In this study, we present the geochemical analysis on 14 samples from seven distinct E–W trending mafic dykes from the Chotanagpur Gneissic Complex. These dykes have not been studied previously and highlight the importance of igneous and tectonic processes in the Chotanagpur Gneissic Complex. The dykes, in terms of modal mineralogy, do not show notable variations, but textural variations are well noticed. These dykes are characterised as basalt and basaltic andesite (SiO₂ = 45.48–54.03 wt.%; Mg# = 21–68.5), and comparable with E-MORB type tholeiitic magma series. The dykes are classified into two groups, low Mg# and high Mg# dykes, based on their Mg# and silica content. The major fractionating mineral phases are olivine, plagioclase, and pyroxene. The dykes are variably contaminated with crustal input, as shown by Nb/U vs. (Th/Nb)_PM, Th/Nb vs. La/Nb, and Th/Yb vs. Nb/Yb. The dykes also underwent post-magmatic hydrothermal alteration after their emplacement. Semi-quantitative trace element modelling suggests that these dykes are derived by partial melting within spinel peridotite-rich mantle and spinel–garnet peridotite-rich mantle source in the transition zone. The low Mg# dykes are consistent with 3–15% partial melting curves, whereas high Mg# dykes are comparable with 15% melting curve. Finally, we present a conceptual and simplified model for the E–W trending mafic dykes of the CGC, based on the geochemical data of the present study and the available information.

在这项研究中，我们展示了来自 Chotanagpur 片麻岩杂岩体的七个不同的东西向基性岩脉的 14 个样品的地球化学分析。这些岩脉以前从未被研究过，突出了 Chotanagpur 片麻岩杂岩中火成岩和构造过程的重要性。就模态矿物学而言，岩脉没有表现出显着的变化，但很明显地注意到了质地变化。这些岩脉的特征是玄武岩和玄武安山岩 (SiO ₂= 45.48–54.03 重量％；Mg# = 21-68.5)，与 E-MORB 型拉斑岩浆系列相当。根据其 Mg# 和二氧化硅含量，岩脉分为两组，低 Mg# 和高 Mg# 岩脉。主要的分馏矿物相是橄榄石、斜长石和辉石。如 Nb/U与. (Th/Nb) _PM , Th/Nb与. La/Nb 和 Th/Yb对比. 铌/镱。岩脉在就位后也经历了岩浆后热液蚀变。半定量微量元素模型表明，这些岩脉是由过渡带中富含尖晶石橄榄岩的地幔和富含尖晶石-石榴石橄榄岩的地幔源内的部分熔融形成的。低 Mg# 岩脉与 3-15% 的部分熔化曲线一致，而高 Mg# 岩脉与 15% 的熔化曲线相当。最后，基于本研究的地球化学数据和可用信息，我们提出了 CGC 东西向基性岩脉的概念和简化模型。