pge geochemical constraints on the origin of the ni-cu-pge sulfide mineralization in the suoi cun...

ORIGINAL PAPER

PGE geochemical constraints on the origin of the Ni-Cu-PGEsulfide mineralization in the Suoi Cun intrusion, Cao Bangprovince, Northeastern Vietnam

Tatyana V. Svetlitskaya & Nadezhda D. Tolstykh &

Andrey E. Izokh & Phuong Ngo Thi

Received: 5 December 2013 /Accepted: 19 November 2014# Springer-Verlag Wien 2014

Abstract The Permian (266–262 Ma) Suoi Cun intrusion inthe Song Hien Rift Zone (NE Vietnam) consists of a sulfide-bearing mafic-ultramafic unit and a sulfide-free mafic unit.The Cu-Ni-PGE mineralization is represented by disseminat-ed sulfides throughout the sulfide-bearing unit containing~0.5 wt.%Ni, ~0.05 wt.%Cu, and ~0.2 ppm PGE. The sulfideschlieren have a limited distribution and contain ~2.6 wt.%Ni,~0.5 wt.% Cu, and ~2.6 ppm PGE. The Suoi Cun rockscontaining disseminated sulfides display moderately fraction-ated mantle-normalized PGE patterns with positive Pd andnegative Ru anomalies. In contrast, the sulfide schlieren showenrichment in Ru with lower contents of other PGE except Pd.The low Cu/Pd ratios (1,385–11,529) throughout the intrusionindicate that all sulfides were separated from a PGE-undepleted magma as a result of a single sulfide segregationevent. We suggest that sulfides segregated from Mg-richbasaltic magmas in a deep-seated magma chamber due tocrustal contamination with country rocks. Then, the sulfideliquid along with early crystallizing olivines and Cr-spinelswere pushed out upwards into an upper magma chamber bynew pulses of magma. Two processes were important for

understanding the PGE distribution: 1) fractionation of thesulfide liquid gave rise to PGE distribution observed in thedisseminated ore and, 2) the interaction of oxidized silicatemelts with the sulfide liquid was the responsible for the lowPGE contents in the sulfide schlieren due to PGE transfer fromthe oxidized sulfide liquid to the silicate melt.

Introduction

Open magma conduit systems are exceptionally effective toform high-grade Ni-Cu-PGE magmatic sulfide deposits asthey provide interaction of sulfides with a large volume ofmagma, which is a prerequisite for sulfides to become suffi-ciently enriched in PGE. Recent models of formation of somehigh-grade deposits invokemultistage upgrading processes, inwhich multiple later pulses of S-undesaturated magma reactwith an early-formed sulfide liquid, dissolving FeS andupgrading sulfides in PGE (Kerr and Leitch 2005; Wanget al. 2010). However, since these magma plumbing systemsare intrinsically self-destructive, the potentiality for the for-mation and the economic significance of Ni-Cu-PGE depositis strongly dependent on the extent to which the redox poten-tial of successive magma pulses will differ from that for themagma from which sulfides were segregated. The redox po-tential of later magma batches controls the rate of dissolutionof the sulfide liquid and its metal contents, providing, in somecases, strong enrichment in PGE of sulfides, and, in othercases, a complete destruction of sulfides and return of allmetals to later magma batches. Thus, if the silicate magma isoxidized, sulfides could become depleted in PGE due to PGEtransfer from oxidized sulfides to silicate magmas (Halteret al. 2005; Moretti and Baker 2008; Laurenz et al. 2013).This is possible because a strong preference of PGE to bondwith sulfur diminishes progressively under wide-scale sulfideoxidation conditions due to the oxidation of S2− in the sulfide

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Electronic supplementary material The online version of this article(doi:10.1007/s00710-014-0361-3) contains supplementary material,which is available to authorized users.

T. V. Svetlitskaya (*) :N. D. Tolstykh :A. E. IzokhRussian Academy of Sciences, Siberian Branch, VS SobolevInstitute of Geology and Mineralogy, 3 Koptyuga Avenue,Novosibirsk 630090, Russiae-mail: [email protected]

A. E. IzokhNovosibirsk State University, Novosibirsk 630090, Russia

P. N. ThiVietnamese Academy of Science and Technology, Institute ofGeological Sciences, Hanoi, Vietnam

Miner PetrolDOI 10.1007/s00710-014-0361-3

http://dx.doi.org/10.1007/s00710-014-0361-3

phase to SO42− (Jugo et al. 2005, 2010; Métrich et al. 2009). A

good example to illustrate this mechanism is the sulfide min-eralization hosted by the Suoi Cun intrusion of the Cao BangComplex, NE Vietnam.

In the Song Hien Rift Zone of Northeastern Vietnam, LatePaleozoic mafic-ultramafic intrusions of the Cao BangComplex are comparable in age to flood basalts and associatedintrusions of the Emeishan large igneous province in the southof the Yangtze Platform (Izokh et al. 2005; Borisenko et al.2006; Hoa 2007; Hoa et al. 2008a). The largest, the Suoi Cunintrusion is located in the northeastern part of the Cao Bangprovince and hosts magmatic Ni-Cu-PGE sulfide mineraliza-tion. The intrusion consists of a sulfide-bearing mafic-ultra-mafic unit which is composed of plagioclase-bearinglherzolite, olivine melanogabbro, plagioclase-bearing wehrliteand gabbronorite, and a sulfide-free mafic unit which is com-posed of olivine-free dolerite, gabbronorite, diabase and gab-bro. During detailed prospecting in the 1960s, three drill holeswere drilled to depths of 124m (Hole 1), 68.45 m (Hole 2) and175.35 m (Hole 3) in the southeastern part of the Suoi Cunintrusion with an average grade of 0.5 wt.% (from 0.2 to1.3 wt.%) Ni and 0.05 wt.% (from 0.01 to 0.23 wt.%) Cu(Ryamzin and Frolov 1960). One of the most significantintersections was from Hole 1 where 30.5 m grading0.9 wt.% Ni and 0.08 wt.% Cu was reported. Previous studiesestablished that sulfides are enriched in PGE, in particular, Pd(from 28 to 2600 ppb) (Glotov et al. 2004; Balykin et al. 2006;Svetlitskaya et al. 2011). Glotov et al. (2004) and Balykinet al. (2006) studied the distribution of Pt, Pd and Rh in thesulfide-bearing rocks of the Suoi Cun intrusion andenvisioned that sulfide segregation occurred at depth beforeolivine crystallization, but a model for the formation of the Ni-Cu-PGE mineralization remains an open question. In thisstudy, we present new chalcophile, major and trace elementdata for the sulfide-bearing rocks of the Suoi Cun intrusiontogether with PGE, major and trace element data published byGlotov et al. (2004) and Balykin et al. (2006). The combineddata provide a better understanding of the sulfide saturationhistory of the magmas from which the Suoi Cun intrusion wasformed, the role of crustal contamination in the formation ofsulfide-bearing rocks and factors controlling the distributionof PGE in the sulfides.We also discuss an integrated model forthe formation of the Ni-Cu-PGE sulfide mineralization of theSuoi Cun intrusion.

Geological setting

In Northern Vietnam, two major crustal blocks, the SouthChina block and the Indochina block, are separated by theSong Ma Suture zone, which is a segment of the Jinshajiang –Ailao Shan Suture (Fig. 1). The Jinshajiang – Ailao ShanSuture is the result of amalgamation of the South China and

Indochina blocks at ~230 Ma (Nam 1998; Carter et al. 2001;Zhang et al. 2013). This age is interpreted as the closure age ofthe Paleotethys Ocean, and the collision of the two blocks inthe Indosinian Orogeny (Krobicki et al. 2008; Lepvrier et al.2008; Hoa et al. 2008a, b). The Jinshajiang –Ailao Shan shearzone is Paleogene in age (Schärer et al. 1990; Schärer et al.1994) and was caused by the India-Eurasia collision(Tapponnier et al. 1990; Leloup et al. 1995).

Northern Vietnam is divided into two structural-tectonic units by the Ailao Shan – Red River fault (Hoa2007; Krobicki et al. 2008; Khuong 2009; Tran et al.2011) (Fig. 1, insert). The North-West block (termed theLaos-Vietnam Fold Region) includes parts of theIndochina, South China and Sibumasu blocks; these rocksexperienced intense deformation during the IndosinianOrogeny and the collision between India and Eurasia.The North-East block (termed the Vietnamese segmentof the Vietnam-China Fold Region) belongs to the south-ern margin of the South China plate and comprises weak-ly dislocated rocks of Middle Paleozoic – Early Mesozoicage. The Song Hien Zone is located within the North-Eastblock (Fig. 1). It is a NW-SE trending tectonic zone about200 km in length composed of Permian-Triassic andTriassic volcanic-sedimentary sequence of the Song HienFormation with subordinate Middle – Late Paleozoicterrigenous-carbonate rocks. The Song Hien Zone isinterpreted to be a Middle Paleozoic – Early Mesozoicintracontinental rift basin that may be related to theEmeishan Plume (Izokh et al. 2005; Hoa et al. 2008a;Polyakov et al. 2009; Vladimirov et al. 2012) or a LatePaleozoic – Early Mesozoic back-arc basin that wasformed by rifting of the northern margin of the amalgam-ated Indochina – South-China block caused by accretionof the Sibumasu plate to it (Tran et al. 2011 and refer-ences therein).

The Song Hien Zone magmatic rocks belong to the CaoBang Complex. This complex includes: (i) volcanic rocks of arhyodacite-rhyolite association and acid intrusions of a gran-ite–granophyre association; (ii) volcanic rocks of an andesite–basalt association and mafic intrusions of a gabbrodolerite–diabase association, and (iii) mafic to ultramafic intrusions ofa lherzolite–gabbronorite association. Relatively small intru-sions of the lherzolite–gabbronorite association are wide-spread within the Song Hien Zone. They form a near-linear,NW trending chain of bodies, which are confined to NWtrending suture faults separating Permian-Triassic volcanic-sedimentary sequences and Paleozoic terrigenous-carbonaterocks. Some intrusions (Suoi Cun, Bo Ninh, Dong Chang,Khuoi Ziang and some other) contain magmatic Ni-Cu sulfidemineralization. Mafic to ultramafic rocks of the lherzolite–gabbronorite association are commonly spatially associatedwith mafic rocks of a gabbrodolerite–diabase association andfelsic intrusive rocks of the Cao Bang Complex. Previous

T.V. Svetlitskaya et al.

studies of the mafic to ultramafic intrusions of the Cao BangComplex indicated that they are part of a single association(Dovzhikov et al. 1965; Tri 1979; Balykin et al. 2006). Morerecent works show that they can be broken out into differentassociations based on mineralogical, geochemical andmetallogenic features (Hoa 2007).

Geology of the Suoi Cun intrusion

The Suoi Cun intrusion is a lenticular subvolcanic body~3.5 km long and from 0.5 to1.0 km wide (Fig. 2). Theintrusion is broken into two blocks by a NW-trending fault.The eastern segment is 2.5 km long, 0.1–1.0 km wide, and

Fig. 1 Location of major structural units of Northern Vietnam on thetectonic scheme of the Southeast Asia: I –Nam Co; II – Tu Le; III – PhanSi Pan; IV – Song Chay; V – Lo Gam and Phu Ngu; VI – Ha Lang; VII –An Chau; VIII – Quang Ninh. Q – Quaternary sediments. Song Da andSong Hien structural units are also shown. Major faults in NorthernVietnam: 1 – Song Ma; 2 – Song Da; 3 – Song Hong; 4 – Song Chay;

5 –YenMinh–Ngan Son; 6 –Cao Bang–Tien Yen; 7 – Song Thuong. Theinset shows the location of the North-West (NWSB) and North-East(NESB) structural-tectonic blocks within Northern Vietnam by the AilaoShan–Red River fault (ASRRF) and the SongMa suture (SMS). Compiledfrom Findlay and Trinh (1997), Hoa (2007), Khuong (2010) and Lepvrieret al. (2011), with some updates

PGE constraints on the origin of the Suoi Cun Ni-Cu-PGE intrusion

~150 m in thickness. It is composed of two discrete bodies ofplagioclase-bearing lherzolite, olivine melanogabbro andplagioclase-bearing wehrlite. The plagioclase-bearinglherzolite is cut by late gabbronorite dykes. The westernsegment consists of dolerite, gabbronorite, diabase andolivine-free leucogabbro (Fig. 2). Disseminated sulfides arehosted by the eastern segment, whereas the western block isalmost devoid of sulfide mineralization but locally enriched inilmenite (Ryamzin and Frolov 1960).

