ome

,b,

o b

s (U, DF

c CNPq - Conselho Nacional para o Desenvolvimento Cientco e Tecnolgico, Braslia, DF, Brazil

a r t i c l e i n f o

Article history:Received 30 September 2011Accepted 8 April 2012Available online 16 April 2012

Lithos 144145 (2012) 5672

Contents lists available at SciVerse ScienceDirect

Lith

j ourna l homepage: www.e l1. Introduction

Recent compilations of carbonatite and phoscorite occurrencesshow that nearly all known phoscorites are associated with carbonatites and, in many cases, with alkaline silicate rocks (Krasnova et al.,2004) and that approximately 76% of carbonatites (whether associated with phoscorites or not) are temporally and spatially associatedwith alkaline silicate rocks (Woolley and Kjarsgaard, 2008). In relatively rare cases, these three rock series occur together in multiphaseintrusions with complex petrologic evolution. The best examples ofthis occurrence are the Phalaborwa complex in South Africa and

Maimecha Kotui and Kola Alkaline Provinces of Russia and the AltoParanaba Igneous Province (APIP) of Brazil. Such associations areof great petrological interest because they allow investigation ofthe relationships between highly contrasting (silicate, phosphateoxide, carbonate) types of magma. These associations are also economically important, as the complexes may contain world class depositsof magmatic phosphate (Kola, APIP, Phalaborwa), niobium (APIP),and copper (Phalaborwa), as well as deposits of titanium, rare earthelements (REE), iron (magnetite), vermiculite, and several possibleby products.

Provinciality exerts an important control on the petrographic types

the phoscorite carbonatite alkaline silicate

Corresponding author at: Instituto de Estudos Scio AUniversidade Federal de Gois (UFG), CEP 74.001-970, G8167 4534; fax: +55 62 3521-1077.

E-mail addresses: elisa.barbosa@uol.com.br (E.S.R. B(J.A. Brod), tcjbrod@iesa.ufg.br (T.C. Junqueira-Brod), elcordeiropfo@gmail.com (P.F.O. Cordeiro), caroline.gomi

0024-4937/$ see front matter 2012 Elsevier B.V. Alldoi:10.1016/j.lithos.2012.04.013the APIP. 2012 Elsevier B.V. All rights reserved.Keywords:APIPBebedouriteCarbonatitePhoscoriteUltrapotassic magmatisma b s t r a c t

Bebedourite is a cumulate rock composedof variable but roughly equant amounts of diopside, apatite,magnetite,phlogopite, and a Ca Ti phase (mostly perovskite, more rarely titanite and/or Ti garnet). Other minerals may bemodally important, such as olivine and K feldspar in the least and most evolved members of the bebedouriteseries, respectively. The magmatic evolution in bebedourites is accompanied by a progressive increase inSiO2 activity, which results in the transformation of perovskite into titanite and titanite into Ti garnet. Althoughthe SiO2 increasemay, in some cases, result from crustal contamination, it seems to be a localized effect and cannot account for the evolution of the whole bebedourite series. Crystal fractionation is supported by the chemicalvariation of key mineral phases such as pyroxene and phlogopite. The Salitre complex is an ultrapotassiccarbonatite and phoscorite bearing plutonic complex belonging to the Late Cretaceous Alto Paranaba IgneousProvince (APIP) and consisting of three main bodies (Salitre I, II, and III). The complex is composed mainly ofbebedourite, with lesser amounts of carbonatite and phoscorite in its central north portion. A particular typeof bebedourite, where themain Ca Ti phase is Ti garnet, dominates the southern part of Salitre I and also occursas dikes crosscutting older bebedourites, suggesting that Ti garnet bebedourites form an independent intrusion.Sr and Nd isotopic data indicate that the parental magmas to the bebedourites in the Salitre complex originatedin a metasomatized sub continental lithospheric mantle similar to that involved in the origin of the rest ofBebedourite from its type area (Salitre I cLate-Cretaceous Alto Paranaba kamafugitcentral Brazil

Elisa Soares Rocha Barbosa a,b,c,, Jos Affonso Brod a

Elton Luiz Dantas b,c, Pedro Filipe de Oliveira Cordeira Instituto de Estudos Scio Ambientais, Campus Samambaia, Universidade Federal de Goib Instituto de Geocincias, Universidade de Braslia, Campus Asa Norte, 70.910-900 Brasliarock complexes in the

mbientais, Campus Samambaia,oinia, GO, Brazil. Tel.: +55 62

arbosa), j.a.brod@iesa.ufg.brton@unb.br (E.L. Dantas),de@gmail.com (C.S. Gomide).

rights reserved.plex): A key petrogenetic series in thecarbonatitephoscorite association,

c, Tereza Cristina Junqueira-Brod a,c,,c, Caroline Siqueira Gomide a,b,c

FG), CEP 74.001-970, Goinia, GO, Brazil, Brazil

os

sev ie r .com/ locate / l i thosof silicate rocks produced in each case. For example, rocks of the ijoliteseries are common in several of the Kola complexes (Krasnova et al.,2004) but are absent in the APIP complexes and Phalaborwa, indicatingamore sodic parental composition for Kola, whereas Phalaborwa andthe APIP have ultrapotassic afnities (Brod et al., 2000; Eriksson,1989; Gibson et al., 1995a). The alkaline silicate rocks in the lattertwo localities typically form a bimodal ultramac felsic association,comprising dunite, pyroxenite, bebedourite (a diopside , apatite ,

57E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672perovskite , phlogopite , and magnetite rich rock), and syenite. Inthe case of APIP, these rocks are genetically linked with kamafugiticlavas and pyroclastics (Brod et al., 2000; Lloyd and Bailey, 1991;Lloyd et al., 1996). Associations of potassic ultramac rocks (dunite,clinopyroxenite) and syenites have also been reported from theAldan Shield, Russia (Mitchell and Vladykin, 1996; Mues Schumacheret al., 1996).

Bebedourite is a conspicuous rock type in all carbonatite complexes of the APIP, and it appears to be a hallmark of carbonatite andphoscorite bearing complexes of ultrapotassic afliation. Bebedouriteis also the primary source of important residual phosphate and titaniummineralization in theweathering cover of some complexes (e.g., Tapira,Brod et al., 2004). Nevertheless, this rock type has received little attention from researchers over the years, and few details are available on itsmineralogy and chemistry.

In some APIP complexes, such as Catalo I and Arax, bebedouritesare strongly converted tometasomatic phlogopitite through interactionwith carbonatite magma or uids. In other cases, such as Salitre andTapira, large portions of bebedourite are preserved from metasomaticalteration, and fresh samples are available from drill cores.

In this paper,we use petrographic,mineral composition,whole rockgeochemistry, and Sr Nd isotope data to characterize well preservedbebedourites from their type area and to investigate their origin andmagmatic evolution.

2. Regional geological setting

The Late Cretaceous Alto Paranaba Igneous Province (Almeida,1983; Gibson et al., 1995a) in central southeastern Brazil comprisesa voluminous ultrapotassic magmatism emplaced in Neoproterozoicrocks of the Braslia Belt in a relatively narrow NW trending area between the SW margin of the Archaean So Francisco Craton and theNE margin of the Paleozoic Paran Basin. Most works report a narrowage range for the province between 80 and 90 Ma (Gibson et al., 1995a;Sgarbi et al., 2004; Sonoki and Garda, 1988; Ulbrich and Gomes, 1981).This magmatism has been interpreted as the result of the initial impactof the Trindade mantle plume under the lithosphere of central Brazil(Gibson et al., 1995a,b, 1997; Thompson et al., 1998). Gibson et al.(1995a) concluded that, in the case of the APIP, the Trindade plumeacted only as a heat source for the melting of the overlying subcontinental lithospheric mantle, which explains the lack of a plumesignature in the APIP magmas. Other authors argue against the involvement of the Trindademantle plume in the generation of theAPIPmagmason the basis of (a) the lack of a plume related isotopic signature andof a clear array of progressively younger ages along the plume trail(e.g., Riccomini et al., 2005); and (b) palaeomagnetic reconstructions(Ernesto, 2005). In any case, there is general consensus that the APIPmagmas were generated from the sub continental lithospheric mantle.The Nd model ages throughout the APIP suggest that a relatively old(0.9 1.3 Ga) event was responsible for the enrichment of this mantlesource.

The APIP (Fig. 1) is composed mainly of kamafugites, which occuras small intrusions (e.g., Arajo et al., 2001; Gibson et al., 1995a), andas lavas and pyroclastic deposits covering large areas of the province(Mata da Corda Group, Gibson et al., 1995a; Seer and Moraes, 1988;Sgarbi and Valena, 1993). Subordinate amounts of kimberlites andrare lamproites (e.g., Arajo et al., 2001; Gibson et al., 1995a; Gonzagaand Tompkins, 1991) also occur in the province. A number of large(up to 65 km2) carbonatite and phoscorite bearing alkaline complexesoccur in the APIP, comprising Catalo I and II, Serra Negra, Salitre I, II,and III, Arax, and Tapira (Brod et al., 2004; Gomes et al., 1990;Morbidelli et al., 1997; Traversa et al., 2001).

The intrusion of the plutonic complexes generated dome structures.Intense tropical weathering and the inward drainage patterns resultingfrom the weathering resistant country rock surrounding the domes

(Danni et al., 1991; Mariano and Marchetto, 1991) produced a thicksoil cover in most of the complexes, favoring the development ofsupergenic deposits of phosphate and niobium mined in the region,in addition to yet unexploited rare earth elements (REE), titanium,and vermiculite occurrences. Outcrops are rare, and the best samplesfor petrographic and geochemical studies are restricted to drill coresand a few exposures within mining pits.

The presence of abundant xenoliths of dunite, pyroxenite, bebedourite,melilitite, and syenite in theMata da Corda (Fig. 1) volcanic rocks ledSeer andMoraes (1988) to suggest the existence of carbonatite bearingcomplexes at depth in that region. The mineralogical compositionand textures of these xenoliths closely resemble those of the bebedourites in the APIP plutonic carbonatite complexes (Brod et al.,2000; Lloyd and Bailey, 1991). Lloyd and Bailey (1991) suggested aparental relationship between the APIP kamafugites and bebedourites. Brod (1999) and Brod et al. (2000) proposed an ultramac,ultrapotassic, carbonated magma (phlogopite picrite, Gibson et al.,1995a) of kamafugitic afliation as the parent for both the silicaterocks and the carbonatites in the APIP plutonic complexes, thusestablishing a kamafugite carbonatite association in the province.Morbidelli et al. (1997) mentioned the rare occurrence of melilite,monticellite, and kalsilite in the Salitre ultramac assemblages, andBrod et al. (2000) reported the presence of kalsilite in one sampleof a Salitre syenite, which gives additional support to a kamafugiticafliation for the complex. Phoscoritic rocks have been increasinglydescribed from the APIP plutonic complexes (e.g., Brod et al., 2004;Cordeiro et al., 2010a,b; 2011; Fontana, 2006; Ribeiro et al., 2005),leading to the recognition of a kamafugite carbonatite phoscoriteassociation.

