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A novel origin for PGE reefs: A case study of the J-M Reef

September 8, 2022

The origin of meter scale stratiform layers of disseminated sulfides in enriched platinum group element (PGE) tenors and grades, called reef-type deposits, are the world’s most significant source of PGEs. Their origin in layered mafic intrusions remains debated, but in general, most researchers favor an orthomagmatic origin for reef-type deposits and agree that their formation requires the equilibration of an immiscible sulfide liquid with a significantly larger mass of silicate magma (i.e., silicate:sulfide mass ratios of 104 to 106). However, where, and how this chemical equilibration process takes place in the magmatic system is poorly constrained. In this contribution, we propose a new model for the origin of PGE reef deposits. We demonstrate that finely disseminated, resident sulfide liquid hosted within cumulate mush can be upgraded by incoming batches of S-undersaturated and PGE-undepleted silicate melt. We demonstrate this model through a case study of the J-M Reef deposit of the Stillwater Complex, the world’s highest-grade PGE deposit (14 ppm Pd over 1.8 m).

Publication Year 2023
Title A novel origin for PGE reefs: A case study of the J-M Reef
DOI 10.1080/25726838.2022.2084233
Authors Michael Jenkins, James E. Mungall, Michael L. Zientek, Gelu Costin, Zhuo-sen Yao
Publication Type Conference Paper
Publication Subtype Conference Paper
Index ID 70240169
Record Source USGS Publications Warehouse
USGS Organization Geology, Minerals, Energy, and Geophysics Science Center