The Khetri Copper Belt of the Aravalli-Delhi Fold Belt in western India hosts Cu (± Au ± Ag ± Co ± Fe ± REE ± U) mineralization that is likely of iron oxide-copper-gold (IOCG) type. The study on the Madan-Kudan deposit in this belt documents four vein types: Type-1 (pyrite ± chalcopyrite ± magnetite ± biotite ± scapolite ± amphibole ± chlorite), Type-2 (chalcopyrite-pyrrhotite-pyrite-magnetite-amphibole-chlorite), Type-3 (chalcopyrite-pyrrhotite-pyrite-dolomite-quartz), and Type-4 (chalcopyrite-pyrrhotite-biotite). Pyrite is grouped on texture and major and trace element chemistry into Pyrite-1A, Pyrite-1B, Pyrite-1C (Type-1 veins), Pyrite-2 (Type-2 veins), Pyrite-3A, and Pyrite-3B (Type-3 veins). This sequence documents changing fluid composition and suggests that sulfide mineralization was associated with Na-Ca-K alteration (Type-1 and Type-2 veins), carbonate alteration (Type-3 veins), and K-Fe-Mg alteration (Type-4 veins). The C and O isotope composition of dolomite from Type-3 veins suggests that the ore fluid contained mantle-derived carbon (possibly carbonatite-related) and mixed with an isotopically heavier fluid or exchanged isotopes with crustal rocks. A strong positive correlation between Au and Cu is interpreted to reflect their “coupling” in the pyrite structure. In contrast, Pb, Zn, Bi, and Ag are present in mineral inclusions. Intragrain Fe, Co, As, and Ni variability in pyrite suggests that replacement by coupled dissolution-precipitation and formation of overgrowths were important. Pyrite-1A has high Co (up to 3.3 wt%) and Co/Ni ratios (500 to 16,000) that have not been reported elsewhere. The Co/Ni ratios of KCB pyrite are similar to those from iron oxide-apatite and other IOCG deposits, although the latter do not have a characteristic Co/Ni ratio but consistently have high Co concentrations (up to 1 wt% or more).

中文翻译：

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印度西部 Khetri 铜矿带的成矿过程：黄铁矿微量元素化学和碳酸盐 CO 同位素组成的限制

印度西部 Aravalli-Delhi 褶皱带的 Khetri 铜带拥有 Cu (± Au ± Ag ± Co ± Fe ± REE ± U) 矿化，可能属于氧化铁-铜-金 (IOCG) 类型。对该带的 Madan-Kudan 矿床的研究记录了四种矿脉类型：Type-1（黄铁矿±黄铜矿±磁铁矿±黑云母±方柱石±角闪石±绿泥石），Type-2（黄铜矿-磁黄铁矿-黄铁矿-磁铁矿-角闪石-绿泥石） )、Type-3（黄铜矿-磁黄铁矿-黄铁矿-白云石-石英）和 Type-4（黄铜矿-磁黄铁矿-黑云母）。黄铁矿按质地和主要和微量元素化学分为 Pyrite-1A、Pyrite-1B、Pyrite-1C（Type-1 矿脉）、Pyrite-2（Type-2 矿脉）、Pyrite-3A 和 Pyrite-3B（类型-3 脉）。该序列记录了流体成分的变化，并表明硫化物矿化与 Na-Ca-K 蚀变（Type-1 和 Type-2 脉）、碳酸盐蚀变（Type-3 脉）和 K-Fe-Mg 蚀变（Type- 4 条静脉）。来自 3 型脉的白云岩的 C 和 O 同位素组成表明，矿流体包含地幔衍生的碳（可能与碳酸岩有关）并与同位素较重的流体混合或与地壳岩石交换同位素。Au和Cu之间的强正相关被解释为反映了它们在黄铁矿结构中的“耦合”。相比之下，Pb、Zn、Bi 和 Ag 存在于矿物包裹体中。黄铁矿中的晶粒内 Fe、Co、As 和 Ni 的变异性表明，通过耦合溶解-沉淀和过度生长的形成进行替代很重要。Pyrite-1A 具有高 Co（高达 3. 3 wt%) 和 Co/Ni 比率（500 到 16,000），这些都没有在其他地方报道过。KCB 黄铁矿的 Co/Ni 比率类似于来自氧化铁磷灰石和其他 IOCG 矿床的 Co/Ni 比率，尽管后者没有特征 Co/Ni 比率但始终具有高 Co 浓度（高达 1 wt% 或更高）。