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首页> 外文期刊>Journal of Asian earth sciences >Coexistence of MORB and OIB-type mafic volcanics in the Manipur Ophiolite Complex, Indo-Myanmar Orogenic Belt, northeast India: Implication for heterogeneous mantle source at the spreading zone
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Coexistence of MORB and OIB-type mafic volcanics in the Manipur Ophiolite Complex, Indo-Myanmar Orogenic Belt, northeast India: Implication for heterogeneous mantle source at the spreading zone

机译：印度东北部印度－缅甸造山带曼尼普尔蛇绿岩群中的MORB和OIB型镁铁质火山共存：对扩展区的地幔源的影响

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This paper presents the first report of the coexistence of tholeiitic mid -ocean ridge basalt (MORB) - type and alkaline ocean island basalt (OW) - type mafic volcanics from the Manipur Ophiolite Complex (MOC), Indo-Myanmar Orogenic Belt, northeast India. The MORB-types have comparatively lower TiO2 concentrations (0.6-1.6 wt.%), show almost flat REE patterns with depleted LREEs [(La/Sm)(N) = 0.62-1.03]. However, few samples in the MORB group show enrichment in LREE [(La/Sm)(N) = 2.83-2.95] which is the typical composition of P-MORB. Alkaline OIB-types are characterized by high concentration of TiO2 (1.7-3.5 wt.%) with highly enriched LREE pattern as compared to their HREE [(LaiSm)(N) = 2.27-3.44, (Sm/Yb)(N) = 2.56-3.29]. Such geochemical variation implies more than two sources. Possibly, one for OIBs (enriched mantle) and several ones for MORBs; from depleted MORB mantle (DMM) source to significantly enriched DMM source by OIB-type components. Petrogenetic modeling suggests that 20% partial melting of depleted mantle within spinel stability facies zone (shallow depth) is responsible for generation of MORB tholeiites and 5-10% partial melting of enriched mantle or plume material at garnet facies stability zone (deeper depth) is responsible for production of alkaline OIB-type. Geochemical signatures of variably enriched MORB and P-MORB samples further suggest possible scenario of mixing of depleted N-MORB and enriched OIB melt. It is therefore likely that mafic volcanics of the MOC were derived from chemically heterogeneous mantle sources erupted at the sea floor spreading zone as MORB generated by partial melting of depleted upper mantle and as OIB generated by partial melting of enriched mantle or a plume source, which was proximal to the spreading axis. Later, due to prolonged subduction of the Indian plate beneath the Myanmar plate and afterward collisional activity, they might have accreted along the Indo-Myanmar Orogenic Belt as upthrust ocean crust. (C) 2015 Elsevier Ltd. All rights reserved.
机译：本文提出了印度东北部印度-缅甸造山带的曼尼普尔蛇绿岩复合体（MOC）的中生洋中脊玄武岩（MORB）型和碱性海洋岛玄武岩（OW）型镁铁质火山共存的第一份报告。 。 MORB型具有相对较低的TiO2浓度（0.6-1.6 wt。％），显示几乎平坦的REE图案，其中LREE耗尽[（La / Sm）（N）= 0.62-1.03]。然而，在MORB组中，几乎没有样品显示出LREE的富集[（La / Sm）（N）= 2.83-2.95]，这是P-MORB的典型组成。碱性OIB类型的特征是高浓度的TiO2（1.7-3.5 wt。％）具有与其HREE [（LaiSm）（N）= 2.27-3.44，（Sm / Yb）（N）= 2.56-3.29]。这种地球化学变化意味着两个以上的来源。可能是一个用于OIB（富集地幔），几个用于MORB。从耗尽的MORB地幔（DMM）来源到OIB型组件显着丰富的DMM来源。岩石成因模拟表明，尖晶石稳定相带（浅层深度）内枯竭地幔的20％部分熔融是MORB冲孔岩生成的原因，石榴石相稳定区（更深深度）是富地幔或羽状物质的5-10％部分熔融。负责生产碱性OIB型。可变富集的MORB和P-MORB样品的地球化学特征进一步表明了贫N-MORB和富集的OIB熔体混合的可能情况。因此，MOC的镁铁质火山岩可能来自于在海床扩散区喷出的化学非均质地幔源，这是由于贫化上地幔部分熔融而产生的MORB，以及由于富集地幔或羽状源的部分熔融而产生的OIB。靠近扩张轴。后来，由于印度洋板块在缅甸板块下面的俯冲时间延长，并且随后发生了碰撞活动，它们可能沿印度-缅甸造山带沿上地壳洋积。 （C）2015 Elsevier Ltd.保留所有权利。

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