Pindell et al., 2005; Stanek et al., 2009). As a result,

several ophiolitic massifs were emplaced in the collisional zone, which are particularly well exposed

in Cuba along the so-called “Northern Cuban Ophiolite Belt” (Iturralde-Vinent, 1996; Kerr et al.,

1999; Lewis et al., 2006; Marchesi et al., 2006; Proenza et al., 2006).

These ophiolites extend for more than 1000 km along the northern half of the Cuban mainland and

comprise dismembered mafic-ultramafic bodies, with diverse supra-subduction, back-arc and mid-

ocean spreading-ridge geochemical signatures (Stanek et al., 2009). As a consequence, the Cuban

ophiolites have been interpreted as oceanic lithospheric slabs either from a proto-Caribbean back-arc

basin related to NE subduction of the Pacific plate, remnants of the SW subducting proto-Caribbean

oceanic lithosphere emplaced onto the Pacific paleomargin, or fore-arc lithosphere built on the

Pacific paleomargin (Cobiella-Reguera, 2009; García-Casco et al., 2008; Kerr et al., 2003; Pindell et

al., 2005, 2006). Marchesi et al. (2006) highlights the need to clarify the Pacific and proto-Caribbean

provenance of the different Cuban ophiolites, if the included residual peridotites were affected by

subduction-related processes and the genetic links between ophiolitic lower crustal gabbros and

upper crustal arc volcanics. In particular, this information is crucial to propose any geodynamic

model for the evolution of the Greater Antilles orogenic belt.

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The Puerto Plata ophiolitic complex (PPC) occupies a key position in the Hispaniola segment of the

Greater Antilles orogenic belt, because it is situated close to the main proto-Caribbean suture zone

(Escuder-Viruete et al., 2011a, 2013a). Located in northern Hispaniola, this complex is the

westernmost and structurally highest unit in a series of accreted ophiolites, ophiolitic mélanges,

intra-oceanic volcanic arcs and fragments of the southern margin of the North America continent,

which are here collectively termed the northern Caribbean subduction-accretionary prism (or

complex). The prism records, therefore, the Mesozoic history of generation and accretion of intra-

oceanic terranes to the southern North America margin, as well as representing an important period

of ocean closure and continental growth. However, its tectonic evolution has until recently been

poorly constrained due to limited field, structural, petrological, geochemical and geochronological

data.

Recent re-evaluation of the Hispaniola segment of the northern Caribbean subduction-accretionary

prism has shown that the constituent tectonic units were deformed progressively younger to the

east/northeast, indicating a general migration of deformation in this direction from the late

Cretaceous to the earliest Miocene (Escuder-Viruete et al., 2011a, b; 2013a). The propagation of the

deformation resulted from the initial subduction to the SW of arc, oceanic and continental terranes

and their subsequent tectonic incorporation to the developing Caribbean subduction-accretionary

prism. In this tectonic context, the PPC holds the key to the early evolution of this subduction zone,

because it is the oldest and structurally highest component of the northern Caribbean subduction-

accretionary prism.

This paper presents new detailed maps, lithostratigraphy, structure, mineral chemistry, in situ trace

element composition of clinopyroxene, and bulk rock geochemical data for mafic and ultramafic

rocks representative of all lithological units of the ophiolitic complex. These data allow us to argue

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that the PPC (a) represent tectonically disrupted crust and mantle sections of oceanic lithosphere, (b)

originated during the initiation of subduction at least to 126 Ma, and (c) records a complex history of

extreme crustal thinning and related supra-subduction zone magmatism prior to the accretion to

North America continental margin. This constrains the age of the early evolution of a W/SW-dipping

subduction zone in the northern Caribbean convergent margin and provides an important step in

understanding both the formation of the intra-oceanic Caribbean island-arc, and the evolution of the

subduction-accretionary prism.

2. Geological framework

Located on the northern margin of the Caribbean plate, the Island of Hispaniola (Fig. 1) is a tectonic

collage produced by the oblique convergence to final collision of the Caribbean island-arc/back-arc

system with the North American plate, which began in the Lower Cretaceous (Mann et al., 1991;

Draper et al., 1994). The presence of ophiolitic mélanges in northern Hispaniola indicates that an

intermediate proto-Caribbean oceanic basin was consumed by SW-directed subduction during

convergence (Draper and Nagle, 1991; Lewis et al., 2006; Pindell and Kennan, 2009; Pindell et al.,

2005; Saumur et al., 2010; Escuder-Viruete et al., 2011a, c). The arc-related rocks of the Caribbean

upper plate have ages that span the Cretaceous and are regionally overlain by Paleocene/Lower

Eocene to Holocene siliciclastic and carbonate sedimentary rocks (Draper et al., 1994; Escuder-

Viruete et al., 2006, 2008; Kesler et al., 1990, 2005). This sedimentary cover post-dates the volcanic

activity in the island-arc and records the oblique arc-continent collision in the northern Hispaniola

area, as well as the intra-arc and retroarc deformation in the central and southern areas of the island.

Northern Hispaniola (Fig. 1) is geologically composed of arc, oceanic and continental margin

derived units assembled during arc-continent convergence. These units form several inliers, termed

El Cacheal, Palma Picada, Pedro García, Puerto Plata, Río San Juan y Samaná complexes, which

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constitute the pre-Eocene igneous and metamorphic substratum (Draper and Nagle, 1991). These six

complexes form the Caribbean subduction-accretionary complex in Hispaniola (Escuder-Viruete et

al., 2011a, 2013a), and include, from E to W: metasedimentary rocks of the subducted continental

margin of North America; ophiolitic fragments of the proto-Caribbean lithosphere; serpentinitic-

matrix mélanges, containing blocks of blueschists and eclogites; plutonic and volcanic rocks related

to the Caribbean island-arc; and non-metamorphic rocks deposited in pre-collisional fore-arc

sedimentary basins (Escuder-Viruete et al., 2011b, c). In the Puerto Plata and Río San Juan

complexes, the first deposits which record the collisional process are the unconformable

Paleocene?/Lower Eocene serpentinite-rich olistostromes of the Imbert Formation (Fm; Draper et al.,

1994), which contain clastic elements derived from both the uplifted subduction-accretionary

complex as the Cretaceous volcanic arc.

The Puerto Plata complex (Figs. 2, 3) is located north of the Camú fault zone and is composed of

pre-Eocene ophiolitic basement rocks and Tertiary sedimentary cover composed of clastic and

carbonate rocks (Nagle, 1979; Eberle et al., 1982; de Zoeten and Mann, 1991; Pindell and Draper,

1991; Hernáiz-Huerta et al., 2012). The PPC consists of serpentinized peridotite, layered (cumulate)

ultramafic and mafic rocks, massive gabbroic rocks, and volcanics of basic to intermediate

composition, locally pillowed with rare inter-pillow cherts and limestones (Pindell and Draper,

1991). These lithologies occur as decametric to hectometric fault-bounded sections of rock in a

structurally disrupted or dismembered manner, where fault zones are typically 0.5 to 2 m thick and

hydrothermally altered. The basal structural contact of the PPC is not exposed. Saumur et al. (2010)

interpreted samples of serpentinite from the complex as hydrated abyssal peridotite.

The ophiolitic basement is overlain by the Paleocene?-Lower Eocene >500-m-thick section of the

Imbert Fm (Nagle, 1979), which is composed of fine-grained turbidites interbedded with white and

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turquoise, very fine-grained tuffs, pelagic sediments, rare radiolarian cherts and basaltic sills. The

base of the unit is not exposed. The upper stratigraphic levels are characterized by thick-bedded

turbidites of sandstone and conglomerate, which include clasts of all rock types from the ophiolitic

basement. Therefore, the Imbert Fm probably rests unconformable over the PPC basement. These

lithologies may be contemporaneous or slightly older than the serpentinite clast-rich units of

megabreccias, breccias and conglomerates (e.g., Barrabás Mélange), and the shallow-water algal

limestones of the La Isla Fm of late Paleocene to early Eocene age (Pindell and Draper, 1991;

Monthel et al., 2010). These rocks are unconformably overlain by the late Eocene to early Miocene

Altamira Fm and Luperón Fm, which comprise 1500 m of calcareous mudstones and siltstones, thin-

bedded sandstones and conglomerates (Nagle, 1979). These rocks are in turn overlain by the San

Marcos chaotic unit, which is composed of a mud-matrix mélange. Recently, Suárez-Rodríguez et al.

(2013) suggest a lower to middle Miocene age based on paleontological data of the matrix.

3. The Puerto Plata ophiolitic complex: field relations and petrography

Our mapping at the 1:25,000 scale covered the western half of the PPC and complemented the work

of Pindell and Draper (1991) and Monthel (2010). In this area, the PPC is a strongly faulted, up to 15

km2, mafic-ultramafic massif (Fig. 1), which is described below and in Appendix A. Cross-section

and orientation data (Fig. 1) show that the complex dips to the W-SW. In the western area of the

complex, mafic and ultramafic rocks similar to those constituents of PPC form polymictic breccias of

the Imbert Fm, undated serpentinite-rich olistostromes and metric to hectometric tectonic blocks in

the San Marcos Mélange. This study is only concerned with the ophiolitic rocks of the basement.