In the southeastern part of the Suoi Cun intrusion, thenortheastern contact of the plagioclase-bearing lherzolite dipssouthwest toward the center of the intrusion at an angle of 70–80°. The southwestern contact of this rock with sulfide-freegabbroic rock also dips to the southwest, but at a lower angle

(see the cross section of E–F in Fig. 2). The same dip is notedin the southwestern contact of the sulfide-free gabbroic rockwith country rocks (Ryamzin and Frolov 1960).

The geological relationships between the mafic-ultramaficand mafic units of the Suoi Cun intrusion, such as late olivine-free gabbroic dykes cutting the plagioclase-bearing lherzoliteand xenoliths of the plagioclase-bearing lherzolite and olivinemelanogabbro in the olivine-free gabbroid (Ryamzin andFrolov 1960; Dovzhikov et al. 1965; Balykin et al. 2006),indicate that the sulfide-bearing rocks were formed earlierthan sulfide-free rocks. A SHRIMP U-Pb zircon dating givesof 273.9±3.1 Ma, 263.7±3.0 Ma and 260.0±3.5 Ma forgabbrodolerite (Hoa et al. 2008a). These analyses yield aweighted mean U-Pb age of 266±3.7 Ma, which is interpreted

Fig. 2 Geological map and cross sections of the Suoi Cun intrusion. Thesample locations used in this study are shown in the figure. Compiledfrom Ryamzin and Frolov (1960), Dovzhikov et al. (1965), Glotov et al.

(2004), Balykin et al. (2006) and Geological and mineral resources mapof Viet Nam (2000) using material of authors


to be the crystallization age of the gabbrodolerite. A U–Pbzircon age for plagioclase-bearing lherzolite obtained fromone grain of zircon is 262±2.7 Ma (Hoa et al. 2008a). Insummary, the crystallization ages of the plagioclase-bearinglherzolite and gabbrodolerite from the Suoi Cun intrusion aresimilar; their variations are within the analytical errors. At thesame time, the ages obtained do not provide an unambiguousanswer to the question about the temporal relationship be-tween the mafic-ultramafic and mafic units, and geologicalobservations are much more reliable.

The country rocks adjacent to the Suoi Cun intrusioncomprise shales, sandstones, dacites and rhyolites, spilitesand basalts of the Song Hien Formation (Fig. 2). Shales andsandstones are transformed into hornfels consisting of thefine-grained albite–clinopyroxene–actinolite aggregate withtitanite and ore minerals in the 20–30-m zone at the contactwith the Suoi Cun intrusion. Awhole-rock Ar/Ar age of basaltnear the town of Cao Bang is 263–244 Ma (Hoa 2007), and aU-Pb zircon age of rhyolite is 248±4.5 Ma (Hoa et al. 2008a).These data indicate that the felsic rocks of volcanic–plutonicassociations in the Song Hien Zone have a Permian – Triassicmagmatic age.

Petrology and mineralogy of the sulfide-bearing rocks

The Suoi Cun intrusion comprises plagioclase-bearinglherzolites and wehrlites, and olivine melanogabbros. Theplagioclase-bearing lherzolite is located in the central part ofthe intrusion, and the melanogabbro are confined to its mar-ginal parts. The plagioclase-bearing wehrlite is less abundantand forms a quenched contact zone between the olivinemelanogabbro and the country rocks. The gabbronorite occursas dykes cutting the plagioclase-bearing lherzolite. The dykesare 30–40 cm thick, extend conformably with the generalelongation of the intrusion and dip to the northeast at anglesof ~15° (Ryamzin and Frolov 1960) (see the cross section ofE–F in Fig. 2).

Major rock types include plagioclase-bearing lherzolite,plagioclase-bearing wehrlite and olivine melanogabbro.Plagioclase-bearing lherzolite and olivine melanogabbro havea cumulus hypidiomorphic-granular texture (Fig. 3a). The firstconsists of 50–60 vol.% olivine, 10–20 % clinopyroxene,~10 % orthopyroxene, and ~10 % plagioclase, the second iscomposed of 30–40 vol.% olivine, 30–40 % pyroxenes, andfrom 15 to 30 % plagioclase. Rounded and granular olivinegrains in the rocks are variable in size from 0.2 to 3 mm,whereas rounded olivine grains enclosed in pyroxene arerelatively small, ranging from 0.2 to 0.8 mm. Clino- andorthopyroxene grains are anhedral and range in size from 0.2to 3 mm. Plagioclase occurs as either euhedral laths (from 0.2to 0.6 mm in length) enclosed in clino- and orthopyroxene orsub- and anhedral grains (from 0.3 to 0.8 mm) occurred in the

interstices between olivine and pyroxene grains. Some of theeuhedral plagioclase grains are interstitial. Sulfide content isup to 10–15 vol.%. Most sulfides are interstitial to silicates,but some of them are rounded and enclosed in olivine and Cr-spinel (Fig. 3b, c). Biotite, Cr-spinel, ilmenite and magnetiteoccur in minor amounts. Plagioclase-bearing wehrlite has aporphyritic texture and contains about 80–85 vol.% olivinephenocrysts with a grain size from 0.2 to 1.5 mm (Fig. 3d).The groundmass consists of small anhedral clinopyroxenegrains (5–10 vol.%) and euhedral laths of plagioclase(~10 vol.%). Biotite, sulfides, Cr-spinel, magnetite and ilmen-ite occur in minor amounts. Fo contents of the olivine grainsfrom major rock types range from 81 to 85 mol%(Supplementary Materials Table ESM1). The contents of Niin olivine are between 1100 and 1890 ppm (at an average,1400 ppm).

Gabbronorite consists of pelitized and saussuritized plagio-clase (60 vol.%) and ortho- and clinopyroxene (up to35 vol.%). Clinopyroxene (mainly augite) prevails in volumeover orthopyroxene (mainly hypersthene). Chlorite, apatiteand sulfides occur in small amounts (up to 5 vol.%)(Ryamzin and Frolov 1960).

Sulfide mineralization

The Ni–Cu–PGE sulfide mineralization of the Suoi Cun in-trusion is represented by disseminated and schlieren types.Disseminated sulfides occur interstitially to the silicatesthroughout the plagioclase-bearing lherzolite, melanogabbroand plagioclase-bearing wehrlite in amounts of 3 to 10 vol.%(Figs. 2 and 4a). A schlieren mineralization was established inthe northwestern part of the Suoi Cun intrusion as a fragmen-tary unit at the contact between the plagioclase-bearinglherzolite and melanogabbro (see the cross section of AB inFig. 2). The sulfide schlieren up to 15–30 cm in diameter formlenticular lode of 1.5 m long with apparent thickness of 2–3 m(Fig. 4b). A melanogabbro with poor sulfide disseminations(up to 1.5 vol.%) overlies the schlieren unit.

The disseminated sulfides comprise pyrrhotite (50–80 vol.%), pentlandite (15–30 vol.%), and chalcopyrite (10–30 vol.%) (Fig. 4c). Violarite, cubanite, sphalerite,mackinawite, pyrite, arsenopyrite, bornite, and covellite areless abundant. The proportions of pyrrhotite, pentlandite, andchalcopyrite in the disseminated sulfides are about 50–60:25:15–20 for the plagioclase-bearing lherzolite, about60–70:20:10–15 for the melanogabbro and about 70–80:15:5–10 for the plagioclase-bearing wehrlite. Theplagioclase-bearing lherzolite of the central part of themafic-ultramafic bodies contains troilite, Fe-pentlanditeFe6Ni3S8, chalcopyrite, and cubanite (Glotov et al. 2004).The sulfide assemblage of the melanogabbro in the marginalparts of these intrusive bodies consists of hexagonal pyrrhotite


Fe0.90–0.95S with troilite lamellae, pentlandite Fe5.0–4.5Ni5.0–4.5S8, chalcopyrite, and violarite. Pyrite, sphalerite,mackinawite, bornite, and covellite occur in insignificantamounts (Svetlitskaya et al. 2011). Sulfides of the quenchedplagioclase-bearing wehrlite comprise monoclinic pyrrhotiteFe0.88–0.89S, pentlandite Fe4.5Ni4.5S8 and chalcopyrite (Glotovet al. 2004).

The sulfide schlieren are characterized by zonal struc-ture: сoarse-grained hexagonal pyrrhotite Fe0.90–0.91S withlamellae of monoclinic pyrrhotite (60–70 vol.%) is rimmedby small-grained violarite (10–25 vol.%) (Fig. 4d). Thehost matrix is represented by magnetite and iron hydroxide(limonite, goethite and hydrogoethite) and contains isolat-ed grains of chalcopyrite (5–15 vol.%). Pyrrhotite is par-tially replaced by fine-grained aggregate of the magnetite-pyrite-marcasite composition. Pentlandite Fe4.5Ni4.5S8, py-rite, sphalerite, mackinawite, and arsenopyrite are lessfrequent (Svetlitskaya et al. 2011).

Base-metal sulfides, largely pyrrhotite and less frequentlypentlandite and chalcopyrite, contain microinclusions of gale-na, hessite, native Bi, Ag–Pb–Te and Au–Ag compounds(Svetlitskaya et al. 2011). Froodite (PdBi2) is the most com-mon platinum-group mineral (PGM) in both disseminated andschlieren sulfides (Svetlitskaya et al. 2011). In the disseminat-ed sulfides, froodite grains have a size up to 10 μm and areenclosed in pyrrhotite, and rarely in pentlandite, or in silicates(partially altered clinopyroxene) adjacent to sulfides. In thesulfide schlieren, froodite grains occur as relatively largegrains (from 1–2 to 40 μm) associated with violarite andchalcopyrite or included in pyrrhotite. In one case, frooditegrain occurs intergrown with Au-Ag compound (supposedly,electrum), both enclosed in pyrrhotite. Froodite grains contain20.9 to 22.0 wt.% Pd, 76.9 to 78.9 wt.% Bi, with minoramount of Te (0.2 to 0.3 wt.%). Some froodite grains havesmall amounts of Ni (up to 1.2 wt.%) and Fe (up to 1.0 wt.%)(Svetlitskaya et al. 2011).

Fig. 3 Microphotographs of sulfide-bearing rocks from the Suoi Cunintrusion: (a) Plagioclase-bearing lherzolite (sample ir52) showingcumulative hypidiomorphic-granular structure. Anhedral clinopyroxene(Cpx) and orthopyroxene (Opx) are located between rounded andgranular olivine (Ol) grains and contain the inclusions of small olivinegrains and euhedral laths of plagioclase (Pl). Sulfide (Sulf) is interstitial tosilicates. Cross polar, transmitted light; (b) Rounded sulfide «drop»

enclosed in olivine grain from the plagioclase-bearing lherzolite(sample ir52). Cross polar, transmitted light; (c) Rounded sulfide«drop» enclosed in Cr-spinel (Cr-Spl) grain from the plagioclase-bearing lherzolite (sample ir52). Reflected light; (d) Plagioclase-bearingwehrlite (sample ir94) with porphyritic structure contains up to 80 vol.%olivine phenocrysts and minor interstitial sulfide. Cross polar, transmittedlight


Analytical methods

The samples used in this study were collected from outcrops atthe Suoi Cun intrusion. The published data of Glotov et al.(2004) and Balykin et al. (2006) on the major and traceelements and base metal, PGE and S contents in the sulfide-bearing rocks are included in our study. The relative locationsof the samples are shown in Fig. 2.

