Zambales ophiolite,Philippines

The Acoje massif is part of a mafic-ultramafic complex, the Zambales ophiolite, and is a fragment of Mesozoic oceanic crust. This paper documents the occurrence and phase relations of sulfides and associated phases in the critical zone of the Acoje massif. The Acoje critical zone (ACZ) forms the basal cumulate sequence of the massif and consists of a variably serpentinized lower ultramafic zone and a relatively less altered upper mafic zone. Two distinct sulfide associations have been identified: (1) a troilite (±pyrrhotite)-dominated group hosted by the mafic zone and (2) a pentlandite-dominated group hosted by the ultramafic zone. Troilite-dominated assemblages represent the original mineralogy of magmatically precipitated sulfides in the entire cumulate sequence. The pentlandite-dominated group appears to have evolved from the primary magmatic sulfides during low-temperature re-equilibration. The paragenetic evolution from the magmatic assemblage to the low-temperature assemblage appears to have proceeded as follows: (1) S-rich hexagonal pyrrhotite+pentlandite+chalcopyrite (or cubanite)+magnetite, (2) S-poor hexagonal pyrrhotite+pentlandite+intermediate solid solution (iss) phase (and/or cubanite)+magnetite, (3) troilite (or mackinawite)+pentlandite+iss+magnetite, (4) troilite (or mackinawite)+pentlandite+iss+native Cu+magnetite, (5) pentlandite+native Cu+magnetite, and (6) pentlandite+native Cu+Fe-Ni alloy+magnetite. This evolutionary trend, in conjunction with the observed textural, chemical, and sulfur-isotopic relations, indicates that the native metal and alloy phases in the ACZ were produced by low-temperature reduction of the primary magmatic sulfides. Correlations between sulfide assemblages and coexisting silicate-hydrosilicate-oxide assemblages further indicate that this alteration occurred during retrograde serpentinization of the Acoje massif. Two end-member models that could explain the inferred low-temperature mineralogic evolution of the ACZ sulfides are described: (1) an isothermal reduction model and (2) a non-isothermal equilibration model. Both isothermal and non-isothermal effects apparently were involved in the development of variably reduced sulfide-oxide-metal assemblages from the initial magmatic sulfides.     

Refractory- and metallurgical-type chromite ores,Zambales ophiolite,Luzon, Philippines

The Zambales ophiolite is the major source of chromite ore in the Philippines. The chromitites are concordant cumulates and are associated with distinct chromitite-bearing sequences within the mantle peridotites. Refractory and metallurgical chromite deposits are spatially separated and related to different lithologic associations, which crystallized from different parental magmas. — Refractory chromite ores (30–44 wt% Cr₂O₃; 20–30 wt% Al₂O₃) are linked with the peridotite-troctolite-olivine gabbro lineage. Two main types were found: (1) Al-rich refractory ores associated with harzburgites and feldspathic periodotites and (2) more Cr-rich varieties associated with lherzolites. — Metallurgical chromite ores (45–53 wt% Cr₂O₃; 12–18 wt% Al₂O₃) are linked with the peridotite-pyroxenite-norite lineage. Two main types were also found: (1) Cr-rich metallurgical ores associated with orthopyroxenites and (2) more Al-rich varieties related to clinopyroxenites. — The chemical composition of chromite within the deposits varies depending on the chromite/silicate ratios of the ore types and grades continuously into accessory chrome spinels in the wall-rock peridotites. — The geochemistry of accessory chrome spinels in various peridotites and mafic cumulates depends on the mineralogical composition and the stratigraphic position of their host rocks.New address: BEB Erdgas und Erdöl GmbH, Riethorst 12, D-3000 Hannover 51The terms chrome-spinels and chromite are used as follows: 1. Chrome-spinel is only used for those occuring as accessory minerals in various ultramafic and mafic rocks (= accessory chrome-spinels). Their chemical composition has been determined only by microprobe analysis. — 2. Chromite is used for ore and ore deposits (=chromitites); the chemical composition has been determined by wet chemistry (AAS) or by microprobe analysis     