The PPC massif is made up of a section composed from bottom to top of upper mantle peridotites

(1.5-2.0 km thick), layered gabbroic rocks of the lower oceanic crust (0.5-0.8 km thick) and basaltic

pillow lavas, volcanic breccia and radiolarites (at least 0.5 km thick) of the upper crust (Fig. 2). The

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Moho Transition Zone is not seen, but isotropic gabbros and a sheeted-dyke complex, typical of a

conventional ophiolite sequence, are present. This is most likely due to tectonic omission as in some

localities peridotites are juxtaposed against layered gabbros, and basaltic pillow lavas directly overlie

gabbros (Fig. 3a). The field description below mainly corresponds to observations in good exposures

of the massif exposed in the localities of Cerro Cofresí (upper mantle), Punta La Playa (lower crustal

gabbros) and Puerto Plata-Imbert road (upper crustal volcanics).

The mantle section is mainly composed of harzburgite with tectonite texture locally capped by

dunite. Minor dunite and pyroxenite are enclosed in harzburgite as lenticular bodies parallel to the

tectonite foliation or discordant dykes. Other dykes are constituted by gabbroic rocks, dolerite and

pegmatitic trondhjemite. The tectonite foliation is generally flat-lying or dipping at a low-angle to

the SW (Fig. 3). Point-counting and petrographic observations show that PPC ultramafic rocks are

clinopyroxene-poor harzburgites. Many samples lack clinopyroxene, except for interstitial elongated

lobate blebs and tiny exolutions in orthopyroxene. In terms of olivine and pyroxene modal

compositions, these harzburgites are similar to supra-subduction zone (SSZ) peridotites (Fig. 4),

although such harzburgites are also common in some orogenic and abyssal peridotite exposures.

Harzburgites display a porphyroclastic texture of ophiolite tectonite, characterized by plastically

deformed orthopyroxene megacrysts up to 1.5 cm long. The rock matrix is mainly composed of 0.2-

0.5 mm serpentinized olivine and orthopyroxene, minor interstitial clinopyroxene and 0.3-2 mm

anhedral or vermicular spinel (Fig. 5). Dunites show equigranular textures made up of 1-3 mm

weakly deformed olivine, very rare orthopyroxene and scattered anhedral to euhedral spinel. On the

other hand, the presence of a Moho Transition Zone on top of the mantle section is indirectly

deduced from the rock-types (dunite, wehrlite and rare pyroxenite) included as blocks in the San

Marcos Mélange. Serpentinization in ultramafic rocks is very variable (30-95 vol.%). Olivine is

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commonly replaced by lizardite-magnetite assemblages displaying mesh texture. Pyroxene is also

affected by alteration and pseudomorphic (bastite) replacement has been observed.

Ferroxyhydroxides and clay minerals have been detected in some samples. An Ar-Ar plateau age

obtained from a sill of leucotonalite in the foliated serpentinites gives a low-temperature (T)

deformation of the harzburgites at 111.1±9.3 Ma (Escuder-Viruete, 2010).

The gabbroic crustal section of the PPC can be subdivided into three fault-bounded parts (Fig. 2).

The lowermost 100-250 m of the exposed section is composed of coarse-grained layered

gabbronorites and subordinate olivine gabbros. Modal layering, defined by variations of the mafic

mineral/plagioclase ratio at the millimeter to meter scale (Fig. 3), is generally oriented WNW-ESE

and dips a low to moderate angle to the SW. The contact between the different gabbroic rocks is

transitional in the field. Layering in the gabbronorites is commonly boudinaged and locally

isoclinally folded, suggesting deformation and foliation development at high-T. Less deformed

gabbronorites exhibit equilibrated equigranular (2-10 mm) to unequilibrated cumulate texture (Fig.

5).

The gabbros vary locally from granular plagioclase with an equilibrium texture to a partly

equilibrated geometry with notched grain boundaries to aligned laths and tablets of plagioclase with

a non-equilibrated geometry. Deformed gabbronorites exhibit penetrative grain-shape fabrics defined

by polycrystalline ellipsoidal clusters of pyroxene alternating with bands of elongate plagioclase

grains (Fig. 5). The grain boundaries range between straight and lobate. Lobate grain boundaries are

consistent with dynamic recrystallization at relatively high-T (Passchier and Trouw, 2005).

Clinopyroxene is in rare occasions rimmed by green amphibole. Brownish orthopyroxene (20-40

vol.%) is more abundant modally than clinopyroxene (<15 vol.%). Exsolved pyroxene lamellae are

typically present and zoning is absent in all phases. Green spinel occurs interstitially. In olivine

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gabbros, olivine forms 0.5-1.5 mm grains dispersed between dominant subhedral plagioclase and

clinopyroxene. In these rocks, orthopyroxene is generally interstitial between plagioclase laths and

clinopyroxene. Secondary magnetite, as product of olivine serpentinization, is the only oxide present.

Overlying the gabbronorites are 200-350 m of coarse-grained layered troctolites, subordinate olivine

gabbro and rare gabbroic anorthosite and anorthosite (Fig. 2). These rocks preserve cumulate igneous

textures, contain rare centimetre-sized enclaves of foliated gabbronorites, and show no evidence of a

penetrative high-T deformation event. These field relationships imply that an early gabbronorite-

forming phase was deformed, and then intruded by a second troctolite-forming magmatic phase.

Troctolites have adcumulate textures (Fig. 5), and commonly exhibit well-defined, layer-parallel

shape-preferred orientations defined by plagioclase laths and, locally, elongated olivines. Troctolites

have variable proportions of plagioclase (20-90 vol.%), but rocks with approximately 60%

plagioclase and 40% olivine are particularly abundant. Olivine is 0.5-3 mm, sub- to euhedral,

variably serpentinized, and locally surrounded by coronas of pale-green amphibole. Plagioclase is

subhedral, 1-8 mm sized, locally recrystallized into polygonal aggregates, and partly sericitized.

Associated olivine gabbros are cumulates dominated by plagioclase and clinopyroxene, with minor

olivine. Zircons are extremely rare and of very small size in the troctolites. A single fraction yielded

a concordia age of 126.1±0.3 Ma, interpreted as the crystallization age of the troctolite (Monthel,

2010).

The upper 100-250 m of the gabbroic zone is composed of medium- to coarse-grained gabbros,

olivine-gabbros and subordinated gabbronorites. They range from massive to layered, with layering

defined by subtle variations in modal content of plagioclase, clinopyroxene, orthopyroxene and

olivine on a millimetre to decimetre scale. In general, these rocks are cumulates dominated by

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plagioclase and clinopyroxene. Ophitic and subophitic textures textures have been also locally

observed (Fig. 5). The gabbros are characterized by subhedral, 2-5 mm-sized plagioclase laths and

0.5-8 mm-sized anhedral clinopyroxene. Locally, clinopyroxene occurs interstitially between

plagioclase. Fe-Ti oxides occur as irregular shaped grains that appear to have overgrown and partly

replaced plagioclase and clinopyroxene.

Hydrothermal metamorphic overprints are variably developed. In general, alteration becomes more

pervasive up section and is commonly related to greenschist-facies mylonitic shear zones and veins.

It is characterized by extensive replacement of clinopyroxene by white and green amphibole, and

growth of small amphibole grains along grain boundaries and cracks in plagioclase. Sericitization of

plagioclase and formation of epidote occur only in the most altered samples.

The volcanic rocks of the Los Caños Fm are at least 150 m thick and composed of dark green to

brown and black tholeiitic basalt to basaltic andesite, forming pillow lavas, massive flows,

autoclastic breccias and rare syn-volcanic intrusions of microgabbro and dolerite (Fig. 3). The

coherent rocks are ortho and clinopyroxene-bearing porphyritic basalts and plagioclase-phyric

basalts, with minor olivine and clinopyroxene-bearing basalts. The textures are porphyritic, fluidal

and vesicular/amygdaloidal (Fig. 5). Autoclastic breccias are generally composed of monogenetic

clasts. These rocks were erupted and deposited as submarine lava flows and volcanic debris flows

respectively. Microgabbros and dolerites are interpreted as the internal part of lobes and feeder

dykes. Volcanic rocks are locally overlain or interbedded by ribbon cherts (Fig. 3c). Microfossils in

the inter-pillow micritic material yield a Lower Cretaceous age (in Monthel, 2010).

The Cacheal complex crops out about 50 km west of Puerto Plata (Fig. 1) and is composed of >250

m of basalts and basaltic andesites (Abad, 2010). These volcanic rocks are unconformably overlain

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by a thick-bedded sequence of volcaniclastic sandstones, siltstones and light-grey biomicritic

limestones with upper Aptian to lower Albian-age fossils (Hoplitidae and Filoceratidae Ammonites;

Bernárdez, 2004). Therefore, these volcanic rocks are of Lower Cretaceous age and possibly

correlate with the basalts of the Los Caños Fm. Lithologically, the Cacheal complex is dominated by

spilitized, polymict volcanic breccias and flows of boninitic and tholeiitic basalt to andesite, with

local pillow lavas and interbedded, well-stratified, fine-grained volcaniclastic rocks (Escuder-

Viruete, 2010). These volcanic rocks are erupted in a submarine environment and are intruded by

synvolcanic dykes/sills of microgabbro and by late rhyolite dykes. Coarse- to medium-grained

volcaniclastics occur toward the upper part of the exposed section.

The basalts are brown to dark green and texturally range from porphyritic (predominantly) to

vesicular/amygdaloidal and aphyric. They contain orthopyroxene, clinopyroxene and plagioclase

phenocrysts, with rare serpentinite pseudomorphs after olivine. Andesites are characterized by

glomeroporphyritic aggregates of plagioclase, pyroxene and iron oxide. Plagioclase is the most

abundant phenocryst phase and roughly equals proportions of euhedral/subhedral ortho and

clinopyroxene. Five zircon fractions recovered from a sample of late rhyolite yielded 206

Pb/238

U

weighted average ages from three points of 122.7±0.3 Ma and from two points of 90.9±0.5 Ma. The

older zircons have been interpreted as xenocrysts inherited from the protolith melted in the deep arc

crust and the younger zircons as magmatic crystals formed during crystallization of the felsic magma

in sub-volcanic conditions (Escuder-Viruete, 2010).

