Petrogenesis of Malaysian granitoids in the Southeast Asian tin belt: Part 1. Geochemical and Sr-Nd...

Petrogenesis of Malaysian granitoids in the Southeast Asian tin belt: Part 1

Geological Society of America Bulletin, v. 127, no. 9/10 1209

Petrogenesis of Malaysian granitoids in the Southeast Asian tin belt: Part 1. Geochemical and Sr-Nd isotopic characteristics

Samuel Wai-Pan Ng1,†, Sun-Lin Chung2,3, Laurence J. Robb1, Michael P. Searle1, Azman A. Ghani4, Martin J. Whitehouse5, Grahame J.H. Oliver6, Masatoshi Sone4, Nicholas J. Gardiner1, and Muhammad H. Roselee4

1Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK2Institute of Earth Sciences, Academia Sinica, Taipei 10529, Taiwan3Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan4Department of Geology, University of Malaya, 50603 Kuala Lumpur, Malaysia5Swedish Museum of Natural History, and Nordic Center for Earth Evolution, Box 50007, SE-104 05 Stockholm, Sweden6Department of Geography, National University of Singapore, Singapore 117570

ABSTRACT

The Malaysian granitoids of the Southeast Asian tin belt have been traditionally divided into a Permian to Late Triassic “I-type”–dominated arc-related Eastern province (Indochina terrane) and a Late Triassic “S-type”–dominated collision-related Main Range province (Sibumasu terrane), sepa-rated by the Bentong-Raub Paleo-Tethyan suture that closed in the Late Triassic. The present study, however, shows that this model is oversimplified and that the direct application of Chappell and White’s (1974) I- and S-type classification cannot account for many of the characteristics shared by Malaysian granitoids. Despite being com-monly hornblende bearing, as is typical for I-type granites, the roof zones of the Eastern province granites are hornblende free. In addi tion, the Main Range province gran-itoids contain insignificant primary musco-vite, and are dominated by biotite granites, mineralogically similar to many of the plu-tons of the Eastern province. In general, the Malaysian granitoids from both provinces are more enriched in high field strength ele-ments than typical Cordilleran I- and S-type granitoids. The mineralogy and geochemis-try of the Eastern province granitoids, and their relationship with contemporaneous volcanics, confirm their I-type nature. The bulk liquid lines of descent of both granitic provinces largely overlap with one another. Sr-Nd isotopic data further demonstrate that

the Malaysian granitoids, especially those of the Main Range, were hybridized melts derived from two “end-member” source re-gions, one of which is isotopically similar to the Kontum orthoamphibolites and the other akin to the Kontum paragneisses of the Indo-china block. However, there are differences in the source rocks for the two provinces, and it is suggested in this paper that these are re-lated to differing proportions of igneous and sedimentary protoliths. The incorporation of sedimentary-sourced melts in the Eastern province is insignificant, which allowed the granites in this belt to maintain their I-type nature. The presence of minor primary tin mineralization in the Eastern province com-pared to the much more significant tin en-dowment in the Main Range is considered to reflect the incorporation of a smaller pro-portion of sedimentary protolith in the melt products of the former.

INTRODUCTION

Since Chappell and White’s (1974) landmark paper describing two contrasting granite types in the Australian Lachlan fold belt, the I- and S-type classification system has been applied to many granitic terranes, which include the Malaysian granitoids and the Andean-Cor di-lleran chain (Beckinsale, 1979; Grosse et al., 2011). Chappell and White (1974) described the granites formed by igneous-sourced melt as “I type”, and those formed from sedimentary-sourced melt as “S type”. A further classifica-tion of “M-type” granites was later assigned to the products derived from partial melting of mantle or relatively juvenile crust (White, 1979)—this type is, however, normally con-

sidered as a subdivision of the I type (Pitcher, 1997; Frost et al., 2001). In this scheme, I-type granites are characterized mineralogically by the presence of hornblende and sphene, while S-type granites are typified by muscovite, andalusite, cordierite, and garnet (Chappell and White, 1974). The I- and S-type granites can also be discriminated from each other by their different geochemical and isotopic behav-ior, as reflected by the aluminum saturation index, proportion of potassic to sodic oxides, and Sr-Nd isotopic compositions (Table 1). A fourth classification of “A-type” granites was later proposed by Loiselle and Wones (1979), referring to alkali granites formed in within-plate environments. A-type granites are charac-terized geochemically by having low aluminum saturation index, but high abundance of high field strength elements, such as Hf, Ga, Ta, Nb, Y, and Zr (Cobbing et al., 1992).

The I- and S-type granite classification scheme was first applied to the Southeast Asian tin belt granitoids by Beckinsale (1979) (Fig. 1). For the Malay Peninsula, it was sug-gested that granitoids to the east of the Bentong-Raub suture zone (Eastern province) are mostly hornblende-bearing I types formed above an east-dipping Paleo-Tethyan subduction zone, while those to the west (Main Range province) are younger and are mostly hornblende-free S types, formed as a result of crustal thickening following the collision between the Sibumasu and Indochina–East Malaya blocks (Fig. 1). Although this model is accepted by many workers (Cobbing et al., 1992; Schwartz et al., 1995; Hutchison, 2007; Hutchison and Tan, 2009), the I- and S-type designation of the Malaysian granitoids has recently been chal-lenged by Ghani (2000), Searle et al. (2012),

GSA Bulletin; September/October 2015; v. 127; no. 9/10; p. 1209–1237; doi: 10.1130/B31213.1; 19 figures; 4 tables; Data Repository item 2015108; published online 3 April 2015.

†Current address: Department of Earth Sciences, The University of Hong Kong, Pok Fu Lam Road, Pok Fu Lam, Hong Kong; waipanng@ hku .hk.

For permission to copy, contact [email protected] © 2015 Geological Society of America

Ng et al.

1210 Geological Society of America Bulletin, v. 127, no. 9/10

and Ghani et al. (2013b). These workers sug-gested that the mineralogical differences between the two provinces are not as distinc-tive as suggested by Cobbing et al. (1986), and that previous workers had overlooked the com-monalities shared by the two granitic provinces. Both provinces comprise hornblende-bearing and hornblende-free granitoids and are made up of intrusions of batholithic dimensions. The “S-type” Main Range granitoids are quite unlike the collisional S-type leucogranites found in the Himalayan region, as the latter are not batho-lithic or voluminous at all, but are associated with widespread exposure of regions character-ized by Barrovian metamorphism and partial melting, which are absent in the Main Range. Both provinces on the Malay Peninsula also show common geochemical similarities, such as having high aluminum saturation index and a decreasing trend in P2O5 content as the granit-oids become more felsic (Table 1) (Ghani et al., 2013b). All these features suggest that the Main Range province granitoids are not typically S type, and that the distinction of the two prov-inces in terms of Chappell and White’s (1974) I- and S-type system needs to be reconsidered.

In this study, about 100 granitoid samples from the Malay Peninsula were collected for petrographic observations, geochemical and isotopic analyses, and U-Pb dating. In Part 1 (this paper), the field observations, petrogra-phy, geochemistry, and Sr-Nd isotopic charac-teristics of the Malaysian granitoids are pre-sented and a petrogenetic model proposed. In a complementary study (Part 2) (Ng et al., 2015), ion microprobe U-Pb zircon ages of these gran-itoids are presented, followed by a discussion of the emplacement history and evolution of the Malaysian granitoids.

GEOLOGICAL BACKGROUND

The Eastern Province

Granitoids of the Eastern province of Malay-sia were emplaced into the Indochina–East Malaya terrane, which is made up of Lower Carboniferous to Cretaceous marine-fluvial

sediments and volcanics underlain by Meso-proterozoic continental basement (Hutchison, 2007; Metcalfe, 2013). However, the continental basement is not exposed in the Malay Peninsula, and the evidence of its existence consists mainly of 1100–1300 Ma inherited zircon ages from the Eastern province granitoids on the eastern coast of the Malay Peninsula (Liew, 1983; Liew and McCulloch, 1985). Additional evidence is also provided by the new Nd depleted mantle model ages and inherited U-Pb zircon ages pre-sented in the accompanying paper (Part 2) (Ng et al., 2015). Recent work by Metcalfe (2013) suggested that the Eastern province granitoids were emplaced into the Sukhothai arc terrane, the latter traced from Northern Thailand and sandwiched between the Indochina and Sibu-masu terranes. However, there is no on-land field evidence for Mesozoic back-arc rifting in the Malay Peninsula, and this is also not sup-ported by the geochemistry of the Eastern prov-ince granitoids, which will be presented and discussed in the following section. The East-ern province granitoids have magmatic ages younging from the eastern coast (289 ± 2 Ma) to the Bentong-Raub suture zone (220 ± 4 Ma), while scattered Cretaceous granitoids were also identified in the Stong region (76 ± 1 to 84 ± 1 Ma) and on Tioman Island (80 ± 1 Ma) (Ng et al., 2015).

Hornblende-Biotite Granitoids and Biotite Granitoids

Although local workers further divided the Eastern province into Eastern belt granitoids and Central belt granitoids based on the stratigraphy of the host rocks (Hutchison and Tan, 2009; Metcalfe, 2013; Oliver et al., 2014), no signifi-cant geochemical difference is evident between the Eastern belt and the Central belt granitoids (Cobbing et al., 1992). In addition, the scattered Cretaceous granitoids now documented in the Eastern province are also mineralogically and geochemically similar to the Permo-Triassic granitoids that dominate the belt.

In general, the Eastern province comprises small batholithic granitic bodies up to 1000 km2 in size with a wide spectrum of lithologies,

ranging from hornblende-biotite granodiorite to adamellite (quartz monzonite) to more frac-tionated biotite granite in the Harpum (1963) granite classification (Fig. 2). The most frac-tionated biotite granite at Maras-Jong (sample MA50) has only insignificant hornblende and is mineralogically similar to an S-type granitoid. Approximately two-thirds of the exposed East-ern province comprises hornblende-bearing biotite granitoids (Fig. 3A), while the remain-ing one-third is made up of hornblende-free biotite granitoids (Cobbing et al., 1986, 1992). Field relationships suggest that the hornblende-biotite granitoids form the main body of the plutons, with more fractionated hornblende-free phases typically occurring in the roof zone. Transitions into more fractionated portions of granitoid bodies are characterized by gradual textural and mineralogical variation. Indica-tions of hydrothermal activity, such as chlori-tization of biotite and sericitization of feldspars (Figs. 3C and 3D) and vein development, are usually associated with the roof zone. These greisenized plutonic roof zones are the host environment for primary Sn-W mineralization in the Malay Peninsula (Cobbing et al., 1992; Schwartz et al., 1995). In the Eastern province granitoids, accessory minerals typically include apatite, secondary epidote, zircon, allanite, sphene, and magnetite (Table 2A; Figs. 3E and 3F). Although magnetite is the dominant iron-oxide phase, ilmenite is also detected in these rocks, suggesting that both magnetite-series and ilmenite-series granitoids are found in the province (Ishihara et al., 1979; Yeap, 1993). Mafic enclaves are found in some Eastern province granitoids, but these are not common (Fig. 3B).

Alkali GranitoidsSyenites are found on Perhentian Island

(sample MA48) and in Benom (MA03). These syenites are Permo-Triassic in age (Ng et al., 2015), containing K-feldspar, plagioclase, hornblende, pyroxene, quartz, and biotite, in decreasing abundance. They are interpreted as the fractionated product of alkali basalt (Ghani, 2001, 2003; Yong et al., 2004; Ghani, 2006).

TABLE 1. COMPARISON BETWEEN CHAPPELL AND WHITE’S (1974) I- AND S-TYPE GRANITES (CHAPPELL AND WHITE, 1974, 1992; MCCULLOCH AND CHAPPELL, 1982; CLARKE, 1992; COBBING ET AL., 1992; PITCHER, 1997; GHANI ET AL., 2013B)

sdiotinargepyt-Ssdiotinargepyt-IscitsiretcarahCtenrag,etinemli,etinamillis,etitoib,etivocsuMetitengam,enehps,etitoib,ednelbnroHslarenimevitacidnI

stnemidesateMsevalcneralunargorcimcitiroidotcfiaMsevalcnESiO2 %tw97–56%tw67–35Na2 K%tw5ta%tw2.3<tub%tw2.2>%tw2.3>O 2OP2O5 Decrease with increasing SiO2 Increase with increasing SiO2

OiSgnisaercnihtiwesaercni,1.1<KNC/A 2 >1.1, decrease with increasing SiO2

%lom1>%lom1<mudnurocWPIC(87Sr/86Sr)i 807.0>807.0<εNd(t ) 71–ot4–9.8–ot4.0+

Note: A/CNK—molar ratio Al2O3/[(CaO - 1.67 P2O5) + Na2O + K2O]. CIPW—normative mineralogy designed by Cross, Iddings, Pirsson and Washington (1903).