The association between carbonatites and ultrapotassic volcanicrocks such as kamafugites has also been described from other provinces and localities, such as Italy (Stoppa and Cundari, 1995; Stoppaet al., 2003), the western branch of the African Rift (Eby et al., 2009;Lloyd et al., 1999), Russia (Mitchell and Vladykin, 1996), and China(Yang and Woolley, 2006). Gaspar and Danni (1981) described someof the top lava ows in the Santo Antnio da Barra kamafugites (GoisAlkaline Province, central Brazil) as carbonatitic, a description conrmed by data from Junqueira Brod et al. (2005a, 2005b).

3. Salitre complex

3.1. Rock nomenclature considerations

The ultramac silicate rocks of the APIP complexes are mostly cumulates, consisting of variable modal proportions of olivine, clinopyroxene,phlogopite, apatite, perovskite, Ti garnet, titanite, and magnetite, withrare occurrences of chromite (in the least evolved rocks) and K feldspar(in the most evolved rocks). Many of these phases are not taken into account in general rock classication systems (e.g., Le Maitre, 2002), butthey may be essential components of bebedourites.

We determined the modal variability of 93 samples of bebedouritesfrom the Salitre (this work) and Tapira (Brod, 1999) complexes inthe APIP. At least 1000 points were counted in each thin section.Coarse grained to pegmatoidal varieties were not included in thisstudy. These rocks have been generically described in the literature asclinopyroxenites, but in approximately 65% of them the clinopyroxeneabundance is below 50 vol.%. Only one sample has over 80 vol.% clinopyroxene, and none has over 90 vol.%.

The classication of these rocks in a simplied framework (i.e.,considering only olivine and clinopyroxene) would result in a progression from dunite through wehrlite to clinopyroxenite. However,because in most cases the sum of modal apatite, perovskite, magnetite,and phlogopite exceeds that of olivine and clinopyroxene, such classication is inadequate to describe their composition, facies variations, andstrongly alkaline character.

A slightly more accurate approach would be to add the prex alkali

(e.g., alkali pyroxenite). The recommended criteria for the application

58 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672of this prex are the following (Le Maitre, 2002): 1) the occurrence ofmodal feldspathoids and/or alkali pyroxene/amphibole or 2) thepresence of normative feldspathoids or acmite. With extremely rareexceptions, the ultramac rocks in the APIP plutonic complexes do notcontain feldspathoids, and their clinopyroxene is diopsidic, hence failing the rst criterion. Additionally, the use of normative compositionfor cumulate rockswith signicant facies variation is not advisable, rendering the second criterion inapplicable. Moreover, the use of the namealkali pyroxenite could induce confusionwith jacupirangite, a variety ofalkali pyroxenite intimately associated with carbonatite complexes ofsodic afliation, but which differs from the APIP rocks in that the latterdo not contain nepheline.

Trger (1928, 1935) dened bebedourite as a biotite andperovskite rich clinopyroxenite that typically contains 54% aegirinicdiopside, 21% biotite, 14% perovskite, 10% opaque minerals, and accessory apatite, K feldspar, and olivine. The type locality for thisrock is the Bebedouro area at Salitre Hill, Minas Gerais State, Brazil(i.e., the Salitre complex in the APIP). This denition is a close enoughmatch for most of the pyroxene rich ultramac plutonic rocks of theAPIP. The name bebedourite has often been applied in connectionwith the alkaline carbonatite complexes of the province (e.g.,Gibson et al., 1995a; Gomes et al., 1990; Lloyd and Bailey, 1991;Morbidelli et al., 1997) and is most successful at emphasizing the differences between the APIP ultrapotassic ultramac rocks and thesodium rich ultramac rocks associated with many other carbonatite complexes.

In this work, we adopt the term bebedourite to designate a suite ofconsanguineous cumulate rocks consisting of diverse modal proportions of diopside, perovskite, apatite, magnetite, phlogopite, Ti garnet,titanite, and olivine. Some of the more evolved members of the suite

Fig. 1. Geological map of the AltoAdapted from Oliveira et al. (200contain potassium feldspar, indicating their afnity to the extrusiveultrapotassic magmatism of the APIP. Olivine and Ca Ti minerals, suchas perovskite, titanite, and Ti garnet, are used to distinguish betweendifferent bebedourite varieties, resulting in a mineralogical geneticclassication scheme of the style used by Mitchell (1997) and Mitchelland Bergman (1991), in which a stem name with prexes is used todescribe a suite of rocks that do not t IUGS classications.

3.2. The Salitre complex

The Salitre I, II, and III intrusions (Fig. 2) are located to the south ofthe Serra Negra Complex, in the Patrocnio region, Minas Gerais State.Salitre I has a distorted oval shape that is approximately 7 km N Sand 5 km E W. Salitre II is a small (2.5 km2) plug located betweenSalitre I and Serra Negra. Salitre III is approximately 2 km in diameterand has no topographic expression.

K/Ar dating of phlogopite from a Salitre bebedourite yielded anage of 86.35.7 Ma (Sonoki and Garda, 1988). Gomes et al. (1990)compiled K/Ar ages for the Salitre complex in the range of 79 94.5 Ma.Morbidelli et al. (1997) concluded that the preferred age for Salitre is82 Ma. Comin Chiaramonti et al. (2005) give an average age of 84 Mafor the complex.

The petrographic types described from the Salitre complex includesilicate rocks varying from ultramac cumulates to syenitic rocks, carbonatites, and phoscorites (Haggerty and Mariano, 1983; Mariano andMarchetto, 1991; Morbidelli et al., 1997). It is noteworthy that macand intermediate feldspar or feldspathoid bearing rocks are missingat Salitre, similarly to all other plutonic complexes of APIP (e.g., Brodet al., 2004).

Paranaba Igneous Province.4).

59E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672Morbidelli et al. (1997) studied the few pyroxenite and syenite outcrops available at Salitre I, and the abundant fresh drill cores fromSalitre I and II (see Fig. 2 for locations). They concluded that SalitreI and II are dominated by silicate rocks, mainly clinopyroxenites inSalitre I and perovskite dunites in Salitre II. They also reported carbonatites from both intrusions and indicated that both carbonatitesand silicate cumulates may grade to phoscoritic rocks.

Available data on Salitre III are still scarce, but preliminary information suggests that it is essentially composed of bebedourites locallyassociated with phoscorite series rocks.

Renewed interest in the Salitre I phosphate deposits has motivatedadditional drilling campaigns by Fosfertil S/A. We were able to accessand/or sample drill cores from 145 new drillings, to extend the rangeof bebedourites in the complex both geographically and petrographically. Of these drillings, 62 were sampled for geochemical and mineralogical studies. The drilling locations are shown in Fig. 2.

Fig. 2 presents an interpretive geological sketch of Salitre I. This sketchis based on our own observations of the drill cores and petrographicresults (Barbosa, 2009) combined with data from the literature (Brod

Fig. 2. Interpretive geological sketch of the Salitre complex (Barbosa, 2009) showing the arethis work. Some B2-type bebedourites (B2a and B2c) are mostly dikes crosscutting the B1et al., 2004; Morbidelli et al., 1997) and an interpretation of geochemical exploration data and detailed geophysical images (C. C. Ribeiro, Pers.Comm.). Salitre I complex is composed of at least three major intrusivesystems:

1) The northern part of the complex is occupied by perovskitebebedourites (B1). In Fig. 2, these rocks are further subdividedinto olivine bearing (B1a, corresponding to the perovskite richdunites and pyroxenites of Morbidelli et al., 1997) and olivinefree (B1b). Similarly to other APIP complexes, important modalvariations occur, including facies rich in olivine, phlogopite, perovskite, and apatite in addition to typical bebedourite; however,apart from the olivine rich rocks, these are not individualized inFig. 2. The crescent shape of the areas occupied by olivine bearingrocks and their occurrence as a segmented ring around the olivinefree bebedourites suggest that these two rock types are part of acumulate pile.

2) The southern part of the complex is occupied by more homogeneous olivine free bebedourites characterized by Ti garnet as the

as studied by Morbidelli et al. (1997) and the drill cores examined and sampled duringintrusion and are not representable at this scale. See the text for further explanation.

main Ca Ti phase. This unit is further subdivided according to thedominant Ca Ti phase into B2a (perovskite+titanite+Ti garnet),B2b (Ti garnet only), and B2c (titanite only and/or titanite+Tigarnet). However, we could not establish the geometric relationships between these three types at the current level of drill coreinformation. These rocks are also common as dikes within B1 rocksand are thus interpreted as intrusive in that unit. The remnant areasof B1 in the southern part of the complex probably represent portionsof the cupola that were preserved during the intrusion of B2.

3) A system of ring+radial dikes of phoscorite and carbonatite intrudes the central part of the B1 unit. The carbonatite series rockscomprise a) calcite carbonatite, with variable amounts of olivine,apatite, and opaque minerals, and accessory dolomite and phlogopite; and b) dolomite carbonatite with irregularly shaped apatitepockets. The phoscorite series rocks include phoscorite and, morerarely, apatitite, nelsonite, and magnetitite, characterized by modalvariations in the amounts of olivine, apatite, and magnetite. Theaccessories comprise carbonate, pyrochlore, ilmenite, and suldes(pyrite and pyrrhotite).

Note that the presence of multiple intrusions is consistent withthe kidney shaped outline of Salitre 1 (Fig. 2).

The syenites occur mostly as dikes, but Morbidelli et al. (1997)reported that they may also be present at the top of the cumulate sequence, suggesting that these rocks are the evolved endmembers ofthe bebedourite series. This interpretation is in good agreement withthe presence, albeit rare, of K feldspar in some evolved bebedouritesfrom the Tapira complex in the APIP (Brod et al., 2005).

When intruded by carbonatite dikes and veins, bebedourites areoften converted to metasomatic phlogopitite, with implications forboth the mineralogical and geochemical characteristics of theserocks (e.g., the transformation of perovskite into anatase).

3.3. Petrography of the Salitre bebedourites

We studied a total of 62 Salitre bebedourite samples. These rocksvary from ne to coarse grained, and more rarely pegmatoidal, andthey may occur both as cumulates and as dikes intruding other alkalinerocks. Table 1 summarizes the units, rock types, and ranges and averages of the modal compositions for each intrusion. The average modalcomposition and mineral compositions determined by electron microprobe were used to calculate a theoretical chemical composition foreach rock type, shown in the bottom part of Table 1.

The B1 intrusion comprises olivine bearing (B1a) and olivine lacking(B1b) rocks, where perovskite is the only Ca Ti phase present, except for the very rare occurrence of titanite (b1%) in a few samples.The bebedourites in this intrusion are typically medium to coarsegrained, green, and show brown or black patches formed, respectively,by phlogopite or magnetite+perovskite concentrations. Although thedrill core scale is not ideal, some evidence of magmatic layering is recognizable in these rocks.

In the B1a bebedourites, olivine and perovskite occur as subhedralto anhedral cumulus grains with variable amounts of intercumulusdiopside, magnetite, phologopite, and rare apatite. Perovskite is perfectly preserved and often optically zoned.

In the B1b bebedourites, diopside and subordinate perovskite arethe dominant cumulus constituents, but the latter may also occur assmall crystals in the intercumulus material. The cumulus perovskitevaries in size and may be optically zoned (Fig. 3a). Phlogopite occursas subhedral, often slightly deformed lamellae whose borders appearto be locally recrystallized. The magnetite is intercumulus, anhedraland may contain ilmenite exsolution lamellae. The apatite is anhedraland interstitial.

