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oai:docta.ucm.es:20.500.14352/74952023-08-27T19:26:23Zcom_20.500.14352_14col_20.500.14352_15

Mechanisms for Pdsingle bondAu enrichment in porphyry-epithermal ores of the Elatsite deposit, Bulgaria González Jiménez, José María Piña García, Rubén Kerestedjian, Thomas N. Gervilla, Fernando Borrajo, Iñigo Farré de Pablo, Julia Proenza, Joaquín Tornos, Fernando Roqué, Josep Nieto, Fernando 553.25 Platinum-group elements Porphyry copper Telluride melts Hydrothermal pyrite Elatsite Mineralogía (Geología) 2506.11 Mineralogía Porphyry Cu can contain significant concentrations of platinum-group elements (PGE: Os, Ir, Ru, Rh, Pt, Pd). In this study, we provide a comprehensive in situ analysis of noble metals (PGE, Au, Ag) for (Cusingle bondFe)-rich sulfides from the Elatsite, one of the world's PGE-richest porphyry Cu deposits. These data, acquired using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicate that Pd was concentrated in all the (Cusingle bondFe)-rich sulfides at ppm-levels, with higher values in pyrite (~6 ppm) formed at the latest epithermal stage (i.e., quartz–galena–sphalerite assemblage) than in bornite and chalcopyrite (<5 ppm) from the hypogene quartz–magnetite–bornite–chalcopyrite ores. Likewise, Au is significantly more concentrated in pyrite (~5 ppm) than in the (Cusingle bondFe)-rich sulfides (≤0.08 ppm). In contrast, Ag reaches hundreds of ppm in pyrite and bornite (~240 ppm) but is in much lesser amounts in chalcopyrite (<25 ppm). The inspection of the time-resolved spectra collected during LA-IPC-MS analyses indicates that noble metals are present in the sulfides in two forms: (1) structurally bound (i.e., solid solution) in the lattice of sulfides and, (2) as nano- to micron-sized inclusions (Pdsingle bondTe and Au). These observations are further confirmed by careful investigations of the PGE-rich (Cusingle bondFe)-rich sulfides by combining high-spatial resolution of field emission scanning electron microscope (FESEM) and focused ion beam and high-resolution transmission electron microscopy (FIB/HRTEM). A typical Pd-bearing mineral includes the composition PdTe2 close to the ideal merenskyite but with a distinct crystallographic structure, whereas Au is mainly found as native element. Our detailed mineralogical study coupled with previous knowledge on noble-metal inclusions in the studied ores reveals that noble metal enrichment in the Elatsite porphyry ores was mainly precipitated from droplets of Au-Pd-Ag telluride melt (s) entrained in the high-temperature hydrothermal fluid. These telluride melts could separate at the time of fluid unmixing from the silicate magma or already be present in the latter either derived from deep-seated crustal or mantle sources. Significant enrichment in Pd and Au (the latter correlated with As) in low-temperature pyrite is interpreted as remobilization of these noble metals from pre-existing hypogene ores during the epithermal overprinting. Ministerio de Ciencia e Innovación (MICINN) Ministerio de Economía y Competitividad (MINECO) Depto. de Mineralogía y Petrología Fac. de Ciencias Geológicas TRUE pub 2023-06-17T08:55:33Z 2023-06-17T08:55:33Z 2021-01 journal article https://hdl.handle.net/20.500.14352/7495 0375-6742 10.1016/j.gexplo.2020.106664 eng RTI2018-099157- A-I00 (CGL2015-65824-P; CGL2016-81085-R; RYC-2015-17596) Atribución 3.0 España https://creativecommons.org/licenses/by/3.0/es/ restricted access application/pdf Elsevier