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MigmatitesLarge-scale migmatitic bodies are found in

the Stong region of the Central belt (Hutchison, 2007; Searle et al., 2012). The Stong Complex comprises three unrelated components, the Berangkat tonalite (samples MA35 and MA36), Kenerong leucogranite (MA37–MA44), and Noring granite (MA45); with the exception of the Late Triassic Berangkat tonalite, the Stong Complex is Late Cretaceous in age (Ng et al., 2015). The U-Pb zircon ages (Ng et al., 2015) suggest that the highly deformed Berangkat tonalite (MA35 and MA36) has been intruded by the Kenerong and Renyok leucogranites (MA37–MA44), which are in turn cut by the Noring granite (MA45). Migmatitic gneisses of tonalitic composition with leucosomes are observed along the Kenerong River and Renyok River (Fig. 4). In contrast, the youngest Noring granite is undeformed, and is characterized by the presence of pink rounded K-feldspar grains.

Doleritic Dikes and VolcanicsThe Eastern province granitic batholiths are

locally cut by mafic doleritic dikes, which are significantly younger than the granitoids and range in age from 79 ± 2 Ma to 179 ± 2 Ma (Ghani et al., 2013a). Clearly, they are not related to the Permo-Triassic Eastern province magmatism. The I-type Eastern province gran-itoids are also associated with acidic to interme-diate calc-alkaline Andean-type volcanics, tuff, rhyolite, andesite, and ignimbrite. These rocks form volcanic complexes, such as those crop-

ping out in Eastern Pahang, Southern Johor, and off the southeastern Malay Peninsula. Volcanic features such as rhyolitic flows and gas pipes are associated with the Cretaceous granitoids on some Eastern offshore islands, such as in the Tioman Island volcanic complex (samples MA78–MA103).

Main Range Province

The Main Range province granitoids are even more voluminous than the Eastern province granitoids. They were emplaced as large batho-lithic bodies as much as several thousands of square kilometers in area. They are not appar-ently associated with a regional migmatite ter-rane, do not appear to be associated with a Bar-rovian metamorphic sequence (unless it remains unexposed in the lower crust), and are not linked to contemporaneous thrusting or normal faults. These observations suggest that they differ, in terms of field characteristics, from purely crustal-derived S-type Himalayan leucogranites (Searle et al., 2010). The Main Range province granitoids were emplaced into the Sibumasu basement comprising Upper Cambrian to Upper Permian metasediments and shallow-marine shelf sediments that are overlain by Mesozoic carbonates and turbidites (Abdullah, 2009; Ghani et al., 2013a). While the Precambrian geology of the Sibumasu terrane is not well understood, Hutchison (2007) suggested that some of the metamorphic outcrops exposed in northern and central Thailand may represent the

original Precambrian basement of the Sibumasu terrane (Hutchison, 2007). Paleoproterozoic to Mesoproterozoic basement ages have been indi-cated by the inherited zircons extracted by Liew and Page (1985), and supported by the detrital zircon core ages presented by Sevastjanova et al. (2011), the Nd depleted mantle ages pre-sented in this paper, and the new U-Pb inher-ited zircon ages presented by Ng et al. (2015). The emplacement of these batholiths into thick carbonate country rocks caused extensive skarn formation, where tin mineralization is also found (Hutchison, 2007). Good exposures of such relationships can be seen on Tuba Island near Langkawi (samples MA27–MA29; Fig. 5A), in which the skarn body is characterized by the presence of biotite, cordierite, garnet, and sphene. It is reported that minor tin deposits are hosted in these skarn bodies (Cobbing et al., 1992; Schwartz et al., 1995).

Hornblende-Biotite Granitoids and Biotite Granitoids

The Main Range province, sometimes termed the Western belt granitoids in local lit-erature (Cobbing et al., 1992; Ghani, 2000), has a rather restricted range of lithologies: Most of the granitoids are coarse K-feldspar–phyric bio-tite granites, with occasional K-feldspar–phyric hornblende-biotite adamellites, such as the Bintang batholith near Taiping (sample MA16) (Fig. 6A; Table 2B). The mineral assemblage of pristine Main Range province granitoids is K-feldspar, quartz, plagioclase, and biotite, in decreasing abundance. K-feldspar phenocrysts are observed in all granites, but are locally megacrystic in laths up to a few centimeters long in the most fractionated granite. Biotite grains in the hornblende-bearing Taiping gran-ite are in most cases low in Al and associated with sphene and in some places with actinolite (Ghani, 2000). This resembles the mineralogi-cal characteristics of I-type granitoids. The field relationships between the hornblende-bearing granites and the hornblende-absent granites are similar to those observed in the Eastern prov-ince, with the hornblende-absent phase devel-oped in the plutonic roof zones. Accessory minerals such as primary and secondary musco-vite, apatite, zircon, secondary epidote, allanite, sphene, and ilmenite are typically present in the Main Range granitoids, similar to the accessory mineral assemblage of the Eastern province granitoids (Table 2B; Figs. 4E and 4F) (Ghani, 2000). Most of the Main Range province granit-oids appear to be ilmenite-series granites (Ishi-hara et al., 1979), suggesting that they may be more reduced than many of the Eastern prov-ince granites. The Main Range province gran-itoids are more severely altered by hydrothermal

Granite

Adamellite(Quartz monzonite)

Granodiorite

Tonalite

Granite

Adamellite(Quartz monzonite))

Granodiorite

Tonalite

K2O (wt%)

Na2O (wt%)

Main Range Province granitoids

Cretaceous granitoids

Permo-Triassic granitoidsAlkali granitoids

Eastern Province

Figure 2. Comparison of the Eastern province and Main Range granitoids on a plot of K2O versus Na2O after Harpum (1963).



Figure 3. Textural and petrographic features of the Eastern province granitoids. (A) Hornblende-biotite granite at Kuantan (sample MA55). (B) Mafic hornblende-biotite enclave in the Kapal granite (MA51). (C) The Perhentian syenite is made up of K-feldspar, biotite, hornblende, and quartz. Biotite is chloritized (MA48; cross-polarized image). (D) Sericitized K-feldspar and chloritized biotite in the Boundary Range hornblende-biotite granite (MA52; cross-polarized image). (E) Scanning electron microscope (SEM) image of sample MA52, from the Bound-ary Range batholith, showing an accessory mineral assemblage comprising ilmenite, apatite, and allanite. (F) SEM image of sample MA74, from the Singapore granite, showing the presence of magnetite rather than ilmenite. Mineral abbreviations: Aln—allanite; Ap—apatite; Bt—biotite; Chl—chlorite; Hbl—hornblende; Ilm—ilmenite; Kfs—K-feldspar; Mag—magnetite; Pl—plagioclase; Qtz—quartz; Ser—sericite.

Ng et al.


activity, such as chloritization of biotite and sericitization of feldspars (Fig. 6B). The roof zones of the plutons are widely greisenized and replaced by a muscovite + quartz + cordierite assemblage. Quartz-tourmaline veins (Fig. 5B) and miarolitic cavities (Fig. 6C) are commonly developed. Secondary muscovite and chlorite are commonly observed (Fig. 6D), with lesser pyrite and fluorite (Fig. 5C). The tin deposits of the Main Range province are typically restricted to greisen-bordered veins concentrated in the roof zones. Well-known Main Range primary tin fields are located in the Kinta Valley and near Kuala Lumpur.

MAJOR AND TRACE ELEMENT ANALYSES

Major and trace element geochemistry is used to examine the differences between the Main Range and Eastern province granitoids and also to compare and contrast the characteristics of Malaysian granitoids with classic Cordilleran I- and S-type examples. The sample locations used in this study are presented in Figure 1B.

Samples were crushed and powdered by jaw crusher and corundum mill. The samples were then fused into glass beads. Major ele-ment compositions were determined by X-ray fluorescence using the Rigaku RIX-2000 spec-trometer in the Department of Geosciences, National Taiwan University (NTU). The ana-lytical procedures are described by Wang et al.

(2007) and the GSA Data Repository1, with the loss on ignition determined separately by rou-tine procedures. For trace element analysis, the

glass beads produced for major element analy-sis were crushed, weighed, and digested into sample solutions, which were then analyzed by

Figure 4. Late Triassic Berangkat migmatitic gneiss of tonalitic composition (samples MA35 and MA36), possibly representing a migmatized basement, cut by the Late Cretaceous Kenerong leucogranite (MA42) at Renyok River.

1GSA Data Repository item 2015108, methodology on major element, trace element and Sr-Nd isotope analy-ses, is available at http:// www .geosociety .org /pubs /ft2015 .htm or by request to editing@ geosociety .org.

TABLE 2A. FEATURES INDICATIVE OF I- AND S-TYPE GRANITES PRESENT IN THE EASTERN PROVINCE GRANITOIDS

rehtOmlIgaMpAnlAhpSsMxPlbHevalcnEnoitacoLygolohtiL.onelpmaSYYYYxpCYcfiaMmoneBetineyS30AM

YeniMdloGmojnePekidetisleF33AM Y Y Y Y YMA36 Kfs-phyric Hbl-Bt tonalite Berengkat–Kampong Jerek Dioritic Y Y Y Y Y Y

YgnoreneKetitamgimtB-lbH-trG93AM Y Y Y Y YYYYYYreviRkoyneRetilanotcititamgiM24AM

ekidcitinargocueL34AM Y Y Y YYgniroNetinargtB-lbHciryhp-sfK54AM Y Y Y Y Y

yPYYYdnalsInaitnehrePetinargtB74AMYYYYxpCYcfiaMetineyS84AM

MA50 Kfs-phyric (Hbl)-Bt granite with Qtz-Tour miarolitic cavities

ruoT,trGYYSYgnoJ-saraM

YegnaRyradnuoBetinargtB-lbH25AM Y Y Y YYYYYnatnauKetinargtB-lbH55AM

MA57 Kfs-phyric (Hbl)-Bt granite Gunung Ledang Y S Y Y YYYYSYetinargtB-)lbH(ciryhp-sfK–ocueL85AMYYYYtahaPutaBetinargtB-lbHciryhp-sfK46AMYYYxpCYukeBkayniMetinargtB-lbH-xpC66AMYYSyrrauQnosnaH–tahaPutaBsnievruoT-ztQhtiwetinargtBciryhp-sfK96AMYYYSYdnalsInibUetinargcititamgiM37AM

MA77 Kfs-phyric Hbl-Bt granite Bukit Batupejal Quarry Y Y Y Y Y YxpCYslefnroHdnalsInamoiTetinargtB-lbH-xpC87AM Y Y Y Y Y

etinargtB18AM Y Y Y YYYSYslefnroHetinargtB-)lbH(38AM

YetinargtB-)lbH(78AM Y Y Y YYYSYekidcitinargorciM09AM

ruoTYYScfiaMetinargruoT-sM79AMetinargcititamgiM001AM Y Y Y Y Y

YYYYgnaulK–enaulameJetinargtB-lbHciryhp-sfK401AMYYYYnahameKetinargtBciryhp-sfK901AM

Note: Y—present; S—secondary. Mineral abbreviations: Aln—allanite; Ap—apatite; Bt—biotite; Cpx—clinopyroxene; Grt—garnet; Hbl—hornblende; Ilm—ilmenite; Kfs—K-feldspar; Mag—magnetite; Ms—muscovite; Px—pyroxene; Py—pyrite; Qtz—quartz; Sph—sphene; Tour—tourmaline.



inductively coupled plasma–mass spectrometry using an Agilent 7500cx quadrupole spectrom-eter, also at NTU. Detailed sample handling and preparation procedures followed those of Lee et al. (2012) and described in the Data Reposi-tory (see footnote 1). Reported precision is ±5% (2s), and the results are presented in Tables 3A and 3B. The new geochemical data are inter-preted together with the data provided by Cob-bing et al. (1992), forming a combined data set (n = 197). The combined data set has been divided into two major groups: the Main Range granitoids (samples collected west of the Ben-tong-Raub suture zone) and the Eastern prov-ince granitoids (samples collected east of the Bentong-Raub suture zone). Among the Eastern province samples, it is evident, as detailed in the complementary U-Pb zircon geochronology paper (Ng et al., 2015), that certain granitoid samples are Cretaceous in age, and these are discussed separately.

