Platinum-Group Minerals in Ophiolitic Chromitites and Alluvial Placer Deposits, Meratus-Bobaris Area, Southeast Kalimantan

Burgath, Klaus-Peter

doi:10.1007/978-94-009-1353-0_40

Cited by 18 publications

(30 citation statements)

References 9 publications

(10 reference statements)

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“…The chromitites in the Meratus-Bobaris ophiolite in the Southeast Kalimantan are high in Ru, As, and Ir, and they contain grains of Ir-and Osbearing laurite and rarely of osmian iridium (Burgath, 1988). These laurite grains were subjected to Os-isotope analyses.…”

Section: Description Of Studied Samplesmentioning

confidence: 99%

“…PGM from placers in the Southeastern Kalimantan are mostly alloys of Os, Ir and Ru of varied proportions, and Pt-Fe alloys (Burgath, 1988). The PGM nuggets are variably abraded, sub-angular to semi-rounded in shape.…”

Section: Description Of Studied Samplesmentioning

confidence: 99%

“…The PGM nuggets are variably abraded, sub-angular to semi-rounded in shape. Some grains show irregular surface with embayments and some contain silicate inclusions (Burgath, 1988). Four PGM nuggets were selected for Osisotope analysis: sub-rounded platinian osmian iridium, sub-angular ruthenian iridian osmium, sub-angular platinian osmian iridium, and semirounded osmian iridium.…”

Section: Description Of Studied Samplesmentioning

confidence: 99%

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Os-isotope study of platinum-group minerals in chromitites in Alpine-type ultramafic intrusions and the associated placers in Borneo

Hattori¹,

Burgath

Hart

1992

Mineral. mag.

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AbstracttS7Os/lS6Os ratios were determined for in-situ laurite grains in Alpine-type chromitites and platinumgroup minerals (PGM) in the associated alluvial placers in Borneo, Indonesia/Malaysia. The Osisotope ratios of laurite grains in chromite defne an t87Os/186Os ratio for the 100 Ma mantle source of 187 t86 ms nfir essential derlv ton of these latlnum rou c. 1.04. ThelowOs/ Os ratios in all gra" co mthe " " at" p " -g p elements (PGE) from the mantle. A minor variation in 1870S/186Os ratios was detected among PGM from placers, but no variation was found within individual grains, including a grain with chemical inhomogeneity. The values are similar to those for PGM in the associated chromitites. The data are consistent with a detrital origin of PGM in placers: the placer PGM originated in the ultramafic section of ophiolities and the release of these grains from igneous rocks and their deposition in placers was almost entirely by mechanical processes.

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Section: Description Of Studied Samplesmentioning

confidence: 99%

Section: Description Of Studied Samplesmentioning

confidence: 99%

Section: Description Of Studied Samplesmentioning

confidence: 99%

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Os-isotope study of platinum-group minerals in chromitites in Alpine-type ultramafic intrusions and the associated placers in Borneo

Hattori¹,

Burgath

Hart

1992

Mineral. mag.

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“…In this area, the PGM have been described from placers deposits [1], which are considered to have derived from the erosion of podiform (ophiolite)-type chromitites [2][3][4] and of Alaskan-type complexes [5], as well as skarn deposits [6]. Borneo is also the type locality of two PGM, the rare vincentite, ideally (Pd,Pt) 3 (As,Sb,Te) [7], and the most common Ru-bearing mineral, laurite, ideally (Ru,Os)S 2 ([8] and the references therein). However, mineralogical data on PGM found in lode deposits of the Indonesian Archipelago are limited [2,3,5], and information about the presence of PGM on Sulawesi Island is not available.…”

Section: Introductionmentioning

confidence: 99%

“…Borneo is also the type locality of two PGM, the rare vincentite, ideally (Pd,Pt) 3 (As,Sb,Te) [7], and the most common Ru-bearing mineral, laurite, ideally (Ru,Os)S 2 ([8] and the references therein). However, mineralogical data on PGM found in lode deposits of the Indonesian Archipelago are limited [2,3,5], and information about the presence of PGM on Sulawesi Island is not available. Generally, chromitites host a number of PGM representing pristine magmatic phases, trapped into crystallizing chromite at high temperatures.…”

