The importance of light-stable isotopes and their mass-dependent fractionations in understanding past geological processes is enormous. The present research delivers precise, high-resolution, in-situ oxygen (O) and triple sulfur (S) isotope ratios from quartz and sulfide minerals found in the CuAu Kendadih deposit located along the Mesoproterozoic (∼1.6 Ga) Singhbhum Shear Zone (SSZ) in eastern India. Oxygen and sulfur isotope analyses were carried out on quartz and pyrite-chalcopyrite pairs that are in textural equilibrium, using the most advanced Large Geometry-Secondary Ion Mass Spectrometer (LG-SIMS; CAMECA IMS-1300HR). The results show restricted ranges for δO (+6 to +7.7‰; average: 6.9 ± 0.9‰, = 50) and δS (+11.4 to +11.9‰; average: 11.79 ± 0.2‰, = 62). This isotopic homogeneity suggests a single, uniform fluid source for the ore-forming metals. The combined oxygen, sulfur isotope ratios, and fluid inclusion data are consistent with a hydrothermal fluid derived from an “I-type” granitic melt. This study incorporates existing fluid inclusion, stable, and radiogenic isotope data from temporally similar deposits within the shear zone, reevaluating their implications in light of the new findings. It proposes that, around 1.6 billion years ago, underplating the Singhbhum Craton by the Dalma Plume resulted in the remelting of the lower crust. This remelting is attributed to the plume's introduction of a significantly elevated thermal perturbation. The process is hypothesized to have led to the generation of second-order granitic melts. Upon emplacement in the lower crust, these granitic melts became the potential source for essential metals, ligands, and hydrothermal fluids, contributing to mineralization within the deep-seated Singhbhum Shear Zone. This research attempts to comprehensively describe the “source-to-sink” ore genesis model by proposing potential magma chamber processes that concentrate metals and ligands at the roof zone, followed by the separation of metal-rich hydrothermal fluids, fluid-rock interaction, and the physicochemical conditions governing the deposition of the extensive polymetallic deposit. This work offers novel insights into the Mesoproterozoic metallogenesis along the Singhbhum Shear Zone, challenging existing paradigms that favored evaporite or seawater brine sources. Furthermore, it sheds light on the Mesoproterozoic sub-crustal processes beneath the Indian Craton in this region.

中文翻译：

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利用氧和硫同位素特征解读矿石成因：印度东部 Singhbhum 剪切带的案例研究


光稳定同位素及其质量相关的分馏对于理解过去的地质过程具有巨大的重要性。目前的研究提供了精确、高分辨率的原位氧 (O) 和三硫 (S) 同位素比，这些矿物来自位于中元古代 (∼1.6 Ga) Singhbhum 剪切带 (SSZ) 的 CuAu Kendadih 矿床中发现的石英和硫化物矿物）在印度东部。使用最先进的大几何二次离子质谱仪（LG-SIMS；CAMECA IMS-1300HR）对处于结构平衡的石英和黄铁矿-黄铜矿对进行氧和硫同位素分析。结果显示 δ18O（+6 至 +7.7‰；平均值：6.9 ± 0.9‰，= 50）和 δS（+11.4 至 +11.9‰；平均值：11.79 ± 0.2‰，= 62）的限制范围。这种同位素同质性表明成矿金属存在单一、均匀的流体源。综合氧、硫同位素比和流体包裹体数据与源自“I型”花岗岩熔体的热液流体一致。这项研究结合了剪切带内时间相似沉积物的现有流体包裹体、稳定和放射性同位素数据，根据新发现重新评估了它们的含义。它提出，大约 16 亿年前，达尔马地幔柱对辛格布姆克拉通的底侵导致了下地壳的重熔。这种重熔归因于羽流引入了显着升高的热扰动。据推测，该过程导致了二级花岗岩熔体的产生。在进入下地壳后，这些花岗岩熔体成为必需金属、配体和热液的潜在来源，促进了深部 Singhbhum 剪切带的矿化。 本研究试图通过提出潜在的岩浆室过程来全面描述“源-汇”成矿模型，该过程将金属和配体集中在顶部区域，随后富金属热液的分离、流体-岩石相互作用以及控制大面积多金属矿床沉积的物理化学条件。这项工作为辛格布姆剪切带沿线的中元古代成矿作用提供了新颖的见解，挑战了有利于蒸发岩或海水卤水来源的现有范式。此外，它还揭示了该地区印度克拉通下方的中元古代地壳下过程。