Comparison Between Eastern Province and Main Range Province Granitoids

Aluminum Saturation Index (A/CNK)Granitoids of the Eastern province and the

Main Range were originally distinguished, according to their contrasting mineralogy and geochemistry, in terms of Chappell and White’s (1974) I- and S-type classification scheme. In this

system, I- and S-type granitoids are geochemi-cally discriminated primarily by their aluminum saturation index (A/CNK which comes from the abbreviation of its formula Al2O3/[(CaO - 1.67 P2O5) + Na2O + K2O]). The division is drawn where A/CNK = 1.1 (Fig. 7A), such that I-type granitoids are essentially metaluminous and gradually become weakly peraluminous with increasing silica contents, while S-type gran-itoids are typically peraluminous (Chappell and White, 1974, 1992; Ghani et al., 2013b). The Eastern province granitoids and the Main Range granitoids generally follow the trend of I-type and S-type granitoids respectively. The “S-type” Eastern province geochemical outliers suggest that some of the Eastern province granitoids are highly fractionated, while the metaluminous nature of Main Range outliers can be explained by the presence of, for example, the hornblende-bearing Bintang batholith. There is an overlap-ping area in A/CNK space (1.0 < A/CNK < 1.1) where a large number of both Eastern province and Main Range granitoids plot. Hence, the A/CNK plot for the Malaysian granites does not discriminate the two provinces effectively.

Alkali OxidesAnother geochemical scheme used for I- and

S-type discrimination is the proportion of alkali oxides, namely K2O and Na2O, in the granitoids, reflecting the K-feldspar–to–plagioclase ratio. It

is known that I-type granites tend to be more sodic in composition, whereas S-type granites are more potassic (Table 1) (Chappell and White, 1974, 1992; Clarke, 1992; Cobbing et al., 1992; Pitcher, 1997; Ghani et al., 2013b), as indicated by the I-S division line in Figure 7B. The East-ern and the Main Range provinces largely plot in the I- and S-type fields respectively.

Trace ElementsThe trace element compositions of granites

are useful in pointing to the tectonic setting in which the magmas were formed (Pearce et al., 1984; Harris et al., 1986). In the tectonic model proposed by Beckinsale (1979) and Cobbing et al. (1986, 1992), the Eastern province granit-oids were interpreted as pre-collision arc-related granites, while the Main Range province gran-itoids were interpreted as collisional in nature. Pearce et al. (1984) and Harris et al. (1986) showed that collisional granites are character-ized by high Rb contents, which are related to the incorporation of more evolved (crustal) source material into the parental magma, or to Rayleigh fractional crystallization of the magma (Halliday et al., 1991). In the Pearce et al. (1984) plot (Fig. 8A), the present data suggest that the majority of the Main Range province gran-itoids fall within the syn-collisional granite field (syn-COLG), with some outliers falling into the within-plate granite field (WPG). By contrast,

Figure 5. Features of hydro-thermal alteration and mineral-ization in Malaysian granitoids. (A) Skarn development (MA27) during the emplacement of the Tuba two-mica microgranite (MA29) into carbonates, Main Range. Endoskarn is character-ized by the presence of garnet, cordierite, biotite, and sphene. Hornfels is developed beyond the skarn. Ruler is 20 cm long. (B) Greisen-bordered quartz-tourmaline vein (arrow) in the roof zone of the Taiping granite (sample MA16). (C) Secondary fluorite (arrow) in the Taiping granite (MA17) indicating one of the manifestations of hydro-thermal alteration in the Main Range.

Ng et al.


Figure 6. Textural and petrographic features of the Main Range province granitoids. (A) K-feldspar megacrysts are a common feature of the Main Range granitoids (sample MA16, Taiping granite). (B) Chloritized biotite and sericitized K-feldspar in hydrothermally altered Cameron Highlands granitoid (MA13; cross-polarized image). (C) Quartz-tourmaline miarolitic cavity observed in the Langkawi biotite granite (MA30). (D) Association of secondary muscovite with K-feldspar of the Penang granite (MA19; cross-polarized image). (E, F) Scan-ning electron microscope images of the Main Range batholith (MA11) showing typical accessory mineral assemblage comprising ilmenite, apatite, and allanite. Ms—muscovite; see Figure 3 for other mineral abbreviations.



most of the Eastern province granitoids strad-dle the syn-COLG–WPG–volcanic arc granite (VAG) fields, which reflects an enrichment of high field strength elements (HFSEs) such as Y and Nb. In the Harris et al. (1986) diagram (Fig. 8B), both Eastern and Main Range province granitoids generally follow the pattern shown in the Pearce plot (Fig. 8A). Here, no outliers are found in the WPG field, as no Rb depletion is observed in the Malaysian granitoids, indicat-ing that the Malaysian granitoids are unlikely to have formed in a WPG setting.

Fractionation Processes in Malaysian Granitoids

Harker diagrams (Fig. 9) show that the Malaysian granitoids in both granitic provinces have undergone significant fractionation, and that the fractionation trends for the Eastern and Main Range provinces exhibit a large degree of overlap. It is, however, clear that the Main Range province granitoids are generally more fractionated than those of the Eastern province. In general, as the silica contents increase in the Malaysian granitoids, TiO2, Al2O3, FeO, MgO, CaO, and P2O5 decrease, while K2O is alone in showing a positive correlation with silica. A poor correlation is observed with respect to Na2O.

Compatible trace elements Ba, Sr, and Fe were selected to compare with Rb (an incompatible element) in various bivariate diagrams in Figures 10A–10C. The Ba, Sr, and Fe contents decrease by up to two orders of magnitude with increas-ing Rb contents, suggesting that fractionation of feldspars (decrease in Sr and Ba) and biotite and hornblende (decrease in Fe) were likely to have played a role in the evolving magmatic systems. Bulk liquid lines of descent (LLODs) were plot-ted in each diagram to demonstrate the com-posite effect of K-feldspar, plagioclase, biotite, and hornblende fractionation (Figs. 10A–10C). Plots demonstrate that the LLODs of the Eastern province and Main Range province have simi-

lar slopes, and that the compositions may have evolved by similar processes (Figs. 10A and 10B). However, it is also clear that the LLODs of the Eastern province granitoids and the Main Range granitoids have different hypothetical starting points and, therefore, source materials. Moreover, the high Rb/Sr ratios observed in the Main Range province granitoids (Figs. 10A and 10D) suggest that they are generally more frac-tionated than the Eastern province granitoids.

Granite Fractionation and Tin MetallogenesisBecause Sn data are not available from this

study, inferences regarding the relation between granitoid fractionation and whole-rock Sn con-tents are based on the data provided by Cobbing et al. (1992). In Figure 10D, the trace element ratio Rb/Sr is used as an index of fractionation. It is observed that the whole-rock Sn contents of the granitoids have a positive correlation with the fractionation index Rb/Sr, which is to be expected because the more fractionated Main Range gran-itoids are more commonly tin mineralized.

Comparison Between Malaysian Granitoids and Cordilleran I- and S-Type Granites

In Figure 8A, it is observed that both granitic provinces have data that fall into the WPG field, suggesting that Malaysian granitoids from both granitic provinces are enriched in some of the HFSEs, such as Nb and Y. Although this trend is not evident in the Harris diagram (Fig. 8B), enrichment of other HFSEs, such as Ga, Zr, and Ce, is also evident in the plots of Whalen et al. (1987) (Fig. 11), in which it appears that some Malaysian granitoids fall into the A-type field. Enrichments of HFSEs to this degree are unusual for typical I- and S-type granites. Spi-der diagrams (normalized to primitive mantle) of the Malaysian granitoids (Fig. 12) were cre-ated to compare the trace element geochemistry of the Malaysian granitoids with that of more

typical Cordilleran I- and S-type granites, such as the Famatinian magmatic arc in northwestern Argentina (Grosse et al., 2011), and the A-type granites of northeastern China (Wu et al., 2002). These spider diagrams show that the Malaysian granitoids are more enriched in HFSEs (e.g., Zr, Nb, and rare earth elements [REEs]) than typi-cal Cordilleran I- and S-type granites. Certain elements, for example La, Ce, Zr, and Nb, were also compared with corresponding Rb/Sr ratios, which have a positive correlation with granite fractionation, in various bivariate plots (Fig. 13). It is seen that the content of the HFSEs remains relatively constant with increasing Rb/Sr, sug-gesting that their enrichment in Malaysian granitoids is not a product of fractionation, but possibly a primary concentration inherited from the source. The HFSE enrichment in the Malaysian granitoids is considered relevant because both Sn and W are chemically simi-lar to the HFSEs. These elements form large, highly charged cations , which are not compati-ble with the polymerized framework of granitic magma (Eugster, 1985). Accordingly, they tend to be concentrated in the roof zones of plutons where cations are mobile and depolymerization occurs. This implies that high primary Sn and W concentrations in the granite magmas were likely inherited from the source protoliths.

Comparison Between Permo-Triassic and Cretaceous Granitoids

Cretaceous granitoids have to date been identified only in the Eastern province, namely in the Stong region and on Tioman Island. Malaysian Cretaceous granitoids are very similar, mineralogically and geochemically, to the Permo-Triassic granitoids of both Eastern and Main Range Provinces, with the excep-tion of a slight depletion of heavy REEs (e.g., Tb, Dy, Ho, Er, Tm, Yb, and Lu; Fig. 12B) in the former in the Cretaceous granitoids.

TABLE 2B. FEATURES INDICATIVE OF I- AND S-TYPE GRANITES PRESENT IN THE MAIN RANGE PROVINCE GRANITOIDS

rehtOmlIgaMpAnlAhpSsMxPlbHevalcnEnoitacoLygolohtiL.onelpmaSdrCYYYSsdnalhgiHnoremaCetinargtB-drCciryhp-sfK60AM

MA07 Fe-stainning stained Bt granite Y Y YdrCYSetinargtB-drCciryhp-sfK90AMruoTYYYYruoT-ztQetinargtB-ruoT11AM

YYYSsMetinargtB-sMciryhp-sfK31AMMA14 Kfs-phyric Ms-Bt microgranite Y Y Y Fl

yPYYYShopIetinargtB-sMciryhp-sfK51AMYruT-ztQgnipiaTetinargtB-lbHciryhp-sfK61AM Y Y Y Y Y

YYYSruT-ztQdnalsIgnanePetinargtBciryhp-sfK91AMYYSetinargorcimciryhp-sfK02AM

yPYYYSetinargtBciryhp-sfK32AMYSruT-ztQdnalsIiwakgnaLetinargtBciryhp-sfK62AMYSruT-ztQetinargorcimtB-sMciryhp-sfK03AMYYS+PdnalsIabuTetinargorcimtB-sM92AMYYrupmuLalauKetinargtBciryhp-sfK13AMYYroMtikuBetinargtBciryhp-sfK26AM

Note: Y—present; P—primary; S—secondary. Mineral abbreviations: Aln—allanite; Ap—apatite; Bt—biotite; Crd—cordierite;Fl—fl uorite; Hbl—hornblende; Ilm—ilmenite; Kfs—K-feldspar; Mag—magnetite; Ms—muscovite; Px—pyroxene; Py—pyrite; Qtz—quartz; Sp—sphene; Tour—tourmaline.

Ng et al.


TAB

LE 3

A. M

AJO

R A

ND

TR

AC

E E

LEM

EN

T D

ATA

OF

TH

E M

ALA

YS

IAN

EA

ST

ER

N P

RO

VIN

CE

GR

AN

ITO

IDS

55A

M25

AM

05A

M84

AM

74A

M93

AM

63A

M30

AM

elpma

S Latit

ude

04°0

0′42

.1″N

05°0

8′22

.2″N

05°1

7′49

.7″N

05°5

5′16

.5″N

05°5

5′16

.5″N

05°2

0′47

.6″N

04°5

9′21

.6″N

03°5

0′19

.7″N

Long

itude

101°

57′3

2.0″

E10

1°58

′49.

5″E

101°

57′5

0.2″

E10

2°43

′23.

