The Proterozoic Chotanagpur Granite Gneiss Complex (CGGC) at the northern boundary of the Central Indian Tectonic Zone (CITZ) of the eastern Indian shield preserves relics of fossilized oceanic back-arc crust. We describe the field, petrographical and geochemical characteristics of the mafic rocks comprising pillow basalts and dolerites from the Bathani area of the northern fringe of the CGGC, eastern India. The basalts consist of plagioclase feldspar, hornblende, opaque minerals (Fe–Ti oxide) and chlorite, and the dolerite consists of plagioclase, hornblende and opaque minerals. Our data indicate that the Bathani mafic rocks have tholeiitic to transitional composition and are overprinted by greenschist facies metamorphic conditions; however, REE and fluid immobile elements preserve their primary geochemical signatures. The (La/Sm)N ratios (1.38–2.15) and chondrite-normalized REE patterns point to an enriched mid-ocean ridge basalt (E-MORB) mantle source. Geochemical characteristics indicate a mixed signature of MORB and arc tholeiite with enrichment of Ba, Th, Eu and Sr, similar to that of back-arc supra-subduction zone ophiolites. These mafic rocks are the product of MORB-like magma derived from a depleted mantle corresponding to < 2% partial melting of spinel lherzolite, enriched by subduction-induced slab metasomatism and melting. The Bathani mafic rocks are representative of the upper part of a supra-subduction zone columnar ophiolite section, which was emplaced onto the present-day northern margin of the CGGC during suturing of the northern and southern Indian block at c. 1.9 Ga during the Nuna amalgamation.

中文翻译：

---

来自印度 Chotanagpur 花岗岩片麻岩复合体的具有弧后 E-MORB 亲和力的镁铁质岩石：元古代蛇绿岩组的遗迹

位于印度东部地盾的中印度构造带 (CITZ) 北部边界的元古代 Chotanagpur 花岗片麻岩杂岩体 (CGGC) 保存着大洋弧后壳化石的遗迹。我们描述了来自印度东部 CGGC 北部边缘的 Bathani 地区的由枕状玄武岩和辉绿岩组成的基性岩的场、岩石学和地球化学特征。玄武岩由斜长石、角闪石、不透明矿物（Fe-Ti氧化物）和绿泥石组成，辉绿岩由斜长石、角闪石和不透明矿物组成。我们的数据表明，Bathani 基性岩具有拉斑到过渡成分，并被绿片岩相变质条件叠印；然而，稀土元素和流体固定元素保留了它们的主要地球化学特征。(La/Sm)ñ比率（1.38-2.15）和球粒陨石标准化 REE 模式指向富集的洋中脊玄武岩（E-MORB）地幔源。地球化学特征表明 MORB 和弧斑斑矿的混合特征，富集 Ba、Th、Eu 和 Sr，类似于弧后超俯冲带蛇绿岩。这些镁铁质岩石是类似 MORB 的岩浆的产物，这些岩浆来源于贫化的地幔，对应于 < 2% 的尖晶石菱辉石部分熔融，通过俯冲诱导的板片交代作用和熔融而富集。巴塔尼基性岩是超俯冲带柱状蛇绿岩段上部的代表，该段在印度北部和南部地块在C。Nuna 合并期间的 1.9 Ga。