The presence of perovskite and the lack of Ca Ti silicates in the B1bebedourites indicate a strong degree of silica undersaturation in the

d ty

n

titaes

)

60 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672Table 1Intrusive units, rock-types, and modal composition ranges (averages in brackets and bolcalculated using the average modes and chemical composition of minerals.

B1 intrusion B2 intrusio

Unit B1a B1b B2a

Rock type Olivine-bearingbebedourites

Perovskite bebedourites(olivine-free)

Perovskitebebedourit

Samples 6 16 7

Modal percentages (average in parenthesis)Olivine 352 (33)Perovskite 733 (21) 225 (12) 114 (7)Phlogopite 1046 (24) 342 (20) 650 (32)Diopside 017 (9) 1867 (48) 2255 (36Magnetite 1014 (12) 019 (9) 110 (6)Apatite 02 (1) 034 (11) 57.5 (7)Titanite 02 (1) 711 (8)Melanite 010 (3)Calcite 03 (1) 02 (1)

Calculated average composition (wt.%)SiO2 23.93 30.80 32.62TiO2 14.36 8.59 9.55Al2O3 2.30 2.19 3.20Fe2O3 22.19 17.54 17.63MnO 0.21 0.13 0.24MgO 20.02 10.40 9.56CaO 12.34 22.29 19.78BaO 0.10 0.04 0.02SrO 0.10 0.17 0.12Na2O 0.11 0.21 0.20K2O 1.93 1.62 2.66P2O5 0.37 4.15 2.76LOI 1.11 0.86 1.57Total 99.06 98.97 99.92pe) from the Salitre bebedourites. Also shown are average major-element compositions

B2b B2c

nitemelanite Melanite bebedourites Titanite bebedourites;titanitemelanite bebedourites

18 15

1568 (35) 2376 (40)737 (20) 845 (27)

118 (7)228 (9) 515 (9)

236 (11)762 (34) 013 (6)06 (2)

33.20 33.016.38 5.833.64 3.3915.54 23.220.26 0.308.46 8.5523.17 16.190.07 0.030.09 0.100.18 0.452.96 3.313.49 3.592.09 1.5599.53 99.52

Fig. 3. Petrographic features of Salitre bebedourites. (a) Optically zoned euhedral perovskite crystals in a particularly perovskite-rich bebedourite. (b) Perovskite surrounded by atitanite rim, which is in turn enclosed in anhedral interstitial Ti-garnet, suggesting a change of the CaTi phase as silica activity increases (perovskitetitaniteTi-garnet bebedourite).(c) Perovskite from a perovskitetitaniteTi-garnet bebedourite shielded in a diopside grain. (d) Perovskite inclusion in phlogopite; note that the perovskite is coated in titanite but not inTi-garnet. (e) Poikilitic Ti-garnet crystals in Ti-garnet bebedourite. (f) Titanite bebedourite showing ow-oriented texture. (g) TitaniteTi-garnet bebedourite showing small titanite relicswithin large Ti-garnet crystals. (h) Interstitial (atoll-like) Ti-garnet. ap = apatite; di = diopside; phl = phlogopite; pv = perovskite; grt = Ti-garnet; ttn = titanite.

61E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672

magmas from which they crystallized. Orange red phlogopite locallyoccurs as rims on magnetite.

The B2 intrusion is petrographically subdivided in three groups(B2a, B2b, B2c) on the basis of the dominant Ca Ti mineral. The B2agroup comprises rocks containing perovskite+titanite+Ti garnetas Ca Ti phases. These are relatively rare medium grained rocksthat are generally brown in color with green patches of diopside.Two distinct generations of pyroxene and phlogopite are present:one consists of larger, subhedral phenocrysts, and the other of small,anhedral groundmass crystals. Perovskite is anhedral, not opticallyzoned, often surrounded by a titanite rim, which may in turn be coatedin Ti garnet (Fig. 3b). This textural feature indicates destabilizationof the initially formed Ca Ti phases progressively replaced by moresilica rich equivalents. The replacement or overgrowth of titanite byTi garnet is accompanied by an increase in iron and a concomitant decrease in titanium in the latter (see Tables 6 and 7), but not necessarilyin silica. This may indicate a two step replacement, initially by SiO2 increase (perovskite to titanite or Ti garnet) and then by Fe2O3 increase(titanite to Ti garnet). Alternatively, the contrast in iron content in thetitanite and Ti garnet may be due to crystal chemistry constraints.

Well preserved perovskite crystals are found only as shielded inclusions in pyroxene phenocrysts (Fig. 3c), whereas perovskite included inphlogopite phenocrysts is coated by titanite, but not Ti garnet (Fig. 3d).Similarly, the titanite inclusions in phlogopite phenocrysts are not coatedwith Ti garnet, but the individual titanite crystals from the groundmassare. These features suggest that the transformation of perovskite intoor the overgrowth of perovskite by Ca Ti silicates is a product of a

occurring as large, interstitial anhedral grains, often poikilitic, with irregular shapes and borders. Titanite may be present in subordinateamounts and is always coated in Ti garnet, indicating a preference inthe crystallization of the garnet due to higher silica activity. Carbonateoccurs as small interstitial grains.

The B2c group corresponds to the most evolved members of thebebedourite series in Salitre. These rocks are perovskite free and containeither titanite or titanite+Ti garnet as Ca Ti phases. Titanite only B2cbebedourites (Fig. 3f) are relatively rare in the complex, occurringmainlyas thin, ne grained dikes with a dark green to black color. Flow textureis locally well marked by the orientation of subhedral phlogopite anddiopside. Subhedral titanite and anhedral apatite and magnetite arealso oriented by ow.

B2c bebedourites containing both titanite and Ti garnet are neto medium grained and greenish brown in color. Titanite is subhedralor anhedral, with the latter usually surrounded by a rim of anhedralTi garnet (Fig. 3g). The garnet is often interstitial and poikilitic, resembling an atoll texture (Fig. 3h). Some individual Ti garnet crystals mayoccur in isolation, but it is not clear whether they crystallized directlyor are the result of a complete replacement of the previous titanite.Very rarely, a texture similar to that observed in B2a occurs, wheresmall perovskite relicts are surrounded by titanite, which is in turn coated by Ti garnet.

4. Mineral compositions

Thirteen of the studied samples were selected for mineral chemical

1a

nB

0.14.05.d.4.52.554.42.16.d..119.95.007.001

.305

.012

.661

.004

.002

.992

.845

.155

pyr

62 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672middle to late stage increase in silica activity and that the order of overlapping crystallization of the relevant phases is perovskite diopsidetitanite phlogopite Ti garnet. Aside from coating perovskite, the mostcommon titanite occurrence is as subhedral to anhedral individualcrystals. Most Ti garnet crystals form coatings on titanite, althoughthe garnet may rarely occur as isolated grains in the groundmass.

The B2b bebedourites are characterized by the dominance of Tigarnet as the Ca Ti phase, are medium to coarse grained and varyin color from green when diopside rich to brown when Ti garnet rich.Among the Salitre bebedourites, this is the only type that contains signicant carbonate. Ti garnet (Fig. 3e) is a relatively late stage phase,

Table 2Representative olivine compositions from Salitre B1a bebedourites.

Unit B1a B1a B1a B1a B

Analysis 1 2 3 4 5

UnB UnB UnB UnB U

SiO2 40.00 40.15 39.88 40.19 4TiO2 n.d. 0.07 0.07 0.03 0Al2O3 0.05 0.03 0.03 0.07 nFeO 12.29 13.22 13.50 13.91 1MnO 0.37 0.47 0.51 0.43 0MgO 46.62 46.19 45.00 44.61 4CaO 0.20 0.14 0.24 0.04 0K2O n.d. n.d. 0.02 n.d. nNiO 0.07 0.03 0.17 0.26 0Total 99.61 100.28 99.44 99.53 9Si 0.997 0.998 1.002 1.009 1Ti 0.001 0.001 0.001 0Al 0.002 0.001 0.001 0.002 Fe2 0.256 0.275 0.284 0.292 0Mn 0.008 0.010 0.011 0.009 0Mg 1.733 1.712 1.686 1.670 1Ca 0.005 0.004 0.007 0.001 0K 0.001 Ni 0.001 0.001 0.004 0.005 0Cations 3.002 3.000 2.996 2.989 2Fo 0.871 0.862 0.856 0.851 0Fa 0.129 0.138 0.144 0.149 0

Analyses 1 to 5 are from olivine-rich bebedourites, analyses 6 to 10 are from olivine- and

4 oxygen. n.d. = not detected. UnB = analyses at the University of Braslia, USP = analyseanalyses. The main mineral phases present in the Salitre bebedouriteswere analyzed by WDS using a CAMECA SX 50 electron microprobe atthe University of Braslia and a JEOL JXA 8600 electron microprobe atthe University of So Paulo (olivine, clinopyroxene, phlogopite, andmagnetite). All analyses were performed at 15 kV and 20 nA.

4.1. Olivine

Olivine is a relatively rare constituent in the area of Salitre I studiedhere (Fig. 2, Table 2), although it may reach 50 vol.% in exceptionalcases. However, olivine is abundant in the Salitre II body (e.g.,

B1a B1a B1a B1a B1a

6 7 8 9 10

USP USP USP USP USP

39.65 39.09 39.30 38.93 39.28n.d. n.d. n.d. 0.07 n.d.0.02 n.d. 0.01 n.d. n.d.12.86 13.50 13.75 13.96 14.250.36 0.39 0.39 0.35 0.3546.76 46.20 46.23 46.62 45.930.33 0.17 0.22 0.17 0.250.01 n.d. 0.01 0.01 0.030.20 0.21 0.17 0.21 0.24100.23 99.56 100.08 100.32 100.340.987 0.983 0.984 0.974 0.984 0.001 0.001 0.000 0.268 0.284 0.288 0.292 0.2980.008 0.008 0.008 0.007 0.0071.735 1.732 1.726 1.740 1.7150.009 0.005 0.006 0.005 0.0070.000 0.000 0.000 0.0010.004 0.004 0.003 0.004 0.0053.013 3.017 3.016 3.024 3.0170.866 0.859 0.857 0.856 0.8520.134 0.141 0.143 0.144 0.148

oxene-rich (wehrlitic) bebedourites. Cations per formula unit calculated on the basis of

s at the University of So Paulo.

Morbidelli et al., 1997) and in other Salitre rock types, such as phoscorites and carbonatites (our unpublished data).

Fig. 4 illustrates the ranges and averages of the forsterite (Fo,mol%) content in olivine from various cumulates and ne graineddikes in the APIP complexes. The forsterite content in the olivinesfrom the B1a bebedourites ranges from 83 to 87 mol%, consistent withthose from the Salitre II (Fo82-87, Morbidelli et al., 1997) and Tapira(Brod, 1999) bebedourites. Zoning is common, mostly with Mg decreasing toward the rims, but is sometimes oscillatory. The forsterite content

bebedourites accumulated is more evolved than the typical phlogopitepicrite, although still ultramac in composition. It is possible that thismagma represents the evolution of a phlogopite picrite liquid, aftersome degree of fractionation of dunitic cumulates (e.g., Catalo Icumulates, Fig. 4). The olivine in the APIP kamafugites spans a muchwider range (Fo90-73, Melluso et al., 2008), and fractionation from sucha magma could also have produced our observed Fo range. Smallamounts of MnO (0.27 0.55 wt.%), CaO (up to 0.36 wt.%), and NiO (upto 0.26 wt.%) may be present.