The Acoje Block Platiniferous Dunite Horizon, Zambales Ophiolite Complex, Philippines: Melt Type and Associated Geochemical Controls

Abstract: The Zambales Ophiolite Complex, a supra-subduction zone ophiolite, is made up of the mid-ocean ridge-related Coto block and the island arc-related Acoje block. This crust-mantle sequence hosts platinum-group elements (PGE) in the Acoje block. The melts responsible for the PGE-bearing nickel sulfide and chromitite deposits are of magmatic origin characterized by high-MgO basalt to boninitic composition which, being second or third-stage melts, carry higher PGE budgets. Metal ratio diagrams, utilizing base and precious metals, reveal that the distribution and deposition of the PGE in the Acoje block are affected by olivine, chromite and sulfide crystallization. The generation, accumulation and segregation of the PGE, oxide and sulfide minerals from the melts are governed by the combined factors of high degrees of partial melting, multiple melt replenishment with concomitant magma mixing and fractional crystallization. Although previous sulfide segregation events could have occurred below the PGE-bearing nickel sulfide horizon as shown by the Ni/Cu (>1), the Cu/Pd and Ni/Pd strongly suggest that the main platiniferous zone is confined within the Acoje block transition zone dunite.     

Geochemistry of reduced gas related to serpentinization of the Zambales ophiolite, Philippines

Methane-hydrogen gas seeps with mantle-like C and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the Zambales ophiolite, Philippines. New measurements of noble gas and ¹⁴C isotope abundances, rock/mixed-volatile equilibrium calculations, and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration. The gas seeps are produced in rock-dominated zones of serpentinization, and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization.     

Platinum and palladium stream-sediment geochemistry downstream from PGE-bearing ultramafics, West Andriamena area, Madagascar

Several pilot studies were made in a PGE-mineralized area of central Madagascar in order to compare Pt,Pd halos in heavy mineral concentrates and to select the most suitable stream-sediment fractions, sampling densities and anomaly thresholds for regional PGE surveys. Results show low anomaly thresholds for Pt (30 ppb) and Pd (20 ppb) in the −63 μm fractions of the active sediment, with restricted halos of nearly 300 m for Pt and nearly 500 m for Pd. Using a slightly coarser fraction (−125 μm) increases the anomaly contrast. The Pt anomalies in heavy mineral pan concentrates are considerably enhanced (400–1,000 ppb) but occur further downstream in residual terraces. A regular increase in the weight of the heavy mineral concentrate for a given volume of sediment is noticed downstream. A simple weight correction of the raw Pt grade in the heavy mineral concentrate gives a better definition of the mineralized source upstream. Assessment of the corrected heavy mineral concentrate Pt anomalies together with Pt,Pd anomalies in the finest stream-sediment fraction produces the optimum definition of the target. Optical determination and scanning electron microscope studies of the PGM show sperrylite to be the major Pt-bearing mineral in the stream sediment, whereas the Pd mineralogy remains unresolved. Pt dispersion appears to be a predominantly mechanical process and Pd dispersion a chemical process with deposition controlled mainly by MnO scavenging.     

Structural features of ophiolitic chromitites in the Zambales Range,Luzon, Philippines