4. Results

4.1. Mineral chemistry

4.1.1. Major elements

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Mineral contents of major and minor elements were obtained by EMPA. Representative EMPA data

of minerals, instrumental details and analytical conditions are given in Appendices B and C.

Harzburgite has Mg# [100×Mg/(Mg+Fe2+

)] of 89.6-93.7 and NiO of olivine that varies between

0.32 and 0.44 wt.%. Orthopyroxene has Mg#=91.4-92.8 and clinopyroxene has Mg#=92.0-95.8. Cr#

[Cr/(Cr+Al)] of spinel ranges between 0.48 and 0.58 (Fig. 6). In the gabbroic section, clinopyroxene

range in composition between aluminian-chromian augite to aluminian diopside. In the lower layered

gabbronorites, clinopyroxene has Mg#=89-92 (Fig. 6). In the intermediate troctolites, clinopyroxene

has slightly lower Mg# (86-90) and Al2O3 contents, but higher TiO2 (Fig. 6). Anorthite content of

plagioclase (XAn) ranges between 0.79 and 0.80 in the gabbronorites and between 0.80 and 0.84 in

the troctolites. In both gabbroic rock types, orthopyroxene has Mg#=84-88 wt.%, and olivine has

Mg#=86-88. Clinopyroxene in the upper gabbros and olivine-gabbros is augitic and has Mg#=74-85.

Anorthite content of plagioclase is lower than in layered gabbronorites and troctolites and ranges

between 0.56 and 0.80, where as orthopyroxene has lower Mg# but similar Al2O3 contents

(Appendix C).

A comparison of Al2O3 content versus Mg# is shown in Fig. 6 between clinopyroxene compositions

of the ultramafic and gabbroic rocks of the PPC with the fields of peridotites from Izu-Bonin, mantle

peridotites, arc crustal pyroxenites and arc-related mafic cumulates. Arc-related, ultramafic and

mafic cumulates are generally interpreted as medium to high-P igneous cumulates formed in mid- to

lower crustal magma chambers, some spanning the crust-mantle boundary at the base of an arc

(Girardeu and Ibarguchi, 1991; Garrido and Bodinier, 1999). Clinopyroxenes of the lower

gabbronorites and intermediate troctolites in the PPC overlap the field of arc crustal pyroxenites and

trend toward the composition of the Puerto Plata mantle harzburgites. However, the compositions of

clinopyroxene in the upper gabbros and gabbronorites are similar to those of arc-related mafic

cumulates.

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In Fig. 6, three groups of gabbroic rocks are differentiated according to the TiO2 content in

clinopyroxene. The very low-Ti and unfractionated compositions in the lower gabbronorites are

similar to those of fore-arc peridotites. These clinopyroxene compositions also plot in the more Mg-

rich part of the boninitic Puerca Gorda Schists field (data from Escuder-Viruete et al., 2011b, c). The

low-Ti compositions in the more evolved upper gabbros are similar to those of the island-arc

cumulates and IAT lavas of the Los Ranchos Fm. However, the relative intermediate Ti contents of

clinopyroxene in the intermediate troctolites plot in the field of ocean ridge cumulates. These

relationships are also shown in the Fig. 6, where clinopyroxene of the lower gabbronorites and upper

gabbros plot in the fields of boninites, fore-arc basalts and basaltic andesites and IAT, and

clinopyroxene of the intermediate troctolites fall in the N-MORB and IAT fields.

Clinopyroxene phenocrysts in the mafic lavas of the Los Caños Fm are aluminian-ferrian augites

(Fig. 6). For high Mg# values (76-80), they are characterized by low-TiO2 and Al2O3. In the Fig. 6,

they display compositions comparable to clinopyroxenes from IAT. In the Fig. 6, these

clinopyroxenes plot in the field of the arc-related mafic cumulates, together with the clinopyroxenes

of the upper gabbros.

4.1.2. Trace elements in clinopyroxene

In situ trace element analyses of clinopyroxene were carried out by LA-ICP-MS in 10 of the thick

sections used for EMPA (two harzburgites, six gabbroic rocks, two basalts). Representative LA-ICP-

MS data are given in Appendix D. The chondrite-normalized (C, values are from Sun and

McDonough, 1989) extended REE patterns of clinopyroxene in ultramafic, gabbroic and mafic

volcanic rocks of PPC are displayed in Fig. 7. The concentrations of incompatible trace elements in

spinel harzburgites are extremely low. Th contents are generally below the detection limit and the

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REE contents are very fractionated (Fig. 7). Some clinopyroxenes are depleted in Zr and Hf relative

to adjacent LREE and of Ti relative to HREE, as well as having a negative Eu anomaly. The HREE

concentrations in clinopyroxene are lower in the PPC harzburgites than in abyssal peridotites and in

Massif du Sud peridotites (Marchesi et al., 2009), but are similar to those of the fore-arc peridotites

(Parkinson and Pearce, 1998) and to the most depleted harzburgite from the Oman ophiolite

(Kelemen et al., 1995; Tamura and Arai, 2006).

The incompatible trace elements contents are also very low in the lower layered gabbronorites. The

REE contents are also very fractionated,are convex-upward. These rocks also show a marked

depletion in Zr and Hf relative to adjacent LREE and of Ti relative to the HREE (Fig. 7).

Clinopyroxene grains have a variable positive Eu anomalies. The HREE concentrations in

clinopyroxene are similar to those in gabbros from the Massif du Sud (Marchesi et al., 2009) and

boninite-type cumulates from northern Victoria Land (Tribuzio et al., 2008), as well as LREE-

depleted, low-Ti metabasalts of the Puerca Gorda Schists.

Clinopyroxene in the intermediate layered troctolites have markedly different extended REE patterns

(Fig. 7). Trace elements compositions are less depleted than lower layered gabbronorites. The REE

contents are very fractionated. Trace element patterns are slightly convex-upward, with flat HREE,

and show variable depletion of Nb, Zr and Hf relative to Th and LREE, and Ti relative to HREE.

They lack a negative Eu anomaly, which could mean that the crystallization of clinopyroxene was

not affected by plagioclase fractionation. The HREE concentrations in clinopyroxene are 5-12 times

higher than that in representative boninite-type cumulates.

In the upper gabbros and gabbronorites, clinopyroxene shows two different extended REE patterns

(Fig. 7): one is very similar in shape and absolute abundances to those of the layered troctolites and

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other is extremely fractionated. These two types of patterns have been recognized in an olivine-

bearing gabbro (sample HH9121) and a massive gabbronorite (sample HH9112), respectively. The

age relations between these gabbroic rocks are unclear. REE contents are very fractionated in the

first type and extremely fractionated in the second type (Fig. 7). As in the troctolites, trace element

patterns are convex-upward in the first group and are characterized by negative Nb, Zr, Hf and Ti

anomalies. In contrast, patterns are steeply inclined in the second group and show positive anomalies

in Zr, Hf and Ti. The HREE concentrations in clinopyroxene are subparallel to those in the boninite-

type cumulates for the first group, and similar to those in the Massif du Sub gabbros for the second

group. The HREE enrichment observed in this second type is not observed elsewhere within the PPC

gabbroic rocks.

The extended REE patterns of clinopyroxene phenocrysts in basaltic lava of Los Caños Fm are

displayed in Fig. 7. The REE contents are practically unfractionated with all trace element patterns

being relatively flat and showing depletion in Nb, Zr and Hf relative to Th and LREE, and Ti relative

to HREE. All analyzed phenocrysts lack a negative Eu anomaly, which could mean that the

crystallization of clinopyroxene was not affected by plagioclase fractionation. At slightly higher

absolute abundances, the HREE concentrations in clinopyroxene are subparallel to those in the low-

Ti metabasalts of the Puerca Gorda Schists and low-Ti metapicrites of the Hicotea Schists.

4.2. Bulk rock composition

4.2.1. Major elements

Bulk rock compositions of major and trace elements were obtained by inductively coupled plasma-

mass spectrometry (ICP-MS) analysis with LiBO2 fusion. The results for selected samples of each

geochemical group are reported in Appendix E, as well as details of analytical accuracy and

reproducibility. For a subset of samples, bulk rock trace elements (Th, Nb, Ta, La, Pb, Nd, Sm, Zr

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and Hf) were also analysed by high resolution ICP-MS con high-pressure dissolution and HF–HNO3

digestion (details in Appendix B). Spinel harzburgites in the PPC are very depleted in terms of major

element composition as shown by the very low Al2O3 and CaO contents (Appendix E; see also

Saumur et al., 2010). In the Al2O3/SiO2 versus MgO/SiO2 diagram (Fig. 8), harzburgite plots in the

left region of the terrestrial array (Hart and Zindler, 1986), which represents the most depleted

compositions of residual mantle. Major element concentrations of the gabbroic and volcanic rocks of

the PPC are given in Appendix E. Gabbroic rocks have high Mg# (0.89-0.72) and small

compositional range, with MgO=7.5-12.0 wt.% (one sample 19.5 wt.%) and are characterized by

very low TiO2 contents (Appendix E). Volcanic rocks of the Los Caños Fm have a wider

compositional range (Mg#=0.66-0.42), with similarly TiO2 contents. The composition of lavas and

dykes of the Los Caños Fm define a typical tholeiitic differentiation trend with increasing Fe-content

during differentiation (Escuder-Viruete, 2010), consistent with low-P fractionation of olivine,

pyroxene and plagioclase.

