High-grade Cu mineralization was recently discovered in the Mbesa prospect in southern Tanzania, but its origin is poorly constrained. Herein, we present new major element, trace element, rare earth element (REE), and platinum group element (PGE) geochemistry and petrographic data to constrain the origin of the mineralization. The sulfide mineralization is dominated by chalcopyrite and bornite and characterized by high Cu/Ni over 100 in the massive and disseminated ores. The mineralization lacks pyrrhotite and pentlandite, which are found commonly in magmatic Ni-Cu-PGE sulfide deposits. Platinum group minerals present are michenerite (PdBiTe) and sudburyite (PdSb). PGE concentrations expressed as Pd + Pt + Au are up to 1.31 and 1.04 ppm in the massive and disseminated ores, respectively. The δ³⁴S of chalcopyrite separates range from –3.9 to –0.6‰, bornite separates vary from –1.8 to 1.1‰, and bornite-chalcopyrite mixtures yield –1.3 and 0.6‰, mostly consistent with a magmatic sulfur origin. The sulfides are hosted by coarse-grained plagioclase amphibolite and hornblende gneiss with recrystallization textures suggestive of metamorphism. Both rocks are characterized by enrichment in large ion lithophile elements (LILEs), with negative anomalies of Zr and Nb, consistent with crustal contamination of magmas derived from partial melting of subcontinental lithospheric mantle (SCLM). An SCLM origin is further suggested by the close association of Cu sulfides with carbonates and apatite. It is suggested that the sulfides crystallized from the fractionated Cu-rich sulfide melt enriched in intermediate solid solution (iss) at shallow crustal levels. Sulfide were likely mobilized as droplets attached to CO₂ vapor phase as expressed by close association between carbonates and apatite with the Cu-rich sulfides. Nickel-rich sulfides may remain undiscovered at deeper portions around the Mbesa prospect.

中文翻译：

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坦桑尼亚南部姆贝萨矿区的铜金铂族元素矿化：非常规岩浆硫化物

最近在坦桑尼亚南部的姆贝萨矿区发现了高品位铜矿化体，但其来源尚不清楚。在此，我们提供了新的主量元素、微量元素、稀土元素 (REE) 和铂族元素 (PGE) 地球化学和岩相数据，以约束矿化的起源。硫化物矿化以黄铜矿、斑铜矿为主，块状、浸染状矿石的Cu/Ni含量高达100以上。该矿化体缺乏磁黄铁矿和镍黄铁矿，而这些物质常见于岩浆镍-铜-铂族元素硫化物矿床中。存在的铂族矿物有云云石 (PdBiTe) 和萨德伯里石 (PdSb)。在块状矿石和浸染状矿石中，以 Pd + Pt + Au 表示的 PGE 浓度分别高达 1.31 和 1.04 ppm。黄铜矿分离物的δ ³⁴ S 范围为 –3.9 至 –0.6 ‰，斑铜矿分离物为 –1.8 至 1.1 ‰，斑铜矿-黄铜矿混合物产量为 –1.3 至 0.6 ‰，大部分与岩浆硫成因一致。硫化物以粗粒斜长角闪岩和角闪片麻岩为主，具有表明变质作用的重结晶结构。这两种岩石的特点是富含大离子亲石元素（LILE），Zr和Nb呈负异常，这与次大陆岩石圈地幔（SCLM）部分熔融产生的岩浆的地壳污染一致。硫化铜与碳酸盐和磷灰石的密切结合进一步表明了 SCLM 的起源。这表明硫化物是从浅地壳水平富集中间固溶体（iss）的分馏富铜硫化物熔体中结晶出来的。硫化物可能以附着在CO ₂气相上的液滴形式流动，这通过碳酸盐和磷灰石与富铜硫化物之间的紧密结合来表达。姆贝萨矿区周围较深处的富镍硫化物可能仍未被发现。