The chromitite-bearing peridotites of the Zambales mafic-ultramafic complex form the lowermost level of the Zambales ophiolite, which exposes a complete ophiolitic sequence. The chromitites occur close to the peridotite/gabbro transition zone.The chromite orebodies are structurally classified into three major types: (1) concordant tabular deposits, (2) strings of pods and (3) pocketlike deposits.Concordant tabular deposits show a gradational transition from chromitite to host rock (modal grading) and are characterized by the parallelism of ore and host-rock structures. Primary magmatic features like inch-scale layering, size grading, glomeroporphyric chromite aggregates, skeletal chromite growth and adcumulus growth (cumulus textures) are common.The concordant chromite bodies are often tectonically disrupted and boudined forming strings of pods or fault-controlled pocketlike deposits. With increasing tectonization chromite shows pull-apart textures and lineations (plastic deformation), shearing, prismatic jointing, brecciation and mylonitization (brittle deformation). Recrystallization of cataclastic chromite occurs on a microscopic scale.Plastic deformation is caused by mantle flow and/or the volume increase of the peridotites during serpentinization. The influence of mantle flow is indicated by the orientation of the pod strings and lineations in chromitite perpendicular to the ridge axis. Brittle deformation of chromite (cataclasis) and disruption by faults is related to the emplacement of the ophiolite.     

The Zambales complex: gravity anomalies and a very strange ophiolite

In common with most of the larger ophiolite bodies that were emplaced during the Cenozoic and late Mesozoic and which have experienced relatively little post-emplacement disruption or metamorphism, the Zambales Ophiolite Complex (ZOC) of western Luzon (northern Philippines) is associated with very large gravity anomalies. Worldwide and in the ZOC, peak to trough amplitudes of more than 100 mGal are common and amplitudes in excess of 200 mGal are not unknown     

菲律宾Zambales蛇绿岩套的再研究：对其特提斯来源的启示

A number of geological studies have already been conducted on the Zambales Ophiolite Complex (ZOC), a north-south trending complete ophiolite sequence exposed in the western portion of Central Luzon, Philippines. Previous works recognized the ZOC as being made up of two blocks, the Acoje and the Coto, acting as an arc-back arc pair sometime during the Eocene.     

Evolution of Hydrothermal System at the Dizon Porphyry Cu-Au Deposit, Zambales, Philippines

Abstract. Evolution of hydrothermal system from initial porphyry Cu mineralization to overlapping epithermal system at the Dizon porphyry Cu‐Au deposit in western central Luzon, Zambales, Philippines, is documented in terms of mineral paragen‐esis, fluid inclusion petrography and microthermometry, and sulfur isotope systematics. The paragenetic stages throughout the deposit are summarized as follows; 1) stockwork amethystic quartz veinlets associated with chalcopyrite, bornite, magnetite and Au enveloped by chlorite alteration overprinting biotite alteration, 2) stockwork quartz veinlets with chalcopyrite and pyrite associated with Au and chalcopyrite and pyrite stringers in sericite alteration, 3) stringer quartz veinlets associated with molybdenite in sericite alteration, and 4) WNW‐trending quartz veins associated with sphalerite and galena at deeper part, while enargite and stibnite at shallower levels associated with advanced argillic alteration. Chalcopyrite and bornite associated with magnetite in quartz veinlet stockwork (stage 1) have precipitated initially as intermediate solid solution (iss) and bornite solid solution (bnss), respectively. Fluid inclusions in the stockwork veinlet quartz consist of gas‐rich inclusions and polyphase inclusions. Halite in polyphase inclusions dissolves at temperatures ranging from 360d?C to >500d?C but liquid (brine) and gas (vapor) do not homogenize at <500d?C. The maximum pressure and minimum temperature during the deposition of iss and bnss with stockwork quartz veinlets are estimated to be 460 bars and 500d?C. Fluid inclusions in veinlet stockwork quartz enveloped in sericite alteration (stage 2) consist mainly of gas‐rich inclusions and polyphase inclusions. In addition to the possible presence of saturated NaCl crystals at the time of entrapment of fluid inclusions that exhibit the liquid‐vapor homogenization temperatures lower than the halite dissolution temperatures in some samples, wide range of temperatures of halite dissolution and liquid‐vapor homogenization of polyphase inclusions from 230d?C to >500d?C and from 270d?C to >500d?C, respectively, suggests heterogeneous entrapment of gaseous vapor and hypersaline brine. The minimum pressure and temperature are estimated to be about 25 bars and 245d?C. Fluid inclusions in veinlet quartz associated with molybdenite (stage 3) are dominated by gas‐rich inclusions accompanied with minor liquid‐rich inclusions that homogenize at temperatures between 350d?C and 490d?C. Fluid inclusions in vuggy veinlet quartz associated with stibnite (stage 4) consist mainly of gas‐rich inclusions with subordinate polyphase inclusions that do not homogenize below 500d?C. Fluid inclusions in veinlet quartz associated with galena and sphalerite (stage 4) are composed of liquid‐rich two‐phase inclusions, and they homogenize into liquid phase at temperatures ranging widely from 190d?C to 300d?C (suggesting boiling) and the salinity ranges from 1.0 wt% to 3.4 wt% NaCl equivalent. A pressure of about 15 bars is estimated for the dilute aqueous solution of 190d?C from which veinlet quartz associated with galena and sphalerite precipitated. In addition to a change in temperature‐pressure regime from lithostatic pressure during the deposition of iss and bnss with stockwork quartz veinlets to hydrostatic pressure during fracture‐controlled quartz veinlet associated with galena and sphalerite, a decrease in pressure is supposed to have occurred due to unroofing or removal of the overlying piles during the temperature decrease in the evolution of hydrothermal system. The majority of the sulfur isotopic composition of sulfides ranges from ±0 % to +5 %. Sulfur originated from an iso‐topically uniform and homogeneous source, and the mineralization occurred in a single hydrothermal system.     

