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Critical Metal Particles in Copper Sulfides from the Supergiant Río Blanco Porphyry Cu–Mo Deposit, Chile

1
Department of Geology and Andean Geothermal Center of Excellence (CEGA), Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago 8370450, Chile
2
Millennium Nucleus for Metal Tracing Along Subduction, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago 8370450, Chile
3
Codelco División Andina, Avenida Santa Teresa, N° 513 Los Andes, V Región 2102660, Chile
*
Author to whom correspondence should be addressed.
Minerals 2018, 8(11), 519; https://doi.org/10.3390/min8110519
Received: 14 October 2018 / Revised: 5 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
(This article belongs to the Special Issue Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes)
Porphyry copper–molybdenum deposits (PCDs) are the world’s most important source of copper, molybdenum and rhenium. Previous studies have reported that some PCDs can have sub-economic to economic grades of critical metals, i.e., those elements that are both essential for modern societies and subject to the risk of supply restriction (e.g., platinum group elements (PGE), rare earth elements (REE), In, Co, Te, Ge, Ga, among others). Even though some studies have reported measured concentrations of Pd and Pt in PCDs, their occurrence and mineralogical forms remain poorly constrained. Furthermore, these reconnaissance studies have focused predominantly on porphyry Cu–Au deposits, but very limited information is available for porphyry Cu–Mo systems. In this contribution, we report the occurrence of critical metal (Pd, Pt, Au, Ag, and Te) inclusions in copper sulfides from one of the largest PCDs in the world, the supergiant Río Blanco-Los Bronces deposit in central Chile. Field emission scanning electron microscope (FESEM) observations of chalcopyrite and bornite from the potassic alteration zone reveal the presence of micro- to nano-sized particles (<1–10 μm) containing noble metals, most notably Pd, Au, and Ag. The mineralogical data show that these inclusions are mostly tellurides, such as merenskyite ((Pd, Pt) (Bi, Te)2), Pd-rich hessite (Ag2Te), sylvanite ((Ag,Au)Te2) and petzite (Ag3AuTe2). The data point to Pd (and probably Pt) partitioning in copper sulfides during the high-temperature potassic alteration stage, opening new avenues of research aimed at investigating not only the mobility of PGE during mineralization and partitioning into sulfides, but also at exploring the occurrence of critical metals in porphyry Cu–Mo deposits. View Full-Text
Keywords: platinum-group elements; silver; gold; Pd-tellurides; porphyry Cu–Mo; Rio Blanco-Los Bronces; Chile platinum-group elements; silver; gold; Pd-tellurides; porphyry Cu–Mo; Rio Blanco-Los Bronces; Chile
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Crespo, J.; Reich, M.; Barra, F.; Verdugo, J.J.; Martínez, C. Critical Metal Particles in Copper Sulfides from the Supergiant Río Blanco Porphyry Cu–Mo Deposit, Chile. Minerals 2018, 8, 519.

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