Electron microprobe analyses (EMPA) of olivine werecarried out using a Camebax-micro electron microprobe atthe Institute of Geology and Mineralogy in Novosibirsk,Russia. The experimental conditions are focused beam in spotmode, accelerating voltage at 20 kV, counting times at 10 s,and beam current at 30 nA. The standards used for olivineanalysis were olivine for Mg and Si, fayalite for Fe, diopsidefor Ca, chromite for Cr, manganese oxide for Mn, andnickeline (NiAs) for Ni. Estimated detection limits were0.01 wt.% for MgO, SiO2 and CaO, and 0.02 wt.% for FeO,NiO, Cr2O3 and MnO.

Major element oxides were determined by X-ray fluores-cence spectrometry (XRFS) on fused glass beads using anARL 9900 XP spectrometer at the Institute of Geology andMineralogy in Novosibirsk, Russia. The accuracies of theXRF analyses were estimated to be ±2 % (relative) formajor oxides present in concentrations greater than0.5 wt.% and ±5 % (relative) for minor oxides greater than0.1 wt.%. Trace elements, including V, Cr and rare earthelements (REE), were determined by inductively coupledplasma mass spectrometry (ICP-MS) using an Element 2Finnigan MAT at the Institute of Geochemistry, Irkutsk,Russia. The standards used were pure elemental standardsfor external calibration, and BHVO-1 as a reference mate-rial. The accuracies of the ICP-MS analyses were betterthan ±5 % (relative) for most elements. Whole-rock Scontents were determined using a gravimetric method atthe Institute of Geology and Mineralogy in Novosibirsk,Russia. The detection limit was estimated to be 0.1 % withthe standard geological sample 227 (fluorspar).

Fig. 4 Photographs showing the main types of sulfide mineralizationfrom the Suoi Cun intrusion (a–b) and microphotographs illustrating therelationships between ore-forming sulfide minerals therein (c–d). (a)Disseminated sulfide mineralization in plagioclase-bearing lherzolite;(b) Sulfide schlieren (marked by red dashed lines) at the contactbetween plagioclase-bearing lherzolite and olivine melanogabbro; (c)Mineral association of pyrrhotite (Po), pentlandite (Pn) andchalcopyrite (Cpy) in the disseminated sulfide mineralization (sample

ir52). Reflected light; (d) Relationships between the main sulfideminerals in the sulfide schlieren (sample ir51a). Coarse-grainedpyrrhotite is rimmed by small-grained violarite (Viol). Pyrrhotite ispartially replaced by fine-grains aggregate of magnetite-pyrite-marcasitecomposition (Mg+Py+Mr). The host matrix represented by magnetiteand iron hydroxide (Mg+Fe-Ox) contains isolated grains of chalcopyrite.Reflected light


Ni, Cu, Co, Au and Ag contents were determined by a PyeUnicam SP9 (for Ni, Cu and Co) and a Perkin-Elmer 3030Zeeman ( fo r Au and Ag) A tomic Abso rp t i onSpectrophotometers (AAS) at the Institute of Geology andMineralogy, Novosibirsk, Russia. Precision and accuracywere based on the analyses of the standard geological samplesSGHM-4, SGD-2 (for Ni, Cu, Co), and SZH-3 (for Au, Ag).Detection limits for Cu, Ni, Co, Au and Ag were estimated tobe 2.5, 5, 5, 0.002 and 0.02 ppm, respectively.

The concentrations of PGE (Os, Ir, Ru, Pt, Pd and Rh) weredetermined by an Element 2 Finnigan MAT InductivelyCoupled Plasma Mass Spectrometer (ICP-MS) at theInstitute of Geochemistry, Irkutsk, Russia. The total procedur-al blank was 0.00022 μg/L for Os; 0.0017 μg/L for Ir;0.0024 μg/L for Ru; 0.019 μg/L for Pt; 0.026 for Pd;0.0016 μg/L for Rh. For precision and accuracy control, RP-1 and RP-2massive pyrrhotite ore standard samples and OZE-1 standard sample (China) were used. Results of Os determi-nation are considered approximate because of the lack ofcontrol on CO. Pt, Pd and Rh contents were also obtainedby a Perkin-Elmer 3030 Zeeman AAS with electrothermalatomizer HGA-600 in the Institute of Geology andMineralogy, Novosibirsk, Russia. The accuracy was basedon the analyses of J-3 standard sample and was controlledusing an internal standard (pyroxenite). Detection limits forPt, Pd and Rh were 0.02, 0.005 and 0.002 ppm, respectively.Both methods reveal good convergence of the results. In thisstudy, the AAS data on Pt, Pd and Rh (above detection limit)are used along with ICP-MS data on Ir, Ru, Os, as well as Rhfor the concentrations below the detection limit of AAS.

The isotopic composition of sulfur were analyzed in 3samples of sulfide concentrates (pyrrhotite+pentlandite+chalcopyrite) by a Finnigan MAT 252 precision mass spec-trometer at the Far East Geological Institute, Vladivostok,Russia. The isotopic composition of sulfur is expressed asδ34S unit, in permil (‰), relative to Canyon Diablo Troilitestandard, and its analytical precision is about ±0.2‰.

Analytical results

Major and trace elements

Major and trace element compositions of the sulfide-bearingrocks from the Suoi Cun intrusion are listed in Table 1. Thesamples analyzed are variably altered and therefore havevariable loss-on-ignition (LOI). For comparison we have nor-malized the whole rock row data to anhydrous compositionsby correcting for LOI. We use the normalized values for thediscussions below. MgO contents of plagioclase-bearinglherzolites, melanogabbros and plagioclase-bearing wehrlitesvary between 24.6 and 29.5 wt.%. The rocks contain 42.9–44.5 wt.% SiO2, 6.0–8.2 wt.% Al2O3, 4.3–5.8 wt.% CaO, and

0.31–0.42 wt.% TiO2. In contrast, MgO content ofgabbronorite is much lower, about 11 wt.%, Al2O3

(13.9 wt.%), CaO (19.6 wt.%) and TiO2 (1.44 wt.%) contents

Table 1 Major oxides and trace elements of the sulfide-bearing rocksfrom the Suoi Cun intrusion

Sample No. ir52 ir53 ir54 ir95 ir96

Rock name Plagioclase-bearinglherzolite

Olivine melanogabbro Plagioclase-bearingwehrlite

SiO2, wt% 40.25 41.00 40.82 41.11 40.87

TiO2 0.38 0.37 0.38 0.33 0.29

Al2O3 6.38 5.62 7.57 5.81 5.82

Fe2O3total 14.09 13.87 13.98 14.82 13.99

MnO 0.18 0.20 0.17 0.20 0.20

MgO 24.36 27.31 22.64 28.28 27.40

CaO 4.04 4.07 5.32 4.13 5.12

Na2O 0.08 0.25 0.29 0.76 0.45

K2O 0.64 0.68 0.75 0.34 0.39

P2O5 0.07 0.07 0.07 0.06 0.06

LOI 8.08 5.83 7.40 3.76 5.04

Total 98.55 99.27 99.39 99.60 99.63

MgO# 77.40 79.59 76.24 79.08 79.51

Cr, ppm 752 897 n.a. n.a. n.a.

V 76 75 n.a. n.a. n.a.

Rb 24.00 21.00 24.00 13.30 14.70

Sr 42.00 46.00 40.00 36.00 45.00

Y 8.10 8.20 11.00 8.70 8.70

Zr 43.00 45.00 43.00 34.00 32.00

Ta 0.15 0.15 0.09 0.09 0.06

Nb 1.95 1.86 2.20 1.72 1.51

Cs 28.00 9.90 19.90 4.60 2.80

Ba 85.00 93.00 99.00 53.00 100.00

La 4.35 4.47 4.90 3.40 3.60

Ce 8.80 8.90 9.40 6.90 7.10

Pr 1.06 1.01 1.32 0.99 1.02

Nd 4.66 4.67 5.30 3.70 3.60

Sm 1.21 1.19 1.19 0.86 1.00

Eu 0.31 0.34 0.39 0.30 0.32

Gd 1.42 1.45 1.46 1.10 1.23

Tb 0.24 0.26 0.25 0.20 0.22

Dy 1.49 1.56 1.64 1.34 1.40

Ho 0.33 0.35 0.38 0.30 0.30

Er 0.90 0.99 1.02 0.90 0.87

Yb 0.96 0.98 1.08 0.90 0.85

Lu 0.16 0.16 0.16 0.13 0.13

Hf 1.15 1.10 1.28 0.97 0.96

Th 1.51 1.34 1.95 1.40 1.76

U 0.46 0.45 0.48 0.33 0.30

LOI Loss on ignition. Mg#=[molar 100×MgO/(MgO+FeO)]. n.a. notanalyzed


are much higher, and SiO2 content (43.5 wt.%) is similar tothose of plagioclase-bearing lherzolite (Glotov et al. 2004).Thus, there is a compositional gap between the plagioclase-bearing lherzolite and melanogabbro and the gabbronorite.The mineralogical phases which control the composition ofthe rocks can be determined using the Pearce element ratiodiagram of the molar ratio (Mg+Fe)/Ti against the molar ratioSi/Ti. All plagioclase-bearing lherzolite, melanogabbro andplagioclase-bearing wehrlite samples plot close to the olivinecontrol line (Fig. 5). This clearly indicates that the composi-tional trend of these rocks is mostly controlled by olivine (withminor orthopyroxene) accumulation. The sample ofgabbronorite plots between the orthopyroxene andclinopyroxene control lines, indicating that clino- andorthopyroxene are major fractionating phases in this rock.The Pearce element ration plot hence supports the observedmineral assemblages.

All sulfide-bearing rocks from the Suoi Cun intrusion havesimilar chondrite-normalized REE patterns with modestLREE enrichment ((La/Yb)CN=2.6–3.2) and weak negativeEu anomalies (Eu/Eu* =0.7–0.9) (Fig. 6a). On primitivemantle-normalized trace element spidergrams (Fig. 6b), allsamples display similar patterns, characterized by enrichmentof LILE and negative Nb–Ta anomalies. Thorium exhibitspositive anomalies, whereas Sr displays negative anomalies.These rocks have negative Ti anomalies.

Ni, Cu, PGE, Au and Ag

The Ni, Cu, PGE, Au and Ag contents of the sulfide-bearingrocks from the Suoi Cun intrusion are given in Table 2. Sconcentration in plagioclase-bearing lherzolite, melanogabbroand plagioclase-bearing wehrlite varies from 0.26 to1.08 wt.% (0.62 wt.%, on average), abruptly increasing to7–10 wt.% within the sulfide schlieren unit. Cu, Ni, andPGE concentrations reach a maximum in the sulfide schlieren(2.6 wt.% Ni, 0.5 wt.% Cu, and 2.6 ppm PGE, on average), aminimum (0.16 wt.% Ni, 0.03 wt.%Cu, and 0.2 ppm PGE, onaverage) in plagioclase-bearing wehrlite, and are intermediate(0.30 wt.%Ni, 0.10 wt.%Cu, and 0.35 ppm PGE, on average)in plagioclase-bearing lherzolite and melanogabbro.Gabbronorite contains ~0.2 wt.% Ni, 0.1 wt.% Cu and0.2 ppm PGE (Glotov et al. 2004). All of the samples havelow concentrations of Au (0.006–0.23 ppm, 0.04 ppm, onaverage) and Ag (0.14–1.90 ppm, 0.74 ppm, on average).