Gabbroic and volcanic rocks are plotted and compared with some reference fields in the MgO versus

TiO2 diagram of the Fig. 9. Between these reference fields, the compositions of the coeval volcanic

rocks of the Cacheal complex and the main groups of volcanic rocks in the Lower Cretaceous

primitive Caribbean island-arc/back-arc system of Central and Eastern Hispaniola are of particular

interest. These compositional groups record a progressive increase in TiO2 contents from the

boninites and depleted low-Ti island-arc tholeiites (IAT) to normal IAT and back-arc basin basalts

(BABB; Escuder-Viruete et al., 2008, 2009). Several points emerge from Fig. 9. (1) All studied

samples have lower TiO2 contents than the BABB of the Rio Verde complex, as well as the mid-

oceanic ridge basalts (MORB) glasses recovered from the Clipperton Fracture Zone of the Pacific

Ocean (PetDB, 2007) and the basalts and basaltic andesites of a mid-Ti tholeiitic suite from the

Mariana Arc–Trough system (Gribble et al., 1998). (2) Lower layered gabbronorites and

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intermediate troctolites from the PPC have extremely low-TiO2 contents (<0.1 wt.%) and are less

evolved in terms of MgO contents than any other group of the studied island-arc igneous rocks.

However, these rocks have an obvious cumulate component and their compositions are therefore

strongly controlled by the cumulate phases. (3) Upper olivine gabbros and gabbronorites have low-Ti

contents and plot in the fields of the Caribbean low-Ti IAT and boninites. Also, cumulate minerals

likely affect the composition of the massive gabbros and thus they do not represent liquid

compositions. (4) In terms of MgO contents, basalts, basaltic andesites and andesites of the Los

Caños Fm and Cacheal complex are from moderately to highly fractionated, and include relatively

low- and mid-Ti compositions. These samples provide good estimates of liquid compositions,

because they do not commonly contain abundant phenocrysts. (5) TiO2 contents of the mafic

volcanic rocks of the Los Caños Fm and Cacheal complex relatively higher than the gabbroic rocks

and are similar to those of the low-Ti IAT and boninites of the Los Ranchos Fm.

4.2.2. Trace elements

The spinel harzburgites of the PPC are highly depleted in terms of trace elements as their

concentrations normalized to N-MORB (N) are mostly below 0.1. Nevertheless, they exhibit variable

relative enrichment in the most incompatible trace elements, and this is especially evident for Pb,

relative to the HFSE and HREE (Fig. 10). The normalized trace element patterns of harzburgite are

typically “U shaped”, and this pattern is slightly modified by Sr, Zr and Hf negative anomalies

relative to LREE (Fig. 10). Cs, Rb, Ba, U, Pb and Sr budgets in mantle rocks are commonly

considered largely affected by serpentinization and/or seafloor weathering processes (e.g., Niu,

2004) as these elements are highly mobile during late circulation of aqueous hydrothermal solutions.

For this reason they will not be treated in the following discussion on mantle peridotites.

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In the Nb/Y versus Zr/TiO2 immobile trace elements plot of the Fig. 8, all igneous rocks of the

Puerto Plata and Cacheal complexes are subalkalic and plot in the field of the primitive Caribbean

island arc defined by the mafic volcanic rocks of Los Ranchos, Amina Fm and Maimón. In detail,

gabbroic rocks, and mafic volcanic rocks of the Los Caños Fm and the Cacheal complex mainly

comprise subalkalic basalt, basalt/andesite and andesite compositions, respectively. In Fig. 8, Ti/V

ratios are generally <20 for samples of all rock units and mainly plot in the subduction-related, arc

tholeiites field. For the layered gabbronorites and troctolites, Ti/V ratios are lower than chondrite

(<10), plotting at very low Ti and V values without overlap the compositional field of the mafic

volcanics. These low Ti/V ratios reflect low degrees of mantle source depletion. For the volcanic

rocks of the Los Caños Fm and the Cacheal complex, Ti/V ratios range between 10 and 20 and are

similar to those of the IAT and Low-Ti IAT of the Los Ranchos Fm. However, some basalt and

basaltic andesite samples of the Cacheal complex plot in the MORB and BABB field.

Taken together, the N-MORB-normalized trace elements patterns of igneous rocks of the Puerto

Plata and Cacheal complexes present typical subduction-related features (e.g., Pearce and Peate,

1995): LILE (large-ion lithophile elements) are enriched relative to LREE, and both element groups

are enriched relative to HFSE, giving the characteristic negative Nb-Ta anomalies (Fig. 10).

However, for a similar Mg#, or degree of fractionation, samples show considerable variation in both

the abundance of trace elements and the patterns on normalized plots. As the HFSE and HREE are

not thought to be affected by the subduction related component in arc mafic magmas (Pearce and

Peate, 1995), they can be used as a guide to the composition of the mantle from which these

magmatic rocks were derived. In the studied rocks, several geochemical suites of gabbroic and

volcanic rocks have been recognized, which are described below.

4.2.2.1. Gabbroic rocks

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The incompatible trace-element abundances of the gabbroic rocks are low, whereas compatible

elements such as Ni are high (Appendix E), which may reflect a predominance of cumulate mineral

phases versus interstitial melt. They have moderate to marked positive Eu anomalies, reflecting their

plagioclase-cumulate nature. In their trace element patterns, the LREE are generally depleted and the

LILE (Cs, Rb, K, Sr and Pb) are enriched, with low to very low HFSE contents (Fig. 10). The HREE

patterns are flat and their abundances vary from 0.01 to 0.5 times those in N-MORB. On the basis of

TiO2 contents, the degree of LREE depletion and the extent of Ta-Nb negative anomaly, three

geochemical groups have been recognized, which correlate well with the three field lithological

assemblages recognized in the PPC.

The lower layered gabbronorites have the highest Mg# (0.89-0.85) and the lowest TiO2 contents) of

all the rocks sampled. Incompatible trace-element abundances also are very low, whereas compatible

elements such as Ni are moderately high (Appendix E). In the N-MORB normalized diagram, all

samples are characterized by enrichment in LILEs (Rb, Ba, U, K, Pb and Sr, but no Th) relative to

the HFSE and HREE (Fig. 10). The low incompatible element abundances and the existence of

marked positive Eu anomalies in these diagrams reflect their plagioclase-cumulate nature. These

rocks display a slight LREE depletion and HREE flat pattern, with negative Zr-Hf but no negative

Nb-Ta anomalies. The significant LREE depletion, low TiO2 and HREE levels for high Mg# values

suggest a strongly depleted mantle source and high-degrees of partial melting.

The intermediate layered troctolites have high Mg#=0.85-0.81 and low TiO2 contents, showing

major element chemical patterns dominated by accumulation of plagioclase and olivine.

Incompatible trace elements and compatible elements abundances are also low and high,

respectively. Their N-MORB normalized trace element patterns show marked negative Nb, Zr and

Hf anomalies (Fig. 10), as well moderate to marked enrichment in LILEs (mainly Pb and Sr, but no

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Th). They also have large positive Eu anomalies, reflecting their plagioclase-cumulate nature.

Troctolites display a slight LREE depletion and a HREE enrichment, with a significant negative Zr-

Hf but variable Nb anomalies. These characteristics suggest that they may have crystallized from

melts (and degrees of partial melting) similar to the layered gabbronorites, but their mantle source

probably was slightly less depleted.

The upper gabbros and gabbronorites have high Mg# values, but more fractionated compositions

(0.83-0.67). Incompatible trace-element abundances are also low. However, these rocks have higher

TiO2 contents and absolute HREE abundances than the two other groups of gabbroic rocks (Fig. 10).

Contents of compatible elements such as Ni are more variable. Their N-MORB normalized trace

element patterns show negative Nb, Zr and Hf anomalies, as well moderate to significant enrichment

in LILE (but no Th) relative to the HREE (Fig. 10). These rocks also have positive Eu anomalies,

reflecting plagioclase accumulation, but less marked that in coarse-grained layered gabbronorites.

They have flat to slightly LREE-depleted patterns (except massive gabbronorite HH9112), and flat

HREE, with moderate to marked negative Zr-Hf and Nb negative anomalies (Nb*=0.1-0.7). These

characteristics suggest a source dominated by depleted mantle. However, the higher TiO2 and HREE

contents, as well as the lower Mg# and LREE depletion, suggest that the mantle source for these

rocks was less depleted than for other groups of gabbroic rocks.

4.2.2.2. Volcanic rocks

On the basis of TiO2 contents, degree of LREE depletion and the extent of the Nb negative anomaly,

two geochemical groups have been recognized in the volcanic rocks of the Los Caños Fm and the

Cacheal complex: normal island-arc tholeiites (IAT) and LREE-depleted, low-Ti island-arc tholeiites

(LREE-depleted IAT). Differences between these groups are also reflected in the Zr contents and

Nb/Th and (La/Nd)N ratios (Fig. 9). Massive and pillowed mafic lavas of the Los Caños Fm and part

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of the mafic lavas and monogenetic breccias of the Cacheal complex represent the IAT group.

Collectively, they are characterized by low to moderate MgO (1.6-8.1 wt.%; average 3.8 wt.%), Cr

and Ni, for basalt to andesite range of SiO2 indicating that they are quite fractionated. The N-MORB-

normalized patterns display a slight LREE enrichment and HREE depletion, with minor Zr-Hf but

marked negative Nb-Ta anomalies (Fig. 10). The juvenile (εNd)i values range from +7.07 to +8.59

(t=120 Ma; Escuder-Viruete, 2009). These features, as well as their incompatible element ratios are

very similar to modern IAT (Pearce and Peate, 1995; Kelemen et al., 2003), and suggest a source

dominated by depleted mantle. Their patterns are very similar to the IAT of the Los Ranchos Fm

(Escuder-Viruete et al., 2006).

