The Mariana Trough, a relatively simple intra-oceanic back-arc basin, is ideal for investigating magmatic processes and mantle-crust interaction in a subduction setting. We present new major- and trace element compositions for 31 basaltic lava and glass samples from the Mariana Trough back-arc spreading center. The studied lavas include phenocrysts of plagioclase, olivine and pyroxene. Major element compositions show that these lavas range from tholeiitic basalt to basaltic andesite, and belong to a sub-alkali tholeiitic series produced by fluid-influenced fractional crystallization of primary basaltic melts. Trace element compositions show that these lavas are transitional between typical normal mid-ocean ridge basalts (MORB) and island arc basalt (IAB), and are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs). Trace element ratios, e.g., Ba/Th, Pb/Ce, Th/Nd, La/Sm, Th/Nb, Ba/Nb and Th/Nb, indicate that the mantle from which these lavas were derived underwent modification resulting from the addition of multiple subduction components. Some typical trace element ratios (e.g., Ba/Nb- total subduction component, Ba/Th- shallow subduction, and Th/Nb-deep subduction component) from our new data and the literature suggest that a latitudinal variation exists in addition to subduction components, and indicates a more complex and heterogeneous distribution of subduction components in the Mariana back-arc region. We suggest that, (1) compared to back-arc locations at 18° N and 15.5° N, lavas from back-arc locations at 17° N indicate higher levels of modification by hydrous fluid released from the subducted slab, and (2) compared to back-arc locations at 17° N and 15.5° N, petrogenesis of lavas from back-arc locations at 18° N indicates a greater influence of sediment melt.

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马里亚纳海槽中部和南部轴向熔岩的地球化学及其对弧后岩浆过程的影响

马里亚纳海槽是一个相对简单的大洋内弧后盆地，非常适合研究俯冲环境中的岩浆过程和地幔-地壳相互作用。我们展示了来自马里亚纳海槽弧后扩张中心的 31 个玄武岩熔岩和玻璃样品的新的主要和微量元素组成。研究的熔岩包括斜长石、橄榄石和辉石的斑晶。主要元素组成表明，这些熔岩的范围从拉斑玄武岩到玄武安山岩，属于亚碱性拉斑系，由原生玄武岩熔体受流体影响分步结晶而成。微量元素组成表明，这些熔岩是典型的正常洋中脊玄武岩（MORB）和岛弧玄武岩（IAB）之间的过渡，并且富含大离子亲石元素（LILEs）和轻稀土元素（LREEs）。微量元素比率，例如 Ba/Th、Pb/Ce、Th/Nd、La/Sm、Th/Nb、Ba/Nb 和 Th/Nb，表明这些熔岩的来源地幔经历了添加导致的变化多个俯冲成分。我们的新数据和文献中的一些典型的微量元素比率（例如，Ba/Nb-总俯冲分量、Ba/Th-浅俯冲分量和 Th/Nb-深俯冲分量）表明除了俯冲分量外还存在纬度变化，并表明马里亚纳弧后区域俯冲成分的分布更为复杂和异质。我们建议，(1) 与 18° N 和 15.5° N 处的弧后位置相比，