Naldrett et al. (2000) have shown, for the Voisey’s Baydeposit as an example, that when a sample contains smallamount of sulfide, Ni concentration in the rock-forming

0

50

100

150

200

250

300

0 50 100 150 200 250 300

(Mg+

Fe)/T

i

Si/Ti

2:1

olivin

eco

ntro

l

1:1orth

opyroxene contro

l

1:1 clinopyroxene control

0:1 plagioclase control

P clase-bearinglagio lherzolite

Olivine melanogabbro

P clase-bearinglagi ehrlite

G (dyke)abbronorite

this studyGlotov 4et al. (200 )

this study


Glotov 4et al. (200 )

Fig. 5 Pearce element (Fe+Mg)/Ti vs. Si/Ti diagram showing that thecompositional trend of the sulfide-bearing rocks from the Suoi Cunintrusion is mostly controlled by accumulation of Ol (with minor Opx)except the gabbronorite that is controlled by Cpx and Opx

Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu1

10

100

La

Roc

ks/C

hond

rite

1

10

100

Ba Th Nb Ta La Ce Sr Nd Zr Sm Eu Ti Gd Tb Dy Y Yb LuRbR

ocks

/Prim

itive

man

tle

a

b

Continental Flood Basalts(Crustal ontamination)c

P clase-bearinglagio lherzoliteOlivine melanogabbroP clase-bearinglagio wehrlite

Fig. 6 Chondrite-normalized REE patterns (a) and primitive mantle-normalized spidergrams (b) for the sulfide-bearing rocks of the SuoiCun intrusion. Trace element data are combining from Balykin et al.(2006) and our data. The compositional field of the Continental FloodBasalts (Crustal contamination) is taken from Xia et al. (2005) andincludes the crustally contaminated basalts of the Bushe Formation(Deccan), a group of low-Ti basalts from the East Coast of Madagascar,and the Gramado (low-Ti) basalts from the Paraná province.Normalization values for chondrite and primitive mantle are fromAnders and Grevesse (1989) and Sun and McDonough (1989),respectively


silicates (mainly in olivine) has a significant effect on the totalcontent of this metal in the rock. The plagioclase-bearinglherzolite, plagioclase-bearing wehrlite and olivinemelanogabbro of the Suoi Cun intrusion host the poor sulfidemineralization and they are rich in olivine. Underestimation ofthe contribution of olivine to the bulk mass of Ni in the rockscan lead to substantial errors in studying the content anddistribution of sulfide nickel. To minimize errors, Ni concen-trations in sulfide-bearing rocks were recalculated with allow-ance for amounts of olivine in various types of rocks(~50 vol.% in the plagioclase-bearing lherzolite andplagioclase-bearing wehrlite, and ~40 vol.% in olivinemelanogabbro). The weighted average Ni content in olivinewas estimated as 0.18 wt.% (Supplementary MaterialsTable ESM1). The contents of Ni in rock obtained as a resultof these calculations are shown in Table 2 as NiSul. We use therecalculated values of NiSul for the discussions below. Metalcontents in 100 % sulfide were calculated following Barnesand Lightfoot (2005).

The data on PGE geochemistry of the sulfide-bearing rocksare illustrated in Fig. 7 and in Supplementary MaterialsFigure ESM2. Plagioclase-bearing lherzolite andmelanogabbro show moderately fractionated mantle-normalized chalcophile element patterns with an average(Pt+Pd)/(Ru+Ir+Os) ratio of 15.6 (11.0 to 19.3) and havepositive Pd and slight negative Ru anomalies (Fig. 7a).Plagioclase-bearing wehrlite is distinguished by less fraction-ated patterns with (Pt+Pd)/(Ru+Ir+Os) ratio of 5.9, and nopositive Pd anomaly. Part of plagioclase-bearing lherzolitesand plagioclase-bearing wehrlites has weak negative Pt anom-alies, which are not observed in melanogabbro andgabbronorite (Supplementary Materials Figure ESM2). Thesulfide schlieren shows moderately fractionated patterns with

an average (Pt+Pd)/(Ru+Ir+Os) ratio of 10.8 (6.1 to 19.1)and no negative Ru anomaly, but displays positive Pd andslight negative Pt anomalies (Fig. 7a).

Ni/Cu ratios of the Suoi Cun sulfide-bearing rocks rangefrom 1.6 to 4.8 (average 2.2) in the disseminated sulfide rocksand from 3.6 to 9.5 (average 6.6) in the sulfide schlieren. Allrocks hosting disseminated sulfides have low to moderate Pd/Ir ratios ranging from 5 to 35 with an average value of 17.2,whereas the sulfide schlieren have moderate Pd/Ir ratios vary-ing from 27 to 97 with an average value of 51. Rocks hostingdisseminated sulfides have Cu/Pd ratios varying from 1,890 to12,650 with an average value of 7,500, and the sulfide schlie-ren have Cu/Pd ratios from 1,385 to 6,444 with an averagevalue of 3,160.

Sulfur isotopes

The sulfur isotope value of disseminated sulfides fromplagioclase-bearing lherzolite and olivine melanogabbro sam-ples is −2.0‰ and −2.2‰, respectively. One sample of schlie-ren sulfide has δ34S value of −2.9‰. Thus all sulfide-bearingrock samples show similar, near cero negative sulfur isotopicvalues.

Discussion

Nature of parental magmas

The composition of the sulfide-bearing rocks of the Suoi Cunintrusion does not represent that of the parental magma be-cause they are simply cumulate rocks, which can be

Table 2 Sulfur and chalcophile element concentrations of the sulfide-bearing rocks from the Suoi Cun intrusion

SampleNo.

S (wt%) Ni (ppm) NiSul (ppm) Cu (ppm) Co (ppm) Os (ppb) Ir (ppb) Ru (ppb) Rh (ppb) Pt (ppb) Pd (ppb) Au (ppb) Ag (ppb)

Plagioclase-bearing lherzolite

ir52 1.08 4200 3573 1600 149 1.19 10.87 14.52 7 130 380 46 710


ir54 1.03 3900 3272 1440 128 0.16 11.38 11.58 4.5 120 300 17 660

ir53 0.36 1600 839 375 98 0.2 8.86 4.23 2 46 100 11 140

ir95 0.6 2300 1421 719 118 0.11 7.44 8.04 3 70 150 15 280

Quenched plagioclase-bearing wehrlite

ir94 0.4 1700 843 434 93 0.83 9.72 5.78 3 48 49 14 220

ir96 0.26 1500 681 235 84 0.06 8.15 3.54 1 27 43 6.5 210

Sulfide schlieren

ir51a 9.17 33,400 33,400 9280 660 19.7 47.4 207.43 79 550 1440 62 1600

ir51b 10.68 24,300 24,300 3600 511 5.62 26.9 137.7 69 640 2600 230 1900

ir51c 7.29 22,000 22,000 2310 461 9.14 52.06 218.89 50 310 1400 11 960

NiSul is the Ni concentration in rock corrected for Ni content in olivine (see text for explanation). Os concentrations in whole rocks are approximate


considered as a mixture of silicate melt and cumulus olivine.Ratios of chalcophile elements (Ni, Cu and PGE) can be usedfor discussing the parental magma composition (Naldrett2004; Keays 1995). Ultramafic magmas commonly produceNi-dominated sulfide deposits with low (Pt+Pd)/(Ru+Ir+Os)ratios and Ni/Cu >7, such as the komatiite-related Ni depositsof Kambalda, Western Australia ((Pt+Pd)/(Ru+Ir+Os) =2.1;Ni/Cu =13.8) (Cowden et al. 1986; Naldrett 2004) orThompson, Canada ((Pt+Pd)/(Ru+Ir+Os) =4.4; Ni/Cu=21.6) (Naldrett 2004). In contrast, mafic magmas usually

give rise to Ni-Cu-(PGE) sulfide deposits with high (Pt+Pd)/(Ru+Ir+Os) ratios and Ni/Cu <2, for example, Talnakh,Russia ((Pt+Pd)/(Ru+Ir+Os) =59.4; Ni/Cu =0.66 for dissem-inated ores) (Naldrett 2004) or Jinchuan, China ((Pt+Pd)/(Ru+Ir+Os) =7.7–14.8; Ni/Cu =1.4) (Chai and Naldrett1992). The Suoi Cun rocks hosting disseminated sulfides haveaverage (Pt+Pd)/(Ru+Ir+Os) ratios of 12.4 varying from 5.9to 19.3 and average Ni/Cu ratios of 2.2 with a small rangefrom 1.6 to 4.8 (Table 2). Three samples of sulfide schlierenshow average (Pt+Pd)/(Ru+Ir+Os) ratios 10.8 (from 6.1 to19.1) and average Ni/Cu ratios 6.6 (from 3.6 to 9.5). Theseratios suggest basaltic linkage of the silicate melts rather thanultramafic.

The sulfide-bearing rocks of the Suoi Cun intrusion haverelatively steep patterns and plot between komatiites- andmafic intrusions-related ores on the chondrite-normalizedchalcophile elements diagram (Fig. 7b), indicating that amagnesian basaltic magma appears to be the parental of theserocks. This is broadly consistent with the inferredpicrobasaltic composition (15.4 wt.% MgO and 10.7 wt.%FeO) estimated by Balykin et al. (2006) by calculating aweighted average composition of both sulfide-bearing andsulfide-free rocks of the Suoi Cun intrusion. On a Ni/Cu vs.Pd/Ir diagram (Fig. 8), all the Suoi Cun rock samples plotwithin the high-MgO basaltic and layered intrusion fields,supporting our contention that the parental magma of theSuoi Cun sulfide-bearing rocks is high-MgO basalt.

The closest approximation to the MgO content of the SuoiCun parental magma can be estimated using the compositionof olivine. Olivine from the plagioclase-bearing lherzolite(Supplementary Materials Table ESM1) has the highestforsterite content of 84.6 mol% (44.03 wt.% MgO,14.25 wt.% FeO, and 0.23 wt.% NiO). Using the distribution

East (Ore body No 2)Jinchuan ores

West (Ore body No 24)

Suoi Cun intrusiondisseminated sulfides (average, n=6)sulfide schlieren (average, n=3)

Flood basalt oresArchean (Kambalda) and(Thompson)Proterozoic

komatiite ores

Merensky Reef (Bushveld) and J-M Reef (Stillwater) ores

0.01

0.1

1

10

100

1000

10000

Ni Os Ir Ru Rh PdPt Cu

Roc

k(1

00%

sulfi

de)/C

hond

rite b

Ni Os Ir Ru Rh Pt Pd Au Cu1

10

100

1000

10000a

P (n=1)lagioclase-bearing lherzoliteOlivine melanogabbro (n=3)P (n=2)lagioclase-bearing wehrliteS (n=3)ulfide schlierenG (dyke)(from Glotov et al. (2004))

abbronorite (n=1)

Roc

k(

sulfi

de)/P

rimiti

veM

antle

100%

Fig. 7 Mantle-normalized chalcophile element patterns of sulfide-bearing rocks from the Suoi Cun intrusion (a) and comparison of theSuoi Cun sulfide-bearing rocks with ores of some other deposits related tomafic and ultramafic intrusions (b). Abbreviation: n number of samples.Normalization values for chondrite and primitive mantle are from Andersand Grevesse (1989) and Sun and McDonough (1989), respectively. Orecompositions are recalculated to 100 % sulfide. Data sources: thecompositional fields of Merensky Reef (Bushveld) and J-M Reef(Stillwater) ores, Archean (Kambalda) and Proterozoic (Thompson)ores, and flood basalt ores from Naldrett (2004); Jinchuan ores fromChai and Naldrett (1992)

10-2 10-1 100 101 102 10310-2

10-1

100

101

102

103

104

105

106

Ni/Cu

Pd/Ir

Plagioclase-bearing lherzolite

Plagioclase-bearing wehrliteSulfide schlieren

Olivine melanogabbro + Ol+ CHRmss

+SU

Lor

+PG

M

Cu-richsulfideveins

PGE-reefs

Flood basalts

Layered intrusions

Hight MgO basalts

Ophiolites

ChromititesLayered intrusions

Mantle

KomatiitesChromititesOphiolites

Fig. 8 Ni/Cu vs. Pd/Ir diagram of the Suoi Cun sulfide-bearing rocks.Selected compositional fields from Barnes et al. (1988)


coefficient (KD) of Mg and Fe between olivine and coexistingsilicate liquid of (FeO/MgO)olivine/(FeO/MgO)liquid =0.3±0.03 (Roeder and Emslie 1970), it can be shown that the meltin equilibrium with the Mg-richest olivine in the Suoi Cunintrusion would have a (FeO/MgO) molar ratio of 0.61.Following the procedure of Makkonen (1996), we have cal-culated that the earliest olivine with Fo84.6 crystallized froman initial magma with about 11.2 wt.% MgO. Assuming that(FeO/MgO)liquid =0.61 and MgO =11.2 wt.%, the magmawould contain about 12 wt.% FeO. However, it should benoted that the parental magma of the Suoi Cun sulfide-bearingrocks had most likely slightly higher MgO and FeO contents,than the calculated values of 11.2 wt.% for MgO and 12 wt.%for FeO, due to the fact that such magma should experiencesulfide segregation and crystallization of some amount of Cr-spinel before olivine fractionation.

