Petrogenesis and tectonic implication of lavas from the Yap Trench, western Pacific
Petrogenesis and tectonic implication of lavas from the Yap Trench, western Pacific
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DOI：
10.1007/s13131-021-0185-y
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发表时间：
2021-11
影响因子：
1.4
通讯作者：
Ling Chen;Limei Tang;Jichao Yang;Xiaohu Li;Wen Wang;F. Chu;J. Zhang
中科院分区：
文献类型：
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作者：
Ling Chen;Limei Tang;Jichao Yang;Xiaohu Li;Wen Wang;F. Chu;J. Zhang
本文介绍了西太平洋北方雅普海沟火山岩的主量元素和微量元素数据，并在加罗林海岭和雅普海沟相互作用的框架内讨论了火山岩的成因和构造意义。岩石的地球化学特征与弧后盆地玄武岩（BABB）和洋中脊玄武岩（MORB）相似，包括高Fe含量、拉斑玄武岩亲合性、在一定FeOT/MgO比值下的高TiO 2值、Ti/V比值在20 ~ 50之间、低Ba/Nb比值和Th/Nb比值，以及BABB和MORB共同显示的微量元素模式。与弧熔岩不同这些岩石似乎是在地幔上涌和扩张中心减压熔融过程中形成的。然而，与马里亚纳弧前地区海底扩张产生的典型弧前熔岩（如最南端马里亚纳海沟的始新世早期弧前玄武岩和新近纪晚期弧前熔岩）相比，雅普海沟熔岩来自更肥沃的地幔，俯冲分量更小，因此，它们不是弧前地幔减压熔融的产物。我们认为，向陆斜坡熔岩代表弧后盆地地壳，被推覆到弧前岩石圈的碰撞过程中的卡罗琳岭与雅普海沟（20-25马），这起了关键作用的雅普俯冲系统的演化。此外，向海斜坡熔岩代表俯冲板块地壳，在碰撞过程中增生到深海沟。这一碰撞事件导致雅普弧岩浆活动的停止;因此，以前被认为是弧岩浆产物的雅普海沟火山岩（<25 Ma）实际上可能代表了新生的岛弧熔岩，其俯冲成分低于成熟的马里亚纳弧熔岩。
We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the Caroline Ridge and Yap Trench. Rocks were collected from both landward and seaward trench slopes and exhibited geochemical characteristics similar to backarc basin basalt (BABB) and mid-ocean ridge basalt (MORB), including high Fe content, tholeiitic affinity, high TiO2value at a given FeOT/MgO ratio, Ti/V ratio between 20 and 50, low Ba/Nb ratio and Th/Nb ratio, and trace element patterns commonly displayed by BABB and MORB, which are distinct from arc lava. These rocks seem to have been generated during mantle upwelling and decompression melting at a spreading center. However, compared with typical forearc lava produced by seafloor spreading in the Mariana forearc region, such as the early Eocene forearc basalts and late Neogene forearc lava in the southernmost Mariana Trench, the Yap Trench lava is derived from a more fertile mantle and feature a more minor subduction component; thus, they cannot be the products of forearc mantle decompression melting. We suggest that the landward slope lava represents backarc basin crust that was overthrust onto the forearc lithosphere during the collision of the Caroline Ridge with the Yap Trench (20–25 Ma), which played a key role in the evolution of the Yap subduction system. Moreover, the seaward slope lava represents the subduction plate crust that accreted onto the deep trench during the collision. This collision event resulted in the cessation of Yap Arc magmatism; thus, the Yap Trench volcanic rocks (<25 Ma) previously suggested to be arc magma products may actually represent the nascent island arc lava with a lower subduction component than in the mature Mariana Arc lava.