The present study provides new petrological and geochemical data of the dredged rocks from submarine volcanoes along the Andaman arc and describes the petrogenetic evolution of the arc system in terms of mantle wedge characteristics, nature and quantitative input of subducted slab components, and fractionation processes of precursor magma. The studied rocks include basaltic andesite, andesite, dacite and rhyolite. These volcanic rocks exhibit LILE, LREE enrichments and HFSE depletion, corroborating their generation through subduction processes. High abundances of Th/Nd, La/Sm, LREE/HFSE than LILE/HFSE, LILE/LREE suggest a substantial contribution of sediments from the subducting slab over slab-dehydrated aqueous fluids to the mantle wedge. The Sr/Sr-Ba/La mixing model suggests 0.6–0.8% addition of slab fluid (90:10 AOC: sediment fluid) to account for the fluid signature, whereas the Nd/Nd-La/Sm mixing model envisages ∼3–4% addition of sediment melt to the mantle source, reconciling the sediment signature in Andaman submarine volcanic rocks. The presence of N-MORB type mantle is attributed to the absence and/or inefficient convection of asthenospheric material from the Andaman back-arc basin to the mantle wedge. This ineffective convection can be equated with the flat subduction of the Indian Plate, caused by the convergence of the aseismic Ninety East Ridge. The non-modal batch-melting model suggests that 13–24% partial melting of the spinel lherzolite mantle beneath the Andaman submarine volcanic arc formed the parent magma. The crystallization model invokes up to 60–70% of fractionation of olivine, plagioclase, clinopyroxene, orthopyroxene, sanidine and magnetite in all the rock types with subordinate proportions of amphibole, biotite, apatite, ilmenite, and sanidine in rhyolites. The basaltic andesites, andesites and dacites do not show upper crustal input, while rhyolites indicate crustal contamination from an upper crust and/or arc crust.

中文翻译：

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东北印度洋安达曼俯冲带海底火山弧岩岩石成因：板片成分和地幔楔特征的制约


本研究提供了安达曼弧沿线海底火山挖掘出的岩石的新岩石学和地球化学数据，并从地幔楔特征、俯冲板片成分的性质和定量输入以及前体的分馏过程描述了弧系统的岩石成因演化。岩浆。研究的岩石包括玄武质安山岩、安山岩、英安岩和流纹岩。这些火山岩表现出 LILE、LREE 富集和 HFSE 消耗，证实了它们是通过俯冲过程产生的。 Th/Nd、La/Sm、LREE/HFSE 的丰度比 LILE/HFSE、LILE/LREE 的丰度高，这表明来自俯冲板片的沉积物对板片脱水的含水流体对地幔楔的贡献很大。 Sr/Sr-Ba/La 混合模型建议添加 0.6–0.8% 的板状流体（90:10 AOC：沉积物流体）来解释流体特征，而 Nd/Nd-La/Sm 混合模型设想~3–将 4% 的沉积物熔体添加到地幔源中，协调了安达曼海底火山岩中的沉积物特征。 N-MORB 型地幔的存在归因于从安达曼弧后盆地到地幔楔的软流圈物质的缺乏和/或低效对流。这种无效的对流可以等同于印度板块的平坦俯冲，这是由抗震的九十东脊汇聚引起的。非模态分批熔融模型表明，安达曼海底火山弧下方尖晶石二辉橄榄岩地幔的 13-24% 部分熔融形成了母岩浆。 结晶模型在所有岩石类型中调用了高达 60-70% 的橄榄石、斜长石、单斜辉石、斜方辉石、透尖晶石和磁铁矿的分馏，以及流纹岩中角闪石、黑云母、磷灰石、钛铁矿和透尖石的比例。玄武质安山岩、安山岩和英安岩不显示上地壳输入，而流纹岩则表明来自上地壳和/或弧地壳的地壳污染。