Evidence for early sulfide segregation by extensive crustalcontamination

A textural relationship that the sulfide drops are enclosed inolivine and Cr-spinel (Fig. 3b and c) indicates early sulfidesegregation before or during olivine and Cr-spinel crystalliza-tion. As noted above, the quenched plagioclase-bearingwehrlite of the Suoi Cun Intrusion contains olivine pheno-crysts, Cr-spinel grains and magmatic sulfides. This geologi-cal observation indicates clearly that sulfide segregation, aswell as the crystallization of olivine and Cr-spinel occurred ina deep-seated staging chamber and the magma entered into thechamber of the Suoi Cun intrusion as a sulfide, Cr-spinel andolivine-bearing crystal mush. The presence of magmatic sul-fides in the crosscutting gabbronorite dykes also providesevidence for existence of a magma chamber at depth.

The most important causes of early sulfide segregation arefelsification of mafic magmas through assimilation of crustalmaterial, and the addition of cortical sulfur (Naldrett 2004).The δ34S values of both disseminated and schlieren sulfidesfrom the Suoi Cun intrusion vary in a narrow range of −2.0 to−2.9‰, showing the isotopic characteristics of mantle-derivedsulfur (typical range =0±3‰; Ohmoto 1986). The negativeδ34S values indicate that the parental magmas were not con-taminated by cortical sulfur during its ascent and emplace-ment. Early sulfide segregation was likely triggered by crustalcontamination in a deep-seated magma chamber. The assim-ilation of crustal material by basaltic magmas leads to both adecrease in temperature and an increase in SiO2, alkalis con-tents and oxygen fugacity, promoting decrease of S solubilityin magma, resulting in S-saturation and formation of an im-miscible sulfide melt (e.g., Naldrett 2004).

Crustally contaminated mafic magmas are characterized byenrichments in SiO2, K2O, Rb, Ba, Th, LREE and tend to havehigh Th/Yb, Th/Nb, La/Sm, La/Nb and La/Yb ratios(Lightfoot et al. 1990; Li et al. 2000). La/Nb >1.4, primitive

mantle-normalized (La/Sm)PM >1.5 and Th/Ce >0.05 are typ-ical of rocks with significant crustal contamination. Traceelement geochemical data presented by Balykin et al. (2006)and our data indicate that the Suoi Cun sulfide-bearing rocksare enriched to different degrees in K2O, Rb, Ba and Th(Fig. 6; Table 1). The chondrite-normalized REE patternsfrom these rocks show a weak to moderate enrichment inLREE compared with HREE (Fig. 6a). The plagioclase-bearing lherzolites and wehrlites, and melanogabbros havehigh Th/Nb (0.6–1.2), Th/Yb (0.9–2.1), (La/Sm)MN (1.6–8.1), La/Nb (1.8–3.6), La/Yb (3.4–4.5) and Th/Ce (0.1–0.2)and show primitive mantle-normalized trace element patternswith Nb-Ta negative anomalies, consistent with derivationfrom magma contaminated by crustal materials (Fig. 6b)(Arndt et al. 1998; Zhou et al. 2009). These patterns areanalogous to those of the crustally contaminated basalts ofthe Bushe Formation from the Deccan, a group of low-Tibasalts from the East Coast of Madagascar, and theGramado (low-Ti) basalts from the Paraná province(Fig. 6b). Ratios of primitive mantle-normalized trace elementcontents such as (Nb/Th)PM and (Ta/Th)PM are best used toindicate the extent of Nb and Ta anomalies, whereas (Th/Yb)PM is a sensitive indicator of crustal contamination(Wang et al. 2006; Su et al. 2012). Compared to N-MORB(normal mid-oceanic ridge basalt), the sulfide-bearing rocks ofthe Suoi Cun intrusion have very low (Nb/Th)PM and (Ta/Th)PM but high (Th/Yb)PM ratios, consistent with a highdegree of crustal contamination (Fig. 9a and b). In Fig. 9a,all of the Suoi Cun samples plot within the estimated field forcrustally contaminated magmas (from Tornos et al. 2006).Plots of Ta/Yb and La/Sm versus Th/Yb are also good indi-cators of crustal contamination (e.g., Maier et al. 2008). InFig. 9c–d, the studied samples plot between the values ofprimitive mantle and average upper continental crust close tomixing lines between upper crust and model primitive picriteand contain >20 % of upper crust. However, the crustalcontamination trend seems to have no chemical affinity withupper continental crustal components as demonstrated inFig. 9a–d.

The most compelling evidences that significant crustalcontamination occurred have been obtained from petrological,geochronological and isotopic studies. So, high-Si (62.3–66.5 wt.%) and high-Al (19.3–20.8 wt.%) melt inclusionsstudied by Glotov et al. (2004) in olivine and Cr-spinel fromsulfide-bearing quenched plagioclase-bearing wehrlite havebeen interpreted as a hybrid melt that formed by assimilationof crustal material by a primary mafic magma. Abundantdifferent in age (from 2909±9.9 to 456±3 Ma) xenogeniczircon grains identified in the plagioclase-bearing lherzolites(Hoa et al. 2008a) support this assumption. Other evidence forsignificant crustal contamination includes a high 87Sr/86Srvalue (0.7079) of the plagioclase-bearing lherzolites (Glotovet al. 2004).


Controls on metal distribution in the ores

All rocks containing disseminated sulfides have similarmantle-normalized chalcophile element patterns, suggestingthat the sulfides of the various rock types are co-genetic.Disseminated sulfides are moderately enriched in Pt and Pdcompared to Os, Ir and Ru ((Pt+Pd)/(Ru+Ir+Os) ratio ~12.4)and have low to moderate Pd/Ir ratios ranging from 5 to 35(average 17.2) (Fig. 10a). An increase in (Pt+Pd)/(Ru+Ir+Os) and Pd/Ir ratios from the plagioclase-bearing wehrlites tothe melanogabbros and plagioclase-bearing lherzolites reflectsa moderate fractionation of the sulfide liquid that occurredwithin the magma chamber of the Suoi Cun intrusion (Fig. 10)(Naldrett et al. 1996; Song et al. 2008; Gao et al. 2012). Thisconclusion is consistent with the observed changes in modalproportions of pyrrhotite, pentlandite and chalcopyrite fromthe different rock types. The sulfide schlieren also showmoderately fractionated patterns with an average (Pt+Pd)/(Ru+Ir+Os) ratio of 10.8 (6.1 to 19.1), which is slightly lowerthan that for the disseminated sulfides due to higher Rucontents. They have moderate Pd/Ir ratios varying from 27

to 97 with an average value of 51 (Fig. 10a). The higher Pd/Irratios compared to the disseminated sulfides are due to lowerIr contents (Table 2; Fig. 7a). As can be seen in the diagram of(Pt+Pd)/(Ru+Ir+Os) vs. Pd/Ir (Fig. 10b), the sulfide schlierensamples do not plot on a sulfide liquid fractionation line forthe disseminated sulfides but form their own trend. Thisindicates that the sulfide liquid composition of the schlierenwas qualitatively different from that of the bulk of sulfides inthe Suoi Cun intrusion at the time of its fractionation.

On mantle-normalized chalcophile element patterns, alldisseminated sulfide samples exhibit variable positive Pdand slight negative Ru anomalies, and variable slight negativePt anomalies, whereas the sulfide schlieren have no negativeanomalies in Ru, but display pronounced positive Pd andslight negative Pt anomalies (Fig. 7a). A positive correlationof Ir and Ru with S in the Suoi Cun sulfide-bearing samples(Fig. 11a and b) indicates that the sulfides are the mainconcentrators of these metals in the rock. As can be seen inthe plot of Ir vs. Cu in 100 % sulfide phase, in which Cu isused as the index of fractional crystallization, the contents of Irdecrease with increasing Cu in accordance with the law of

UC

picriteTh

/Yb

PM

Crustalcontamination

trend

0.1

1

10

1 10

d

0.1

0.01

1

10

100

0.001 0.01 0.1 1 10

Th/Y

b OIB

E-MORB

N-MORB

oceanicarcs

active continentalmargin & alkalic“ ”

oceanic arcs

Calc-alkaline series

Tholeiitic series

Shoshonitic series

PM

UC

SC W

f

picrite

MORB

Ipla

teB

ntra-

asalt

s

c

N-MORBE-MORB

OIB

UC

Crustalcontamination

trend

0.1 1 10 100

0.1

0.01

1

10

(Ta/

Th) P

M

(Th/Yb) PM

b

N-MORB

UC

0.1 1 10 100 1000

0.1

0.01

1

10

(Nb/

Th) P

M

(Th/Yb)PM

crustal contamination

E-MORB OIB

a

Mixing between

mantle melt

compositions

UCand

Plagioclase-bearinglherzolite

Olivinemelanogabbro this study)(

Plagioclase-bearing wehrlite

this studyBalykin et al. (2006)

Balykin et al. (2006)this study

Fig. 9 Trace-element diagrams for sulfide-bearing rocks of the Suoi Cunintrusion. (a) Primitive mantle-normalized (Th/Yb)PM vs. (Nb/Th)PMdiagram; (b) (Th/Yb)PM vs. (Ta/Th)PM diagram. The dashed linerepresents likely minimum contamination as estimated from Condie(2003); (с) Ta/Yb vs. Th/Yb diagram (Pearce 1982, 1983). S subductionzone enrichment vector, C crustal contamination vector, W within-plateenrichment vector, f fractional crystallization vector; (d) La/Sm vs. Th/Yb

diagram. The dashedmixing line between upper crust and picrite has beencalculated assuming bulk mixing. Trace element data of the Suoi Cunrocks are combining fromBalykin et al. (2006) and our data. Data sourcesfor PM, N-MORB, E-MORB, OIB are from Sun and McDonough(1989). Composition of average upper crust (UC) is from Taylor andMcLennan (1985), model picrite from Arndt et al. (1993)


Rayleigh fractionation (Fig. 11c) for the disseminated sulfides.Such dependence indicates clearly that the variations of Ircontents in the different rock types are caused by fractionationof the sulfide liquid. In contrast, the concentrations of Ru donot show a clear dependence on Cu content (Fig. 11d), indi-cating that the fractional crystallization of the sulfide liquid isthe main but not the only mechanism that controls the distri-bution of Ru. At the same time, the depletion of Ru isconsistent with early crystallization of some amount ofCr-spinel before sulfide segregation (Capobianco et al.1994; Righter et al. 2004). Both Pt and Pd have a goodpositive correlation with S in the samples (Figs. 11e and8f, respectively), whereas the concentrations of thesemetals in 100 % sulfide phase do not show a cleardependence on Cu contents (Fig. 11g–h). Therefore, thepositive Pd anomaly in both disseminated and schlierensulfides is due to the fact that Pd occurs as discretemineral froodite PdBi2 enclosed in pyrrhotite and rarelyin pentlandite. A slight negative Pt anomaly in the dis-seminated sulfides is more difficult to interpret. The

distribution of Pt in the rocks may reflect local variationsin sulfur/oxygen fugacity during sulfide liquid fraction-ation (Ballhaus and Ulmer 1995; Jugo et al. 1999; Bellet al. 2009) or could be related to nugget effects due toformation of Pt alloys from magma during the earlystages of crystal fractionation (Garuti et al. 1997;Kepezhinskas et al. 2002). The sulfide schlieren aredistinguished by lower contents of all PGE (except Ruand Pd) in 100 % sulfide phase compared to the dissem-inated sulfides (Figs. 7a and 11c, d, g and h). This maybe due to a lower silicate liquid/sulfide liquid ratio (R-factor or N-factor), but the lack of negative Ru anomaliesin the sulfide schlieren indicates that the sulfide liquidinteracted with the magma which did not undergo earlyCr-spinel crystallization.