Microporphyritic mafic lavas, monogenetic breccias and associated mafic dykes of the Cacheal

complex represent the LREE-depleted IAT group. These volcanic rocks are moderately fractionated

(Mg#=49-41) and characterized by low TiO2 contents and a LREE depletion (Fig. 10). They have

low MgO (3.3-5.5 wt.%), Cr, Ni, Nb and Zr contents, for a basalt to andesite range of SiO2 (Fig. 9).

These volcanic rocks display LREE-depleted patterns, with flat HREE and variably negative Nb-Ta

anomalies. In general, these rocks have a lower absolute abundances of HREE) and more prominent

negative Zr-Hf anomalies than of normal IAT group. The LREE depletion, low-TiO2 contents and

lower Ti/V values, as well as lower HREE levels, suggest that the mantle source for these rocks was

more depleted than for the IAT group. Compositionally, they are comparable to the low-Ti IAT

volcanic rocks of the Los Ranchos Fm (Fig. 10).

5. Discussion

5.1. Origin of the highly depleted signature in the PPC peridotites

Experimental studies indicate that progressive melting of fertile spinel lherzolite at 10-20 kbar

rapidly eliminates clinopyroxene and gradually reduces the proportion of orthopyroxene (Kelemen et

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al., 1995). Primary clinopyroxene is normally exhausted after 20-30% partial melting of lherzolite

(e.g., Niu, 2004). As melting procees, Cr# of spinel, forsterite and NiO contents of olivine and Mg#

of pyroxenes increase, and Al2O3 content of spinel and pyroxenes decrease. At high-degrees of

partial melting, these compositional characteristics define a highly depleted signature in the

peridotites (e.g., Marchesi et al., 2009; Pagé et al., 2009). In this sense, PPC harzburgites exhibit a

highly depleted signature in terms of their modal compositions, mineral chemistry and whole rock

contents, suggesting that they are residues after high extents of partial melting. This highly depleted

signature is confirmed by: (1) their lack of primary clinopyroxene; (2) their very high Mg# of olivine

and Cr# of spinel; (3) their very low whole-rock Al2O3 and HREE contents; and (4) their very low

contents in incompatible trace elements (e.g., Th, HFSE and REE) which are well below the

primitive mantle values.

The general absence of primary clinopyroxene in PPC harzburgites indicates its complete exhaustion

at high degrees of partial melting (20-30%; Niu, 2004). The Cr# of spinel is also a good indicator of

the degree of partial melting for mantle-derived peridotites (Dick and Bullen, 1984; Arai, 1994). In

the harzburgites, the Cr# plot at the calculated values of 25-28% partial-melting of fertile MORB

mantle (Fig. 6). High values of Mg# in olivine and Cr# in spinel coincide with the values exhibited

by highly depleted peridotites in supra-subduction zone settings (SSZ). The very low whole rock

Al2O3 and HREE contents of harzburgite are only comparable to those of SSZ and highly depleted

ophiolitic and ocean ridge peridotites. Whole rock low concentrations of incompatible trace elements

(e.g., Th, HFSE and REE) are below primitive mantle values, also suggesting that these rocks are

mantle residues after high-degrees of melt extraction.

Figure 9 displays the chondrite-normalized REE patterns of PPC harzburgite samples, the

compositional range of fore-arc harzburgite and dunite (data from Leg 125, Pearce et al., 1992;

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Parkinson and Pearce, 1998) and the residue curves calculated for non-modal fractional melting of

fertile spinel lherzolite. In the figure, the REE contents in harzburgites are similar to those of fore-arc

peridotites but lower that average abyssal mantle (data from Niu, 2004). HREE variations coincide

with the patterns calculated for 20-24% melt extraction from depleted MORB mantle, further

indicating an origin as residual mantle. The slightly deformed porphyroclastic textures of relict

primary minerals, the irregular shape of spinels, and the mineral models of PPC harzburgites also

indicate that this depleted mantle has undergone high-temperature deformation under upper mantle

plastic flow conditions.

On the other hand, LREE and MREE clearly depart from the melting models and have higher

concentrations. This is a common feature of mantle peridotites from different tectonic settings (e.g.,

Godard et al., 2000; Niu, 2004) and is usually interpreted as evidence of post-melting re-

equilibration with migrating melts (Godard et al., 2000; Kelemen et al., 2003) and/or melt

entrapment as microinclusions in minerals or at grain boundaries (Garrido et al., 2000; Godard et al.,

2000). In the studied harzburgites, however, LREE enrichment is also accompanied by Th, Nb, Ta,

Zr and Hf enrichment, which are elements commonly considered immobile during low-T alteration.

As an alternative to primary mantle processes, this indicates that the PPC harzburgites melting

residues could re-equilibrate with percolating melts during melt transport by reactive porous flow as

observed in other ophiolitic complexes (e.g., Rampone et al., 2004; Marchesi et al., 2012).

The trace element compositions of clinopyroxene also indicate a highly depleted signature in the

PPC harzburgites. Chondrite normalized patterns in Fig. 7 show that concentrations of the most

incompatible trace elements (HFSE and LREE) of clinopyroxene in harzburgites are lower than in

the abyssal peridotites (compiled by Tamura and Arai, 2006) and the Moho transition zone of the

Massif du Sud peridotites (Marchesi et al., 2009). However, the MREE and HREE compositions of

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clinopyroxene are similar to those of the Izu-Bonin-Mariana fore-arc peridotites and harzburgites of

the SSZ Oman ophiolite, which are considered as a residue of higher degree of partial melting

(Parkinson and Pearce, 1998; Tamura and Arai, 2006).

5.2. Signature of melts formed by partial melting of the PPC peridotites

Valuable information on the signature of the melts formed by partial melting of PPC peridotites can

be obtained by the trace element compositions of clinopyroxene. The composition of melts in

equilibrium with spinel harzburgites were calculated using clinopyroxene/melt partition coefficients

by Bédard (2005) and assuming that the trace elements are completely distributed in clinopyroxene.

The chondrite-normalized extended REE patterns of calculated liquids in equilibrium with

clinopyroxene are shown as black lines in Fig. 11. The incompatible trace element abundances of the

model melts are very low, suggesting that they were extremely depleted. The calculated melts are

similar to boninite lavas rather than of N-MORB in terms of HREE concentrations, enriched LREE

pattern and the positive Th, Zr and Hf anomalies. In particular, they coincide with the composition of

an average boninite from the Betts Cove ophiolite (from Bédard, 1999). However, they are more

depleted in incompatible trace elements than boninites from Leg 125 (Pearce et al., 1992) and

boninites from Thetford Mines ophiolite (Pagé et al., 2009). Some calculated melts are similar in

LREE and MREE concentrations relative to the low-Ti boninites of the Betts Cove ophiolite, but are

relatively enriched in HREE. This may indicate that the calculated melts correspond to less depleted

liquids but have a similar slab contribution than the low-Ti boninites. In summary, the melts formed

by partial melting of PPC harzburgites were markedly depleted and similar in trace-element

characteristics to a boninite. It is generally accepted that the high-magnesian characteristics of whole

rock and phenocryst minerals and the very low HFSE, MREE and HREE abundances observed in

boninite result from melting of highly depleted, refractory peridotite (Crawford et al., 1989; Pearce et

al., 1992; Taylor and Nesbitt, 1995; Bédard, 1999).

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5.3. Genetic relationships between gabbroic cumulates and volcanic rocks

A critical issue for the regional geology of the PPC is to establish a genetic relationship between

gabbroic cumulate rocks and spatially related lavas of the Los Caños Fm and the Cacheal complex.

Field and petrographic observations, as well as mineral and whole-rock chemistry, provide evidence

that the layered gabbroic rocks are cumulates that formed from partial crystallization of a magma

from which the remaining liquid was subsequently removed. A logical possibility is that this

remaining liquid was erupted as the basalts and basaltic andesites of the overlying volcanic section of

the ophiolite. Testing if the cumulate gabbroic rocks crystallized in equilibrium with liquids that

formed the volcanic section can demonstrate this possibility. With this goal, the composition of

“equilibrium liquids” was modeled using the trace-element compositions of clinopyroxene in the

gabbros and the dataset of partition coefficients of Bédard (2005), assuming that the clinopyroxenes

have retained their igneous trace-element characteristics. This assumption cannot be correct if post-

cumulus process have altered the original chemistry of a cumulate rock or mineral, as the trapped

melt effect (e.g., Bédard, 1999). For this reason, samples selected in this study have a high

clinopyroxene modal content and, in each sample, several large (0.2-10 mm) cumulus

clinopyroxenes were analyzed. On the scale of the thin section, no significant grain-to-grain variation

in the trace elements composition of clinopyroxene was detected, which suggest that post-cumulus

processes did not significantly affect its trace element characteristics.