4.2. Pyroxene

With the exception of one olivine and perovskite rich sample,pyroxene is present in all studied bebedourites. Representative compositions are given in Table 3. Fig. 5 shows the compositional variationsin the aegirine diopside hedenbergite system. Apart from the olivinerich (B1a) rocks, pyroxenes from all analyzed rock types span relativelywide compositional ranges, resulting in overlapping elds. The pyroxene composition from the Salitre I and II bebedourites (Morbidelli etal., 1997) is similar to B1a. Fig. 5 also shows a comparison of our resultswith clinopyroxene from Tapira (Brod, 1999), other alkaline complexesand provinces (Mitchell and Vladykin, 1996; Sgarbi et al., 2000), andworldwide carbonatites (Reguir et al., 2012). The Salitre pyroxenes donot show the extreme hedenbergite enrichment of some sodic complexes, such as Ilimaussaq, but they also do not t the Hd poor trendof the ultrapotassic complex of Little Murun. The moderate Hd enrichment observed in Salitre is similar to that in Tapira, in Uganda andMata da Corda kamafugites, and in worldwide carbonatites.

4.3. Phlogopite

Fig. 4. Ranges and averages of olivines in cumulate rocks from Catalo I (Arajo, 1996),Salitre II (Morbidelli et al., 1997), Tapira (Brod, 1999), and Salitre I (this work). Composi-tion of olivine phenocrysts in phlogopitepicrite ne-grained dikes from Tapira (Brod,1999) and Catalo II (Melo, 1999) is also plotted for comparison.

B2b

Core

USP

53.60.18

63E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672is slightly lower than that of olivine in primitive phlogopite picritesfrom Tapira (Fo84-90, Brod, 1999) and Catalo II (Fo83.5-89.5, Melo,1999), suggesting that the magma from which the Salitre and Tapira

Table 3Representative compositions of pyroxene from Salitre bebedourites.

Unit B1a B1a B1b B1b B2a B2a B2a B2a

Core/rim Core Rim Core Rim Core Rim Core Rim

Analysis USP USP UnB UnB UnB UnB UnB UnB

SiO2 53.35 52.67 52.67 52.76 52.06 52.14 54.03 53.01TiO2 0.64 1.00 0.90 0.85 1.30 1.30 0.37 0.28

Al2O3 0.50 0.76 0.62 0.61 0.98 0.74 0.02 0.24 0.21Cr2O3 0.04 0.04 0.01 0.04 0.01 n.d. n.d. 0.04 n.d.Fe2O3 2.99 3.19 3.61 1.41 3.51 3.91 2.70 2.31 2.73FeO 0.23 0.33 1.23 3.35 0.72 0.26 1.03 5.59 0.52MnO 0.04 0.08 0.05 0.11 0.08 0.07 0.14 0.23 0.18MgO 16.76 16.32 15.42 14.77 15.98 15.81 16.29 13.40 16.7CaO 25.85 25.91 24.86 24.75 25.52 25.21 25.49 24.09 25.7Na2O 0.23 0.24 0.68 0.50 0.30 0.58 0.44 0.64 0.14K2O n.d 0.02 n.d. n.d. 0.02 0.01 n.d. 0.03 0.01Total 100.63 100.56 100.05 99.15 100.48 100.03 100.51 99.86 100Si 1.939 1.921 1.936 1.961 1.905 1.915 1.968 1.978 1.95Ti 0.017 0.027 0.025 0.024 0.036 0.036 0.010 0.008 0.00Al 0.021 0.033 0.027 0.027 0.042 0.032 0.001 0.011 0.00Cr 0.001 0.001 0.000 0.001 0.000 0.001 Fe3 0.081 0.087 0.100 0.040 0.096 0.108 0.074 0.065 0.07Fe2 0.008 0.010 0.038 0.104 0.022 0.008 0.031 0.174 0.01Mn 0.001 0.002 0.002 0.003 0.002 0.002 0.004 0.007 0.00Mg 0.908 0.887 0.845 0.818 0.872 0.865 0.885 0.745 0.91Ca 1.007 1.012 0.979 0.986 1.001 0.992 0.995 0.963 1.00Na 0.016 0.017 0.048 0.036 0.021 0.041 0.031 0.046 0.01K 0.001 0.001 0.000 0.001 0.00Cations 3.999 3.998 4.000 4.000 3.998 3.999 3.999 3.999 4.00Wo 50.206 50.627 49.871 50.519 50.194 50.210 50.015 49.263 49.9En 45.291 44.369 43.041 41.947 43.732 43.812 44.473 38.128 45.2Fs 4.503 5.004 7.088 7.534 6.074 5.978 5.512 12.609 4.78

Cations per formula unit on the basis of 6 oxygen. Fe3+/Fe2+ ratio estimated by charge balanthe University of So Paulo.Together with clinopyroxene, phlogopite covers the most extensiverange of petrographic compositions in the Salitre bebedourites, andit is also a common mineral in Salitre phoscorites and carbonatites.

B2b B2b B2b B2c B2c B2c B2c B2c B2c

Rim Core Rim

USP UnB UnB USP USP UnB UnB UnB UnB

3 52.99 53.59 53.87 51.32 51.19 52.90 52.03 51.64 53.200.11 0.17 0.18 0.26 0.08 0.23 0.27 0.15 0.250.24 0.40 0.42 0.36 0.16 0.28 0.31 0.23 0.370.01 0.02 0.03 n.d. 0.02 n.d. 0.03 0.01 0.043.47 3.20 0.91 4.29 6.84 2.49 5.94 9.44 1.071.23 6.79 7.93 5.48 5.94 8.75 6.12 5.37 10.440.18 0.30 0.30 0.30 0.25 0.25 0.24 0.32 0.41

8 15.87 11.96 12.85 12.07 10.30 11.24 10.74 9.63 10.816 25.53 22.02 22.79 22.49 20.62 22.54 22.36 19.64 21.51

0.23 1.63 0.92 1.18 2.22 1.20 1.78 2.98 1.29n.d. 0.01 n.d. 0.01 n.d. n.d. 0.02 0.01 0.05

.14 99.86 100.09 100.20 97.76 97.62 99.88 99.84 99.42 99.448 1.952 2.001 2.005 1.966 1.978 1.996 1.966 1.966 2.0185 0.003 0.005 0.005 0.007 0.002 0.007 0.008 0.004 0.0079 0.010 0.018 0.018 0.016 0.007 0.012 0.014 0.010 0.017

0.000 0.001 0.001 0.001 0.001 0.000 0.0015 0.096 0.089 0.026 0.125 0.198 0.071 0.168 0.270 0.0306 0.037 0.213 0.246 0.175 0.192 0.276 0.193 0.171 0.3326 0.006 0.009 0.009 0.010 0.008 0.008 0.008 0.010 0.0133 0.871 0.666 0.713 0.689 0.593 0.632 0.605 0.546 0.6118 1.007 0.881 0.909 0.923 0.854 0.911 0.905 0.801 0.8740 0.016 0.118 0.066 0.088 0.166 0.088 0.130 0.220 0.0950 0.000 0.000 0.001 0.000 0.0020 3.998 4.001 3.998 3.999 3.999 4.001 3.999 3.998 4.00046 49.913 47.413 47.743 48.036 46.240 48.005 48.150 44.528 46.99168 43.171 35.831 37.456 35.870 32.138 33.308 32.180 30.379 32.8596 6.916 16.757 14.801 16.094 21.623 18.688 19.670 25.093 20.150

ce. n.d. = not detected. UnB = analyses at the University of Braslia, USP = analyses at

Representative compositions are given in Table 4. The Fe2+/Fe3+

and structural formulae were calculated according to Brod et al.(2001).

The analyzed mica belongs to the phlogopite annite series, with aslight Fe3+ enrichment. The BaO content reaches up to 0.79 wt.%, andTiO2 reaches up to 3.4 wt.%. A wider Ti variation was reported by

Morbidelli et al. (1997) in phlogopites from the Salitre II cumulates(up to 5.92 wt.% TiO2). Fig. 6 shows that the phlogopite from eachrock type plots within a relatively restricted compositional range, although there is some overlap. The range is comparable to that ofphlogopites in the Tapira bebedourites (Brod et al., 2001), but it extends to lower magnesium contents.

Fig. 5. Aegirinediopsidehedenbergite diagram showing (left) the composition of Salitre bebedourite pyroxenes and (right) a comparison with trends from other complexes andprovinces.

Table 4Representative phlogopite compositions from Salitre bebedourites.

Unit B1a B1a B1b B1b B1b B1b B2a B2a B2a B2b B2b B2b B2b B2c B2c B2c B2c B2c

nB

7.64.530.63.235.05

64 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672Core/rim Core Rim Core Rim Core Rim Core Rim

Analysis USP USP UnB UnB UnB UnB UnB UnB U

SiO2 38.96 39.02 38.61 38.99 38.85 38.92 36.94 37.89 3TiO2 2.21 1.50 3.08 2.78 2.34 2.61 3.15 2.63 2Al2O3 12.68 12.12 12.07 11.33 12.19 12.02 11.80 10.74 1Fe2O3 1.55 2.2 2.17 2.41 2.05 2.12 2.76 2.57 3FeO 3.94 3.75 11.15 11.01 9.81 11.11 15.61 16.02 1

MnO 0.01 0.04 0.22 0.27 0.24 0.34 0.35 0.37 0.30MgO 23.91 24.75 18.90 18.94 20.38 19.23 15.60 15.20 16.02CaO 0.01 n.d. n.d. 0.01 0.03 0.04 n.d. 0.01 n.d.BaO 0.71 0.67 0.07 n.d. 0.08 0.26 0.11 0.06 0.12Na2O 0.18 0.20 n.d. n.d. 0.25 0.28 n.d. n.d. n.d.K2O 10.40 10.08 10.20 10.08 10.11 9.99 10.00 9.99 10.14H2O 3.94 3.91 4.06 4.03 4.08 4.08 3.94 3.91 3.91F 0.38 0.43 n.a. n.a. n.a. n.a. n.a. n.a. n.a.Cl 0.02 0.01 0.02 0.03 0.01 0.01 0.01 n.d. n.d.Total 98.90 98.68 100.55 99.88 100.42 101.01 100.27 99.39 99.57O_F 0.160 0.180 O_Cl 0.005 0.001 0.005 0.006 0.003 0.003 0.002 Si 5.660 5.680 5.670 5.760 5.680 5.690 5.580 5.780 5.720Ti 0.240 0.160 0.340 0.310 0.260 0.290 0.360 0.300 0.290Al 2.170 2.080 2.090 1.970 2.100 2.070 2.100 1.930 1.910Fe3 0.170 0.240 0.240 0.270 0.220 0.230 0.310 0.290 0.370Fe2 0.480 0.460 1.370 1.360 1.200 1.360 1.970 2.040 1.910Mn 0.000 0.000 0.030 0.030 0.030 0.040 0.040 0.050 0.040Mg 5.180 5.370 4.140 4.170 4.440 4.190 3.520 3.450 3.630Ca 0.002 0.002 0.005 0.006 0.001 Ba 0.041 0.038 0.004 0.005 0.015 0.007 0.004 0.007Na 0.050 0.060 0.070 0.080 K 1.930 1.870 1.910 1.900 1.880 1.860 1.930 1.940 1.970Cations 15.923 15.958 15.794 15.772 15.890 15.831 15.817 15.785 15.84OH 3.820 3.800 3.970 3.970 3.980 3.980 3.970 3.980 3.970F 0.170 0.200 Cl 0.000 0.000 0.000 0.010 0.000 0.000 0.000

