Prograde and retrograde metasomatic reactions in mineralised magnesium-silicate skarn in the Cu-Au Ertsberg East Skarn System, Ertsberg, Papua Province, Indonesia

Sieber, Melanie J.; Brink, Frank; Leys, Clyde; King, P. L.; Henley, Richard W.

doi:10.1016/j.oregeorev.2020.103697

Cited by 9 publications

(3 citation statements)

References 46 publications

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“…The system was calibrated against well characterised reference minerals (Astimex). QEMSCAN TM (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) mineral and element mapping were undertaken at the Centre for Advanced Microscopy at the Australian National University using a FEI QEMSCAN TM automated SEM-EDS system on polished samples (for analytical methods, see Sieber et al [80]). Some bulk rock and mineral analyses of B1 xenolith are taken from Del Moro et al [21], where analytical methods and standards can also be found.…”

Section: Methodsmentioning

confidence: 99%

Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism

et al. 2021

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Pyrometamorphism is the highest temperature end-member of the sanidinite facies (high-temperature, low-pressure contact metamorphism) and comprises both subsolidus and partial melting reactions which may locally lead to cryptocrystalline-glassy rocks (i.e., porcellanites and buchites). A wide range of pyrometamorphic ejecta, with different protoliths from Stromboli volcano, have been investigated over the last two decades. Among these, a heterogeneous (composite) glassy sample (B1) containing intimately mingled porcellanite and buchite lithotypes was selected to be studied through new FESEM–EDX and QEMSCAN™ mineral mapping investigations, coupled with the already available bulk rock composition data. This xenolith was chosen because of the unique and intriguing presence of abundant Cu–Fe sulphide globules within the buchite glass in contrast with the well-known general absence of sulphides in Stromboli basalts or their subvolcanic counterparts (dolerites) due to the oxygen fugacity of NNO + 0.5–NNO + 1 (or slightly lower) during magma crystallization. The investigated sample was ejected during the Stromboli paroxysm of 5 April 2003 when low porphyritic (LP) and high porphyritic (HP) basalts were erupted together. Both types of magmas are present as coatings of the porcellanite–buchite sample and were responsible for the last syn-eruptive xenoliths’s rim made of a thin crystalline-glassy selvage. The complex petrogenetic history of the B1 pyrometamorphic xenolith is tentatively explained in the framework of the shallow subvolcanic processes and vent system dynamics occurred shortly before (January–March 2003) the 5 April 2003 paroxysm. A multistep petrogenesis is proposed to account for the unique occurrence of sulphide globules in this composite pyrometamorphic xenolith. The initial stage is the pyrometamorphism of an already hydrothermally leached extrusive/subvolcanic vent system wall rock within the shallow volcano edifice. Successively, fragments of this wall rock were subject to further heating by continuous gas flux and interaction with Stromboli HP basalt at temperatures above 1000 °C to partially melt the xenolith. This is an open system process involving continuous exchange of volatile components between the gas flux and the evolving silicate melt. It is suggested that the reaction of plagioclase and ferromagnesian phenocrysts with SO2 and HCl from the volcanic gas during diffusion into the melt led to the formation of molecular CaCl in the melt, which then was released to the general gas flux. Sulphide formation is the consequence of the reaction of HCl dissolved into the melt from the gas phase, resulting in the release of H2 into the melt and lowering of fO2 driving reduction of the dissolved SO2.

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Section: Methodsmentioning

confidence: 99%

Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism

et al. 2021

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“…Porphyry and skarn alteration and mineralization are in general, closely spatially and temporally related to intrusive activity, especially that of the Grasberg and Ertsberg complexes (Gibbin, Leys et al, 2012;MacDonald and Arnold, 1994;Pollard and Taylor, 2002;Sieber et al, 2020). Grasberg has well-developed porphyrystyle alteration and mineralization comprising a central potassic (K-feldspar-quartz-anhydrite) alteration zone with associated quartz-magnetite stockwork overprinted by chalcopyrite-bornite-(covellite) veins and disseminated mineralization (MacDonald and Arnold, 1994).…”

Section: J O Gmentioning

confidence: 99%

“…The prospect lies ± 3 km lengthways to the strike northwest of the giant Grasberg copper-gold porphyry deposit (MacDonald and Arnold, 1994;Pollard andTaylor, 2002, 2005) with a similar distance at the southwest of the Big Gossan copper-gold skarn deposit (Meinert et al, 1997;Prendergast et al, 2005) and near Kucing Liar deep skarn deposit (New, 2006;Leys et al, 2012). Ertsberg District also contains several skarn bodies associated with the Ertsberg intrusion, including the now mined-out Ertsberg deposit (Gibbin, 2006; I J O G Katchan, 1982), the actively mined Ertsberg East Skarn System (Rubin and Kyle, 1997;Couts et al, 1999;Leys et al, 2012;Sieber et al, 2020), and the Dom (Mertig et al, 1994;Gibbin, 2006). Skarn is the calc-silicate mineral-dominated-rock formed by replacing carbonate-bearing rocks throughout regional or contact metamorphism and metasomatism (Einaudi et al, 1981;Meinert et al, 1997;Idrus et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Multistage Gold Mineralization at The Wanagon Gold Prospect, Ertsberg District, Mimika Regency, Papua Province, Indonesia

Hartiningsih

Syafrizal

Sucipta

et al. 2022

Indonesian J. Geosci.

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The Wanagon Gold prospect area located in the Ertsberg District, Papua Province, the eastern part of Indonesia, is predominantly underlain by Upper Mesozoic to Cenozoic sedimentary rocks intruded by the Wanagon Sill monzodiorite-diorite and andesite intrusion (Wanagon Dike). The study by previous researchers at Wanagon Gold prospect was based on pre-2005 exploration data and did not contain extensive additional drillings in 2007-2011. This paper aims to elucidate the genesis of the Wanagon Gold deposits based on the latest exploration data. The mineralogy was determined by using thin section and polish section analyses, a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and Near-Infrared spectroscopy (NIR). The chemical composition of the rock was identified using an X-ray fluorescence spectrometer (XRF). Gold mineralization is associated with pyrite, of which there are three types of gold-bearing pyrite: (1) massive pyrite, (2) disseminated pyrite, and (3) fine-grained pyrite associated with clay minerals. Only massive pyrite contains visible gold-bearing minerals such as native gold, electrum, and gold-telluride minerals, while in nonmassive pyrite, gold is only detected by the assay. The deposit is interpreted as structurally controlled distal gold skarn. Instead, its local association of gold with arsenic also indicates a minor component of more-distal sediment-hosted type gold mineralization.

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Fluid-rock interaction: A mineral deposits perspective

Lecumberri-Sanchez,

Tutolo,

Barker

2025

Treatise on Geochemistry

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Prograde and retrograde metasomatic reactions in mineralised magnesium-silicate skarn in the Cu-Au Ertsberg East Skarn System, Ertsberg, Papua Province, Indonesia

Cited by 9 publications

References 46 publications

Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism

Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism

Multistage Gold Mineralization at The Wanagon Gold Prospect, Ertsberg District, Mimika Regency, Papua Province, Indonesia

Fluid-rock interaction: A mineral deposits perspective

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