The compositions of the modeled melts are listed in Appendix F and plotted in the normalized

extended REE diagrams of Fig. 11. The model melts that generated the upper olivine gabbros and

gabbronorites have extended-REE plots similar to N-MORB composition. Therefore, their source

was similar to N-MORB mantle source. These melts are slightly more enriched in LREE and

depleted in HREE than the mafic volcanic rocks of the Los Caños Fm and the Cacheal complex,

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which may indicate that they are melts derived from a higher degree of partial melting of a similar

source and contain a larger slab component. This indicates that the upper levels of the gabbroic

section of the PPC and the volcanic rocks of the Los Caños Fm are linked through crystal

fractionation processes. Figure 11 also shows that the liquids in equilibrium with olivine gabbros and

gabbronorites are very similar in trace element composition to the IAT volcanic rocks of the Los

Ranchos Fm (Lewis et al., 2002; Escuder-Viruete et al., 2006, 2009). Therefore, the upper gabbros

and gabbronorite could crystallize in equilibrium with liquids that were extracted and erupted to

produce these IAT. Modeled melts and volcanic tholeiites fit the HFSE and REE abundances and

also have positive Th and negative Nb and Ti anomalies. Tholeiitic lavas of Los Ranchos Fm are

characterized by plagioclase and clinopyroxene phenocrysts, with subordinate olivine and

orthopyroxene, which corresponds to the modal mineralogy in the cumulates.

The model liquids that generated the intermediate layered troctolites have low TiO2, HFSE and REE

contents (Fig. 11), that signal melting of a refractory mantle source, which is typical of boninites

(e.g., Crawford et al., 1989; Kamenetsky et al., 2002). The model liquids correspond reasonably well

with boninites from Los Ranchos Fm, Leg 125 (Pearce et al., 1992), Bay of Islands ophiolite (Bédard

and Hébert, 1998) and Thetford Mines ophiolite (Pagé et al., 2009). This indicates that layered

troctolite cumulate formed from boninite-like magmas. The plagioclase rich nature of the troctolites

may indicate that the parental magmas, if indeed boninitic, were of the high-calcium type, which is

the least depleted of the boninitic subtypes of Crawford et al. (1989). High-Ca boninitic lavas are

characterized by plagioclase phenocrysts associated with clinopyroxene, orthopyroxene and olivine

(Falloon and Crawford, 1991), which correspond to the cumulus phases in the intermediate layered

troctolites.

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The model liquids that generated the lower layered gabbronorites also have a low TiO2, HFSE and

REE contents (Fig. 11). HREE absolute abundances are similar to layered troctolites suggesting a

similar degree of depletion in the source and a genetic link. However, model liquids have a marked

LREE depletion, negative Zr-Hf anomalies, and somewhat lower absolute abundances of the HREE.

These characteristics suggest a more depleted mantle source and/or higher degrees of partial melting,

as well as lower slab component. Liquids in equilibrium with layered gabbronorites are very similar

in composition to the LREE-depleted IAT volcanic rocks of the Cacheal complex, as well as LREE-

depleted IAT and boninites of the Los Ranchos Fm, which probably have a compositional transition

between them. Fallow and Crawford (1991) describe evolved boninite lavas with phenocrysts of

olivine, plagioclase, orthopyroxene and clinopyroxene, which correspond to the cumulus phases in

the lower layered gabbronorites.

The calculated liquids that form the HH9112 massive gabbronorite have distinctive extended REE

patterns, which are characterized by a LREE depletion and HREE enrichment, with positive Th, Zr,

Hf and Ti anomalies. The modelled trace element abundances are very low, suggesting that the

liquids are extremely depleted. The calculated low Mg# of parental melt (0.46) and the accumulation

of Fe-Ti oxides in this sample indicate that the melt was quite evolved. The presence of

orthopyroxene as a cumulus phase suggests that the parental melt was SiO2 saturated. MREE and

HREE absolute abundances of model liquids coincide with the composition of metadacites and

metarhyolites of the Guineal Schist (Fig. 11), which have been interpreted as the differentiate

products of boninitic melts (Escuder-Viruete, 2010). Possibly, these gabbronorites represent relicts

of a boninitic substrate formed by SSZ zone magmas that constitute part of the upper volcanic

sequence.

5.4. Magmatic evolution in a supra-subduction zone setting

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Field and geochemical data show that the PPC is composed of three distinct magma series. The first

phase encompassed the formation of a strongly depleted IAT substrate, represented by the lower

layered gabbronorites of the gabbroic section of the PPC. Ductile stretching, deformative fabrics and

recrystallization microstructures indicates that this substrate was deformed at high-T conditions.

Associated volcanic rocks are probably the LREE-depleted, low-Ti IAT of the Cacheal complex and

the lower Los Ranchos Fm.

The first phase was followed by the intermediate layered troctolites of boninitic affinity at about 126

Ma. These rocks preserve igneous cumulate textures and are not penetrative deformed. Therefore,

the high-T deformation was pre-126 Ma. The massive gabbronorite HH9112 that appears to have

crystallized from an evolved boninitic melt may also have formed during this phase, although

relationships are not clear from field evidence. Regionally-related volcanic rocks are probably the

boninites of the Los Ranchos Fm, which compositionally range to the LREE-depleted IAT.

The boninitic phase was followed by the tholeiitic upper olivine gabbros and gabbronorites, the

overlying IAT lavas of Los Caños Fm, and the IAT lavas of the Cacheal complex. The tholeiitic

magmas initially had a strong SSZ geochemical signature, which apparently became less pronounced

with time. The age gap between the boninitic and tholeiitic series is not well constrained. Regionally

related volcanic rocks are probably the ‘normal’ IAT of the upper Los Ranchos Fm. Finally,

hornblende-bearing tonalitic and trondhjemitic dykes and small stocks cut the entire sequence.

The mineral and geochemical characteristics of the PPC harzburgites indicate that they are a residue

of high-degrees of partial melting. LREE-enriched melt and/or fluid assisted the high-degree

melting. These variously depleted melts migrated through a Moho transition zone into the arc lower

crust and crystallize forming the sequence of gabbroic cumulates. The trace element contents of

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clinopyroxene in some gabbroic rocks show that they were cogenetic with the overlying basaltic to

andesitic volcanic rocks. These lines of evidence indicate the formation and crystallization of arc

magmas in the mantle and crustal sections of the PPC ophiolite, i.e. the PPC contains a record of

SSZ magmatism. The ages and arc-like geochemical similarity of the plutonic and the volcanic rocks

of the PPC, and the volcanic rocks of the Cacheal complex support an interpretation that the pre-

Eocene igneous substrate of central and western Septentrional Cordillera in Hispaniola represents a

single piece of the Caribbean oceanic lithosphere. Further, the genetic relationships between the

igneous rocks of the PPC and the volcanic rocks of the Los Ranchos Fm also suggest that the arc

substrate of the Cordillera Oriental of Hispaniola was also the same.

5.5. Model for Generation of the Puerto Plata ophiolitic complex

Any model for generation of the PPC has to account for the following: (1) an (pre-126 Ma) early

phase of depleted IAT and boninitic magmatism; (2) a high-T deformative event found the early

formed gabbroic rocks; (3) a (post-126 Ma) late phase of subduction-related tholeiitic magmatism;

(4) the intrusion of hornblende tonalites at ~90 Ma, 25-30 Ma after the tholeiitic sequence; and (5)

exhumation of the complex to T<450ºC at 90-82 Ma and to T<150ºC at 35.8 Ma (closure

temperatures of hornblende and plagioclase in the Ar-Ar system, respectively). An additional

constraint is provided by the fact that the PPC igneous rocks correlate well with the volcanic rocks of

the pre-upper Aptian Cacheal complex (Abad, 2010) and the Aptian to lower Albian Los Ranchos

Fm (120-110 Ma), which represent the oldests unit preserved of the primitive Caribbean island-arc in

Hispaniola. Further, there is no record of pre-existing intra-oceanic arc units within the Hispaniola

area of the Caribbean plate that may have contributed to formation of the PPC. Reported (Nd)i values

(t=115) of +7.95 to +9.50 in basalts of the Los Caños Fm (Escuder-Viruete, 2010), of +8.02 to

+10.06 in volcanic rocks of the Los Ranchos Fm, and of +9.76 to +10.30 in metabasalts of Río Verde

complex (Escuder-Viruete et al., 2006, 2009) are in the typical range of intra-oceanic island-arcs.

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Most studies on boninite petrogenesis have reached similar conclusions: (1) boninites are second-

stage melts originating from previously depleted mantle, and (2) boninite melting events occur in the

mantle wedge beneath a forearc region in a SSZ zone and are due to decompression and synchronous

addition of small amounts of an ‘arc component’ composed of fluids/melts rich in H2O derived from

the subducted material (Crawford et al., 1989; Pearce et al., 1992; Bédard, 1999; Garrido et al., 2006;

Pagé et al., 2009). The temperatures required for melting refractory mantle to produce boninites are

higher than those expected in a typical sub-arc mantle wedge, and three end-member processes have

been proposed to explain the elevated mantle temperatures. The first involves introduction of a heat

source into ‘normal’ sub-arc mantle wedge, by subduction of a spreading ridge (Crawford et al.,

1989) or propagation of a spreading center into an arc or fore-arc (e.g., Tonga; Falloon and

Crawford, 1991). The second process invokes rapid upwelling of mantle in response to extension

induced by arc or fore-arc rifting (Bédard et al., 1998) or the initiation of subduction (e.g., Izu-

Bonin-Mariana fore-arc; Stern, 2004; Pearce et al., 1992). The third process involves a high

geothermal gradient produced by the presence of a mantle plume.