9″E

102°

43′2

3.9″

E10

3°02

′12.

5″E

102°

28′5

3.3″

E10

3°21

′07.

1″E

Roc

k ty

peS

yeni

teK

fs-p

hyric

H

bl-B

t ton

alite

Mig

mat

itic

gran

iteB

t gra

nite

Sye

nite

Kfs

-phy

ric

(Hbl

)-B

t gra

nite

Hbl

-Bt g

rani

teH

bl-B

t gra

nite 4.1

±0.072

8.1±

4.842*4.3

±4.982

6.1±

2.4826.1

±6.752

8.0±

9.389.0

±9.132

)aM(

egA M

ajor

ele

men

ts (

wt%

)S

iO2

53.9

665

.09

60.9

774

.91

57.2

465

.38

64.3

674

.17

TiO

20.

660.

701.

170.

120.

730.

130.

660.

12A

l 2O3

17.7

215

.17

16.0

712

.81

16.5

717

.92

16.6

213

.69

Fe 2

O3

64.142.5

91.174.6

08.036.4

96.471.5

)t(20.0

90.020.0

80.010.0

80.070.0

50.0On

M10.0

48.172.0

20.312.0

50.383.2

09.1Og

M29.0

98.226.0

47.537.0

98.461.3

84.8Oa

C Na 2

03.359.3

73.350.4

35.265.3

36.274.3

OK

247.5

67.211.8

04.491.6

06.359.4

81.5O

P2O

50.

450.

340.

540.

050.

570.

220.

160.

03 64.143.2

26.166.1

73.100.2

97.179.2

IOL

19.00109.001

48.8935.001

37.9955.001

69.00110.001

muS Tr

ace

elem

ents

(pp

m)

201217

03010572

2020452

00610591

P2.32

0.0100.8

2.5204.5

1.128.12

7.01c

S806

0583196

0834385

00960414

0793iT

41.13.45

1.01731

46.98.97

3.18121

V0.75

0.180.55

0.79921

201331

621r

C691

176561

0460.97

626565

354n

M00.1

06.902.2

8.5108.3

4.113.31

03.8o

C7.62

4.437.52

9.156.75

2.351.56

7.34i

N81.2

85.513.6

3.734.02

1.011.22

2.47u

C8.05

7.667.42

5.845.41

2.076.35

0.22n

Z4.91

1.912.22

1.128.61

3.029.81

6.91a

G091

661135

781072

291713

962b

R0.28

493631

0531573

0971614

0921r

S7.43

4.225.51

6.835.23

5.714.03

0.52Y

271102

0.17713

221123

933244

rZ

9.2106.7

07.63.82

6.316.03

0.716.11

bN

74.481.5

4.8239.2

29.447.5

9.9134.1

sC

038328

5930501

2240092

04120712

aB

1.171.42

02.6021

0.566.89

3.387.18

a L941

3.748.11

122411

671751

351e

C3.81

55.533.1

5.524.21

4.916.81

2.81r

P5.56

4.0265.4

3.887.83

0.462.56

7.76d

N5.21

13.441.1

6.4126.6

81.93.11

0.21m

S81.1

40.143.0

71.374.0

65.294.2

48.3u

E42.9

89.302.1

4.0134.5

65.538.7

70.8d

G82.1

46.022.0

14.198.0

47.070.1

50.1b

T57.6

47.392.1

99.613.5

24.315.5

50.5y

D92.1

87.042.0

13.111.1

06.050.1

19.0o

H72.3

61.216.0

14.322.3

45.197.2

12.2r

E84.0

33.090.0

05.025.0

12.004.0

92.0m

T09.2

21.206.0

32.315.3

23.195.2

17.1b

Y24.0

23.080.0

94.015.0

91.093.0

62.0uL

14.568.4

28.078.6

34.349.6

62.81.01

fH

48.056.0

70.120.2

82.139.1

75.187.0

aT32.0

38.060.7

78.078.0

62.038.0

70.1W

76.406.4

93.588.3

41.557.5

16.936.5

lT

7.727.23

1.6219.8

6.418.62

20176.7

bP

7.520.21

53.34.23

7.437.54

9.948.55

hT

13.315.3

24.435.7

84.807.3

3.0195.5

U30.1

41.181.1

87.060.1

98.010.1

86.0K

NC/

A33.0

77.098.0

97.042.0

01.118.0

91.1*u

E/uE

93.164.1

04.1)74.2(

33.1)20.2(

56.1)49.2(

M TZ

r397

208027

)767(867

)108(538

)167()

C°((c

ontin

ued

)



TAB

LE 3

A. M

AJO

R A

ND

TR

AC

E E

LEM

EN

T D

ATA

OF

TH

E M

ALA

YS

IAN

EA

ST

ER

N P

RO

VIN

CE

GR

AN

ITO

IDS

.(co

ntin

ued

)

77A

M37

AM

96A

M66

AM

46A

M85

AM

75A

Melp

maS La

titud

e02

°20′

26.1

″N02

°20′

26.1

″N01

°51′

29.2

″N01

°49′

08.8

″N01

°49′

01.0

″N01

°24′

29.0

″N01

°23′

09.6

″NLo

ngitu

de10

2°37

′03.

9″E

102°

37′0

3.9″

E10

2°57

′19.

2″E

102°

54′3

7.3″

E10

2°54

′50.

9″E

103°

59′2

1.8″

E10

4°12

′20.

5″E

ciryhp-sfK

epytkco

R(H

bl)-

Bt g

rani

teLe

uco–

Kfs

-phy

ric

(Hbl

)-B

t gra

nite

(Hbl

)-B

t gra

nite

Hbl

-Bt g

rani

teB

t gra

nite

Mig

mat

itic

gran

iteH

bl-B

t gra

nite

Age

(M

a)22

2.2

± 1

.822

5.5

± 2

.5*

231.

0 ±

2.6

*M

ajor

ele

men

ts (

wt%

)S

iO2

74.9

375

.32

68.4

371

.40

77.6

175

.69

78.1

0Ti

O2

0.19

0.17

0.49

0.32

0.16

0.16

0.11

Al 2O

313

.92

13.7

116

.06

15.6

912

.76

14.0

712

.69

Fe 2

O3

89.091.1

11.109.1

29.266.0

36.0)t(

20.040.0

30.040.0

50.050.0

30.0On

M41.0

91.081.0

65.080.1

90.081.0

OgM

31.097.0

25.089.1

84.297.0

29.0Oa

C Na 2

70.363.3

79.225.3

99.215.3

33.3O

K2

93.522.5

77.412.5

03.501.5

22.5O

P2O

50.

060.

040.

170.

100.

070.

080.

03 02.139.0

38.031.1

37.059.0

79.0I

OL66.001

87.00181.001

27.00179.99

83.00163.001

muS Tr

ace

elem

ents

(pp

m)

214731

873172

7530.29

912P

0.1102.2

5.3106.3

07.205.3

09.3c

S0461

7860501

3370551

297549

iT4.71

37.158.8

34.41.42

42.143.7

V00.8

00.50.01

00.600.8

00.300.4

rC

084401

283932

662163

332n

M03.3

02.008.1

03.102.3

04.008.0

oC

09.239.1

39.395.2

36.422.2

33.2i

N1.52

67.618.4

91.334.4

9.2190.3

uC

3.251.51

2.353.72

5.626.13

1.62n

Z9.81

1.818.82

6.918.61

7.717.71

aG

223402

278265

573213

373b

R802

8320.34

0.15502

121022

rS

7.928.32

4.970.25

3.528.51

4.06Y

281451

951611

051031

331r

Z3.21

01.67.52

9.813.51

0.815.61

bN

7.5324.4

4118.03

6.738.11

4.31s

C898

0611402

841686

516088

aB

1.154.42

5.155.33

5.820.15

6.75aL

3.395.93

2116.27

5.753.79

4.39e

C68.9

41.49.21

73.807.6

2.011.21

rP

5.237.41

1.446.82

6.323.13

8.14d

N51.6

39.27.01

50.740.5

76.462.7

mS

58.090.1

63.042.0

41.188.0

71.2u

E00.5

51.32.01

97.622.4

21.379.6

dG

87.015.0

08.132.1

56.064.0

21.1b

T46.4

24.37.11

29.769.3

15.292.7

yD

69.087.0

74.276.1

28.005.0

76.1o

H57.2

13.211.7

18.413.2

04.190.5

rE

44.063.0

51.187.0

73.032.0

28.0m

T69.2

24.283.7

41.505.2

45.184.5

bY

54.083.0

60.147.0

73.042.0

78.0uL

79.416.4

95.581.4

43.422.4

40.4f

H15.1

15.099.4

39.321.2

94.153.1

aT39.1

05.09.41

01.439.2

37.068.0

W2.11

00.59.42

7.516.01

57.798.8

lT

4.624.22

9.299.75

3.281.14

1.14b

P9.93

4.015.94

3.624.93

6.428.52

hT

6.2194.1

4.731.72

56.962.8

78.7U

41.131.1

71.150.1

70.180.1

90.1K

NC/

A74.0

01.111.0

11.067.0

07.039.0

*uE/u

E02.1

72.181.1

54.184.1

13.113.1

M TZ

r318

397208

557577

577777

)C°(

(con

tinue

d)

Ng et al.


TAB

LE 3

A. M

AJO

R A

ND

TR

AC

E E

LEM

EN

T D

ATA

OF

TH

E M

ALA

YS

IAN

EA

ST

ER

N P

RO

VIN

CE

GR

AN

ITO

IDS

(co

ntin

ued

)

901A

M401

AM

09A

M78

AM

38A

M18

AM

87A

Melp

maS La

titud

e02

°48′

26.1

″N02

°47′

20.7

″N02

°52′

54.3

″N02

°48′

36.0

″N02

°43′

06.9

″N02

°18′

10.4

″N05

°49′

11.1

″NLo

ngitu

de10

4°09

′20.

0″E

104°

12′1

3.8″

E10

4°10

′52.

0″E

104°

09′1

2.0″

E10

4°10

′27.

0″E

103°

39′2

5.2″

E10

1°56

′07.

2″E

Roc

k ty

peC

px-H

bl-B

t gra

nite

Bt g

rani

te(H

bl)-

Bt g

rani

te(H

bl)-

Bt g

rani

teM

icro

gran

itic

dike

Hbl

-Bt g

rani

teB

t gra

nite

6.0±

1.08)a

M(eg

A80

.2 ±

0.7

244.

3 ±

1.8

*22

6.7

± 2

.2M

ajor

ele

men

ts (

wt%

)S

iO2

71.3

368

.32

70.0

169

.68

76.7

275

.54

69.8

6Ti

O2

0.39

0.26

0.23

0.22

0.10

0.16

0.66

Al 2O

315

.28

18.0

116

.03

17.4

813

.76

13.9

615

.14

Fe 2

O3

54.385.1

95.020.1

09.044.1

59.1)t(

40.050.0

50.010.0

20.020.0

40.0On

M55.1

02.041.0

42.061.0

62.046.0

OgM

27.220.1

88.088.0

28.057.0

08.1Oa

C Na 2

93.265.3

57.369.4

17.328.2

88.3O

K2

45.469.4

35.402.6

32.759.8

50.5O

P2O

50.

130.

050.

040.

040.

030.

060.