Cations per formula unit calculated on the basis of 24 O (OH,F,Cl).@n.d. = not detected, n.University of So Paulo.Core Rim Core Rim

UnB USP USP UnB USP USP UnB UnB UnB

39.42 37.08 36.98 38.95 36.08 35.48 37.98 38.23 37.131.52 1.83 1.70 1.85 1.75 2.14 1.83 2.00 2.6910.07 12.15 10.16 11.48 8.32 8.66 9.90 10.14 9.843.30 1.5 4.33 1.69 5.7 5.84 3.33 3.26 3.91111.56 15.01 13.21 12.72 19.11 18.54 15.76 16.35 19.88

0.37 0.25 0.29 0.37 0.35 0.33 0.52 0.55 0.4919.25 16.66 17.72 18.52 13.10 13.09 15.72 15.61 12.510.02 0.07 n.d. 0.02 0.06 0.04 n.d. n.d. n.d.0.11 0.79 0.29 0.10 0.08 0.20 0.12 n.d. n.d.0.17 0.06 0.06 0.12 0.03 0.04 n.d. n.d. 0.0910.05 9.90 10.00 9.80 9.65 9.80 10.13 9.99 9.914.00 3.83 3.88 4.01 3.64 3.61 3.87 3.91 3.83n.a. 0.23 0.05 n.a. 0.22 0.27 n.a. n.a. n.a.0.01 n.d. n.d. 0.03 0.02 0.01 0.02 0.02 0.0299.83 99.36 98.67 99.66 98.11 98.05 99.18 100.06 100.29 0.100 0.020 0.090 0.110 0.002 0.006 0.004 0.003 0.004 0.004 0.0045.866 5.650 5.670 5.796 5.750 5.670 5.830 5.810 5.7490.170 0.210 0.200 0.207 0.210 0.260 0.210 0.230 0.3131.765 2.180 1.830 2.014 1.560 1.630 1.790 1.820 1.7950.369 0.170 0.500 0.189 0.680 0.700 0.380 0.370 0.4561.438 1.910 1.690 1.583 2.550 2.480 2.020 2.080 2.5750.046 0.030 0.040 0.047 0.050 0.040 0.070 0.070 0.0644.271 3.780 4.050 4.110 3.110 3.120 3.590 3.540 2.8880.004 0.011 0.003 0.010 0.007 0.006 0.047 0.017 0.006 0.005 0.013 0.007 0.048 0.020 0.020 0.036 0.010 0.010 0.0271.908 1.920 1.960 1.861 1.960 2.000 1.980 1.940 1.958

7 15.891 15.928 15.977 15.851 15.895 15.930 15.877 15.860 15.824 3.890 3.970 3.870 3.850 3.960 3.960 0.110 0.020 0.110 0.140 0.000 0.000 0.000 0.000 0.000 0.000

a. = not analyzed. UnB = analyses at the University of Braslia, USP = analyses at the

The phlogopite compositions reported by Morbidelli et al. (1997)for Salitre I and II olivine rich cumulates agree well with the observedtrend, with some deviations toward Al depletion, evenmore pronouncedin the Salitre I carbonatites. Similar relationships were observed for theCatalo I and Tapira complexes (Brod et al., 2001). The phlogopitetetra ferriphlogopite solid solution is a common primary (magmatic)feature of carbonatites (e.g., Brod et al., 2001) and carbonatite phoscoriteassociations (e.g., Lee et al., 2003), but its occurrence in the accompanyingsilicate rocks may be the result of different causes, such as carbonatiticmetasomatism or the reaction of early formed aluminous phlogopiteswith a carbonated residual magma.

4.4. Perovskite

Perovskite is a common phase in the APIP complexes. In Salitre, itoccurs in the B1a and B1b bebedourites and, rarely, in B2a. Representative compositions are shown in Table 5.

The Salitre perovskites have a limited composition range near thesensu stricto perovskite composition (CaTiO3 molecule ranging from91 to 98%). Some REE substitution occurs, with the loparite moleculeranging from 1 to 8%. Lueshite is up to 1.5 mol%; tausonite is lowerthan 1 mol% and shows very little variation. These values are comparable to the perovskite in the Salitre I and II perovskitites, dunites, and pyroxenites (Morbidelli et al., 1997), the perovskites in bebedourites fromthe Tapira complex (Brod, 1999), and other ultrapotassic rocks such askimberlites and kamafugites (Mitchell, 2002, and references therein).

Fig. 6. Composition of phlogopites from the Salitre bebedourites in the MgAlFe system.Mica composition fromMorbidelli et al. (1997) for cumulates from both Salitre I and II in-trusions and from Salitre I carbonatites plotted for comparison (dotted outlines). Symbolsas in Fig. 5.

Table 5Representative compositions of perovskite from Salitre bebedourites.

Unit B1a B1a B1a B1b B1b B1b B2a B2a B2a

core/rim rim core rim rim core rim rim core rim

Analysis UnB UnB UnB UnB UnB UnB UnB UnB UnB

Nb2O5 0.33 0.24 0.37 1.22 1.15 1.15 0.50 0.64 0.47Ta2O5 n.d. 0.02 0.03 n.d. 0.06 0.03 n.d. n.d. 0.09SiO2 0.01 0.01 0.02 n.d. n.d. n.d. 0.02 n.d. 0.01TiO2 56.14 54.34 56.40 54.57 54.45 54.53 55.50 55.73 56.28ThO2 0.07 0.28 0.05 0.02ZrO2 0.03 0.07 0.12 0.51Al2O3 0.07 0.16 0.08 0.09La2O3 0.47 1.07 0.44 0.92Ce2O3 1.09 2.85 0.89 1.70Nd2O3 0.51 1.39 0.29 0.60Y2O3 0.01 0.03 0.04 0.04FeO 0.88 1.37 0.68 1.20MnO n.d. n.d. 0.01 0.03MgO 0.01 n.d. n.d. n.d.CaO 39.86 37.28 39.83 37.75SrO 0.39 0.37 0.46 0.58Na2O n.d. 0.45 0.05 0.37Total 99.86 99.94 99.73 99.60Nb 0.0034 0.0026 0.0039 0.0129Ta 0.0001 0.0002 Si 0.0003 0.0003 0.0004 Ti 0.9756 0.9639 0.9785 0.9612Th 0.0003 0.0015 0.0003 0.0001Zr 0.0003 0.0008 0.0013 0.0059Al 0.0020 0.0045 0.0022 0.0026La 0.0040 0.0093 0.0037 0.0079Ce 0.0092 0.0246 0.0075 0.0146Nd 0.0042 0.0117 0.0024 0.0050Y 0.0001 0.0003 0.0004 0.0005Fe2 0.0170 0.0270 0.0130 0.0230Mn 0.0001 0.0007Mg 0.0004 Ca 0.9866 0.9419 0.9843 0.9472Sr 0.0052 0.0051 0.0062 0.0079Na 0.0207 0.0021 0.0167Cations 2.0086 2.0143 2.0065 2.0062

UnB = analyses at the University of Braslia.

65E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672n.d. 0.02 0.03 0.02 0.050.35 0.32 0.03 0.13 0.060.10 0.07 0.07 0.05 0.090.93 0.95 0.61 0.63 0.551.79 1.77 1.01 0.94 1.170.60 0.70 0.44 0.18 0.510.06 0.08 0.06 0.07 0.051.11 1.10 0.94 0.86 0.890.01 n.d. 0.01 0.02 0.030.03 0.01 0.03 0.00 n.d.37.83 38.00 39.10 39.55 39.460.52 0.45 0.37 0.58 0.400.49 0.47 0.17 0.23 0.2299.48 99.64 98.88 99.62 100.280.0121 0.0122 0.0053 0.0067 0.00480.0004 0.0002 0.0005 0.0004 0.00020.9605 0.9606 0.9744 0.9713 0.9752 0.0001 0.0002 0.0001 0.00030.0040 0.0037 0.0003 0.0014 0.00060.0027 0.0019 0.0019 0.0013 0.00230.0080 0.0082 0.0052 0.0054 0.00460.0153 0.0152 0.0086 0.0079 0.00980.0050 0.0059 0.0037 0.0014 0.00420.0007 0.0010 0.0008 0.0009 0.00060.0220 0.0220 0.0180 0.0170 0.01700.0002 0.0001 0.0005 0.00050.0010 0.0005 0.0011 0.0001 0.9506 0.9535 0.9778 0.9820 0.97380.0071 0.0061 0.0051 0.0078 0.00530.0224 0.0211 0.0075 0.0105 0.01002.0120 2.0122 2.0104 2.0143 2.0097

4.5. Ti garnet

Table 6 shows representative compositions of garnet from theSalitre bebedourites. These garnets are typically rich in CaO (3133 wt.%) and TiO2 (4.5 18 wt.%) and poor in Al2O3 (0.1 1.3 wt.%),Cr2O3 (b0.25 wt.%), and MnO (b0.4 wt.%). In most earlier works,similar garnets were documented as belonging to the andraditemelanite schorlomite series. Table 6 shows the endmembers calculated according to Locock (2008). Andradite, morimotoite, schorlomite,and morimotoite Mg, in decreasing order, account for 95%, on average,of the calculated structural formulae. The Salitre garnetsmay contain upto 2% ZrO2, resulting in up to 4.14 mol% of kimzeyite+kimzeyite Fe.The REE+Y (up to 0.35 wt.% La2O3+Ce2O3+Y2O3) are minor constituents. Fig. 7 shows the compositional variation of Salitre bebedouritegarnets in terms of the andradite, morimotoite, and schorlomiteendmembers compared with garnet from other Brazilian alkalinecomplexes.

Ti rich andradite type garnets are a common mineral in alkalinerocks (e.g., Dingwell and Brearley, 1985; Huggins et al., 1977; Keepand Russell, 1992; Vuorinen et al., 2005) and have also been reportedin bebedourites from the Tapira complex (Brod et al., 2003). This typeof garnet has been variably interpreted as primary or metasomatic(Flohr and Ross, 1990; Ulrych et al., 1994). Zr and Ti rich garnetsare considered indicative of magmatism of carbonatitic afnity (Plattand Mitchell, 1979).

4.6. Titanite

Titanite is present in bebedourites as an accessory mineral. It mayoccur as individual crystals and as overgrowth rims on perovskiteand/or overgrown by Ti garnet rims. Representative compositions arepresented in Table 7. Among the analyzed elements, the main tracesare REE (La, Ce, Nd, plus Y, with total REE2O3 up to 0.8 wt.%) and Fe2O3(up to 2.6 wt.%), which is similar to the titanite in the bebedouritesfrom the Tapira complex (our unpublished data).

4.7. Summary of mineral composition evolution

Most of the analyzed minerals show composition trends consistentwith a magmatic evolution in the direction B1a B1b B2a B2b B2c. Asummary of relevant chemical evolution trends is given in Table 8. Relevant characteristics of apatite and magnetite (our unpublished data)are included for comparison.

