Abstract—

This paper discusses the petrological and geochemical characteristics of the acid plutonic rocks (mainly granites of different colors) exposed in Khanak and Devsar areas of Neoproterozoic Malani Igneous Suite (MIS) to understand their magmatic evolution processes, petrogenetic history and tectonic regimes. Petrographically, granites of both areas show porphyritic, hypidiomorphic, granophyric, perthitic and micro-granophyric textures. Geochemically, these acidic rocks having peraluminous nature are enriched in SiO₂, Na₂O + K₂O, Fe/Mg, Rb, Zr, Y, Th, U, REE and depleted in MgO, CaO, Sr, P, Ti, Ni, Cr, V & Eu abundances, which have affinity with A-type granites in extensional environment. The enrichment of trace elements and negative anomalies of Sr, Eu, P & Eu in the multi-element spider diagrams suggest that the emplacement of these granites were controlled by fractional crystallization and crustal contamination of protolith magma. Elemental geochemistry also attests that they are of rare-metal bearing with high heat production (HHP) nature and represent a genetically related post-collisional A₂-type granitic intrusions. Petrogenetic modeling (batch melt related) suggests that the early phase (grey and grayish green colored granites) might have been generated from a gabbroic source by partial melting (5%) leaving a residue with 25% alkali feldspar, 20% quartz, 35% plagioclase, 10% biotite, 8% hornblende, 1% orthopyroxene and 1% clinopyroxene whereas late phase (pink colored granites) might have been generated from a metavolcanic source by partial melting of 2% leaving a residue with 30% alkali feldspar, 15% quartz, 45% plagioclase, 2% biotite, 2% hornblende, 3% orthopyroxene and 3% clinopyroxene. Hence, the petrology and geochemistry of these acid plutonic rocks are consistent with their formation in a plume related rift-magmatic tectonic setting and exhibit complex post magmatic chemical variations.

中文翻译：

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印度西北半岛哈里亚纳邦西南部食源性酸性成岩岩石的成因及构造意义

摘要-

本文讨论了新元古代Malani火成岩套件（MIS）的Khanak和Devsar地区暴露的酸性深部岩石（主要是不同颜色的花岗岩）的岩石学和地球化学特征，以了解它们的岩浆演化过程，成岩历史和构造制度。岩石学上，这两个地区的花岗岩都表现出斑状，亚同形，花状，蠕状和微粒状纹理。在地球化学上，这些具有高铝质性质的酸性岩石富含SiO ₂，Na ₂ O + K ₂O，Fe / Mg，Rb，Zr，Y，Th，U，REE和贫化的MgO，CaO，Sr，P，Ti，Ni，Cr，V和Eu丰度，在延伸环境中与A型花岗岩具有亲和力。在多元素蜘蛛图中丰富的微量元素和Sr，Eu，P和Eu的负异常表明，这些花岗岩的位置受原岩浆的分步结晶和地壳污染控制。元素地球化学也证明它们是具有高热量产生（HHP）性质的稀有金属轴承，代表了与遗传有关的碰撞后A ₂型花岗岩侵入体。岩石成因模型（与批熔有关）表明，早辉石（灰色和灰绿色的花岗岩）可能是由辉长岩来源通过部分熔融（5％）而产生的，残留物中含有25％的碱长石，20％的石英，35％的残余物。斜长石，10％的黑云母，8％的角闪石，1％的邻二甲苯和1％的斜ino石英，45％斜长石，2％黑云母，2％角闪石，3％邻苯二酚和3％斜％石。因此，这些酸性深成岩的岩石学和地球化学与其在羽状裂谷-岩浆构造环境中的形成是一致的，并且表现出复杂的岩浆后化学变化。