21 30.139.0

06.005.0

58.001.1

38.0I

OL75.001

90.10165.001

37.00161.99

88.00194.001

muS Tr

ace

elem

ents

(pp

m)

579532

451931

441481

564P

3.7200.1

2.0105.1

02.108.2

06.7c

S0623

627585

01010711

06210261

iT9.66

44.462.1

02.624.7

4.513.91

V0.04

00.300.5

00.30.01

00.400.8

rC

933714

964411

071941

492n

M07.7

03.105.0

04.000.1

02.108.2

oC

8.5163.2

88.222.2

09.314.3

71.5i

N4.21

44.232.5

83.448.3

77.333.2

uC

3.442.83

3.821.53

5.412.21

4.83n

Z8.81

2.617.91

7.817.71

9.714.51

aG

962343

314811

322953

512b

R032

0.29741

002331

461873

rS

3.822.13

1.622.41

8.911.51

5.71Y

882521

021912

662963

312r

Z8.81

8.112.32

4.118.81

4.019.41

bN

3.017.21

5.8395.2

87.408.8

46.8s

C399

594313

075164

225347

aB

2.565.53

9.627.07

9.362.15

8.35aL

0318.16

2.84341

2311.48

7.98e

C8.41

14.633.5

3.610.51

10.930.9

rP

7.157.02

7.715.35

3.844.72

3.82d

N44.9

52.466.3

67.844.7

78.342.4

mS

16.144.0

95.015.1

61.145.1

59.0u

E08.6

58.393.3

02.556.4

46.259.2

dG

59.046.0

85.007.0

66.004.0

44.0b

T00.5

31.438.3

81.305.3

83.284.2

yD

79.039.0

38.025.0

76.005.0

35.0o

H84.2

88.274.2

03.148.1

35.145.1

rE

53.015.0

34.091.0

82.052.0

52.0m

T21.2

66.351.3

81.149.1

08.137.1

bY

13.085.0

05.081.0

92.092.0

72.0uL

62.789.3

71.441.5

66.606.8

79.4f

H22.1

78.122.3

06.053.1

77.053.1

aT10.1

46.017.4

93.049.0

32.119.0

W92.7

88.775.8

66.279.4

82.989.5

lT

6.051.93

8.049.81

1.639.24

9.41b

P7.74

2.259.83

5.210.02

01.92.91

hT

97.31.02

2.7145.1

21.499.0

74.7U

21.170.1

90.160.1

40.151.1

20.1K

NC/

A16.0

43.015.0

86.006.0

74.128.0

*uE/u

E93.1

43.192.1

94.184.1

93.105.1

M TZ

r148

967077

708628

568408

)C°( N

ote:

M is

defi

ned

as

the

catio

n ra

tio (

Na

+ K

+ 2

Ca)

/(A

l × S

i) (W

atso

n an

d H

arris

on, 1

983)

. Dat

a in

par

enth

esis

wer

e ca

lcul

ated

bey

ond

the

assu

mpt

ion

mad

e by

Wat

son

and

Har

rison

(19

83)

that

M is

less

than

2.

00. A

ges

with

ast

eris

ks (

*) a

re r

efer

ence

mag

mat

ic a

ges

(Ng

et a

l., 2

014)

. LO

I—lo

ss o

n ig

nitio

n. A

/CN

K—

mol

ar r

atio

Al 2O

3/[(

CaO

- 1

.67

P2O

5)

+ N

a 2O

+ K

2O

]. T

Zr i

s de

fi ned

as

12,9

00/{

ln D

+ 3

.80

+ [0

.85(

M -

1)]

},w

here

D is

the

conc

entr

atio

n ra

tio o

f Zr

in z

ircon

(49

6,00

0 pp

m)

to th

at in

the

sam

ple

(Wat

son

and

Har

rison

, 198

3). M

iner

al a

bbre

viat

ions

: Bt—

biot

ite; C

px—

clin

opyr

oxen

e; H

bl—

horn

blen

de; K

fs—

K-f

elds

par.



TAB

LE 3

B. M

AJO

R A

ND

TR

AC

E E

LEM

EN

T D

ATA

OF

TH

E M

ALA

YS

IAN

MA

IN R

AN

GE

PR

OV

INC

E G

RA

NIT

OID

S

91A

M61

AM

51A

M41

AM

31A

M11

AM

90A

M60

AM

elpma

S Latit

ude

04°3

3′50

.4″N

04°3

4′30

.0″N

04°3

3′19

.5″N

04°3

5′00

.3″N

04°3

4′49

.5″N

04°3

2′56

.1″N

04°4

6′54

.9″N

05°2

7′48

.0″N

Long

itude

101°

11′5

5.4″

E10

1°15

′45.

6″E

101°

19′2

6.6″

E10

1°24

′24.

5″E

101°

20′2

2.8″

E10

1°01

′46.

8″E

100°

44′1

1.0″

E10

0°13

′58.

9″E

Roc

k ty

peK

fs-p

hyric

Crd

-Bt

gran

iteK

fs-p

hyric

Crd

-Bt

gran

iteTo

ur-B

t gra

nite

Kfs

-phy

ric M

s-B

t gr

anite

Kfs

-phy

ric M

s-B

t m

icro

gran

iteK

fs-p

hyric

Ms-

Bt

gran

iteK

fs-p

hyric

Hbl

-Bt

gran

iteK

fs-p

hyric

Bt g

rani

te

*9.2±

9.3126.1

±7.512

0.1±

1.0224.2

±3.812

3.1±

4.522*8.2

±1.022

)aM(

egA M

ajor

ele

men

ts (

wt%

)S

iO2

75.7

071

.71

71.8

071

.26

77.1

674

.62

68.1

574

.18

TiO

20.

060.

370.

350.

570.

200.

100.

550.

28A

l 2O3

13.1

414

.03

13.8

412

.97

11.9

513

.76

14.1

912

.34

Fe 2

O3

20.259.2

56.014.1

91.352.2

38.125.0

)t(50.0

50.020.0

30.050.0

30.040.0

30.0On

M63.0

65.131.0

62.033.1

17.065.0

60.0Og

M11.1

47.266.0

44.035.1

18.021.1

17.0Oa

C Na 2

94.257.2

20.337.1

66.215.2

75.281.3

OK

292.4

17.435.5

75.441.4

90.541.6

02.5O

P2O

50.

040.

130.

150.

180.

050.

070.

180.

13 60.289.1

19.027.1

84.241.2

86.141.2

IOL

03.9928.99

74.9925.99

53.00176.99

61.00187.001

muS Tr

ace

elem

ents

(pp

m)

855887

703603

097006

115951

P01.7

1.013.01

5.026.01

6.114.51

9.53c

S0041

0023674

02010333

03710591

183iT

6.314.34

05.175.5

3.331.12

0.9171.1

V0.95

0.690.75

0.270.86

0.650.08

0.24r

C763

114151

572883

832403

012n

M00.3

06.607.0

07.109.6

05.401.3

02.1o

C3.82

1.531.52

0.436.62

2.228.63

7.91i

N01.5

6.1161.8

40.487.7

1.0352.2

70.2u

C1.34

6.6405.5

4.220.99

6.631.23

9.51n

Z5.81

4.911.12

7.917.71

2.713.91

2.42a

G183

824238

975004

453445

0011b

R0.15

1020.52

0.230.58

0.77131

0.32r

S9.84

2.432.74

0.762.93

4.322.64

801Y

371462

0.46541

742131

9910.47

rZ

5.310.32

2.529.42

1.915.31

8.221.92

bN

3.222.05

4.059.11

0.414.21

5.619.47

sC

191575

5110.18

482624

545321

aB

1.830.85

3.416.24

0.540.52

0.949.82

a L1.28

6118.13

6.394.49

2.25201

5.26e

C65.9

9.3117.3

2.111.11

21.61.21

19.7r

P9.33

5.940.21

7.734.93

8.125.14

3.82d

N75.7

24.952.3

08.854.8

36.416.8

17.8m

S16.0

61.151.0

52.087.0

56.057.0

52.0u

E41.7

38.626.3

61.843.7

87.333.7

1.01d

G22.1

30.167.0

45.171.1

16.062.1

10.2b

T76.7

65.596.5

2.0197.6

44.395.7

3.41y

D16.1

01.182.1

51.253.1

86.085.1

81.3o

H75.4

80.399.3

81.616.3

58.173.4

39.9r

E57.0

84.027.0

20.165.0

82.096.0

48.1m

T38.4

80.320.5

74.624.3

97.152.4

1.31b

Y96.0

54.027.0

98.094.0

62.006.0

49.1uL

97.428.6

74.256.4

53.641.3

86.536.3

fH

53.281.3

43.699.3

54.274.1

77.225.9

aT01.1

78.72.81

27.275.1

37.282.1

00.8W

98.70.01

0.813.31

09.849.6

4.312.62

lT

2.334.56

2.038.04

9.235.73

2.541.35

bP

6.923.84

2.520.15

4.534.02

0.254.33

hT

43.88.81

9.424.32

6.011.01

5.116.71

U61.1

99.041.1

04.141.1

62.101.1

90.1K

NC/

A52.0

44.041.0

90.003.0

84.092.0

80.0*u

E/uE

12.185.1

52.169.0

13.161.1

43.192.1

M TZ

r708

718227

118338

787018

037)

C°((c

ontin

ued

)

Ng et al.


TAB

LE 3

B. M

AJO

R A

ND

TR

AC

E E

LEM

EN

T D

ATA

OF

TH

E M

ALA

YS

IAN

MA

IN R

AN

GE

PR

OV

INC

E G

RA

NIT

OID

S (

cont

inue

d)

26A

M06

AM

13A

M03

AM

62A

M32

AM

02A

Melp

maS La

titud

e05

°28′

13.5

″N05

°16′

11.3

″N06

°24′

11.4

″N06

°17′

56.9

″N03

°19′

39.6

″N01

°58′

32.8

″N01

°58′

32.8

″NLo

ngitu

de10

0°11

′31.

1″E

100°

16′5

7.3″

E99

°48′

12.3

″E99

°51′

10.1

″E10

1°44

′52.

0″E

102°

40′2

4.5″

E10

2°40

′24.

5″E

Roc

k ty

peK

fs-p

hyric

mic

rogr

anite

Kfs

-phy

ric B

t gra

nite

Kfs

-phy

ric B

t gra

nite

Ms-

Bt m

icro

gran

iteK

fs-p

hyric

Bt g

rani

teK

fs-p

hyric

Ms-

Bt g

rani

teK

fs-p

hyric

Bt g

rani

te2.1

±4.712

8.1±

4.2227.1

±9.512

6.2±

3.5124.2

±1.212

*5.1±

5.512)a

M(eg

A Maj

or e

lem

ents

(w

t%)

SiO

266

.00

68.6

069

.72

76.9

369

.94

73.9

572

.07

TiO

20.

430.

410.

390.

160.

510.

190.

32A

l 2O3

16.4

814

.71

14.6

112

.55

13.9

814

.24

14.2

3F

e 2O

317.2

86.125.2

61.113.2

97.296.3

)t(60.0

60.050.0

50.050.0

40.070.0

OnM

74.012.0

10.182.0

91.055.0

69.0Og

M59.1

19.029.1

53.013.1

54.143.3

OaC N

a 201.3

85.371.2

90.334.1

57.212.2

OK

284.4

38.471.5

28.482.6

92.667.3

OP

2O

50.

100.

160.

120.

130.

150.

090.

10 60.191.1

69.124.1

01.250.2

92.3I

OL35.001

29.00193.99

39.00115.89

18.9923.001

muS Tr

ace

elem

ents

(pp

m)

486323

627585

586786

675P

09.503.5

6.713.12

3.917.71

06.5c

S0042

2460303

3970402

03120712

iT2.14

68.25.03

46.86.82

9.420.25

V0.91

00.40.26

0.050.66

0.870.94

rC

193663

663773

793853

735n

M04.5

07.007.5

04.209.4

04.402.7

oC

58.710.2

1.129.42

0.238.63

0.12i

N72.4

61.271.8

90.426.4

51.801.4

uC

1.056.62

7.833.53

3.345.94

4.63n

Z9.81

0.714.81

2.617.71

4.029.71

aG

073024

534606

074444

851b

R881

0.96101

0.02501

0.68373

rS

1.624.84

6.130.53

8.430.64

8.52Y

332401

0320.28

171832

681r

Z5.71

4.424.71

6.415.31

1.612.62

bN

4.434.31

8.931.65

4.644.62

55.6s

C739

142076

0.86247

4060101

aB

5.644.72

1.647.31

2.139.74

9.75aL

9.293.65

9.499.03

8.565.79

1.79e

C5.01

25.60.11

97.318.7

6.112.01

rP

4.635.22

6.834.31

9.724.14

0.33d

N09.6

26.535.7

55.399.5

76.896.5

mS

61.143.0

59.002.0

02.151.1

21.1u

E83.5

28.590.6

17.394.5

97.795.4

dG

18.070.1

49.027.0

29.072.1

27.0b

T84.4

73.623.5

69.455.5

15.790.4

yD

88.011.1

60.101.1

71.135.1

88.0o

H04.2

08.298.2

63.353.3

22.425.2

rE

63.034.0

44.016.0

35.046.0

93.0m

T52.2

37.267.2

42.454.3

99.385.2

bY

33.073.0

04.006.0

94.085.0

93.0uL

22.629.2

00.658.2

94.487.5

94.4f

H86.1

51.867.2

98.440.2

28.134.1

aT55.6

89.098.1

5.2148.8

62.243.0

W4.01

8.016.01

5.219.01

07.815.3

lT

0.855.43

6.255.33

9.153.34

6.61b

P0.74

4.921.63

2.510.12

3.236.71

hT

6.111.91

9.318.71

06.676.6

74.2U

60.121.1

21.161.1

82.170.1

12.1K

NC/

A85.0

81.034.0

71.046.0

34.076.0

*uE/u

E93.1

92.143.1

02.151.1

54.103.1

M TZ

r128

857328

547118

818708

)C°( N

ote:

M is

defi

ned

as

the

catio

n ra

tio (

Na

+ K

+ 2

Ca)

/(A

l × S

i) (W

atso

n an

d H

arris

on, 1

983)

. Age

s w

ith a

ster

isks

(*)

are

ref

eren

ce m

agm

atic

age

s (N

g et

al.,

201

4). L

OI—

loss

on

igni

tion.