Slab rollback and microcontinent subduction in the evolution of the Zambales Ophiolite Complex(Philippines):A review

New radiolarian ages show that the island arc-related Acoje block of the Zambales Ophiolite Complex is possibly of Late Jurassic to Early Cretaceous age.Radiometric dating of its plutonic and volcanichypabyssal rocks yielded middle Eocene ages.On the other hand,the paleontological dating of the sedimentary carapace of the transitional mid-ocean ridge-island arc affiliated Coto block of the ophiolite complex,together with isotopic age datings of its dikes and mafic cumulate rocks,also yielded Eocene ages.This offers the possibility that the Zambales Ophiolite Complex could have:(1)evolved from a Mesozoic arc(Acoje block)that split to form a Cenozoic back-arc basin(Coto block),(2)through faulting,structurally juxtaposed a Mesozoic oceanic crust with a younger Cenozoic lithospheric fragment or(3)through the interplay of slab rollback,slab break-off and,at a later time,collision with a microcontinent fragment,caused the formation of an island arc-related ophiolite block(Acoje)that migrated trench-ward resulting into the generation of a back-arc basin(Coto block)with a limited subduction signature.This Meso-Cenozoic ophiolite complex is compared with the other oceanic lithosphere fragments along the western seaboard of the Philippines in the context of their evolution in terms of their recognized environments of generation.     

Multiple ophiolite generation preserved in the northern Philippines and the growth of an island arc complex

Although all oceanic arcs grow through the addition of subduction-generated magmas, the geology of the northern Philippines demonstrates that a major contribution to arc crustal growth can come from repeated, episodic, intra-arc, back-arc, and/or fore-arc oceanic crust generation with subsequent preservation of the basic–ultrabasic units in the arc complex. At least five episodes of oceanic crust generation are represented in the northern Philippines by preserved ophiolitic sequences and recent intra-arc seafloor spreading. Each episode is distinct in age as confirmed by modern dating techniques, with the ages ranging from pre(?)-Jurassic to Quaternary. Although the Philippines is widely regarded as an amalgamation of allochthonous terranes, a review of the available data shows that there is currently no compelling evidence that these ophiolites are of exotic origin and that they have been tectonically accreted to the Philippine arc complex. Rather, the evidence suggests that most—and possibly all—of the ophiolites were generated as back-arc, fore-arc, or intra-arc crust within the Philippine arc complex. Hence, there is a close spatial association of several ophiolitic terranes of diverse ages spanning 150 Myr that formed as part of the arc complex. Such an association may have arisen from episodic generation of oceanic crust during periods of local extension in a suprasubduction zone setting, which has experienced changing and possibly overlapping subduction from the east and west sides (in the current reference frame). Disruption of the ophiolitic basement terranes has been, and continues to be, effected primarily by wrench faulting. This style of arc growth has implications for the paleotectonic interpretation of ancient ophiolite-arc terranes in continents and the petrologic evolution of island arcs.     

