Geochemistry of diverse lava types from the Lau Basin (South West Pacific): Implications for complex back-arc mantle dynamics
Geochemistry of diverse lava types from the Lau Basin (South West Pacific): Implications for complex back-arc mantle dynamics
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劳盆地（西南太平洋）不同熔岩类型的地球化学：对复杂弧后地幔动力学的影响
DOI：
10.1002/gj.3354
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发表时间：
2019
影响因子：
1.8
通讯作者：
Shi Xuefa
中科院分区：
文献类型：
--
作者：
Zhang Haitao;Yan Quanshu;Li Chuanshun;Zhu Zhiwei;Zhao Renjie;Shi Xuefa
来自弧后盆地的熔岩总体上是多种多样的，其地球化学成分表明它们在成岩过程中受到了俯冲成分的不同贡献。获得整个弧后盆地的综合地球化学特征，有助于更好地理解弧后演化的复杂性。本文系统地综述了流盆熔岩的常量元素和微量元素组成。该数据集覆盖了盆地的所有主要构造单元，如东部刘氏扩张中心(ELSC)、华法海脊(VFR)、中央刘氏扩张中心(CLSC)、西北刘氏扩张中心(NWLSC)、东北刘氏扩张中心(NELSC)、曼加托卢三联结(MTJ)和丰努阿雷扩张中心(FSC)。这些地点的熔岩类型多样，包括拉斑玄武岩、碱性玄武岩、玄武岩安山岩、安山岩、英安岩和流纹岩。此外，NELSC和FSC还含有玻安岩。在这项研究中，这些不同类型的岩石的地球化学成分被用来研究刘盆地弧后的扩张动力学。结果表明：(A)俯冲成分主要包括从俯冲板块释放的含水流体和直接从熔融的俯冲沉积物中释放的含水熔体，俯冲成分对地幔楔体和刘盆地中部和南部熔岩成因的影响随着距离汤加海沟的增加而减小；(B)在萨摩亚地幔向刘盆地的传播和扩散过程中，来自NELSC、NWLSC、MTJ甚至来自FSC北部的熔岩可能受到不同程度的萨摩亚烟柱的影响；印度类MORB地幔向南迁移到太平洋地幔与刘盆地的开放是一致的。随着印度地幔逐渐向刘盆地迁移，形成了一系列的扩张中心，依次为NWLSC、CLSC、ELSC和传播的VFR。
Lavas from back‐arc basins are generally diverse, and their geochemical compositions indicate that they received variable contributions from subduction components during petrogenesis. Obtaining comprehensive geochemistry characteristics for the entire back‐arc basin are helpful in gaining a better understanding of the complexities of back‐arc evolution. In this study, we systematically reviewed the major and trace element compositions of Lau Basin lavas. This data set covered all of the major tectonic units of the basin, for example, the Eastern Lau spreading center (ELSC), the Valu Fa ridge (VFR), the Central Lau spreading center (CLSC), the Northwestern Lau spreading center (NWLSC), the Northeastern Lau spreading center (NELSC), the Mangatolu Triple Junction (MTJ), and the Fonualei Spreading Center (FSC). The lava types from these locations are diverse, including tholeiitic basalts, alkali basalts, basaltic andesites, andesites, dacites, and rhyolites. In addition, the NELSC and FSC contain boninites. In this study, the geochemical compositions of these diverse rock types are used to investigate the spreading dynamics of the Lau Basin back‐arc. We conclude that (a) the subduction components mainly include hydrous fluids released from the subducted slab, and hydrous melt directly from the melting subducted sediment, and the influence of the subducted components on the mantle wedge and the petrogenesis of the central and southern Lau Basin lavas decreases with increasing distance from the Tonga Trench; (b) during the propagation and spreading of the Samoan mantle into the Lau Basin, lavas from the NELSC, NWLSC, MTJ, and even from the northern part of the FSC may receive variable degrees of influence from the Samoan plume; and (c) the migration of Indian MORB‐like mantle southwards into the Pacific mantle is consistent with the opening of the Lau Basin. With the gradual migration of Indian mantle into the Lau Basin, a series of spreading centers were formed, for example, in order, the NWLSC, CLSC, ELSC, and the propagating VFR.