A/C

NK

—m

olar

rat

io

Al 2O

3/[(

CaO

- 1

.67

P2O

5)

+ N

a 2O

+ K

2O

]. T

Zr i

s de

fi ned

as

12,9

00/{

ln D

+ 3

.80

+ [0

.85(

M -

1)]

}, w

here

D is

the

conc

entr

atio

n ra

tio o

f Zr

in z

ircon

(49

6,00

0 pp

m)

to th

at in

the

sam

ple

(Wat

son

and

Har

rison

, 198

3).

Min

eral

abb

revi

atio

ns: B

t—bi

otite

; Crd

—co

rdie

rite;

Hbl

—ho

rnbl

ende

; Kfs

—K

-fel

dspa

r; M

s—m

usco

vite

; Tou

r—to

urm

alin

e.



The Cretaceous granitoids are also charac-terized by low Y/Nb ratios in Eby’s (1992) Y-Nb-Ce and Y-Nb-Gax3 diagrams (Fig. 14), but because they are not depleted in Rb (Fig. 8B), and many of them do not fall in the A-type field in Figure 11, this diagram serves only to discriminate between Cretaceous and Permo-Triassic granitoids in the Eastern province. Hutchison (2007) suggested that the occur-rence of Cretaceous rift-related granitoids in

the Malay Peninsula might be related to the opening of the Straits of Malacca and the Gulf of Thailand, but no evidence was provided to support this postulate.

Sr-Nd ISOTOPIC ANALYSIS

Initial 87Sr/86Sr ratios and eNd(t) values are often useful as indicators of the nature of the magmatic source for granitoids and have been

used to discriminate between I- and S-type gran-ites (Table 1) (Cobbing et al., 1986; Chappell and White, 1992; Ghani et al., 2013b). In this study, Sr and Nd isotopic data were collected in the Department of Geosciences, National Tai-wan University, using a multi-collector–induc-tively coupled plasma–mass spectrometer, the Thermo Electron Finnigan Neptune. Detailed sample handling and preparation procedures are described in Lee et al. (2012) and in the Data Repository (see footnote 1).

New Sr-Nd isotopic data of the Malaysian granitoids are presented in Tables 4A and 4B. It should be noted that the Sr isotopic data for the Main Range granitoids have limited applica-bility because many of these samples have high (>10) Rb/Sr ratios, resulting in impre-cise initial 87Sr/86Sr ratio calculations. This is because the calculation involves subtraction of the radiogenic components from the mea-sured 87Sr/86Sr ratio. Accordingly, these data are omitted from the discussion. In general, however, the new data of the Eastern province granitoids show an initial 87Sr/86Sr ratio rang-ing from 0.7004 to 0.7074, while those from the Main Range province granitoids range from 0.7062 to 0.7159. In contrast, the Nd isotopic data are more reliable, as both Sm and Nd are less mobile than the Rb-Sr pair. The initial Nd isotope ratios for the majority of the Eastern province granitic samples in the present data set range from 0.5120 to 0.5123, giving a variety of eNd(t) values, ranging from –2.4 to –5.3 (except for sample MA36 with a rather low eNd(t) value at –10.01, and the Perhentian syenite sample, MA48, with a slight positive value of +0.62). The eNd(t) values calculated for the Main Range province granitoids are more restricted, varying from –7.8 to –9.6. These data are combined with those from Cobbing et al. (1992) and Liew and McCulloch (1985) to form a more representa-tive data set, presented in Figures 15A and 15B. In the combined data set, the Eastern province Permo-Triassic granitoids have initial 87Sr/86Sr ratios ranging from 0.7004 to 0.7143 and eNd(t) values ranging from –0.7 to –5.8, whereas the Main Range granitoids have initial 87Sr/86Sr ratios ranging from 0.7062 to 0.7243 and eNd(t) values ranging from –5.4 to –9.6.

The combined data show that the Nd isotope ratio is a reliable discriminator of Malaysian granitoids (Fig. 15). However, the depleted-mantle model ages (TDM) calculated from the Sm-Nd isotopic values may be unreasonably high if marked fractionation ( f ) has occurred between Sm and Nd to give fSm/Nd values that are higher than that of average continental crust (where fSm/Nd = –0.4; Wu et al., 2002). In such cases, a two-stage neodymium depleted mantle model age (TDM2) is required to correct for the

A

B

Figure 7. Comparison of the Eastern province and Main Range granitoids in terms of alu-minum saturation index (A/CNK which is the molar ratio Al2O3/[CaO - 1.67 P2O5 + Na2O + K2O]) (A) and alkali oxides (B) showing the overlap between the Eastern province and the Main Range granitoids in Chappell and White’s (1974) I- and S-type granite system. The I- and S-type division is after Chappell and White (1974, 1992).

Ng et al.


unrealistically high values obtained. This cal-culation assumes that the protolith shares the same Sm/Nd ratio as the average continental crust (Keto and Jacobsen, 1987). The Eastern province granitoids have fSm/Nd values that range from –0.23 to –0.56, yielding TDM ages between 0.89–1.92 Ga (Table 4B). Significant fraction-ation occurred between Sm and Nd in sample MA50 ( fSm/Nd = –0.23), and TDM2 (1.36 Ga) is, therefore, adopted as the Nd model age instead of TDM (1.92 Ga). Hence, the Nd model ages of the Eastern province granitoids range from 0.89 to 1.36 Ga in the new data (Table 4B). The Main Range province granitoids have fSm/Nd values between –0.05 and –0.40. Significant fraction-ation occurred between Sm and Nd in samples MA06, MA14, and MA30. TDM2 is also, there-fore, adopted as the Nd model age for these samples. In general, the Main Range province granitoids have slightly older Nd model ages, ranging from 1.63 to 1.99 Ga (Table 4B). These isotopic data are again combined with those of Cobbing et al. (1992) and Liew and McCulloch (1985) to form a more representative data set, and presented in Figure 15C. In the combined data set, the Eastern province granitoids have Nd model ages ranging from 0.74 to 1.63 Ga, while those of the Main Range granitoids vary between 1.18 and 1.99 Ga.

DISCUSSION

Possible Protoliths of Malaysian Granitoids

Granites may be formed by the hybridiza-tion or mixing of melts derived from igneous and sedimentary precursors (DePaolo, 1988; Keay et al., 1997; Gray and Kemp, 2009; Kemp et al., 2009). Because Malaysian granitoids are geochemically intermediate between well-con-strained end-member granite compositions such as the I-type Gangdese-Ladakh granites and the S-type Himalayan leucogranites, it is suggested in this study that the parental magmas of the Eastern and the Main Range granitoids may be hybridized products derived from the melting of variable proportions of both igneous and sedi-mentary precursors.

Possible source rocks for Malaysian gran-itoids can be considered by comparing their Sr-Nd isotopic compositions with those of the surrounding basement rocks. In this study, the Sr-Nd isotopic compositions of the East-ern province granitoids are compared with isotope data obtained from the Kontum mas-sif, an ultrahigh-grade metamorphic complex that is exposed some 1500 km to the north of the Maylay Peninsula. Although it is some distance away, the Kontum massif is regarded as a viable analogue of the lower continental

A

B

Figure 8. Rb versus (Y + Nb) plot (A) and Hf–(Rb / 30)–(Ta × 3) plot (B) illustrating the tectonic discriminations between the Eastern province and the Main Range province granitoids, after Pearce et al. (1984) and Harris et al. (1986) respectively. Because no Hf and Ta data are available in Cobbing et al. (1992), only data from this work are presented in B. syn-COLG—syn-collisional granite; WPG—within-plate granite; VAG—volcanic arc granite; ORG—ocean ridge granite.



A B

C D

E F

G H

Figure 9. Harker diagrams of the Malaysian granitoids for various major element oxides, showing the extent to which the Malaysian granites are fractionated and the high degree of compositional overlap between the Eastern and Main Range provinces. Symbols follow Figure 7.

Ng et al.


crust of Indochina and furthermore has Sr-Nd isotopic data available for petrogenetic model-ing. Kontum comprises orthoamphibolites and paragneisses yielding TDM ages of 1.2–2.4 Ga, as well as a component of old granulite dated at 2.7 Ga (Lan et al., 2003). The orthoamphibo-lites of the Kontum massif have been interpreted as metamorphosed intraplate basalt, which was dated as Cambro-Ordovician (U-Pb zircon: 451 ± 3 Ma; 40Ar/39Ar biotite: 424 ± 5 to 339 ± 4 Ma) by Nagy et al. (2001). The paragneisses were interpreted as a Mesoproterozoic sedimen-tary basement older than 1403 ± 34 Ma based on the youngest detrital U-Pb zircon age (Nam et al., 2001). The Kontum orthoamphibolites and paragneisses are enriched in HFSEs (Fig. 16; Lan et al., 2003), which may be relevant to the high HFSE concentrations observed in the Malaysian granitoids. It is suggested that par-tial melting of Kontum-like orthoamphibolites and paragneisses, and the hybridization of these

melts, could have formed the Eastern province parental magma. This hypothesis is also sup-ported by the Cambro-Ordovician and Meso-proterozoic inheritance signatures observed in zircons of the Eastern province granitoids (Ng et al., 2015).

Formation of the Eastern Province Parental Magma by Hybridization of Melts Derived from Kontum Lithologies

The Kontum orthoamphibolite sample TS22A (initial 87Sr/86Sr = 0.7035, eNd(t) = +1.5) and the paragneiss sample KT333/6 (initial 87Sr/86Sr = 0.7800, eNd(t) = –18.0) from Lan et al. (2003) are selected as end members in Figure 15A, as they have the two extremes in Sr-Nd isotopic compositions in the Kon-tum massif. Two hypothetical mixing curves are constructed between these end members (Fig. 15A). Curve A uses the Sr and Nd com-

positions of the Kontum end-member litholo-gies (Srigneous = 200 ppm, Ndigneous = 6 ppm, Srsedimentary = 240 ppm, Ndsedimentary = 45 ppm) (Lan et al., 2003), whereas curve B uses those of average ocean island and average continen-tal crust as end members (Srigneous = 650 ppm, Ndigneous = 25 ppm, Srsedimentary = 150 ppm, Ndsedimentary = 60 ppm) (Pram and Pohl, 1994; Villaseca et al., 1998; Wilson, 2007). It is found that, except for the Berengkat tonalite with its evolved eNd(t) values, 80%–90% of the Eastern province parental magma comes from an igne-ous-sourced melt. Because the incorporation of sedimentary-sourced melt is minimal here, I-type mineralogy and geochemistry are largely retained in the Eastern province. This model is consistent with the less well-developed Sn-W mineralization in the Eastern province com-pared to the Main Range but still allows for the development of primary tin deposits via crystal fractionation and aqueous phase separation.

A

B

C

D

Figure 10. (A–C) Trace element bivariate diagrams of Sr (A), Ba (B), and Fe (C) versus Rb with bulk liquid lines of descent (LLODs), pur-porting to show crystal fractionation as a function of the removal of plagioclase, K-feldspar, hornblende, and biotite . Each increment on an LLOD represents 20% crystallization. The bulk LLOD of the Eastern province granitoids is constructed for fractionation of 10% horn-blende, 1% biotite, 50% plagioclase, and 39% K-feldspar. The bulk LLOD of the Main Range granitoids is constructed for fractionation of 5% hornblende, 1% biotite, 50% plagioclase, and 44% K-feldspar. Partition coefficients used are from Mahood and Hildreth (1983), Ewart and Griffin (1994) and Streck and Grunder (1997). (D) Sn content in Malaysian granitoids as a function of the degree of fractionation, represented by Rb/Sr.