All rocks hosting disseminated sulfides have low Cu/Pd ratios varying from 1,890 to 12,650 with an averagevalue of ~7,500 (Fig. 12). Cu/Pd ratios are variablewithin range 1,890–11,529 (average 8,211) in theplagioclase-bearing lherzolites, 3,750–12,650 (average6,498) in the melanogabbros, 4,286–8,857 (average5,791) in the plagioclase-bearing wehrlites and are about8,115 in the gabbronorite. The Cu/Pd ratios of the sulfideschlieren are also low and range from 1,385 to 6,444with an average value of ~3,160 (Fig. 12). Similar Cu/Pdratios of the sulfide-bearing rocks which are close to themantle (Cu/Pd =7,000–10,000; Barnes and Maier 1999)indicate that both the disseminated and schlieren sulfideswere separated from a primary relatively PGE-undepletedmagma as a result of a single sulfide segregation event(Barnes et al. 1993; Maier et al. 1996). The difference inthe partition coefficients of Pd and Cu into a sulfideliquid may be used to deduce the volume of silicatemagma with which a sulfide liquid interacted (Barneset al. 1993). For R-factor (or N-factor) <1,000, sulfideliquid would be equally enriched with Cu and Pd, andmantle-normalized metal patterns would be equallyenriched with Pd and Cu. For R-factor >1,000, sulfideliquid would be more enriched with Pd than with Cu,thus the mantle normalized metal patterns would beenriched in Pd relative to Cu (Barnes and Maier 1999;Barnes and Maier 2002). The Suoi Cun rocks with dis-seminated sulfides have an average (Cu/Pd)PM ratio of1.0, varying within the range 0.3–1.5 in the plagioclase-bearing lherzolites, 0.5–1.7 in the melanogabbros, 0.6–1.2 in the plagioclase-bearing wehrlites, and is about 1.1in the gabbronorites. An average (Cu/Pd)PM ratio close tounity indicates the R-factor is less than 1,000, and thus itis unlikely that the disseminated sulfides interacted witha large volume of fresh magma to become rich in Ni, Cuand PGE, especially as their Cu/Pd ratios are not ex-tremely low. The sulfide schlieren have (Cu/Pd)PM ratiosvarying from 0.2 to 0.9 with an average value of 0.4.

0

5

10

15

20

0 20 40 60 80 100 120

(Pt +

Pd)

/ (Ir

+Ru+

Os)

Pd/Ir

y x= 6.9914ln( )-5.6961r = 0.992

y x= 10.06ln( )-27.017r = 1.002

Disseminatedessulfid

Sulfideschlieren

1

2

1

2

b

10

100

1000

10000Ir

(pbb

) in

100%

sul

fide

1000 10000 100000

Pd (pbb) in 100% sulfide

Pd/Ir = 5

1025

50100


Plagioclase-bearingwehrliteSulfide schlieren


a

Fig. 10 Plots of Pd versus Ir (a) and (Pt+Pd)/(Ir+Ru+Os) versus Pd/Ir(b) for sulfide-bearing rocks of the Suoi Cun intrusion


Lower Cu/Pd ratios in comparison with disseminatedsulfides seem to be related to Cu abundances.Figure 11h clearly shows that Pd contents are similar inschlieren and disseminated sulfides, whereas Cu contentsare quite lower in schlieren. This is consistent with lowerproportions of chalcopyrite in schlieren sulfides than indisseminated sulfides. In view of the above consider-ations, we suggest that the compositional variations be-tween the schlieren and disseminated sulfides are due tothe fact that the composition of the sulfide schlieren wasmodified through their interaction with an S-undersatu-rated, PGE-undepleted oxidized magma.

A model for the formation of the Suoi Cun Ni-Cu-PGEmineralization

The formation of the Suoi Cun sulfide-bearing rocks hostingNi-Cu-PGE mineralization involved an open system of mag-ma conduit (Fig. 13). An early S-undersaturated magnesianbasaltic magma may have reached sulfide saturation due tocrustal contamination and resulted in immiscible sulfide liquidsegregated in a deep-seated staging magma chamber. Becauseall Suoi Cun sulfide-bearing rocks analyzed show evidence ofcontamination, this mechanism is regarded by us as the mostprobable one to trigger sulfide liquid immiscibility. A bit

1

10

100

1000

0.1 1 10 100

Ir (p

pb)

S (wt%)

a

y x= 3.2719 + 7.3693r = 0.562

Sulfideschlieren

Disseminatedsulfides

Ru

(ppb

)

1

10

100

1000

0.1 1 10 100S (wt%)

b

y x= 12.052 + 0.4558r = 0.962

Sulfideschlieren


10

100

1000

10000

11 0

Ir (p

pb) i

n 10

0% s

ulfid

e

Cu (wt%) in 100% sulfide

c

y = 9769.1e-0.615x

r = 0.912


Sulfideschlieren

11 0100

1000

10000d

Ru

(ppb

) in

100%

sul

fide


y = .15e603 -0.051x

r = 0.142

Sulfideschlieren Disseminated

sulfides

1

10

100

1000

0.1 1 10 100

Pt (p

pb)

S (wt%)

e

y x= 112.91 + 3.9944r = 0.792

Sulfideschlieren


1

10

100

1000

0.1 1 10 100

Pd (p

pb)

S (wt%)

f


Sulfideschlieren

y x= 112.91 + 3.9944r = 0.792

1000

10000

11 00

Pt (p

pb) i

n 10

0% s

ulfid

e


g

10

Sulfideschlieren


Plagioclase-bearingwehrlite


Gabbronorite (dyke)(Glotov et al. (2004))




this studyGlotov 4et al. (200 )1000

100000

11 00

Pd (p

pb) i

n 10

0% s

ulfid

e


h

10

10000


Sulfideschlieren

Fig. 11 Plots of S versus Ir (a),Ru (b), Pt (e), Pd (f), and Cu in100 % sulfide versus Ir (c), Ru(d), Pt (g) and Pd (h) in 100 %sulfide for sulfide-bearing rocksof the Suoi Cun intrusion. Metalcontents in 100 % sulfide werecalculated following Barnes andLightfoot (2005)


earlier than this, the crystallization of some amount of Cr-spinel in the staging magma chamber could have caused adecrease in Ru content in a silicate melt as a ruthenium-depletion signature is preserved in the sulfides that segregatedfrom the magma (Fig. 13a). It is likely that the Cr-spinel grainsand the immiscible sulfides may settle along with olivinecrystallizing toward the base of the magma chamber due totheir higher density relative to the silicate melt from whichthey crystallized.

The staging magma chamber subsequently became a mag-ma conduit for later magma pulses. Some part of the earlymagma as a mixture of silicate melt, cumulus olivine, Cr-spinel grains and sulfides would be pushed out toward anupper magma chamber at higher level by a later pulse ofmagma or due to tectonic movements (Fig. 13b).Theoretically, the sulfide liquid trapped by a later pulse ofmagma could be partially dissolved in the silicate melt on theway up to an upper magma chamber (Mavrogenes andO’Neill 1999) and remaining sulfide liquid would becomeenriched in PGE (Kerr and Leitch 2005). But relatively lowPGE abundances overall and low Cu/Pd ratios close to themantle for the Suoi Cun disseminated sulfides argue againstthe interaction of the sulfide liquid with large amounts of S-undersaturated magma. The interaction of sulfides with thesilicate melt in the upper magma chamber would result in theredistribution of PGE during fractional crystallization of thesulfide liquid, which led to the observed Pd/Ir and Cu/Pdvariations in the rocks. We assume that the disseminatedsulfide mineralization of the Suoi Cun intrusion was formedin this way.

The concentrically zoned structure of the sulfide-bearingmafic-ultramafic unit in the Suoi Cun intrusion can be ex-plained by flow differentiation (Barker 1983). The Suoi Cunintrusion may have been a conduit for a flowing silicate melt.When the magma laden with Cr-spinel grains, sulfide dropsand olivine crystals entered into the upper magma chamber,both sulfides and silicates were concentrated toward the centerof the conduit due to the higher velocity of magma in thecenter of the conduit and drag along its margins. As a conse-quence, the cumulate plagioclase-bearing lherzolite is located

Fig. 12 Plot of Pd versus Cu/Pd for sulfide-bearing rocks of the SuoiCun intrusion. PM primitive mantle. Diagram from Barnes and Maier(1999)

Early pulseof S-undersaturatedmagnesian basalticmagma

Deep-seatedstaging

magma chamber

Crust

Surface

Crustal contamination

Sulf

Gr-Spl

Ol

The Suoi Cun uppermagma chamber

Crust

Surface

Later pulse ofmagma

Flow differentiationin the intruding magma

High viscousmelt - crystal

mush

Crust

Surface

Successive pulseof S-undersaturated

oxidized magma

As the conduit widened,the velocity of the magmadecreased and higherdensity sulfide schlierenbecame trapped here

Suoi Cunintrusion

Disseminateds in rockssulfide

Sul

PGE - S compounds

?

PGE-enriched lavas

Transfer of PGEfrom the sulfide liquidto the silicate meltunder kinetic control

Oxidation of thesulfide liquid due toits reaction withoxidized magmas

Gr-Spl - Cr-spinelOl Olivine-Ol Drops of immiscible-

sulfide melt

Early-stageCr-spinelcrystallizationbefore sulfidesegregation

Sulfide liquidis depletedin Ru

a

b

c

Fig. 13 A schematic model for the formation of the Suoi Cun Ni-Cu-PGE sulfide mineralization. See text for explanation


in the central part of the intrusion, and the melanogabbro areconfined to its marginal parts. Apparently due to the highviscosity of the melt–crystal mush, no near-bottom depositsof massive Cu-Ni ores were formed at the base of the SuoiCun intrusion, and the bulk of mineralization is represented bydisseminated sulfides.

The formation of the sulfide schlieren is most likely resultof interaction processes between early-formed sulfide liquidsand fresh magma pulses (Fig. 13c). Successive magma pulsespassing through the deep-seated staging chamber would stirup the sulfides, which have been segregated from the earlymagnesian basaltic magma and settled at the bottom of thestaging magma chamber, and moved them toward the SuoiCun magma chamber. This magma was most likely undersat-urated in sulfur and also did not experience any early-stage Cr-spinel crystallization as the schlieren sulfides display low Cu/Pd ratios and do not have negative Ru anomalies. If themagma is just S-undersaturated and PGE-undepleted, its in-teraction with the schlieren sulfides would have led to partialdissolution of FeS of pre-existing sulfides with upgrade of aremaining sulfide liquid in PGE (Kerr and Leitch 2005). Theascent of a magma batch towards the Suoi Cun upper magmachamber could well lead to the same result. However, themodel of PGE enrichment of sulfide liquid due to partialdissolution of FeS does not explains the observed distributionof PGE in the schlieren sulfides, in particular, lower contentsof Ir, Rh and Pt and a higher content of Ru compared todisseminated sulfides. If so, we assume that a S-undersaturated PGE-undepleted magma which reacted withthe sulfide schlieren liquid was oxidized.