Both clinopyroxene and phlogopite evolve mostly along a trend ofMg Fe substitution (diopside hedenbergite and phlogopite annite,respectively), although with wide overlap (Figs. 5 and 6), and theirMgO/(MgO+FeO) is highest in B1a and lowest in B2c. In the pyroxene, this evolution is accompanied by Na2O and Fe2O3 enrichmentat a relatively constant hedenbergite/aegirine ratio (Fig. 5). In phlogopite, there is a small increase in Fe2O3 and a corresponding decreasein Al2O3, suggesting minor tetra ferriphlogopite substitution, but the

Table 6Representative compositions of Ti-garnet from Salitre bebedourites.

Unit B2a B2a B2a B2b B2b B2b B2b B2c B2c B2c

Analysis UnB UnB UnB UnB UnB UnB UnB UnB UnB UnB

SiO2 28.18 28.96 29.47 26.12 28.31 28.29 29.35 29.87 30.51 33.32TiO2 15.11 13.32 12.96 17.31 14.28 13.11 12.08 11.76 9.58 5.64ZrO2 0.82 1.63 0.99 0.81 0.91 0.80 0.50 0.99 1.36 0.37Al2O3 0.40 0.33 0.42 0.72 0.59 1.08 0.74 0.27 0.38 0.19Cr2O3 0.04 0.03 0.03 0.01 0.02 0.04 n.d. 0.02 n.d. n.d.La2O3 0.09 0.05 n.d. 0.08 0.10 0.03 0.04 n.d. n.d. 0.10Ce2O3 0.09 0.01 0.07 0.05 0.06 0.10 0.25 0.11 0.06 n.d.Y2O3 n.d. 0.10 0.02 0.07 0.11 0.02 0.05 0.09 0.14 0.14Fe O 17.35 18.15 18.39 16.68 18.30 19.98 19.98 20.39 21.17 24.69

66 E.S.R. Barbosa et al. / Lithos 144145 (2012) 56722 3

FeO 4.66 4.64 4.37 4.26MnO 0.34 0.28 0.27 0.24MgO 0.83 0.83 0.83 1.05CaO 32.22 32.14 32.27 31.92NiO 0.01 0.01 0.08 0.08Total 100.12 100.48 100.17 99.38REE2O3(*) 0.17 0.16 0.09 0.20Si 2.4120 2.4732 2.5141 2.2590Ti 0.9734 0.8559 0.8318 1.1258Zr 0.0343 0.0680 0.0413 0.0339Al 0.0405 0.0329 0.0422 0.0735Cr 0.0024 0.0020 0.0020 0.0004REE3+(*) 0.0000 0.0045 0.0009 0.0033Fe3 1.1178 1.1663 1.1806 1.0853Fe2 0.3338 0.3312 0.3120 0.3081Mn 0.0243 0.0202 0.0195 0.0178Mg 0.1059 0.1053 0.1056 0.1356Ca 2.9557 2.9404 2.9501 2.9572Ni 0.0000 0.0000 0.0100 0.0100Cations 8.0000 8.0000 8.0100 8.0100End-members (%)Andradite 27.04 31.86 35.23 19.63Morimotoite 33.38 33.12 31.20 30.81Schorlomite 27.38 22.94 22.18 33.38Morimotoite-Mg 8.59 6.59 7.51 11.07Schorlomite-Al 0.31 0.05 1.98Kimzeyite 1.71 1.65 2.06 1.70Kimzeyite-Fe 1.76Calderite 0.81 0.67 0.65 0.59Khoharite 0.67 1.09 0.97 0.67Cations per formula unit calculated on the basis of 12 O, following the method of Locock (23.79 2.44 2.82 3.78 3.45 2.460.31 0.29 0.27 0.41 0.34 0.310.90 0.90 0.95 0.76 0.70 0.2932.40 32.58 32.37 32.26 31.89 32.66n.d. 0.05 0.01 0.02 0.01 n.d.100.08 99.72 99.40 100.72 99.60 100.170.27 0.16 0.35 0.20 0.20 0.242.4214 2.4224 2.5167 2.5388 2.6185 2.82470.9188 0.8443 0.7794 0.7519 0.6186 0.35970.0378 0.0333 0.0210 0.0409 0.0570 0.01540.0598 0.1091 0.0743 0.0273 0.0380 0.01900.0010 0.0025 0.0014 0.0052 0.0010 0.0023 0.0041 0.0065 0.00631.1780 1.2875 1.2893 1.3039 1.3673 1.57520.2710 0.1748 0.2025 0.2685 0.2473 0.17410.0225 0.0212 0.0197 0.0295 0.0246 0.02200.1150 0.1147 0.1208 0.0962 0.0897 0.03652.9694 2.9892 2.9740 2.9374 2.9324 2.9671 0.0000 0.0000 0.0000 0.0000 8.0000 8.0000 8.0000 8.0000 8.0000 8.0000

32.20 40.95 43.26 41.62 49.26 70.1627.10 17.48 20.25 26.85 24.73 17.4125.94 23.43 20.45 21.02 16.23 7.8210.70 11.47 11.45 6.31 4.68 2.571.10 3.79 2.66 0.181.89 1.67 1.05 1.37 1.90 0.77

0.68 0.950.75 0.66 0.98 0.82 0.730.01 0.09 0.90 1.10 0.05008). n.d. = not detected. UnB = analyses at the University of Braslia.

compositions do not depart signicantly from the phlogopite anniteseries (Fig. 6). Ti in both minerals initially increases, peaking at B2a,and then decreases toward B2c. The early TiO2 increase is probablyrelated to the progressively diminishing amount of co crystallizing

decrease and Fe2O3 increase, which is consistent with trends fromother Brazilian alkaline complexes. TiO2 and Cr2O3 are minor constituents in magnetite, but they peak at B1a and B2a, suggesting a highercrystallization temperature for these rocks.

Although SiO2 increases in whole rock from B1a to B2c (Tables 1and 8), this is not necessarily reected in the SiO2 content of individual silicate minerals, probably because of the crystal chemistry restrictions of Si substitution in the tetrahedral site. However, the SiO2increase in the magma does result in a progressively higher modalcontent of silicate minerals with evolution.

The main REE bearing minerals in bebedourites coexist in theB2a rocks, providing an opportunity to assess the REE partition between co crystallizing minerals. The average La2O3+Ce2O3 contentsfollow the order perovskite>apatite>titanite>melanite. In the otherbebedourite units, where only some of these minerals occur, thisorder is maintained. When present, perovskite is the main LREEbearing phase. In B2a, the LREE content in this mineral is 2.6 timesthat of apatite, 5.2 times that of titanite and 24 times that of Tigarnet. However, the partition coefcients are not constant, as theLa2O3+Ce2O3 content in the perovskite decreases in the sequenceB1a B1b B2a but increases in the apatite from B1 to B2, peaking atB2a (LREEperovskite/apatite varying from 12.1 to 2.6). When perovskitecrystallization ceases, apatite becomes the main LREE carrier amongthe analyzed minerals. The very low La2O3+Ce2O3 contents in the Tigarnetmay be at least partly explained by crystal chemistry constraints,as garnets tend to be naturally enriched in the heavier REE.

Overall, the mineral composition variations indicate that the evolution of the Salitre bebedourites begins with olivine and perovskitebearing rocks (B1a) followed by a second stage where olivine disappears (B1b). The Ti garnet rich bebedourites are interpreted as a

Fig. 7. Composition range of Ti-rich garnets from Salitre bebedourites in terms of theschorlomite (Schrlm), andradite (Andr) and morimotoite (Mrmt) endmembers (Locock,2008). Also shown are the evolution trends of garnet from other Brazilian alkaline com-plexes from Ruberti et al. (2012) and references therein.

67E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672perovskite. In the late stages, TiO2 decreases in the magnetite and garnet as well as in the diopside and phlogopite, suggesting a gradualtitaniumconsumption in the magma. The Ti garnet compositionsfrom B2a and B2b overlap, but the B2c garnets show a marked increase in the andradite molecule (Fig. 7), corresponding to a TiO2

Table 7Representative titanite compositions from Salitre bebedourites.Unit B2a B2a B2a B2c

Analysis UnB UnB UnB UnB

SiO2 30.47 30.64 30.78 30.02TiO2 37.72 34.95 37.45 37.66Al2O3 0.20 0.20 0.26 0.13La2O3 0.11 0.13 0.09 0.05Ce2O3 0.16 0.15 0.20 0.12Nd2O3 0.07 0.11 0.04 0.13Y2O3 0.06 0.00 0.02 n.d.Fe2O3 1.32 3.71 1.57 1.71MnO 0.02 0.03 n.d. n.d.MgO 0.02 0.09 0.02 0.02CaO 28.65 28.91 28.56 28.51Na2O n.d. 0.27 n.d. 0.06K2O 0.01 n.d. 0.01 n.d.Total 98.81 99.19 98.99 98.41Si 4.049 4.085 4.078 4.012Ti 3.770 3.505 3.732 3.786Al 0.031 0.031 0.041 0.020La 0.006 0.006 0.005 0.003Ce 0.008 0.008 0.010 0.006Nd 0.003 0.005 0.002 0.006Y 0.005 0.001 Fe3 0.132 0.372 0.156 0.172Mn 0.002 0.004 Mg 0.004 0.019 0.004 0.004Ca 4.079 4.130 4.054 4.083Na 0.069 0.016K 0.002 0.001 0.001 Cations 12.090 12.084 12.083 12.108

Cations per formula unit calculated on the basis of 20 oxygen. n.d. = not detected. UnB =separate batch of magma that intruded independently in the southernpart of the complex (see Fig. 2) and as dikes cutting B1. Our data indicate that this second magma batch evolved in the direction B2aB2b B2c, although with extensive composition overlap between B2aand B2b.

B2c B2c B2c B2c B2c

UnB UnB UnB UnB UnB

30.54 30.90 30.35 30.28 30.0136.74 38.65 38.63 37.86 37.820.25 0.03 0.12 0.12 0.130.05 0.06 0.10 0.10 0.120.02 0.21 0.34 0.23 0.280.04 0.02 0.12 0.12 0.12n.d. 0.05 0.09 n.d. n.d.1.49 1.23 1.36 1.37 1.36n.d. n.d. n.d. 0.03 0.01n.d. n.d. n.d. 0.01 0.0128.33 28.52 28.47 28.06 27.99n.d. 0.08 n.d. 0.02 n.d.0.01 0.02 0.01 n.d. n.d.97.45 99.76 99.57 98.19 97.864.103 4.060 4.008 4.047 4.0283.713 3.820 3.838 3.807 3.8190.039 0.004 0.018 0.018 0.0210.002 0.003 0.005 0.005 0.0060.001 0.010 0.016 0.011 0.0140.002 0.001 0.006 0.006 0.006 0.003 0.006 0.150 0.121 0.135 0.138 0.137 0.004 0.001 0.002 0.0034.077 4.015 4.028 4.018 4.026 0.019 0.004 0.002 0.003 0.001 12.089 12.059 12.061 12.060 12.061analyses at the University of Braslia.

dou

68 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672Table 8Summary (averages and ranges) of mineral composition changes between different bebeand magnetite (our unpublished data).