Formation of the Main Range Province Parental Magma

The Main Range province hosted by the Sibumasu terrane comprises predominantly biotite granite, with subordinate hornblende-biotite granodiorite and adamellite. This implies that the source of the Main Range granitoids is largely metasedimentary, but with the possibil-ity of a minor igneous-sourced magma input.

No Precambrian Sibumasu basement rocks are exposed in the Malay Peninsula, and although high-grade metamorphic rocks are reported in northern and eastern Thailand, their ages are Late Triassic (229 ± 3 to 193 ± 4 Ma; Mac-Donald et al., 2010; Kawakami et al., 2014), which rules them out as possible source rock. Although there is no candidate source material to use for modeling purposes, the isotopic ratios of samples from the Main Range are neverthe-

less plotted in Figure 15A because they are likely to have been derived from similar pre-cursors to the parental magmas of the Eastern province. This is supported by the observation that the Main Range granitoids also have an enriched HFSE signature (Fig. 12C), as well as Cambro-Ordovican and Mesoproterozoic zircon inheritance ages as shown in Ng et al. (2015). The Main Range points also plot on the mix-ing trend between Kontum-like meta-igneous

A

B

Figure 11. Plots after Whalen et al. (1987) showing the com-parisons between fields for I- and S-type and A-type gran-itoids in terms of high field strength elements (HFSEs). While the majority of Malay-sian granitoids clearly have I- and S-type affinities, a signifi-cant proportion is enriched in elements such as Zr, Nb, Ce, and Y (like A-type granites) suggest-ing that the source rocks may themselves have been enriched in HFSEs. FG—fractionated granite; OGT—unfractionated I- and S-type granites.

Ng et al.


A

B

C

Figure 12. Spider diagrams of the Malaysian granitoids showing the enrichment of high field strength elements (left) and rare earth elements (REEs, right) relative to typical Cordilleran I- and S-type granitoids (light gray shading) (Grosse et al., 2011) and north-eastern China A-type granitoids (dark gray shading) (Wu et al., 2002). (A) Eastern province Permo-Triassic granitoids. (B) Eastern province Cretaceous granitoids. (C) Main Range granitoids. The spider diagrams on the left-hand panels are normalizaed to primi-tive mantle, while those on the right are normalized to chondrites (Sun and McDonough, 1989).



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and metasedimentary protoliths. However, the incorporation of Kontum-like sedimentary-sourced melt in the Main Range parental magma is much more significant (up to 40%) than in the Eastern province. This explains the enhanced peraluminosity of the Main Range granitoids, and restricts the crystallization of hornblende (Zen, 1986) such that the Main Range prov-ince is dominated by biotite granite. The higher degree of involvement of a predominantly sedi-mentary-sourced melt would also have lowered the oxygen fugacity of the Main Range paren-tal magma, producing predominantly ilmenite-series granitoids and favoring the formation of primary tin deposits (Lehmann, 1990).

The Malaysian Granitoids in the I- and S-Type Granite Classification

Beckinsale (1979) and Cobbing et al. (1986, 1992) separated the Malaysian granitoids into an I-type Eastern province and an S-type Main Range province, according to their mineral-

ogical and geochemical differences. This study has confirmed that the hornblende-bearing granitoids of the Eastern province have typical I-type mineralogy and geochemical signatures. Mineralogically, they contain I-type indica-tive minerals like hornblende and sphene, and geochemically they are more sodic and meta-luminous to weakly peraluminous in com-position. These I-type granites are, however, not wholly restricted to the Eastern province; the hornblende-bearing Bintang batholith in the Main Range province is also an I-type com-plex. Although Sr-Nd isotopic data suggest that as much as 10%–20% of sedimentary-sourced melt was incorporated into the parental magma of the Eastern province granitoids, the I-type mineralogy and geochemistry is still largely retained.

In contrast, the Main Range province is dominated by hornblende-free biotite granites, interpreted as “S-type” by Beckinsale (1979) and Cobbing et al. (1986, 1992) because they are generally more potassic and peraluminous.

These characteristics are also found in fraction-ated I-type pluton roof zones in the Eastern province, and make the Main Range granitoids mineralogically and geochemically indistin-guishable from them. One of the ways to dis-criminate Main Range granitoids from those of the Eastern province is using Sr-Nd isotope compositions. The Main Range granites have higher initial Sr isotope ratios, but lower eNd(t) values. These values are intermediate in the range of values of potential igneous and sedi-mentary end-member sources (Fig. 15A), sug-gesting that these granitoids are formed from hybridized parental magma with significant input from both an igneous precursor and a sedimentary precursor. Hence, it is suggested that the Main Range province granitoids is tran-sitional I/S type, whereas the incorporation of sedimentary-sourced melt into the Eastern prov-ince parental magma was not significant enough to be reflected in mineralogy. Hence, its I-type signature largely retains.

Comparison of the Malaysian and Himalaya-Tibetan Granitoids

The tectonic relationship between pre-col-lision I-type granites and syn-collision S-type granites is best demonstrated by the granitoids intruded along the India-Asia collision in the Himalaya and south Tibet (Fig. 17). The Malay Eastern province granitoids are comparable in some ways to the pre-collision arc-related I-type Gangdese-Ladakh granites in geom-etry, morphology, and mineralogy (Chiu et al., 2009). Both of them are batholithic in size and are associated with contemporaneous calc-alkaline andesites, dacites, and rhyolites (Linzi-zong volcanics in Tibet and Pahang volcanics in the Eastern province). However, differences do occur, including the fact that Malaysian Eastern province granitoids are slightly more enriched, especially in REEs and HFSEs, than the Tibetan Gangdese-Ladakh granites (Fig. 18A) (Wen et al., 2008). In addition, the East-ern province granitoids have lower eNd(t) values than the Gangdese-Ladakh granites (Fig. 15A) (Wen et al., 2008), probably reflecting the incor-poration of metasedimentary material into the parental magma of the Malay Eastern province granites. The formation of large granitic batho-liths involves large amounts of heat and water, which could only be supplied by fluids driven off a subduction zone. Timing constraints of both the Tibetan Gangdese and Malay Eastern province granites show that magmatism ended soon after the continental collision and closure of the suture zone.

The “collision-related” Main Range prov-ince granitoids have also been compared to

A

B

Figure 14. A-type granite dis-crimination diagrams after Eby (1992) showing that the Creta-ceous granitoids in the Eastern province have slightly lower Y/Nb ratios than the dominant Permo-Triassic granitoids.



the Greater Himalayan tourmaline two-mica leucogranites. The Himalayan leucogranites are entirely of sedimentary origin, have silli-manite, andalusite, and cordierite in the melt phase, have abundant magmatic tourmaline from boron-rich fluids, occur as in situ melts within sillimanite-grade migmatites, and are associated with widespread regional Bar-rovian metamorphism and partial melting at pressures varying from ~10 to 4 kbar (Searle et al., 2010). These Himalayan leucogranites and their migmatitic host rocks occur along a mid-crustal channel, bounded by a crustal-scale thrust fault along the base (Main Central thrust) and by a crustal-scale low-angle normal fault (the South Tibetan detachment) along the top. None of these features compare with the morphology and geometry of the Main Range province granitoids. The Main Range prov-ince granitoids are of batholithic proportions far greater than the Himalayan leucogranites. The Malaysian Main Range granitoids are not

apparently associated with a regional migma-tite terrane (at least not an exposed one), do not appear to have a Barrovian metamorphic sequence (unless it remains unexposed in the lower crust), and are not associated with con-temporaneous thrust or normal faults. Clearly the Malay Main Range granites required a far greater heat source than the Himalayan leucogranites. Internally derived heat from crustal thickening is only sufficient to derive relatively small volumes of Himalayan leuco-granite melts, not large batholiths. Besides, the surface geological evidence for major crustal thickening (e.g., the uplifting of 1500 m of the Cameron Highlands) and regional metamor-phism (typically in greenschist facies) in west-ern Malaysia cannot explain the enormous heat required for the Main Range magmatism. The only other source of heat is from the mantle; therefore some sort of magmatic underplating above a Triassic subduction zone is proposed to account for this extra heat.

Petrogenetic Model for Malaysian Granitoids

We have proposed that the generation of the voluminous Main Range province granitoids required huge amounts of heat and water, which could not have been provided solely by post-collision crustal thickening as we see in the for-mation of the Greater Himalayan leucogranites. Hence, the formation of the Malaysian granit-oids likely resulted from subduction processes rather than from continental collision. During subduction, fluids are driven off the subducting slab, and these fluids can induce melting at the base of the crust. Magmatic underplating would seem to be a logical process to generate both extra heat and the fluid-induced melting to make the Main Range batholith. Partial melting of the upper-amphibolite to granulite facies middle and lower crust could be achieved with or with-out the presence of water by the fluid-present or fluid-absent melt reactions.

TABLE 4A. Sr ISOTOPIC DATA OF THE MALAYSIAN GRANITOIDS

Sample Rock typeAge(Ma)

Rb(ppm)

Sr(ppm) 87Rb/86Sr (87Sr/86Sr)m ±2σ (87Sr/86Sr)i

MA06 Kfs-phyric Crd-Bt granite 220.1 ± 2.8* 1100 23.0 138 1.030768 1.5E-05 0.5904MA13 Kfs-phyric Ms-Bt granite 225.4 ± 1.3 400 85.0 13.6 0.759570 6E-06 0.7159MA14 Kfs-phyric Ms-Bt microgranite 218.3 ± 2.4 579 32.0 52.4 0.833845 1.3E-05 0.6713MA19 Kfs-phyric Bt granite 213.9 ± 2.9* 381 51.0 21.6 0.771932 1.1E-05 0.7062MA23 Kfs-phyric Bt granite 212.1 ± 2.4 444 86.0 15.0 0.756029 5E-06 0.7109MA26 Kfs-phyric Bt granite 215.3 ± 2.6 470 105 13.0 0.751779 8E-06 0.7121MA30 Ms-Bt microgranite 215.9 ± 1.7 606 20.0 87.7 0.926408 1.5E-05 0.6572MA31 Kfs-phyric Bt granite 222.4 ± 1.8 435 101 12.5 0.754962 9E-06 0.7155MA36 Kfs-phyric Hbl-Bt tonalite 231.9 ± 0.9 317 416 2.20 0.728782 9E-06 0.7215MA39 Migmatitic granite 83.9 ± 0.8 192 1790 0.31 0.707854 7E-06 0.7075

4407.060-E9640217.080.25730726.1±6.752etinargtB74AM6507.060-E5232707.004.005317816.1±2.482etineyS84AM

MA50 Kfs-phyric (Hbl)-Bt granite 289.4 ± 3.4* 531 136 11.3 0.744183 6E-06 0.6976MA52 Hbl-Bt granite 248.4 ± 1.8 166 394 1.21 0.711707 8E-06 0.7074MA55 Hbl-Bt granite 270.0 ± 1.4 190 82.0 6.71 0.726117 8E-06 0.7004

Note: (87Sr/86Sr)i = 87Sr/86Sr – (87Rb/86Sr) × (e–λ – 1), where λ is the decay constant and where λRb–Sr = 0.0142 Ga–1; 87Rb/86Sr = (Rb/Sr) × 2.8956. T is the age of the sample. (87Sr/86Sr)m is the measeured Sr ratio. Ages with asterisks (*) are reference magmatic ages (Ng et al., 2015). Mineral abbreviations: Bt—biotite; Crd—cordierite; Hbl—hornblende; Kfs—K-feldspar; Ms—muscovite.