Sulfate is the dominant sulfur species in oxidized magmasbecause above FMQ+0.5, sulfur is progressively oxidized toSO4

2− (e.g. Jugo et al. 2005, 2010; Métrich et al. 2009). Thus,the interaction of sulfide liquid with oxidized silicate meltswould promote the destruction of sulfides through their oxi-dation. The sulfide component that is most easily oxidized isFeS. The oxidation of FeS stabilizes magnetite and releasessulfur in the form of S2 compound (Vaughan and Craig 1978),which would also be oxidized to SO4

2−under high partialpressure of oxygen (pO2) in magma. In theory, Ru is highlycompatible into the magnetite structure (Righter et al. 2004;Capobianco et al. 1994), but this element partitioned exclu-sively into co-crystallizing Fe-rich monosulfide solid solution(mss) rather into magnetite in natural sulfide–silicate systems(e.g., Dare et al. 2011; Dare et al. 2012). Thus, enrichment ofthe schlieren sulfides with Ru could not be caused by Rupartitioning into magnetite during the oxidation of sulfideliquid. However, under the condition of progressive oxidationof the sulfide melt, the preference of PGE to bond with sulfurwould diminish because PGE cationic species are not expect-ed to associate with the SO4

2− anionic species. With increas-ing oxidation of silicate melt, O2− anions will gradually takeover as the principal PGE ligand, at the expense of S2−

(Laurenz et al. 2013), and PGE would diffuse from sulfideliquid to silicate melt in the form of PGE–O compounds(Fig. 11c). If so, the observed PGE variations in the schlierensulfides are well explained by the kinetic model described byMungall (2002). During the transfer of PGE from oxidizedsulfide liquid to silicate melt, Os and Ru as high field strengthelements (HFSE) with the smallest diffusivities would beexpected to be significantly fractionated from Ir, because Irhas larger diffusivity (Mungall 2002). As a result, rutheniumwould be more slowly extracted from sulfide liquid, leading torelative enrichment of the schlieren sulfide liquid with Ru,compared to other PGE. A moderate depletion of Ir, Rh and Ptin the schlieren sulfide liquid is in good agreement withmoderate diffusivities for these intermediate field strengthelements (IFSE). Palladium is also IFSE, but its content hasremained more or less unchanged in the schlieren sulfideliquid apparently due to the fact that the bulk of Pd wasbonded to bismuth and not sulfur, resulting in frooditePdBi2. The oxidation of sulfide liquid assumed in this workis consistent with the mineralogical observations that a largeamount of magnetite is present in the schlieren ore association.Thus, the sulfides which had been depleted in Ru due to early-stage Cr-spinel crystallization were equilibrated with S-undersaturated PGE-undepleted oxidized magmas to gainlower metal contents, although this process was able to dimin-ish the depletion of Ru in the sulfide schlieren.

In addition, the later magma pulses that reacted with theschlieren sulfide liquid may become enriched in PGE to formPGE-enriched volcanic rocks and/or intrusive elsewhere(Fig. 13c). If this had happened, the intrusions and/or volcaniclavas in this region could be enriched in Ir, Pt and Rh relativeto Ru and Pd.

Conclusions

The Suoi Cun weakly mineralized intrusion is a good exampleto show that the process of the interaction of a sulfide liquidwith fresh batches of magma in a magma conduit system doesnot always lead to the formation of high-grade Ni-Cu-PGEdeposits. After the S-undersaturated magnesian basaltic mag-ma reached sulfide saturation due to crustal contamination andearly-stage Cr-spinel crystallization in a deep-seated stagingmagma chamber, segregated sulfide liquid was transported bya later pulse of magma to the Suoi Cun upper magma cham-ber. The redistribution of PGE during fractional crystallizationof the sulfide liquid in the upper magma chamber led to theformation of the disseminated mineralization in the Suoi Cunintrusion.

A successive pulse of S-undersaturated PGE-undepletedoxidized magma that passed through the staging chamberstirred up early-segregated sulfides and transported them tothe Suoi Cun magma chamber. During this process, the


interaction of the oxidized silicate melt with the sulfide liquidled to the intensive oxidation of the latter and triggered thetransfer of PGE from the oxidized sulfide liquid to the silicatemelt that was controlled by kinetic factors, resulting in lowerPGE contents in the sulfide schlieren.

Acknowledgments We thank Tran Tuan Anh, Tran Trong Hoa, Bui AnNien, and the staff of the Institute of Geological Sciences, the VietnameseAcademy of Science and Technology for their assistance in carrying outthis research. We also thank the reviewers for their constructive review,editorial handling and helpful comments all of which greatly improvedthis manuscript. This study was funded by the Russian Foundation forBasic Research (project 12-05-00112) and the Division of Earth Sciences,Russian Academy of Sciences (program ONZ-2).

References

Anders E, Grevesse N (1989) Abundances of the elements: meteoritic andsolar. Geochim Cosmochim Acta 53:197–214

Arndt NT, Czamanske GK, Wooden JL, Fedorenko VA (1993) Mantleand crustal contributions to continental flood volcanism.Tectonophysics 223:39–52

Arndt NT, Chauvel C, Fedorenko VA, Czamanske GK (1998) Twomantle sources, two plumbing systems: tholeiitic and alkalinemagmatism of the Maymecha River basin, Siberian flood volcanicprovince. Contrib Mineral Petrol 133:297–313

Ballhaus C, Ulmer P (1995) Platinum-group elements in the Merenskyreef: II. Experimental solubilities of platinum and palladium in Fe1-xS from 950 to 450oC under controlled ƒS2 and ƒH2. GeochimCosmochim Acta 59:4881–4888

Balykin PA, Polyakov GV, Hoa TT, Lavrenchuk AV, Izokh AE, PhuongNT, Glotov AI, Thanh HH, Petrova TE, Vasyukova EA (2006)Conditions of formation of the Late Permian Cao Bang PGE-Cu-Ni-bearing lherzolite-gabbronorite-dolerite complex (northeasternVietnam). Russ Geol Geophys 47(7):825–837

Barker DC (1983) Igneous rocks. Prentice-Hall, Englewood CliffsBarnes S-J, Lightfoot PC (2005) Formation of magmatic nickel–sulfide

ore deposits and processes affecting their copper and platinum-group element contents. Econ Geol 100:179–213

Barnes S-J, Maier WD (1999) The fractionation of Ni, Cu and the noblemetals in silicate and sulfide liquids. In: Keays RR, Lesher CM,Lightfoot PC, Farrow CEG (eds) Dynamic processes in magmaticore deposits and their application in mineral exploration, vol. 13.Geological Association of Canada, Short Course Notes, pp 69–106

Barnes S-J, Maier WD (2002) Platinum-group element distributions inthe Rustenberg Layered Suite of the Bushveld Complex, SouthAfrica. In: Cabri LJ (ed) The Geology, geochemistry, mineralogyand mineral beneficiation of platinum-group elements, vol. 54.Canadian Institute of Mining, Metallurgy and Petroleum, Canada,pp 431–458

Barnes S-J, Kornelliussen BR, NilssenA, Often LP, Pedersen RB, RobinsB (1988) The use of mantle normalization and metal ratios indiscriminating the effects of partial melting, crystal fractionationand sulfide segregation on platinum group elements, gold, nickeland copper: examples from Norway. In: Prichard HM, Potts PJ,Bowles JFW (eds) Geo-platinum, vol. 87. Elsevier, London, pp113–143

Barnes S-J, Couture JF, Sawyer EW (1993) Nickel–copper occurrences inthe Belleterre–Angliers belt of the Pontiac subprovince and the useof Cu–Pd rations in interpreting platinum-group element distribu-tions. Econ Geol 88:1402–1418

Bell AS, SimonA, GuillongM (2009) Experimental constraints on Pt, PdandAu partitioning and fractionation in silicate melt–sulfide–oxide–aqueous fluid systems at 800 °C, 150 MPa and variable sulfurfugacity. Geochim Cosmochim Acta 73:5778–5792

Borisenko AS, Sotnikov VI, Izokh AE, Polyakov GV, Obolensky AA(2006) Permo–Triassic mineralization in Asia and its relation toplume magmatism. Russ Geol Geophys 47(1):166–182 (in Russian)

Capobianco CJ, Hervig RL, Drake MJ (1994) Experiments on crystal/liquid partitioning of Ru, Rh and Pd for magnetite and hematite solidsolutions crystallized from silicate melt. Chem Geol 113(1–2):23–43

Carter A, Roques D, BristowC, Kinny P (2001) Understanding mesozoicaccretion in Southeast Asia: significance of triassic thermotectonism(Indosinian orogeny) in Vietnam. Geol 29:211–214

Chai G, Naldrett AJ (1992) Characteristics of Ni-Cu-PGE mineralizationand genesis of the Jinchuan deposit, Northwest China. Econ Geol87:1475–1495

Condie KC (2003) Incompatible element ratios in oceanic basalts andkomatiites: tracking deep mantle sources and continental growthrates with time. Geochem Geophys Geosyst 4:1–28

Cowden A, Donaldson MJ, Naldrett AJ, Campbell IH (1986) Platinum-group elements and gold in the komatiite-hosted Fe-Ni-Cu sulfidedeposits at Kambalda, Western Australia. Econ Geol 81:1226–1235

Dare SAS, Barnes S-J, Prichard H, Fisher PC (2011) Chalcophile andplatinum-group (PGE) concentrations in the sulfide minerals fromtheMcCreedy East deposit, Sudbury, Canada, and the origin of PGEin pyrite. Miner Deposit 46(4):381–407

Dare SAS, Barnes S-J, Beaudoin G (2012) Variation in trace elementcontent of magnetite crystallized from a fractionating sulfide liquid,Sudbury, Canada: implications for provenance discrimination.Geochim Cosmochim Acta 88:27–50

Dovzhikov AE, My BP, Vasilevskaya ED, Zhamoida AI, Ivanov GV,Izokh EP, Nhu LD, Mareichev AM, Tien NV, Trinh NP, Luong TD,Quang PV, Long PD (1965) Geology of North Vietnam. Science andTechnology Publishing House, Hanoi (in Russian)

Findlay RH, Trinh PT (1997) The structural setting of the Song Maregion, Vietnam and the Indochina–South China plate boundaryproblem. Gondwana Res 1:11–33

Gao J-F, Zhou M-F, Linghtfoot PC, Wang CY, Qi L (2012) Origin ofPGE-poor and Cu-rich magmatic sulfides from the Kalatongkedeposit, Xinjiang, Northwest China. Econ Geol 107:481–506

Garuti G, Fershtater G, Bea F, Montero P, Pushkarev EV, Zaccarini F(1997) Platinum-group elements as petrological indicators in mafic-ultramafic complexes of the central and southern Urals: preliminaryresults. Tectonophysics 276:181–194

Geological and mineral resources map of Viet Nam (1:200 000) (2000)Chinh Si – Long Tan (F-48-XI & F-48-XVII). Department ofGeology and Minerals of Vietnam, Hanoi

Glotov AI, Polyakov GV, Hoa TT, Phuong NT, Izokh AE, Kovyazin SV,Balykin PA, Thanh HH, Niеn BA, Dung PT (2004) The latePermian Cao B ng PGE–Cu–Ni-bearing complex of the Sông Hi nstructure, Northeastern Vi t Nam. J Geol 23:89–98

Halter WE, Heinrich CA, Pettke T (2005) Magma evolution and theformation of porphyry Cu-Au ore fluids: evidence from silicateand sulfide melt inclusions. Miner Deposita 39:845–863

Hoa TT (2007) Within-plate magmatism of Northern Vietnam and itsmetallogeny. Dissertation, VS Sobolev Institute of Geology andMineralogy SB RAS, Novosibirsk (in Russian)

Hoa TT, Anh TT, Phuong NT, Dung PT, Anh TV, Izokh AE, BorisenkoAS, Lan CY, Chung SL, Lo CH (2008a) Permo-Triassic intermedi-ate–felsic magmatism of the Truong Son belt, eastern margin ofIndochina. Compt Rendus Geosci 340:112–126

Hoa TT, Izokh AE, Polyakov GV, Borisenko AS, Anh TT, Balykin PA,Phuong NT, Rudnev SN, Van VV, Nien BA (2008b) Permo–Triassicmagmatism and metallogeny of Northern Vietnam in relation to theEmeishan plume. Russ Geol Geophys 49(7):480–491


Izokh AE, Polyakov GV, Hoa TT, Balykin PA, Phuong NT (2005)Permian–Triassic ultramafic–mafic magmatism of NorthernVietnam and Southern China as expression of plume magmatism.Russ Geol Geophys 46:942–951 (in Russian)

