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 (Cu-Fe)-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 (Cu-Fe)-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 (Cu-Fe)-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 indicate 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 (Pd-Te and Au). These observations are further confirmed by careful investigations of the PGE-rich (Cu-Fe)-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.

中文翻译：

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保加利亚 Elatsite 矿床斑岩-浅成热液矿中 Pd-Au 的富集机制

斑岩铜可以包含显着浓度的铂族元素（PGE：Os、Ir、Ru、Rh、Pt、Pd）。在这项研究中，我们对 Elatsite 中富含 (Cu-Fe) 的硫化物的贵金属（PGE、Au、Ag）进行了全面的原位分析，Elatsite 是世界上最富含 PGE 的斑岩铜矿床之一。这些数据是使用激光烧蚀电感耦合等离子体质谱仪 (LA-ICP-MS) 获得的，表明 Pd 以 ppm 级浓缩在所有富含 (Cu-Fe) 的硫化物中，黄铁矿 (~ 6 ppm) 形成于最新的超热液阶段（即石英-方铅矿-闪锌矿组合），而不是在来自次成系石英-磁铁矿-斑铜矿-黄铜矿的斑铜矿和黄铜矿（<5 ppm）中形成。同样，Au 在黄铁矿（~5 ppm）中的浓度明显高于（Cu-Fe）富硫化物（≤0.08 ppm）。相比之下，Ag 在黄铁矿和斑铜矿中的含量达到数百 ppm（~ 240 ppm），但在黄铜矿中的含量要少得多（< 25 ppm）。对 LA-IPC-MS 分析期间收集的时间分辨光谱的检查表明，贵金属以两种形式存在于硫化物中：(1) 结构结合（即固溶体）在硫化物晶格中，(2)作为纳米到微米大小的夹杂物（Pd-Te 和 Au）。通过结合场发射扫描电子显微镜 (FESEM) 的高空间分辨率和聚焦离子束和高分辨率透射电子显微镜 (FIB/ HRTEM）。典型的含 Pd 矿物包括 PdTe2 接近理想的美伦斯基矿，但具有独特的晶体结构，而 Au 主要作为原生元素被发现。我们详细的矿物学研究结合先前对所研究矿石中贵金属夹杂物的了解表明，Elatsite 斑岩矿石中的贵金属富集主要是从高温热液中夹带的 Au-Pd-Ag 碲化物熔体的液滴中沉淀出来的。体液。这些碲化物熔体可能在流体与硅酸盐岩浆分离时分离，或者已经存在于后者中，要么来自深部地壳或地幔来源。低温黄铁矿中 Pd 和 Au（后者与 As 相关）的显着富集被解释为这些贵金属在超热套印过程中从预先存在的低成因矿石中重新迁移。我们详细的矿物学研究结合先前对所研究矿石中贵金属夹杂物的了解表明，Elatsite 斑岩矿石中的贵金属富集主要是从高温热液中夹带的 Au-Pd-Ag 碲化物熔体的液滴中沉淀出来的。体液。这些碲化物熔体可能在流体与硅酸盐岩浆分离时分离，或者已经存在于后者中，要么来自深部地壳或地幔来源。低温黄铁矿中 Pd 和 Au（后者与 As 相关）的显着富集被解释为这些贵金属在超热套印过程中从预先存在的低成因矿石中重新迁移。我们详细的矿物学研究结合先前对所研究矿石中贵金属夹杂物的了解表明，Elatsite 斑岩矿石中的贵金属富集主要是从高温热液中夹带的 Au-Pd-Ag 碲化物熔体的液滴中沉淀出来的。体液。这些碲化物熔体可能在流体与硅酸盐岩浆分离时分离，或者已经存在于后者中，要么来自深部地壳或地幔来源。低温黄铁矿中 Pd 和 Au（后者与 As 相关）的显着富集被解释为这些贵金属在超热套印过程中从预先存在的低成因矿石中重新迁移。