Abstract

The Meso-Neoarchean Kudremukh greenstone belt (KGB) of Western Dharwar craton comprises predominant metabasalts associated with banded iron formations (BIFs). The metabasalts are characterized by moderate MgO (7.23–8.97 wt.%), Ni (48–374 ppm), Cr (33–188 ppm) with a wide variation in \(\sum \)PGE (21.8–215.7 ppb) contents with 15.8–115.9 ppb Pd, 3.7–105.2 ppb Pt and 0.7–8.5 ppb Rh. Among IPGE group, Iridium, Osmium and Ruthenium range from 0.2–5.9, 1.4–7 and 1.8–7.8 ppb, respectively. These metabasalts are relatively enriched in \(\sum \)PPGE (21.8–215.7 ppb) than \(\sum \)IPGE contents (3.6–18.6 ppb). Their Pd/Ir (7.6–100.7) and Pd/Pt (0.8–5.5) ratios correspond to moderate to lower degree of melting. The abundance of PGEs in Kudremukh metabasalts is dominantly controlled by sulphide and chromite fractionation trend of the parent magma. Sulphur undersaturated nature of the parent magma is evidenced through the relationship of Pd vs. Cu. Further,̄ the Cu/Pd ratios of the studied volcanics (Cu/Pd = 1277–5747) is lower than primitive mantle (Cu/Pd = 7000), indicating early sulphide removal and S-undersaturation during magmatic differentiation. PGEs geochemistry of the studied rocks suggest early removal of sulphide melts followed by pronounced sulphide fractionation and the mantle melting episode is followed by metasomatism of the refractory mantle wedge by the fluids/melts derived from the subducting slab in a convergent margin setting.

Research Highlights

• PGE systematics on the metabasalts from Kudremukh greenstone belt, western Dharwar Craton, India.

• The KGB metabasalts are characterised by low- moderate degrees of partial melting and high degrees of sulphide fractionation.

• PGE geochemistry of the KGB metabasalts infers the early sulphur undersaturated nature of magmas.

中文翻译：

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了解印度达尔瓦尔克拉通西部 Kudremukh 绿岩带变玄武岩成因中亲硫-嗜铁元素的作用：铂族元素地球化学视角

摘要

西达尔瓦尔克拉通的中-新太古代 Kudremukh 绿岩带 (KGB) 包括与带状铁地层 (BIF) 相关的主要变玄武岩。的玄武岩与在一个广泛的变化，其特征在于温和的MgO（7.23-8.97重量％），镍（48-374 PPM），铬（33-188 PPM）\（\总和\） PGE（21.8-215.7 ppb）的内容含 15.8–115.9 ppb Pd、3.7–105.2 ppb Pt 和 0.7–8.5 ppb Rh。在 IPGE 组中，铱、锇和钌的含量分别为 0.2-5.9、1.4-7 和 1.8-7.8 ppb。这些变玄武岩在\(\sum \) PPGE (21.8–215.7 ppb) 中比\(\sum \)相对丰富IPGE 含量 (3.6–18.6 ppb)。它们的 Pd/Ir (7.6–100.7) 和 Pd/Pt (0.8–5.5) 比率对应于中等至较低的熔化程度。Kudremukh变玄武岩中PGEs的丰度主要受母岩浆的硫化物和铬铁矿分馏趋势控制。母岩浆的硫不饱和性质通过 Pd与. 铜。此外，所研究火山岩的 Cu/Pd 比率（Cu/Pd = 1277-5747）低于原始地幔（Cu/Pd = 7000），表明岩浆分异过程中硫化物早期去除和 S 欠饱和。所研究岩石的 PGEs 地球化学表明，硫化物熔体的早期去除，随后是显着的硫化物分馏，地幔熔融事件之后是难熔地幔楔的交代作用，由俯冲板片在收敛边缘环境中产生的流体/熔体进行交代。

研究亮点

• 印度达尔瓦尔克拉通西部 Kudremukh 绿岩带变玄武岩的 PGE 系统学。

• 克格勃变玄武岩的特点是部分熔融程度低，硫化物分馏程度高。

• 克格勃变玄武岩的 PGE 地球化学推断岩浆的早期硫不饱和性质。