Geochemistry of Dharwar ultramafics and the Archaean mantle

Geochemical and petrological studies on serpentinised ultramafics of Kadakola, Mysore State, India, indicate that the Archaean mantle beneath the Indian Shield was of peridotitic in nature. This protomantle in the Archaean period was undifferentiated with higher concentrations of siderophile and transitional elements.     

新疆蛇绿岩带的分布、特征及研究新进展

新疆位于亚洲大陆的北部,构造上跨越了古亚洲和特提斯两大构造域,现今主要由中新生代盆地和其间的古生代造山带组成。古生代造山带主要由陆缘岩系和岩浆岩组成,其中夹有洋壳残片和前寒武结晶基底的碎块;洋壳残片从北向南大致分布12条,其中出露较集中的约30多处。这些蛇绿岩,以塔里木盆地为界,北部主要为古亚洲洋的洋壳残片,南部主要为特提斯洋的洋壳残片。在介绍其基本特征的同时,本文侧重报道了近年来新疆区域地质调查的一些成果。     

A structural record of the emplacement of the Pozanti-Karsanti ophiolite onto the Menderes-Taurus block in the late Cretaceous, eastern Taurides, Turkey

The Aladag region of eastern Taurides, Turkey, is characterized by an imbricated thrust structure developed during late stage emplacement of the Pozanti-Karsanti ophiolite onto the Menderes-Taurus block in the late Cretaceous. The mid to late Cretaceous dynamothermal metamorphic sole and the underlying unmetamorphosed mélange, here named the Aladag accretionary complex, were accreted to the base of the Pozanti-Karsanti ophiolite during intra-oceanic subduction, transport and final obduction of the ophiolite onto the Menderes-Taurus block.In the dynamothermal metamorphic sole, intensity of deformation and degree of metamorphism increase from the base to the top, and at least three episodes of foliation, lineation and fold development are recognized. The asymmetry of quartz c-axis fabrics, tightness and asymmetry of folds of the same generation, and curvature of fold hinge lines increase from base to top, indicating that non-coaxial progressive deformation prevailed during the development of the metamorphic sole. The mélange is divided into three major thrust fault-bounded tectonic slivers, each of which is characterized by distinctive types of matrix and block lithologies, structures and deformation style. Kinematic analyses of the dynamothermal metamorphic sole and the mélange reveal that the tectonic transport direction of the Pozanti-Karsanti ophiolite during its emplacement was from north-northwest to south-southeast, suggesting that the Pozanti-Karsanti ophiolite was derived from a Neo-Tethyan ocean to the north of the Menderes-Taurus block.     

西藏永珠蛇绿岩带地质特征

详细地描述了永珠蛇绿岩带的地质特征、岩石化学特征、稀土元素特征和微量元素特征,并把它与典型的蛇绿岩带进行对比,发现它除了具有典型的蛇绿岩带特征外,还具有其特殊性。结合区域沉积环境确定该蛇绿岩带的构造环境为扩张历史暂短、洋陆转换不彻底、发育于消减带上的弧间裂谷盆地。     

Deformation fabric and microstructures in ophiolitic chromitites and host ultramafics,Sultanate of Oman

