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Distribution of platinum-group elements in magmatic and altered ores in the Jinchuan intrusion, China: an example of selenium remobilization by postmagmatic fluids

Distribution of platinum-group elements in magmatic and altered ores in the Jinchuan intrusion, China: an example of selenium remobilization by postmagmatic fluids
Distribution of platinum-group elements in magmatic and altered ores in the Jinchuan intrusion, China: an example of selenium remobilization by postmagmatic fluids
The division of platinum-group elements (PGE) between those hosted in platinum-group minerals (PGM) versus those in solid solution in base metal sulfides (BMS) has been determined for ores from the PGE-bearing Ni-Cu-rich Jinchuan intrusion in northwest China. All the BMS are devoid of Pt and Ir, and magmatic BMS are also barren of Rh. These PGE may have been scavenged by arsenic to form PGM during magmatic crystallization of the BMS. Pd, Os, and Ru are recorded in BMS and Pd is predominantly in solid solution in pentlandite. Unlike the fresh magmatic ores, in altered or serpentinized ores, Pd-PGM are present. Froodite is hosted in magnetite, formed during alteration of BMS, accompanied by sulfur loss and liberation of Pd. Michenerite ([Pd,Pt]BiTe), sperrylite (PtAs2), and Au-bearing PGM are located in altered silicates. Irarsite (IrAsS) occurs mainly enclosed in BMS. Padmaite (PdBiSe), identified at the junctions of magnetite and BMS, was the last PGM to form and locally partially replaces earlier non-Se-bearing PGM. We propose that padmaite formed under oxidizing conditions during late local remobilization of Se from the BMS. Se-bearing PGM are rare and our review shows they are frequently associated with carbonate, suggesting that Pd and Se can be mobilized great distances in low pH oxidizing fluids and may be precipitated on contact with carbonate. S/Se ratios are used by researchers of magmatic Ni-Cu-PGE ores to determine sulfur loss, assuming Se is immobile and representative of magmatic sulfur content. This study shows that Se as well as S is potentially mobile and this should be considered in the use of S/Se ratios.
Jinchuan, Platinum, Base metal sulphides, Selenium, Carbonate
0026-4598
767-786
Prichard, Hazel M.
350afc38-8066-4f05-8db1-d91a6273813d
Knight, Robert D.
04d3bfd0-6c52-495f-954f-aa605ee9be2e
Fisher, Peter C.
35da1065-9f37-4d83-a114-194c84aef15d
McDonald, Iain
22362420-baf6-46c4-8623-8db5be2ea46e
Zhou, Mei-Fu
2d7aeb7e-efb5-4aa7-8ec0-455505f3de57
Wang, Christina Y.
821a1e52-2043-405f-91a0-dd16228306fd
Prichard, Hazel M.
350afc38-8066-4f05-8db1-d91a6273813d
Knight, Robert D.
04d3bfd0-6c52-495f-954f-aa605ee9be2e
Fisher, Peter C.
35da1065-9f37-4d83-a114-194c84aef15d
McDonald, Iain
22362420-baf6-46c4-8623-8db5be2ea46e
Zhou, Mei-Fu
2d7aeb7e-efb5-4aa7-8ec0-455505f3de57
Wang, Christina Y.
821a1e52-2043-405f-91a0-dd16228306fd

Prichard, Hazel M., Knight, Robert D., Fisher, Peter C., McDonald, Iain, Zhou, Mei-Fu and Wang, Christina Y. (2013) Distribution of platinum-group elements in magmatic and altered ores in the Jinchuan intrusion, China: an example of selenium remobilization by postmagmatic fluids. Mineralium Deposita, 48 (6), 767-786. (doi:10.1007/s00126-013-0454-7).

Record type: Article

Abstract

The division of platinum-group elements (PGE) between those hosted in platinum-group minerals (PGM) versus those in solid solution in base metal sulfides (BMS) has been determined for ores from the PGE-bearing Ni-Cu-rich Jinchuan intrusion in northwest China. All the BMS are devoid of Pt and Ir, and magmatic BMS are also barren of Rh. These PGE may have been scavenged by arsenic to form PGM during magmatic crystallization of the BMS. Pd, Os, and Ru are recorded in BMS and Pd is predominantly in solid solution in pentlandite. Unlike the fresh magmatic ores, in altered or serpentinized ores, Pd-PGM are present. Froodite is hosted in magnetite, formed during alteration of BMS, accompanied by sulfur loss and liberation of Pd. Michenerite ([Pd,Pt]BiTe), sperrylite (PtAs2), and Au-bearing PGM are located in altered silicates. Irarsite (IrAsS) occurs mainly enclosed in BMS. Padmaite (PdBiSe), identified at the junctions of magnetite and BMS, was the last PGM to form and locally partially replaces earlier non-Se-bearing PGM. We propose that padmaite formed under oxidizing conditions during late local remobilization of Se from the BMS. Se-bearing PGM are rare and our review shows they are frequently associated with carbonate, suggesting that Pd and Se can be mobilized great distances in low pH oxidizing fluids and may be precipitated on contact with carbonate. S/Se ratios are used by researchers of magmatic Ni-Cu-PGE ores to determine sulfur loss, assuming Se is immobile and representative of magmatic sulfur content. This study shows that Se as well as S is potentially mobile and this should be considered in the use of S/Se ratios.

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More information

Published date: 2013
Keywords: Jinchuan, Platinum, Base metal sulphides, Selenium, Carbonate
Organisations: Geochemistry

Identifiers

Local EPrints ID: 370547
URI: http://eprints.soton.ac.uk/id/eprint/370547
ISSN: 0026-4598
PURE UUID: d575b258-63ad-47a0-a33e-a7f450b7d871

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Date deposited: 28 Oct 2014 16:43
Last modified: 14 Mar 2024 18:18

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Contributors

Author: Hazel M. Prichard
Author: Robert D. Knight
Author: Peter C. Fisher
Author: Iain McDonald
Author: Mei-Fu Zhou
Author: Christina Y. Wang

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