TABLE 4B. Nd ISOTOPIC DATA OF THE MALAYSIAN GRANITOIDS

Sample Rock typeAge(Ma)

Sm(ppm)

Nd(ppm) 147Sm/144Nd (143Nd/144Nd)m ±2σ fSm/Nd εNd(t )

TDM

(Ga)TDM2

(Ga)MA06 Kfs-phyric Crd-Bt granite 220.1 ± 2.8* 8.71 28.3 0.186 0.512213 3.3E-06 −0.05 −8.00 5.16 1.63MA13 Kfs-phyric Ms-Bt granite 225.4 ± 1.3 8.45 39.4 0.130 0.512049 5.5E-06 –0.34 −9.56 1.99MA14 Kfs-phyric Ms-Bt microgranite 218.3 ± 2.4 8.80 37.7 0.141 0.512101 3.2E-06 −0.28 −8.93 2.19MA19 Kfs-phyric Bt granite 213.9 ± 2.9* 7.57 33.9 0.135 0.512143 2.9E-06 −0.31 −7.98 1.95MA23 Kfs-phyric Bt granite 212.1 ± 2.4 8.67 41.4 0.127 0.512140 3.6E-06 −0.36 −7.82 1.77MA26 Kfs-phyric Bt granite 215.3 ± 2.6 5.99 27.9 0.130 0.512103 2.6E-06 −0.34 −8.60 1.89MA30 Ms-Bt microgranite 215.9 ± 1.7 3.55 13.4 0.160 0.512132 2.3E-06 −0.19 −8.86 2.86 1.70MA31 Kfs-phyric Bt granite 222.4 ± 1.8 7.53 38.6 0.118 0.512038 2.7E-06 −0.40 −9.48 1.77MA36 Kfs-phyric Hbl-Bt tonalite 231.9 ± 0.9 11.3 65.2 0.105 0.511986 3.0E-06 −0.47 −10.0 1.63MA39 Migmatitic granite 83.9 ± 0.8 9.18 64.0 0.087 0.512393 3.8E-06 −0.56 −3.60 0.91

90.193.2−74.0−60-E8.3853215.0301.07.8326.66.1±6.752etinargtB74AM98.026.0+94.0−60-E0.4094215.0001.03.886.416.1±2.482etineyS84AM

MA50 Kfs-phyric (Hbl)-Bt granite 289.4 ± 3.4* 1.14 4.56 0.151 0.512358 2.7E-06 −0.23 −3.79 1.92MA52 Hbl-Bt granite 248.4 ± 1.8 4.31 20.4 0.128 0.512257 3.3E-06 −0.35 −5.25 1.58MA55 Hbl-Bt granite 270.0 ± 1.4 12.5 65.5 0.116 0.512364 3.5E-06 −0.41 −2.55 1.22

Note: (143Nd/144Nd)i = 143Nd/144Nd – (147Sm/144Nd) × (eλT – 1), λ is the decay constant where λSm–Nd = 0.00654 Ga–1; 147Sm/144Nd = (Sm/Nd) × 0.60456. εNd(t ) = [(143Nd/144Nd)Sample(T )/(143Nd/144Nd)CHUR(T ) – 1] × 104; (143Nd/144Nd)CHUR(T ) = 0.512638 – 0.1967 × (eλT – 1) where T is the age of the sample.TDM = 1/λSm–Nd × ln{1 + [((143Nd/144Nd)Sample – 0.51315)/((147Sm/144Nd)Sample – 0.2137)]} where TDM is the depleted mantle model age and TDM2 is the two-stage depleted mantle model age. fSm/Nd = [(147Sm/144Nd)/0.1967] – 1, where fSm/Nd is the fractionation factor of the sample and (143Nd/144Nd)m is the measured Nd ratio. All the modern Sm/Nd values in CHUR (chondritic uniform reservoir) and DM (depleted mantle) are as suggested by Goldstein et al. (1984) and Peucat et al. (1988). Mineral abbreviations: Bt—biotite; Crd—cordierite; Hbl—hornblende; Kfs—K-feldspar; Ms—muscovite. Ages with asterisks (*) are reference magmatic ages (Ng et al., 2015).

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A

B

C

Figure 15. (A) Sr-Nd isotope characteristics of the Malaysian granitoids in comparison with other granitic terranes in the world. The Sr-Nd isotope data of the Gangdese I-type granitoids and Himalayan S-type leuco granites are provided by Wen et al. (2008) and Guo and Wilson (2012), while those of the Cordilleran–Famatinian I- and S-type granitoids are provided by Grosse et al. (2009). The Lachlan fold belt Sr-Nd data are provided by Chappell and White (1992). The Kontum massif Sr-Nd data are from Lan et al. (2003). Curve A uses the Sr and Nd compositions of the Kontum end-member lithologies (Srigneous = 200 ppm, Ndigneous = 6 ppm, Srsedimentary = 240 ppm, Ndsedimentary = 45 ppm) (Lan et al., 2003), whereas curve B uses those of average ocean island and average continental crust as end members (Srigneous = 650 ppm, Ndigneous = 25 ppm, Srsedimentary = 150 ppm, Ndsedimentary = 60 ppm) (Pram and Pohl, 1994; Villaseca et al., 1998; Wilson, 2007). Numbers on curve represent proportion of sedimentary-sourced melt incorporated in the parental magma. (B, C) The Sr-Nd isotope character-istics of the Malaysian granitoids show good discrimination between the Eastern prov-ince and Main Range granitoids. CHUR—Chondritic Uniform Reservoir.



The mineralogical and geochemical differ-ences between the Eastern province granitoids and the Main Range province granitoids are con-trolled mainly by the compositional difference between their source regions (Fig. 19; Chappell and White, 1974; Clemens and Stevens, 2012).

This study suggests that the parental magmas of the Eastern province were derived mainly from a Kontum-like igneous precursor (I type), hybridized with a minor amount of Kontum-like sedimentary-sourced melt, as suggested by the Sr-Nd isotope data. This implies that the lower-

crust basement of the Indochina–East Malaya terrane is dominated by granulite facies meta-igneous material, together with a minor amount of sedimentary protoliths. In contrast, the paren-tal magma forming the Main Range province granitoids was probably a hybridized magma

Figure 16. Spider diagrams of the Kontum orthoamphibolites and Kontum paragneisses provided by Lan et al. (2003). Samples TS22A and KT333/6 were selected as end members for the purposes of the Sr-Nd isotope modeling of Figure 15A. The spider diagrams are normalizaed to primitive mantle. (Sun and McDonough,1989).

Figure 17. Schematic cross-section illustrating the Indo-Asian collision in the Miocene and the spatial relationship between the pre-collision Andean I-type Gangdese-Ladakh granites and the post-collision S-type Greater Hima-layan leucogranites, after Searle et al. (2010, 2011). Ages are provided by Chiu et al. (2009) and Chu et al. (2006).

Ng et al.


with significant input from both Kontum-like igneous and sedimentary precursors (transi-tional I/S type), with sedimentary-sourced melt contributing up to 40% of the Main Range parental magma. Hence, the lower crustal base-ment of the Sibumasu terrane should also have considerable amounts of both Kontum-like igneous and sedimentary precursors. According to the field relationship and geochemistry of the Malaysian granitoids in both provinces, horn-blende-bearing granitoids were fractionated to form hornblende-free roof zones at the top of plutons, which is essentially a zone character-ized by hydrothermal alteration and mineraliza-

tion. Contact metamorphic skarns are developed where the Main Range granites are in contact with the sedimentary country rocks, dominantly carbonates (Fig. 5B).

All these observations are summarized into a petrogenetic model for the Malaysian granitoids (Fig. 19). Hornblende-biotite granitoids of the Eastern province were formed from igneous-dominated protoliths forming the basement and/or lower crust beneath Indochina–East Malaya. These granitoids were emplaced and subsequently fractionated in situ to form horn-blende-free phases typically concentrated in the pluton roof zones. Contributions to the magma

generation from metapelitic and carbonate continental crust resulted in the generation of minor S-type magmas in the Eastern province allowing for limited Sn-W metallogenesis in this province. Fractionated melts derived from alkali basaltic underplating crystallized to form the syenites on Perhentian Island and in Benom.

By contrast, the basement beneath the Sibu-masu terrane is dominated by crustal metasedi-ments, the melting of which favored the formation of more peraluminous biotite gran-itoids exhibiting pronounced fractionation and incompatible element enrichment. The Taiping hornblende-biotite granite in the Main Range

A

B

Figure 18. (A) Spider diagrams comparing the trace element geochemistry of the Eastern province Permo-Triassic granitoids to the Gangdese-Ladakh I-type granites (gray shading) (Wen et al., 2008). (B) Spider diagrams comparing the trace element geochemistry of the Main Range granitoids to the Greater Himalaya S-type leucogranites (gray shading) (Bikramaditya Singh, 2013). The spider diagrams are normalized to primitive mantle, while those on the right are normalized to chondrites after Sun and McDonough (1989). REEs—rare earth elements.



province is exceptional in that it appears to have been derived from a more primitive protolith, more akin to that beneath the Eastern province. The presence of significant metasedimentary source material for the Main Range magmas otherwise resulted in a reduced oxidation state of the intruding magma, promoting large-scale Sn-W mineralization in this region.

Tin Metallogenesis in the Malaysian Granitoids

Tin mineralization is usually hosted within greisen veins associated with fractionated S-type granites (Groves and McCarthy, 1978; Babu, 1993; Esmaeily et al., 2005; Mlynarc-zyk and Williams-Jones, 2005). In the Malay Peninsula, tin deposits are mainly hosted in the greisen-bordered veins and pegmatite of the transitional I/S-type hornblende-free biotite granites of the Main Range province, which is more fractionated than the Eastern province gran itoids. Fewer tin deposits are also hosted in the hornblende-free pluton roof zones of the I-type Eastern province granitoids, where the granitoids are commonly greisenized, hydro-thermally altered, and also geochemically frac-tionated. Hence, there is a correlation between fractionated granites and tin metallogenesis. The association of tin with I-type granitoids is rarely seen worldwide because tin tends to be frac-tionated into aqueous fluid in a more reduced environment (Taylor, 1979). The existence of reduced, ilmenite-series granitoids in both the Main Range and Eastern province granitoids is undoubtedly one reason why Sn-W mineraliza-tion is associated with both belts.

The association of Sn-W mineralization with the Eastern province granitoids is, nevertheless, a feature that remains enigmatic. It is suggested that the latter are more reduced than typical Cor-dilleran I-type granites, which usually belong to the magnetite series (Ishihara, 1977; Ishihara et al., 1979; Clarke, 1992; Pitcher, 1997; Frost et al., 2001). The incorporation of sedimentary-sourced melts into the Eastern province parental magma may have played a role, as suggested above. Moreover, the Malaysian granitoids are generally enriched in HFSEs such as Nb and Ta, and by inference Sn and W, which could reflect inheritance from the Kontum-like source protoliths.

CONCLUSIONS

The Malaysian granitoids can be divided into an I-type Eastern province and a transitional I/S-type Main Range province by the Bentong-Raub suture zone. Geochemical analyses sug-gest that compared to the Cordilleran I- and

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Ng et al.


S-type granitoids, the Malaysian granitoids are more enriched in HFSEs. Such enrichment is independent of the fractionation of granitoids, and is suggested to be the result of melting of a fertile protolith such as the Kontum massif. The Sr-Nd isotopic data also suggest that sed-imentary-sourced melts were incorporated into the parental magmas of the Eastern province granitoids and the Main Range granitoids. How-ever, the involvement of sedimentary-sourced melts is much more significant in the Main Range province, which resulted from the partial melting of sedimentary-dominated Sibumasu basement. The incorporation of sedimentary-sourced melts increased the peraluminosity but reduced the oxidation state of the Main Range parental magma and promoted the fractionation of tin into the magmatic aqueous phase.

ACKNOWLEDGMENTS

This paper is dedicated to the memory of Charles Hutchison, who sadly passed away in October 2011. Azman Ghani and Masatoshi Sone acknowl-edge University of Malaya High Impact Research Grants (UM.C/HIR/MOHE/SC/27 and UM.C/625/1/HIR/140 respectively) for support during fieldwork. WYNG Foundation (Hong Kong) and Raphael Mar-tin of Dark Capital Group are also gratefully acknowl-edged for finding support. H.-Y. Lee, C.-H. Chu, and C.-H. Hung of the Department of Geosciences, Na-tional Taiwan University, are also acknowledged here for their technical support in geochemical analyses. The Penjom gold mine, the Batu Pahat Hanson quarry, Bukit Batupejal quarry, and the Jeli Blunero quarry are thanked for approving and guiding our visits and sampling. We would also like to thank C.K. Morley and A.J. Barber for reviewing this article.

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Science editor: david ian Schofield aSSociate editor: Jean Bédard

ManuScript received 29 SepteMBer 2014 reviSed ManuScript received 18 deceMBer 2014 ManuScript accepted 10 feBruary 2015

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Petrogenesis of Malaysian granitoids in the Southeast Asian tin belt: Part 1. Geochemical and Sr-Nd...

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