Harzburgite and dunite from the Oman ophiolite display a strong olivine fabric and microstructures typical for high temperature mantle deformation. The syntectonic, magmatically formed, chromitites occurring throughout the mantle sequence vary from almost undeformed (resembling chromitite from stratiform complexes) to highly deformed. Usually the interstitial silicates in the deformed ore possess a fabric similar to those of the host rocks, whereas a weak or poikilitic fabric is observed on relatively undeformed deposits. Chromite grains are elongated and flattened, defining strong foliations and lineations, in disseminated ore, and pull-apart-like structures perpendicular to the lineation form in the coarser massive ore. No preferred crystallographic orientation of chromite has been detected with the X-ray-texture goniometer, and it is proposed that chromite mainly deforms by passive rotation in the weaker silicate matrix, cataclasis and diffusion creep.

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Zusammenfassung Die Dunite und Harzburgite, die im Ophiolit des Oman auftreten, zeigen ein Olivingefüge und Mikrostrukturen, die typisch sind für Manteldeformationen bei hohen Temperaturen. Die syntektonischen, magmatisch gebildeten Chromitite sind über die gesamte Abfolge der Mantelgesteine zu finden. Das Ausmaß der Deformation der Chromitite reicht von gering bis stark. Fast undeformierte Chromitite gleichen denen stratiformer Komplexe. Im deformierten Erz zeigen die in Zwickeln auftretenden Silikatminerale im allgemeinen ein ähnliches Gefüge wie das Wirtsgestein; in relativ undeformierten Vorkommen zeigen sie ein schwaches oder poikilitisches Gefüge. Die Chromitkörner haben einen plattigen Habitus und bilden im Sprenkelerz ein deutliches Flächen- und Lineargefüge. Im grobkörnigen Derberz entstehen hingegen Dehnungsstrukturen (pull-apart textures) senkrecht zur Lineation. Röntgentexturgoniometrische Untersuchungen ergaben keine Regelung des Chromits, und es wird daher angenommen, daß der Chromit aufgrund passiver Rotation in der schwächeren Silikatmatrix deformiert wurde, weiterhin kommen auch Kataklase und Diffusionsmechanismen in Frage.

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Résumé Les dunites et harzburgites du complexe ophiolitique d'Oman présentent une forte fabrique de l'olivine et des microstructures typiques de déformations mantelliques de haute température. Les chromitites, d'origine magmatique syntectomque, qui se trouvent le long de la séquence mantellique varient entre des termes presque non déformés (ressemblant aux chromitites des complexes stratiformes) jusqu'à des termes très déformés. Les silicates interstitiels du minerai déformé présentent fréquemment une fabrique semblable à celle des minéraux de la roche hôte alors que l'on observe une fabrique peu développée ou bien une texture poecilitique dans les minerais des gisements relativement peu déformés. Les cristaux de chromite sont allongés et aplatis, définissant une foliation et une linéation très marquées dans les minerais disséminés; des structures d'étirement (pull-apart) perpendiculaires à la linéation apparaissent dans les minerais plus massifs. Aucune orientation cristallographique préferentielle n'a pu être mise en évidence au goniomètre de texture; on propose donc que la chromite se déforme principalement par rotation passive dans une matrice silicatée plus fragile, par cataclase et par fluage-diffusion.

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Geobotanical and biogeochemical reconnaissance of the ultramafics of Central Iran