Although we cannot rule out the influence of a mantle plume, we have not found evidence of

volcanic rocks with an oceanic island, seamount or oceanic plateau basalt-like geochemical

signatures within the PPC. Therefore, a plume was not likely the primary cause of boninite

generation in the PPC. On the other hand, as mentioned above, there is no record of an intra-oceanic

arc of the appropriate age (>126 Ma) and structural position associated with the PPC. The absence of

an associated intra-oceanic arc indicates the boninitic magmas did not form by arc or forearc rifting

or propagation of a spreading center into an arc. The other possibility is that the PPC may have been

generated in a peri-continental intra-arc rift basin separating the peri-North American Guerrero and

the Cordilleran continental arcs (in the sense of Ratschbacher et al., 2009; Hastie et al., 2009, 2010;

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Neill et al., 2012). However, three lines of arguments indicate this scenario is unlikely. (1) Boninites

have not been observed in young oceanic basins that formed by rifting of continental arcs, such as

the Japan Sea and the Gulf of California (e.g., Saunders et al., 1982). (2) There is a remarkable

scarcity of clastic sedimentary rocks within the Lower Cretaceous Caribbean island-arc, and the PPC

in particular, contrary to what would be expected within an immature rift separating two continental

blocks. (3) Nd-isotopic data for all Lower Cretaceous Caribbean island-arc units in Hispaniola, as

described above, are very juvenile ([εNd]i range between +8.0 and +10.0), inconsistent with a crustal

or lithospheric mantle contribution.

Stern (2004) describe a scenario in the Izu-Bonin-Mariana fore-arc, where the early stage of

subduction was characterized by widespread boninitic magmatism (200 km wide) in a strongly

extensional environment. Following these authors, rollback of the old Pacific plate in the early stages

of subduction produces a large-scale extensional process. Rapid extension allowed for the ascent of

mantle to shallow levels, leading to the high geothermal gradient required for boninite genesis. In

this scenario, decompression melting of the mantle, as well as contact melting of the overlying

depleted mantle, aided by slab-derived fluids, would have yielded the boninites. Therefore, a

possibility for the generation of boninitic melts in the absence of an associated intra-oceanic arc

allows us to propose a similar scenario in which the PPC formed during initiation of subduction (Fig.

12).

Subduction initiated outboard of the North American continent, in the Pacific realm (Mann et al.,

2007), perhaps along a preexisting weak zone in the oceanic crust (Fig. 12a). Subduction initiation

caused extension in the overriding plate, leading to stretching and eventual breakup. Melt production

during stretching and initial breakup was probably minor, due to a low geothermal gradient and

absence of fluids derived from the subducting slab. Once started, rollback proceeded extremely fast,

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leading to very quick influx of hot mantle from below (Stern, 2004). At this stage, boninitic magmas

would have formed when the depleted mantle reached a level where it was fluxed with fluids derived

from the subducted slab (Fig. 12b). These magmas generated crust now preserved as the lower

layered gabbronorites and intermediate layered troctolites of the PPC. Regionally associated volcanic

rocks are the LREE-depleted IAT and boninites of Los Ranchos Fm and Cacheal complex. These

volcanic rocks have not been observed in the PPC. However, they may have been tectonically

removed during rollback-induced extension of the boninitic substrate, possibly by low-angle

detachment faulting similar to that occurring along mid-ocean ridges (Stern, 2004). Subduction

initiation must have occurred prior to 126 Ma, the age of the intermediate troctolites of boninitic

affinity.

The plagioclase fractionation signature in the gabbroic section of the PPC is unusual for common

high-P (~1 GPa) lower crustal cumulates in island-arc settings, as the relatively high H2O content at

the base of the arc crust should suppress the crystallization of plagioclase (e.g., Müntener et al.,

2001). Instead, the presence of plagioclase in the gabbroic cumulates, particularly in the intermediate

layered troctolites, indicates relatively low pressures of crystallization (probably ~0.2 GPa; Collot et

al., 1987). These conditions, coupled to its ultra-depleted composition, also indicate that the Puerto

Plata crust formed during the early stages of the arc igneous activity when the fore-arc region was

dominated by extensional tectonics similar to regimes at mid-ocean ridges (Bédard et al., 1998;

Stern, 2004). This scenario is also consistent with the lack of an evident (LREE-enriched) slab

component in melts in equilibrium with clinopyroxene of the lower layered gabbronorites (Fig. 11),

as limited transfer of trace elements from the subducting slab to the mantle wedge is expected during

the arc infancy (e.g., Dhuime et al., 2009). Fore-arc spreading recorded in the PPC is in good

agreement with field data of the ophiolite sequence, where due to tectonic omission peridotites are

juxtaposed against layered gabbros, and gabbros are directly overlain by basaltic pillow lavas.

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As extension proceeded, fertile mantle may have decompressed enough to initiate melting (e.g.,

Pearce and Peate, 1995), an effect that would have been amplified if the rising fertile mantle entered

the region of the mantle wedge that was fluxed by fluids expelled from the subducting slab (Fig.

12c). In the PPC, this process may have yielded ‘normal’ tholeiitic SSZ magmas post-126 Ma, which

generated the upper olivine gabbros and gabbronorites, and the IAT pillow lavas of the Los Caños

Fm. Regionally associated volcanic rocks are the IAT of the Los Ranchos Fm and the Cacheal

complex. Extension may have contributed to breakup of the boninitic substrate, producing the

current configuration of the ophiolite in fault-bounded blocks. As the convergence rate and

subduction angle stabilized, a true magmatic arc may have formed after ca. 15 Ma (Stern, 2004). The

presence of more evolved andesites and dacites in the upper stratigraphic levels of the Los Ranchos

Fm suggests that the Aptian to Lower Albian Caribbean island-arc reached this stage of a magmatic

arc (Kesler et al., 1990, 2005; Lewis et al., 2002). Note that a similar tectonomagmatic evolution

from boninite and depleted IAT to less depleted IAT compositions has been proposed for the

volcanic rocks of the Los Ranchos Fm by Escuder-Viruete et al. (2006). In the Hispaniola segment

of the primitive Caribbean island arc the boninitic and tholeiitic magmatism ceases after ~10 Ma of

activity at about 110 Ma (Escuder-Viruete et al., 2009), and the volcanic rocks are unconformably

covered by upper Lower Albian shallow-water carbonate platform deposits (Myczynski and

Iturralde-Vinent, 2005). The cessation of the primitive Caribbean island-arc volcanism and the

heterogeneous ductile deformation, uplift and erosion of the volcanic and tonalitic rocks has been

related to its oblique collision with the southern extension of the Guerrero arc, as suggested the age

data and P-t relations obtained in the arc-like mafic igneous protoliths of the southern Río San Juan

complex (Escuder-Viruete et al., 2013a, b).

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Finally, the geologic significance of the hornblende-bearing tonalite magmatism at ~90 Ma in the

PPC is uncertain. However, it matches with higher rates of subduction erosion along the northern

Caribbean convergent margin and a fundamental temporal change in the renewed Late Cretaceous

Caribbean island-arc magmas to more adakitic geochemical characteristics. The exhumation of the

PPC at the Maastrichtian-lower to middle Eocene is related to collision of the Caribbean plate with

the North American continental margin, which took place at about 60±5 Ma (see Escuder-Viruete et

al., 2011a, b).

Acknowledgements

The authors wish to thank Gren Draper and Peter Baumgartner for their comments on the geology of

Dominican Republic and the Caribbean paleogeography. We thank Angela Suárez-Rodríguez

(IGME) and Jacques Monthel (BRGM) for their involvement in mapping and sampling the Puerto

Plata area. The Servicio Geológico Nacional of the Dominican Government is also thanked for

collaboration, particularly to Santiago Muñoz. Alan Hastie, Andrew Kerr and an anonymous

Reviewer provided careful and constructive reviews. The research has been funded by Spanish

MECD, through the PRX12/00152 grant of the National Program of Human Resources Mobility to

the first author. Funding by the CGL2009-08674/BTE and CGL2012-33669/BTE projects is

gratefully acknowledged.

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Figure Captions

Fig. 1. (a) Map of the northeastern Caribbean plate margin showing location of the main geotectonic

units in the Greater Antilles orogenic belt. DR, Dominican Republic; H, Haiti. (b) Simplified

geological map of central and western Septentrional Cordillera in Dominican Republic,

modified from Draper and Nagle (1991), Pindell and Draper (1991), Monthel (2010) and

Escuder-Viruete et al. (2011a, 2013a), showing location of inliers of arc, oceanic and

continental margin derived units. Box shows location of the Puerto Plata area.(c) Schematic

geological map of the Puerto Plata complex and (d) I-I’ cross section shown the stratigraphic

and structural relationships between the pre-Eocene ophiolitic basement rocks and the

Tertiary sedimentary cover.

Fig. 2. Schematic lithostratigraphic columns of Puerto Plata and Cacheal volcanic.

Fig. 3. Field features of ophiolitic rocks from Puerto Plata complex. (a) Normal fault contact

between layered troctolites (g; 126 Ma, U-Pb in zircon) and mafic volcanic rocks of the Los

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Caños Fm (v) at Punta La Playa. (b) Layered gabbronorites and leucogabbros deformed by a

network of low-angle conjugate extensional shear zones. The layering consist of varying

modal proportions of clinopyroxene, orthopyroxene and plagioclase. Quarry located eastern

Cerro Cofresí. Wild of view=25 m. (c) Folded layers of ribbon chert alternating with very

fine-grained pelagic sediments, eastern cliffs of Punta La Playa. Arrow points to a coin for

scale. (d) Volcanic breccias of the Los Caños Fm at Punta de la Guardia. (e) Basaltic pillow

lavas deformed by a system of conjugate normal faults with related formation of a cataclastic

tectonic matrix. (f) Layered troctolites surrounded by low-angle bands of strongly sheared

and foliated gabbroic rocks, eastern cliffs of Punta La Playa. Arrow points to a book for scale.

