We report mineral compositions and bulk rock geochemistry of mafic dykes intruded in the western part of Bastar craton, comprising of Archaean Amgaon Group and Proterozoic Dongargarh Supergroup of rocks. Field relations show two distinct trends of these dykes which are almost perpendicular to each other but having similar mineralogical and geochemical characteristics. Dykes are mostly composed of pyroxenes, plagioclase and subordinate amount of amphiboles and Fe-Ti oxides (magnetite and ilmenite). These hypersthene normative basaltic dykes show tholeiitic trend and are characterised by narrow compositional variations of MgO (6.06–7.08 wt%), FeO t (15.06–17.78 wt%), TiO 2 (1.18–2.24 wt%), Al 2 O 3 (11.96–15.54 wt%) and low Mg# [atomic Mg/(Mg + Fe 2+ ) × 100] values in the range of 37–48. Low loss on ignition (LOI) values <2 wt% and significant trends of trace elements (Nb, La, Th, Sr) with Zr indicate insignificant effects of post magmatic processes in these dykes. Smooth correlations between major oxides and MgO, among trace element ratios (Ce/La, Th/Yb, Nb/Yb) and negative Nb-Ta anomalies without positive Zr and Hf anomalies negate the crustal contamination effects. The correlations of compatible (e.g. Cr, Ni) and incompatible (e.g. Ba, Rb) elements show involvement of both fractional crystallisation and partial melting processes in their formation. Flat heavy rare earth element (HREE) pattern with low (Tb/Yb) n values reveal their genesis from a mantle source without involvement of garnet and geochemical models suggested in the present study indicate melting from spinel lherzolite mantle source. Strong geochemical similarities of present dykes with those of earlier reported Lakhna (1.46 Ga) and Bandimal (1.42 Ga) dykes of northern Bastar craton suggest a widespread mafic magmatic event across the Bastar craton during 1.42–1.46 Ga. Present dykes therefore represent a subduction related outgrowth of Columbia supercontinent due to the accretion of continental margins.

中文翻译：

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印度中部巴斯塔克拉通西部基性岩脉的岩石成因及其与哥伦比亚超大陆延伸的关系

我们报告了侵入 Bastar 克拉通西部的镁铁质岩脉的矿物成分和大块岩石地球化学，包括太古宙 Amgaon 群和元古代 Dongargarh 超群岩石。场关系显示这些岩脉有两种截然不同的趋势，它们几乎相互垂直，但具有相似的矿物学和地球化学特征。岩脉主要由辉石、斜长石和少量角闪石和铁钛氧化物（磁铁矿和钛铁矿）组成。这些超硬质玄武岩脉显示拉斑化趋势，其特征是 MgO (6.06–7.08 wt%)、FeO t (15.06–17.78 wt%)、TiO 2 (1.18–2.24 wt%)、Al 2 O 3 ( 11.96-15.54 wt%) 和低 Mg # [原子 Mg / (Mg + Fe 2+) × 100] 值在 37-48 范围内。低烧失量 (LOI) 值< 2 wt% 和微量元素（Nb、La、Th、Sr）与 Zr 的显着趋势表明这些岩脉中的后岩浆过程影响不显着。主要氧化物和 MgO 之间、微量元素比率（Ce / La、Th / Yb、Nb / Yb）和 Nb-Ta 负异常之间的平滑相关性，而没有正 Zr 和 Hf 异常，否定了地壳污染效应。相容（例如 Cr、Ni）和不相容（例如 Ba、Rb）元素的相关性表明，在它们的形成过程中涉及分步结晶和部分熔化过程。具有低 (Tb / Yb) n 值的扁平重稀土元素 (HREE) 模式揭示了它们来自地幔源的成因，而不涉及石榴石，本研究中建议的地球化学模型表明来自尖晶石二长橄榄石地幔源的熔融。