Unit B1a B1b B2a B2b B2c5. Whole-rock geochemistry

The chemical composition of 29 samples from the Salitre bebedouriteswas determined by ICP AES and ICP MS on samples fused with LiBO4

Average Average Average Average Average

ClinopyroxeneModal % 9 48 36 20 27SiO2 52.8 53.3 52.2 53.1 52.2TiO2 0.8 0.8 0.9 0.2 0.2Al2O3 0.59 0.59 0.65 0.37 0.25Fe2O3 3.2 1.6 2.9 2.5 4.6FeO 0.2 2.7 2.7 4.6 6.2MgO 16.5 15.7 14.9 13.8 11.7CaO 25.7 25.0 24.6 23.7 21.9Na2O 0.2 0.3 0.5 0.8 1.5

PhlogopiteModal % 24 20 32 35 40SiO2 39.2 38.3 37.5 38.1 37.5TiO2 1.6 2.7 2.6 1.7 1.9Al2O3 11.7 11.8 10.9 10.9 9.5Fe2O3 2.3 2.1 2.4 2.3 3.7FeO 3.4 10.7 15.8 13.5 16.1MgO 24.5 19.1 15.3 17.6 15.2

PerovskiteModal % 21 12 7TiO2 55.4 55.5 56.0Nb2O5 0.31 0.83 0.50ThO2 0.11 0.03 0.04ZrO2 0.08 0.26 0.07CaO 38.9 38.7 39.3SrO 0.40 0.51 0.40

ApatiteModal % 1 11 7 9 9CaO 54.7 54.0 53.9 54.1SrO 0.9 1.3 1.0 1.2

TitaniteModal % 1 8 11SiO2 30.3 30.0TiO2 37.5 37.2Fe2O3 1.5 1.6CaO 28.3 28.1

Ti-garnetModal % 3 34 6SiO2 28.8 28.0 30.9TiO2 13.8 14.2 9.3ZrO2 1.10 0.76 0.96Al2O3 0.4 0.8 0.3Fe2O3 17.7 18.9 21.6FeO 4.5 3.3 3.3MgO 0.9 1.0 0.6CaO 32.1 32.3 32.1

MagnetiteModal % 12 9 6 7TiO2 5.3 1.6 2.9 1.5Fe2O3 57.2 64.4 60.8 63.4FeO 31.8 31.0 33.5 31.7Cr2O3 1.54 0.06 0.97 0.01MgO 1.99 0.57 0.26 0.09

La2O3+Ce2O3 (wt.%)Perovskite 2.12 2.05 1.71Apatite 0.17 0.65 0.48 0.48Titanite 0.33 0.27Melanite 0.07 0.08 0.09Whole-Rock 0.39 0.18 0.20 0.10 0.14rite units in the Salitre complex. Also included are the relevant characteristics of apatite

B1a B1b B2a B2b B2cat the Acme Analytical Laboratories, Vancouver, and at the Universityof Braslia.

Because bebedourites are cumulate rocks, the use of differentiationindices is complex, as thedistribution ofmany elementsmay be strongly

Range Range Range Range Range

017 1867 2255 737 84551.853.8 50.254.5 51.254.0 51.155.0 49.855.20.41.1 0.41.7 0.31.3 0.10.9 0.11.1

0.220.87 0.252.18 0.021.14 0.010.67 0.070.521.83.8 03.9 0.84.9 05.9 010.40.10.6 0.06.7 0.25.8 0.39.0 2.912.5

16.116.9 13.416.6 11.616.3 11.616.8 7.715.125.325.9 23.225.9 22.525.5 21.625.8 15.424.40.10.3 0.10.9 0.01.3 0.11.6 0.34.5

1046 342 650 1568 237638.639.6 36.839.1 36.338.6 36.739.6 33.740.30.82.2 1.83.2 1.93.4 1.31.9 1.02.8

10.012.7 11.112.4 9.712.1 9.212.1 7.510.71.24.1 1.32.8 1.43.7 1.04.86 2.35.82.24.0 4.712.9 14.217.4 12.015.0 10.520.8

23.925.6 17.323.0 14.016.6 16.718.5 10.520.1

733 225 11452.456.6 53.856.8 55.556.60.180.40 0.231.32 0.450.640.020.31 0.000.36 0.010.070.020.14 0.040.73 0.030.1335.840.2 37.140.1 38.739.60.300.50 0.260.74 0.320.58

02 034 57.5 228 51553.5551 52.654.3 52.754.7 53.255.00.61.5 0.91.6 0.81.3 0.71.6

02 711 23629.830.8 29.230.935.938.2 35.138.71.11.7 1.02.6

27.828.7 27.428.5

010 762 01327.832.1 25.630.0 29.833.79.316.1 9.818.1 4.511.8

0.051.89 0.121.97 0.371.660.30.8 0.31.3 0.20.4

14.820.8 15.522.1 20.225.52.96.2 1.95.3 1.34.2

0.721.14 0.601.18 0.290.9031.732.6 31.632.8 31.632.7

1014 019 110 1184.17.5 0.74.4 2.25.6 0.53.1

52.459.6 57.367.0 52.163.2 60.466.830.732.8 29.831.6 32.836.1 29.733.41.381.91 0.00.12 0.781.16 0.000.051.492.92 0.211.12 0.060.47 0.000.22

1.064.61 1.053.87 1.402.050.00.43 0.291.13 0.020.81 0.001.28

0.140.47 0.050.520.000.19 0.000.30 0.000.25

0.150.71 0.130.25 0.120.33 0.070.14 0.060.28

controlled by the distribution of specic minerals. Therefore, wheneverpossible, we restrict our discussion to ne grained rocks occurring asdikes in an attempt to minimize mineral accumulation effects. Exceptfor B1a, where representative dikes were not available, all other averages and ranges in Table 9 are calculated from ne grained (althoughnot aphanitic) dike rocks. The results agree fairly well with theoreticalmajor oxides calculated for the whole set of samples from averagemodal content and mineral compositions (see Table 1).

The data from Table 9 indicate that SiO2 increases, whereas bothMgO and TiO2 decrease from B1 to B2, reecting olivine and perovskitefractionation in the early stages ofmagmatic evolution. This progressiondrives CaO and P2O5 to increase, leading to the crystallization of abundant diopside and apatite in B1b and then in B2. The more evolved B2magmas then become enriched in alkalis and Al2O3, resulting in thecrystallization of more abundant phlogopite, initially as an intercumulus phase and later as well formed lamellae.

The trace element contents of the Salitre bebedourites highlightsome important differences between the olivine bearing and olivinelacking rocks. The olivine rich bebedourites (B1a) contain signicantamounts of Cr (up to 1122 ppm) and Ni (up to 1291 ppm), suggesting that they derive from a relatively unevolved magma, whereasin olivine lacking bebedourites (both dikes and cumulates), the Crcontent is below 100 ppm and the Ni content below 115 ppm. The

olivine lacking bebedourites also have substantially higher concentrations of Sr, Zr, and Hf.

Fig. 8a shows average patterns for the different types of Salitrebebedourites in chondrite normalized trace element diagrams. TheB1a bebedourites show a distinct behavior, as the average contentsfor this unit are calculated from cumulate rock samples and do notrepresent liquids. An ICP MS perovskite analysis from Tapira (Brod,1999) is plotted in Fig. 8, showing the strong effect of perovskiteaccumulation on the B1a whole rock composition.

The average REE patterns for the various types of Salitre Bebedouritesare shown in Fig. 8b. The REE patterns are similar among differentbebedourite types, with CeN/YbN in the range of 40 93. The exceptionsare olivine and perovskite rich samples, which show a stronglyfractionated pattern (CeN/YbN=240), a probable effect of perovskiteaccumulation. The Ti garnet bebedourites have the least fractionatedREE (CeN/YbN=26).

6. Sr and Nd isotopes

Seven selected samples of Salitre bebedourites were analyzed forSr and Nd isotopes (Table 10). The sample preparation for the Ndisotope analyses was according to Gioia and Pimentel (2000). Thesamples for Sr isotope analyses were dissolved in HF HNO3 in closed

Table 9Whole-rock composition averages and ranges of Salitre ne-grained bebedourite dykes (except B1a=average of cumulate rocks).

Unit B1a B1b B2a B2b B2c B1a B1b B2a B2b B2c

Average Average Average Average Average Range Range Range Range Range

SiO2 24.9 32.1 31.5 32.9 34.9 1733 3133 2933 3134 3238TiO2 14.7 8.1 5.2 4.7 6.0 6.122 5.69.6 4.16.4 4.15.6 4.68.6Al2O3 2.4 1.4 3.0 4.0 3.0 0.55.4 0.82.0 1.24.2 1.65.9 0.64.2Fe2O3 20.9 17.0 15.7 15.3 17.4 1724 1520 1318 1416 1520MnO 0.3 0.2 0.2 0.3 0.3 0.20.3 0.160.2 0.180.28 0.200.30 0.240.35MgO 21.2 10.9 10.9 9.7 9.3 1331 1011 9.612 8.411 5.911.4CaO 11.5 23.0 21.3 20.8 17.7 6.715 2125 1923 1625 1521Na2O 0.12 0.33 0.46 0.39 0.93 0.090.16 0.270.41 0.360.65 0.310.47 0.352.05K2O 2.2 1.2 2.7 3.6 3.3 0.514.72 0.552.25 0.694.38 2.015.21 0.454.88P2O5 0.14 4.12 5.91 4.96 3.71 0.040.24 3.216.27 4.698.20 3.308.06 1.625.38BaO 0.11 0.05 0.10 0.12 0.07 0.020.24 0.030.08 0.040.13 0.040.21 0.030.09SrO 0.12 0.21 0.28 0.18 0.20 0.050.15 0.200.23 0.240.29 0.170.22 0.130.32LOI 0.9 1.2 2.6 2.7 2.8 0.41.3 0.32.1 1.64.5 1.94.2 1.13.8TOTAL 99.4 99.8 99.8 99.6 99.6 99100 99100 99100 99100 99100CO2 0.6 0.8 1.8 1.1 1.5 0.50.8 0.41.1 1.13.1 0.81.8 0.92.6