Jugo PJ, Candela PA, Piccoli PM (1999) Magmatic sulfides and Au: Curatios in porphyry deposits: an experimental study of copper andgold partitioning at 850oC, 100 MPa in a haplogranitic melt-po-intermediate solid solution-gold metal assemblage, at gas saturation.Lithos 46:573–589

Jugo PJ, Luth RW, Richards JP (2005) Experimental data on the specia-tion of sulfur as a function of oxygen fugacity in basaltic melts.Geochim Cosmochim Acta 69:497–503

Jugo PJ, Wilke M, Botcharnikov RE (2010) Sulfur K-edge XANESanalysis of natural and synthetic basaltic glasses: Implications forS speciation and S content as function of oxygen fugacity. GeochimCosmochim Acta 74:5926–5938

Keays RR (1995) The role of komatiitic and picritic magmatism and S-saturation in the formation of ore deposits. Lithos 34:1–18

Kepezhinskas P, Defant MJ, Widom E (2002) Abundance and distribu-tion of PGE and Au in the island-arc mantle: implication for sub-arcmetasomatism. Lithos 60:113–128

Kerr A, Leitch AM (2005) Self-destructive sulfide segregation systemsand the formation of high-grade magmatic ore deposits. Econ Geol100:311–332

Khuong TH (2009) Tectonics and magmatism in Northwest Vietnam.Geologia 35:345–351

Khuong TH (2010) The complex tectonic events and their influence onformation of mineral deposits in northwest Vietnam. Dissertation,Akademia Górniczo-Hutnicza im. Stanisława Staszica, Krakow

Krobicki M, Golonka J, Hung KT (2008) Major tectonic events andplates of Northwest Vietnam. In: Proceedings of the InternationalSymposia on Geosciences Resources and Environments of AsianTerranes (GREAT 2008), 4th IGCP 516, and 5th APSEG.Chulalongkorn University, Bangkok, pp 101–104

Laurenz V, Fonseca ROC, Ballhausa C, Jochumb KP, Heusera A,Sylvesterc PJ (2013) The solubility of palladium and ruthenium inpicritic melts: 2. The effect of sulfur. Geochim Cosmochim Acta108:172–183

Leloup PH, Lacassin R, Tapponnier P, Scharer U, Zhong DL, Liu XH,Zhang LS, Ji SC, Trinh PT (1995) The Ailao shan–Red river shearzone (Yunnan, China), tertiary transform boundary of Indochina.Tectonophysics 251:3–84

Lepvrier C, Vuongb NV, Maluskic H, Thib PT, Vub TV (2008)Indosinian tectonics in Vietnam. Compt Rendus Geosci 340:94–111

Lepvrier C, Faure M, Van VN, Vu TV, Lin W, Trong TT, Hoa PT (2011)North-directed Triassic nappes in Northeastern Vietnam (East BacBo). J Asian Earth Sci 41:56–68

Li C, Lightfoot PC, Amelin Y, Naldrett AJ (2000) Contrasting petrolog-ical and geochemical relationships in the Voisey’s Bay andMushuauintrusions, Labrador, Canada: implications for ore genesis. EconGeol 95:771–799

Lightfoot PC, Naldrett AJ, Gorbachev NS, Doherty W, Fedorenko VA(1990) Geochemistry of the Siberian Trap of the Noril’sk area,USSR, with implications for the relative contributions of crust andmantle to flood basalt magmatism. Contrib Mineral Petrol 104:631–644

MaierWD, Barnes SJ, DeklerkWJ, Teigler B,Mitchell AA (1996) Cu/Pdand Cu/Pt of silicate rocks in the Bushveld complex: implicationsfor platinum-group element exploration. Econ Geol 91:1151–1158

Maier WD, Barnes S-J, Chinyepi G, Barton JMJ, Eglington B, Setshedi I(2008) The composition of magmatic Ni-Cu-(PGE) sulfide depositsin the Tati and Selebi-Phikwe belts of eastern Botswana. MinerDeposita 43:37–60

Makkonen HV (1996) 1.9 Ga tholeiitic magmatism and related Ni–Cudeposition in the Juva area, SE Finland. Geol Surv Finland Bull 386:1–101

Mavrogenes JA, O’Neill HSC (1999) The relative effects of pressure,temperature and oxygen fugacity on the solubility of sulfide inmaficmagmas. Geochim Cosmochim Acta 63:1173–1180

Métrich N, Berry AJ, O’Neill HSC, Susini J (2009) The oxidation state ofsulfur in synthetic and natural glasses determined by X-ray absorp-tion spectroscopy. Geochim Cosmochim Acta 73:2382–2399

Moretti R, Baker DR (2008)Modeling the interplay of ƒO2 and ƒS2 alongthe FeS – silicate melt equilibrium. Chem Geol 256:286–298

Mungall JE (2002) Kinetic controls on the partitioning of trace elementbetween silicate and sulfide liquids. J Petrol 43(5):749–768

Naldrett AJ (2004) Magmatic sulfide deposits: geology, geochemistry,and exploration. Springer Berlin Heidelberg, New York

Naldrett AJ, Fedorenko VA, Asif M, Lin S, Kunilov VE, Stekhin AI,Lightfoot PC, Gorbachev NS (1996) Controls on the composition ofNi-Cu sulfide deposits as illustrated by those at Noril’sk, Siberia.Econ Geol 91(4):751–773

Naldrett AJ, Asif M, Krstic S, Li C (2000) The composition of mineral-ization at the Voisey’s Bay Ni-Cu sulfide deposit, with specialreference to platinum-group elements. Econ Geol 95:845–866

Nam TN (1998) Thermotectonic events from early Proterozoic toMiocene in the Indochina craton: implication of K–Ar ages inVietnam. J Asian Earth Sci 16:475–484

Ohmoto H (1986) Stable isotope geochemistry of ore deposits. In: ValleyJW, Taylor HPJ, O’Neil JR (eds) Stable isotopes in high temperaturegeological processes. M.S.A. Rev Mineral Geochem, vol 16, pp491–559

Pearce JA (1982) Trace element characteristics of lavas from destructiveplate boundaries. In: Thorpe RC (ed) Orogenic andesites and relatedrocks. Wiley, Chichester, pp 528–548

Pearce JA (1983) The role of sub-continental lithosphere in magmagenesis at destructive plate margins. In: Hawkesworth CJ, NorryMJ (eds) Continental basalts and mantle xenoliths. Shiva, Nantwich,pp 230–249

Polyakov GV, Shelepaev RA, Hoa TT, Izokh AE, Balykin PA, PhuongNT, Hung TQ, Nien BA (2009) The Nui Chua layered peridotite-gabbro complex as manifestation of Permo-Triassic mantle plume innorthern Vietnam. Russ Geol Geophys 50:501–516

Righter K, Campbell AJ, Humayun M, Hervig RL (2004) Partitioning ofRu, Rh, Pd, Re, Ir, and Au between Cr-bearing spinel, olivine,pyroxene and silicate melts. Geochim Cosmochim Acta 68(4):867–880

Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. ContribMineral Petrol 29:275–289

Ryamzin NV, Frolov VP (1960) Report on prospecting for nickel in theCao Bang province. Main Geological Survey attached to Council ofMinisters of the DRV, Hanoi (in Russian)

Schärer U, Tapponnier P, Lacassin R, Leloup PH, Zhong D, Ji S (1990)Intraplate tectonics in Asia: a precise age for large-scale Miocenemovement along the Ailao Shan-Red River shear zone, China. EarthPlanet Sci Lett 97(1–2):65–77

Schärer U, Zhang L-S, Tapponnier P (1994) Duration of strike-slipmovements in large shear zones: the Red River belt, China. EarthPlanet Sci Lett 126(4):379–397

Song XY, Zhou M-F, Tao Y, Xiao J-F (2008) Controls on the metalcompositions of magmatic sulfide deposits in the Emeishan largeigneous province, SW China. Chem Geol 253:38–49

Su B-X, Qin K-Z, Sun H, Tang D-M, Sakyi PA, Chu Z-Y, Liu P-P, XiaoQ-H (2012) Subduction-induced mantle heterogeneity beneathEastern Tianshan and Beishan: Insights from Nd-Sr-Hf-O isotopicmapping of Late Paleozoic mafic-ultramafic complexes. Lithos134–135:41–51

Sun S-S, McDonough WF (1989) Chemical and isotopic systematics ofoceanic basalts: implications for mantle composition and progresses.In: Saunders AD, Norry MJ (eds) Magmatism in the ocean basins,vol. 42, Special Publication. Geological Society of London,London, pp 313–345


Svetlitskaya TV, Tolstykh ND, Izokh AE, Phuong NT (2011) Cu–Ni–PGE mineralization in the northern part of the eastern block of theSuoi Cun intrusion, northeastern Vietnam. Proceedings of SiberianDepartment of the Section of Earth Sciences, Russian Academy ofNatural Sciences. Geol Prospecting Explor Ore Deposits 1(38):67–77 (in Russian)

Tapponnier P, Lacassin R, Leloup PH, Schärer U, Dalai Z, Haiwei W,Xiaohan L, Shaocheng J, Lianshang Z, Jiayou Z (1990) The AilaoShan Red River metamorphic belt: left-lateral shear betweenIndochina and China. Nat 343:431–437

Taylor ST, McLennan SM (1985) The continental crust: its compositionand evolution. Blackwell, Oxford, p 312

Tornos F, Galindo C, Casquet C, Pevida LR, Martínez C, Martínez E,Velasco F, Iriondo A (2006) The Aguablanca Ni-(Cu) sulfide deposit,SW Spanin: geologic and geochemical controls and the relationshipwith amidcrustal layeredmafic complex.Miner Deposita 41:737–769

Tran HT, Thanh NX, Halpin JA, Zaw K (2011) The occurrence ofophiolite-style assemblages along Sino-Vietnam border,Northeastern Vietnam and its implication to the tectonic evolutionof Northeastern Indochina. In: Proceedings of the InternationalConference on Geology. Geotechnology and Mineral Resources ofIndochina (GEOINDO 2011), Khon Kaen, pp 479–488

Tri TV (1979) Geology of Vietnam (the North part). Science andTechnology Publishing House, Hanoi

Vaughan DJ, Craig JR (1978) Mineral chemistry of metal sulfides.Cambridge University Press, Cambridge

Vladimirov AG, Balykin PA, Anh PL, Kruk NN, Phuong NT, Travin AV,Hoa TT, Annikova IY, Kuybida ML, Borodina EV, Karmysheva IV,Nien BA (2012) The Khao Que-Tam Tao gabbro-granite massif,Northern Vietnam: a petrological indicator of the Emeishan plume.Russ J Pac Geol 6:395–411

Wang CY, Zhou M-F, Keays RR (2006) Geochemical constraints on theorigin of the Permian Baimazhai mafic-ultramafic intrusion, SWChina. Contrib Mineral Petrol 152:309–321

Wang CY, Zhou M-F, Qi L (2010) Origin of extremely PGE-richmafic magma system: an example from the Jinbaoshan ultra-mafic sill, Emeishan large igneous province, SW China.Lithos 119:147–161

Xia L-Q, Xia Z-C, Xu X-Y, Li X-M, Ma Z-P, Wang L-S (2005) Nature ofthe mantle source of the Tianshan Carboniferous rift-related basalts.Nov embe r 2 0 05 L I P o f t h e Mon t h . h t t p : / /www.largeigneousprovinces.org/05nov

Zhang RY, Lo C-H, Chung S-L, Grove M, Omori S, Iizuka Y, Liou JG,Tri TV (2013) Origin and tectonic implication of ophiolite andeclogite in the Song Ma Suture Zone between the South Chinaand Indochina Blocks. J Metamorph Geol 31:49–62. doi:10.1111/jmg.12012

Zhou MF, Zhao JH, Jiang CY, Gao JF, Wang W, Yang SH (2009)OIB-like, heterogeneous mantle sources of Permian basalticmagmatism in the western Tarim Basin, NW China: implica-tions for a possible Permian large igneous province. Lithos113:583–594


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pge geochemical constraints on the origin of the ni-cu-pge sulfide mineralization in the suoi cun...

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