In Iran, ultramafic rocks cover substantial areas at many locations in the country. These rocks consist predominantly of peridotite which has been serpentinized to some degree. Anarak and Nain are two ultramafic areas in Central Iran comprising about 180 and 270 km², respectively, located in a coloured melange zone. There is little information available regarding the geobotany and biogeochemistry of these areas. They have a dry climate, with low rainfall and high temperatures in summer which encourages mostly annual and perennial herbaceous types of plants. In this paper, we report a reconnaissance study of these two ultramafic areas of Iran. Soil analysis of total elements indicates that typical concentrations of Ni, Cr, Co, Mn, Fe, Mg and Ca are about 1500, 300, 75, 800, 45.000 150.000 and 2000 μg g^− 1, respectively. During this study 176 plant species were collected, belonging to 29 families. The species diversity at Anarak is more than at Nain, possibly due to microclimatic differences and a greater precipitation. The number of plants endemic to ultramafic soils of these two areas is very low. The herb Cleome heratensis (Capparaceae) appears to be an indicator of ultramafics in Central Iran. Populations of this plant cover quite extensive areas during summer and autumn when there is no rainfall. Analysis of the dry matter of the leaves of all plants collected did not reveal any hyperaccumulator of nickel or any other ‘serpentine’ metals. The ultramafic endemic plant C. heratensis contained low concentrations of all metals and thus it possesses exclusion mechanisms to restrict excessive metal uptake. The Mg/Ca ratio for some plants collected is high—up to 4.9. This initial survey suggests that a more complete investigation of the ultramafic areas of Iran would be valuable.     

Paleomagnetism of ultramafics from the Konder Massif and its age assessment

The petro- and paleomagnetic studies of ultramafic rocks (dunites, clinopyroxenites, kosvites) from the Konder Massif revealed the primary thermal remanance nature of the defined characteristic magnetization components. The calculated coordinates of the paleomagnetic poles are as follows: Plat = −4°, Plong = 178°, d_p = 5°, and d_m = 8° for the dunites; Plat = −2°, Plong = 181°, d_p= 6°, and d_m = 10° for the clinopyroxenites; and Plat = 71°, Plong = 206°, d_p = 5°, and d_m = 6° for the kosvites. Based on paleomagnetic and petromagnetic data, the age is estimated to be the Early Neoproterozoic for the dunites and clinopyroxenites and the Early Cretaceous for the kosvites. The massif as a whole is dated back to the Early Neoproterozoic (1000–950 Ma).     

The halogens in Luna 16 and Luna 20 soils

Cl and P₂U₅ do not appear to exhibit the same correlation in soils from the Luna 20 and possibly the Luna 16 sites as they do in samples from the Apollo 11–15 sites. Nevertheless, the coherence between labile Cl and other KREEP-related elements is maintained.     

Platinum-group minerals and tellurides from the PGE-bearing Xinjie layered intrusion in the Emeishan Large Igneous Province, SW China

The Xinjie layered intrusion is one of a number of major ultramafic-mafic bodies hosting Fe-Ti-V deposits and Cu-Ni-PGE sulfide deposits in the Pan-Xi (Panzhihua-Xichang) area of the Sichuan Province, SW China. The Xinjie ultramafic-mafic layered intrusion, genetically related to the Permian plume-related Emeishan flood basalts, consists of three lithological cycles, each representing a sequence from ultramafic to mafic-felsic composition. The basal part of the intrusion is composed of three lithological units, namely, the Marginal Unit (MU), Peridotite Unit (PeU) and Pyroxenite Unit (PyU). In the present study, three major PGE-mineralised Cu-Ni sulfide layers were discovered within the Marginal and Pyroxenite Units. The major base-metal sulfides (BMS) comprise chalcopyrite, pyrrhotite, and pentlandite. Detailed microscopic and microprobe analyses revealed the presence of the sperrylite and Pd-Pt-Bi-Te minerals (merenskyite, moncheite, and michenerite). These PGMs are commonly associated with the BMS, or magnetite coexisting with BMS in the PGE-enriched layers. The 1:1 substitution between Pt and Pd, as well as between Te and Bi, confirms the complete solid-solution series between moncheite and merenskyite. The textural association of the PGMs with BMS and Fe-Ti oxides (magnetite) suggests that the PGMs may have crystallised slightly later than the hosting magnetite and BMS. The formation of magnetite may have played an important role in producing the sulfur-saturated melt and the PGEs thus concentrated in the sulfide liquid during the crystallisation history. It is therefore suggested that the Cu-Ni-PGE-bearing layers in the basal part of the Xinjie intrusion were generated by magma evolution processes.