01331427113813422270100012273

69E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672S 0.1 0.04 0.04 0.05 0.32V 481.1 223.0 282.3 35.6 297.5Cr 782.3 70.1 29.6 64.0 53.2Ni 654.4 36.9 33.5 35.6 17.8Rb 76.5 36.7 83.0 122.5 101.6Sr 990.8 1781.3 2321.3 1515.0 1673.8Y 69 66.7 97.0 114.4 87.0Zr 189.7 390.9 1011.7 2630.8 1884.4Nb 633.8 496.9 413.7 347.2 535.5Ba 996.7 475.2 864.7 1103.7 639.9La 1014.9 518.7 560.7 321.7 369.0Ce 2283.5 986.7 1125.9 511.3 812.0Pr 257.9 99.4 117.1 55.4 91.6Nd 922.7 351.2 408.0 207.6 329.3Sm 113.5 49.2 55.6 37.4 46.1Eu 29.3 14.6 16.1 11.7 13.0Gd 59.1 34.2 37.1 30.0 30.6Tb 7.7 4.9 5.6 4.2 4.4Dy 24.6 18.7 20.1 20.2 17.4Ho 2.65 2.39 2.91 2.51 2.38Er 4.56 5.10 6.35 7.15 5.67Tm 0.49 0.55 0.76 1.07 0.76Yb 2.46 2.75 4.08 5.60 4.09Lu 0.24 0.31 0.52 0.84 0.56REE 4724 2089 2361 1217 1727Hf 6.4 12.9 23.0 54.7 45.3Ta 48.5 20.0 13.3 8.8 16.2Th 102.9 30.0 32.6 9.2 11.7U 12.1 10.6 6.9 5.2 3.4.00.1 0.010.1 0.030.06 0.010.2 0.060.8851067.4 127367 177354 1.460 57906701122 0.00198 0.082 5087 6.880061292 24.652 6.647 0.0115 2.6432.3176 16.465 16.1130 80202 12.8141241275 16481913 20532474 14051844 105627170.7132 5473 77113 58219 451275248 188611 3602204 9265426 14112418821171 369675 319590 157674 442674592164 231743 4021190 3781891 299792731920 411705 362889 255449 175663694128 7091405 6411893 380755 360176305469 70147 65197 3985 43202881662 241527 241677 143324 1607196209 3967 3886 23.565 27860,394 12.119.6 11.623.7 6.820.6 7.922.85106 29.744 30.448 18.353 19.647.214.8 4.36.0 4.57.2 2.47.6 2.47.7.246.2 15.723.7 18.423.2 10.838 11.225.5.784.95 2.12.8 2.43.2 1.34.6 1.23.9.757.81 4.36.0 5.77.2 3.513.7 3.28.1.170.86 0.440.63 0.600.98 0.462.1 0.411.0.894.30 2.03.2 3.25.3 2.411.1 2.25.4.090.40 0.230.34 0.380.73 0.351.7 0.290.698308629 15532958 14273858 8871830 8153556.38.8 8.617.7 11.843 18.3106 30.355380 12.828.0 7.024.6 6.911.0 8.7393145 8.256 9.776 4.811.8 5.723.8.522 7.313.0 311.9 2.78.7 1.97.4

The analyzed bebedourites are isotopically consistent with otheralkaline rocks of the APIP and with the interpretation (e.g., Gibsonet al., 1995a), that the APIP magmas were generated within readilyfusible portions of the Brazilian sub continental lithospheric mantlein response to the impact of the Trindade mantle plume under centralBrazil during the Late Cretaceous.

Fig. 9 shows that the Salitre I bebedourites have a relatively narrowNd and 87Sr/86Sri range. The analyzed B2b Ti garnet bebedouriteshows a higher Nd (4.97), suggesting that it originated from aslightly less radiogenic source. In terms of the initial 87Sr/86Sr ratio,the samples dene a trend of slightly increasing radiogenic compositions with magmatic evolution, although with a strong overlap. OneB2c sample containing both titanite and Ti garnet yielded the highest Srisotope ratio (87Sr/86Sri=0.70564), which could be related to minorcrustal assimilation.

7. Discussion and conclusions

70 E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672Teon vials. The Sr was separated in Bio Rad AG 50W X8 200 400mesh ion exchange columns. The analyses were performed in a Finnigan MAT 262 mass spectrometer at the University of Braslia..The initial isotope ratios, Nd(T), and Sr(T) were calculated for anage of 86.3 Ma (Sonoki and Garda, 1988).

Fig. 8. (a) Chondrite-normalized (Thompson et al., 1984) trace-element diagrams foraverage ne-grained bebedourite dikes (except B1a=cumulates) from the Salitre com-plex; (b) Chondrite-normalized (Boynton, 1984) REE patterns for average ne-grainedbebedourite dikes (except B1a=cumulates) from the Salitre complex. The result of anICP-MS analysis of perovskite from the Tapira Complex (Brod, 1999) is plotted for compar-ison in both diagrams (stars). Symbols as in Fig. 5.

Table 10Sr- and Nd-isotope data for the Salitre bebedourites.

Sample B1a B1b B1b

Sm (ppm) 46.15 38.80 24.28Nd (ppm) 387.53 241.50 152.93147Sm/144Nd 0.0729 0.1058 0.1026143Nd/144Nd 0.512215 (6) 0.512245 (8) 0.512274 (6)143Nd/144Ndi 0.512177 (7) 0.512190 (9) 0.512220 (7)Nd(0) 8.25 7.67 7.10Nd(T) 6.89 6.67 6.07TDM (Ga) 0.90 1.13 1.0687Rb/86Sr 0.2835 0.0365 0.065387Sr/86Sr 0.7055 (3) 0.70536 (2) 0.70535 (2)87Sr/86Sri 0.70515 (3) 0.70532 (2) 0.70527 (2)Sr(0) 14.19 12.21 12.07Sr(T) 10.71 13.01 12.37

Values in parenthesis are 2 SE.Bebedourites are a major rock type in the alkaline carbonatitephoscorite complexes of the kamafugite carbonatite association inthe Alto Paranaba Igneous Province. Bebedourites are present in all theAPIP complexes, although in some places (e.g., Catalo I and Arax) theyhave been extensively converted to phlogopitite by carbonatitic metasomatism. The bebedourites occur mostly as cumulates, are characterizedby widely variable modal amounts of the essential phases diopside,perovskite, phlogopite, apatite, andmagnetite, andmay contain olivine and Ca Ti silicates such as Ti garnet and titanite. K feldspar hasbeen reported as a minor constituent in evolved bebedourites fromthe Tapira complex (Brod, 1999), and rare melilite, monticellite,and kalsilite were reported from ultramac (Morbidelli et al., 1997)and syenitic (Brod et al., 2000) rocks from Salitre. Other characteristicfeatures are low Ni and Cr contents and the lack of Cr rich spinels(except in the least evolved olivine rich varieties), plagioclase, andnepheline or other feldspathoids. Thus, the bebedourite composition does not t any of the established igneous rock classicationschemes.

In some cases, bebedourites may contain primary concentrationsof minerals of economic interest. These rocks are the original sourcefor the phosphate ores occurring in the lateritic cover of the Tapiracomplex (Brod et al., 2004) and for the Ti deposits in the lateriticcover of the Tapira (Brod, 1999), Salitre, and Catalo I (Ribeiro, 2008)complexes.

Bebedourites may have been overlooked or misclassied as pyroxenites in other alkaline carbonatite complexes, particularly those ofpotassic afliation. For instance, pyroxenites from the Phalaborwacomplex in South Africa (Eriksson, 1989) bear remarkable petrographicsimilarities with the APIP bebedourites, particularly the more evolved(perovskite free, K feldspar bearing) ones. The pyroclastic deposits

B2b B2c B2c B2c

23.00 38.53 27.08 42.76115.52 241.48 159.93 285.060.1325 0.1101 0.1045 0.09710.512347 (13) 0.512283 (9) 0.512266 (8) 0.51225 (9)0.512277 (14) 0.512225 (10) 0.512211 (9) 0.512199 (10)5.68 6.92 7.26 7.574.97 5.97 6.24 6.47

1.30 1.12 1.09 1.040.3719 0.3874 0.2580 0.15890.70559 (2) 0.70611 (8) 0.70554 (3) 0.70538 (2)0.70514 (2) 0.70564 (8) 0.70522 (3) 0.70519 (2)15.47 22.85 14.76 12.4910.46 17.57 11.72 11.17

71E.S.R. Barbosa et al. / Lithos 144145 (2012) 5672of the Mata da Corda kamafugites in the APIP contain pyroxenitenodules that closely resemble bebedourites, both petrographicallyand chemically (Seer and Moraes, 1988).

The Salitre I complex is composed of at least two bebedouriticintrusions: the northern part of the complex (B1) is dominated bya sequence of cumulates, starting with olivine perovskite bearingrocks, followed by olivine free perovskite bebedourites; the southernpart of the complex forms an independent intrusion (B2), whereTi garnet is the main Ca Ti mineral.

Fractional crystallization can explain the evolution of mostbebedourites in the northern part of Salitre, given by the progressionof olivine perovskite bearing bebedourites (B1a) through olivinefree perovskite bebedourites (B1b) on the top of the sequence.The extensive fractionation of olivine, perovskite, and Cr rich spinelin B1a resulted in increasing SiO2, CaO, and P2O5, and decreasingMgO, TiO2, Fe2O3, Cr, and Ni, leading to the crystallization of largeamounts of apatite and diopside in B1b. The evolution from B1a toB1b is also supported by the observed composition of phlogopite

Fig. 9. Sr- and Nd-isotope compositions of Salitre bebedourites, which are consistentwith other APIP rocks. Symbols as in Fig. 5.Fields from Gibson et al. (1995a).and clinopyroxene.The B2 bebedourites result from an independent intrusion of more

siliceous magma, consistent with the mineral composition data andwith the average modal mineral contents (Table 1) as well as withthe expected (Table 1) and average (Table 9) whole rock chemicalcomposition. Locally, where the B2 dikes cut the B1 unit, Ca Timineral variations can occur, such as the presence of titanite andTi garnet surrounding perovskite (B2a and B2c). Because perovskiteis absent in samples from themain B2 intrusion, it is possible that theperovskite in the dikes is xenocrystic, picked up from the B1 countryrock and unstable within the more siliceous B2 magma. Alternatively,very small amounts of perovskite may have crystallized early from B2and quickly reacted with the residual magma. Some minor crustal assimilation may have played a role in the increase in SiO2 activity, but,as suggested by the variations in initial Sr isotope ratios, this featureseems to be restricted to the most evolved rocks.

The chemical and isotopic characteristics of the Salitre silicatemagmas, as well as the remainder of the APIP, are consistent withan origin by partial melting within a metasomatized subcontinentallithospheric mantle heated by the impact of the Trindade MantlePlume during the Late Cretaceous, as suggested by Gibson et al.(1995a). In the APIP carbonatite complexes, this primitive magmais represented by phlogopite picrites (Gibson et al., 1995a) of kamafugitic afnity (Brod et al., 2000). However, the chemical compositionof the olivine and the very low amounts of Cr andNi inmost of our samples suggest that the majority of the Salitre bebedourites accumulatedfrom a slightly more evolved, although still ultramac, magma. Thismagma could have been produced by extensive olivine, chromite,and perovskite fractionation from the original phlogopite picrite parentand would probably be pyroxenitic in composition and, therefore,chemically similar to the Mata da Corda kamafugites. The ne grainedbebedourite dikes occurring in the complexmay be suitable representatives of such a magma. The earliest (phlogopite picrite derived) cumulates, presumably containing higher Fo olivine and high Cr and Ni, wereeither not present in the area covered in this work or are perhaps located in deeper parts of the Salitre magma chamber.

Acknowledgments

The authors thank the CNPq Brazilian Council for Research andDevelopment for Ph.D. grants to E.S.R.B, P.F.O.C, and C.S.G., researchgrants to J.A.B., T.C.J.B., and E.L.D., and nancial support for the project. The University of Braslia is thanked for access to analytical facilities, as is Fosfertil S/A for access and permission to sample the SalitreI drill cores. Professor S. Vlach and the University of So Paulo arethanked for their assistance with additional microprobe analyses.Professors C. G. Oliveira, C. F. Ferreira Filho, and N. F. Botelho at theUniversity of Braslia are thanked for their review and discussions onan earlier version of this manuscript. We are indebted to ProfessorsG. Nelson Eby, Felicity Lloyd and Roger Mitchell for their careful reviews and most valuable suggestions, which helped improve andclarify the submitted manuscript.

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