(g) Modal layering in gabbronorites, defined by variations of the mafic mineral/plagioclase

ratio at the millimeter to decimeter scale. Quarry located eastern Cerro Cofresí. (h)

Harzburgite with a porphyroclastic fabric (Sm) of ophiolite tectonite, characterized by 1-5

mm plastically deformed orthopyroxene megacrysts up to 1.5 cm long.

Fig. 4. (a) Modal compositions of gabbroic rocks of the Puerto Plata complex compared to those of

the lower and middle crustal gabbros) and the Moho Transition Zone sills of the Oman

ophiolite (Marchesi et al., 2006, 2009). (b) Modal compositions of the ultramafic rocks of the

PPC compared to those of the Oman ophiolite peridotites (Godard et al., 2000), ocean ridge

peridotites (Dick and Bullen, 1984) and supra-subduction zone (SSZ) peridotites (Parkinson

and Pearce, 1998). See text for explanation.

Fig. 5. Photomicrographs showing features of the ophiolitic rocks from the Puerto Plata complex. (a)

Clinopyroxene-phyric basaltic lava of the Los Caños Fm with a mesostasia rich in plagioclase

crystals. PPL. (b) Subophitic microstructure in isotropic gabbro containing euhedral

plagioclase (Pl) and intersticial anhedral clinopyroxene (Cpx). Upper olivine gabbros. CPL.

(c) Elongated orthopyroxene (Opx) and clinopyroxene (Cpx) in a matrix of re-crystallized

plagioclase (Pl) defining a sub-solidus foliation (Sm). Lower layered gabbronorites. PPL. (d)

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Euhedral olivine (Ol) associated with intercumulus anhedral plagioclase (Pl). Plagioclase is

partially replaced by pseudomorphic aggregates rich in white mica. Intermediate troctolites.

CPL. (e) Gabbro containing euhedral olivine (Ol), plagioclase (Pl) and intercumulus

clinopyroxene (Cpx). Upper olivine gabbros. CPL. (f) High-T deformative fabric (Sm)

defined by a recrystallized and elongated aggregate of clinopyroxene (Cpx), minor

orthopyroxene and plagioclase (Pl). Lower layered gabbronorite. CPL. (g) Slight deformed

layered gabbronorite, consisting of varying modal proportions of orthopyroxene (Opx),

clinopyroxene (Cpx) and plagioclase (Pl). Lower layered gabbronorites, PPL. (h) Irregular

spinel (Sp) intergrown between bastite after orthopyroxene (Opx) and serpentinized olivine

(Ol) in harzburgite. PPL. Width of field=5mm in all photomicrographs.

Fig. 6. Major and trace elements composition of clinopyroxene phenocrysts from gabbroic rocks and

volcanic rocks (Los Caños Fm) of the PPC. (a) TiO2–Na2O–SiO2/100 (wt.%) discrimination

diagram (Beccaluva et al., 1989) for clinopyroxenes. Fields representing clinopyroxene

compositions in basalts from modern oceanic settings are reported for comparison (Saccani

and Photiades, 2004). Abbreviations: N-MORB, normal MORB; E-MORB, enriched MORB;

ICB, Iceland basalts; IAT, island-arc tholeiites; Bon, boninites; BA-A, intraoceanic forearc

basalts and basaltic andesites. (b) Mg# versus Al3O2 content of clinopyroxene (wt.%).

Compiled fields of arc-related peridotites, mantle pyroxenites and arc related igneous

pyroxenites are from Berly et al. (2006). (c) Mg# versus TiO2 content of clinopyroxene

(wt.%). Fields of ocean ridge cumulates and Izu–Bonin arc volcanic rocks are from Marchesi

et al. (2009) and references therein. Compiled fields of island-arc cumulates (lower crustal

gabbronorites) and depleted forearc peridotites are from Marchesi et al. (2009), respectively.

PGHS, field of clinopyroxene composition in metapicrites from the Hicotea Schists and high-

Mg metabasalts from the Puerca Gorda Schists, southern Río San Juan complex. (d) Mg# of

olivine versus Cr# of spinel in PPC harzburgites. Fields of olivine-spinel mantle array

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(OSMA), supra-subduction zone (SSZ) and abyssal peridotites from Arai (1994). See text for

explanation.

Fig. 7. Representative chondrite-normalized trace element patterns of clinopyroxene in diverse rock

units of the Puerto Plata complex. Field of clinopyroxene composition in metapicrites of the

Hicotea Schists and high-Mg metabasalts of the Puerca Gorda Schists are from Escuder-

Viruete et al. (2011a, b), abyssal peridotites from Tamura and Arai (2006; and references

herein), boninite-type cumulates and Massif du Sud peridotites from Marchesi et al. (2009),

forearc peridotites from Parkinson and Pearce (1998) and Oman harzburgites from Tamura

and Arai (2006). See text for explanation.

Fig. 8. (a) Nb/Y versus Zr/TiO2 diagram (Winchester and Floyd, 1977) and (b) Ti–V diagram for

rocks from the diverse lithological units in the Puerto Plata complex. Los Ranchos, Maimón

and Amina Formations data are from Escuder-Viruete et al. (2006, 2008, 2009). (c) Bull rock

Al2O3/SiO2 versus MgO/SiO2 in Puerto Plata complex spinel harzburgites. Terrestrial array

from Hart and Zindler (1986). See text for explanation.

Fig. 9. Variation diagrams for rocks of the Puerto Plata complex. MgO versus TiO2 (a), SiO2 (b), Zr

(c), and Nb (d). NVTZ, CG and SR fields are respectively for Northern Volcano-Tectonic

Zone, Central Graben and Spreading Ridge fields of the Mariana Arc–Trough system (from

Gribble et al., 1998), which are shown for comparisons with a modern arc-backarc system

analog. MORB glasses are from the Clipperton Fracture Zone (PetDB, 2007). The different

geochemical groups of Lower Cretaceous igneous rocks in Hispaniola are: IAT, normal

island-arc tholeiites; Low-Ti IAT, Low-Ti and LREE-depleted island-arc tholeiites; Bon,

boninites; and felsic volcanic rocks and tonalites (Escuder-Viruete et al., 2006). Ti versus

Nb/Th (e), (La/Yb)N (f), and Zr/Hf (g), and (La/Nd)N versus Nb* (h) diagrams for rocks from

the diverse lithological units in the PPC. See text for explanation.

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Fig. 10. MORB-normalized extended trace-element plots for volcanic rocks of the (a) Los Caños Fm

and (b y c) Cacheal complex. MORB-normalizing values are from Sun and McDonough

(1989). Id. for gabbroic and ultramafic rocks of the Puerto Plata complex: (e) upper gabbros

and gabbronorites; (f) intermediate layered troctolites; (g) lower layered and foliated

gabbronorites; and (h) spinel harzburgites. The diverse geochemical groups of Lower

Cretaceous igneous rocks in Hispaniola shown in (d) are taken from Escuder-Viruete et al.

(2006, 2009) and are: IAT, normal island-arc tholeiites; Low-Ti IAT, LREE-depleted island-

arc tholeiites; and Bon, boninites. MORB-normalizing values are from Sun and McDonough

(1989). See text for explanation.

Fig. 11. Chondrite-normalized extended REE patterns of calculated liquids (black lines) in

equilibrium with clinopyroxene of representative volcanic, gabbroic and ultramafic rocks of

the Puerto Plata complex. To find similarities, modeled compositions of the parental magmas

are compared with the compositional field of coeval groups of volcanic rocks. Fields of

geochemical groups of Lower Cretaceous volcanic rocks in Hispaniola shown in (a) and (b)

are taken from Lewis et al. (2002) and Escuder-Viruete et al. (2006, 2009, 2011c). IAT,

island-arc tholeiites. Other relevant fields are boninites from Leg 125 (Pearce et al., 1992)

and boninites from Thetford Mines ophiolite (Pagé et al., 2009). Average boninite and low-Ti

boninite compositions in Bay of Islands ophiolite are from Bédard and Hébert (1998) and

Bédard et al. (2000). Chondrite-normalizing values are from Sun and McDonough (1989).

See text for explanation.

Fig. 12. Simplified model for generation of the Lower Cretaceous Caribbean island-arc based on the

model of Stern (2004) and the tectonomagmatic relationships observed in the Puerto Plata

ophiolitic complex, Cacheal complex, Los Ranchos Fm and Río Verde complex of

Hispaniola (Escuder-Viruete et al., 2006, 2009). (1) Subduction initiated outboard of the

North American continent, in the Pacific realm, perhaps along a preexisting weak zone in the

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oceanic crust; (2) initiation of subsidence and high-degrees of partial melting of already

depleted MORB mantle (DMM) produce LREE-depleted IAT magmas and very depleted

mantle (VDM) residue; (3) aided by fluids expelled from the downgoing plate, the residual

VDM melts at shallow levels yielding boninites; (4) continuing rollback causes lateral

upwelling of a fertile mantle diapir (DMM), which, in the presence of slab-derived fluids,

melts to yield supra-subduction zone tholeiites (normal IAT). The stabilization of the

magmatic front by continued subduction produce the migration of the locus of extension to a

back-arc position, which resulted the BABB-like magmatism of the Río Verde complex.

Also, melting at the base of the arc crust produced the rhyolite/tonalite magmas.

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Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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Figure 8

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Figure 9

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Figure 10

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Figure 11

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Figure 12

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Graphical abstract

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Highlights

The Puerto Plata ophiolitic complex records the birth of the Caribbean island-arc

Three magmatic episodes have been recognized: depleted IAT, boninitic and tholeiitic

It formed during initiation of W/SW-directed subduction in an intra-oceanic setting

magmatic relationships between depleted mantle harzburgites,...

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