Section: Introductionmentioning

confidence: 99%

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

2016

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Several chromite deposits located in the in the South and Southeast Arms of Sulawesi, Indonesia, have been investigated by electron microprobe. According to the variation of the Cr# = Cr/(Cr + Fe 3+ ), the chromite composition varies from Cr-rich to Al-rich. Small platinum-group minerals (PGM), 1-10 µm in size, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with chlorite along cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with amphibole, chlorite, Co-pentlandite and apatite. Small blebs of irarsite (less than 2 µm across) have been found associated with grains of awaruite and Co-pentlandite in the chlorite gangue of the chromitites. Grains of olivine, occurring in the silicate matrix or included in fresh chromite, have been analyzed. They show a composition typical of mantle-hosted olivine. The bimodal composition and the slight enrichment in TiO 2 observed in some chromitites suggest a vertical zonation due to the fractionation of a single batch magma with an initial boninitic composition during its ascent, in a supra-subduction zone. This observation implies the accumulation of Cr-rich chromitites at deep mantle levels and the formation of the Al-rich chromitites close or above the Moho-transition zone. All of the laurites are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperature of around 1200˝C and a sulfur fugacity below the sulfur saturation. Irarsite possibly represents a low temperature, less than 400˝C, exsolution product.

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Platinum-Group Elements and Gold in Ophiolitic Complexes: Distribution and Fractionation from Mantle to Oceanic Floor

Leblanc

1991

Petrology and Structural Geology

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This review paper attempts to discuss the distribution of noble metals in ophiolitic complexes and suggests new targets for exploration.Platinum-Group Elements (PGE) are nearly unfractionated in the less depleted mantle rocks (lherzolites). Residual dunites are clearly empoverished in Pt, Pd, and Au which were collected by silicate melts during partial melting. The chromite grains of the podiform chromitites, which crystallized early in magmatic conduits in the mantle, include Os-Ir-Ru minerals. Podiform chromitites are PGE-poor (100-500 ppb) or PGE-rich (up to 1 ppm), the highest PGE contents (>ppm) are often related to the presence of interstitial sulphides. In the crustal section PGE are fractionated among the magmatic rocks (Pd/Ir ratio increases from dunite to gabbro). The very low PGE content of the basaltic lavas involves a PGE segregation in a magmatic sulphide phase before emplacement at surface. PGE-rich sulphides are locally present at the base of the crustal section (in chromite-rich dunite or in pyroxenite) or among the upper gabbros. Hydrothermal processes related to serpentinization concentrate mainly gold (1-10 ppm) in sulphide-rich serpentinites, or in carbonatized (listwaenite) or silicified serpentinites where the noble metals are in sulphides and/or arsenides. Convective hydrothermal systems strongly leached the magmatic pile, then precipitated on the ocean floor (i) Massive Sulphide Deposits (Cyprus-type MSD) which may be goldrich (> 1ppm); and (ii) metalliferous sediments displaying slight enrichments in Pt-Pd and Au. Up to 1 ppm Pt may be found in oceanic Mn-nodules. Lastly, weathering and erosion should concentrate PGE in laterites and placers.PGE are an economically important group of elements and new targets should be explored in ophiolites: (1) chromitite pods (Os-Ir-Ru) which may be also Ru-Pt-Pd-rich when sulphides are present; (2) sulphide-rich serpentinites or carbonatized-serpentinites (listwaenites) mainly for gold; (3) sulphidebearing magmatic rocks (Ru-Pt-Pd); (4) exhalative metalliferous sediments; and (5) laterites and placers.

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Platinum-Group Minerals in Ophiolitic Chromitites and Alluvial Placer Deposits, Meratus-Bobaris Area, Southeast Kalimantan

Abstract: Platinum-group mineral (PG M) from alpine-type chromitites and placer deposits in

Cited by 18 publications

References 9 publications

Os-isotope study of platinum-group minerals in chromitites in Alpine-type ultramafic intrusions and the associated placers in Borneo

Os-isotope study of platinum-group minerals in chromitites in Alpine-type ultramafic intrusions and the associated placers in Borneo

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

Platinum-Group Elements and Gold in Ophiolitic Complexes: Distribution and Fractionation from Mantle to Oceanic Floor

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