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首页> 外文期刊>Geochemistry, geophysics, geosystems >Missing western half of the Pacific Plate: Geochemical nature of the Izanagi-Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles
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Missing western half of the Pacific Plate: Geochemical nature of the Izanagi-Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

机译：缺少太平洋板块的西半部：伊萨纳吉-太平洋山脊相互作用的地球化学性质，以及印度洋和太平洋地幔之间的固定边界

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摘要

The source mantle of the basaltic ocean crust on the western half of the Pacific Plate was examined using Pb-Nd-Hf isotopes. The results showed that the subducted Izanagi-Pacific Ridge (IPR) formed from both Pacific (180-similar to 80 Ma) and Indian (similar to 80-70 Ma) mantles. The western Pacific Plate becomes younger westward and is thought to have formed from the IPR. The ridge was subducted along the Kurile-Japan-Nankai-Ryukyu (KJNR) Trench at 60-55 Ma and leading edge of the Pacific Plate is currently stagnated in the mantle transition zone. Conversely, the entire eastern half of the Pacific Plate, formed from isotopically distinct Pacific mantle along the East Pacific Rise and the Juan de Fuca Ridge, largely remains on the seafloor. The subducted IPR is inaccessible; therefore, questions regarding which mantle might be responsible for the formation of the western half of the Pacific Plate remain controversial. Knowing the source of the IPR basalts provides insight into the Indian-Pacific mantle boundary before the Cenozoic. Isotopic compositions of the basalts from borehole cores (165-130 Ma) in the western Pacific show that the surface oceanic crust is of Pacific mantle origin. However, the accreted ocean floor basalts (similar to 80-70 Ma) in the accretionary prism along the KJNR Trench have Indian mantle signatures. This indicates the younger western Pacific Plate of IPR origin formed partly from Indian mantle and that the Indian-Pacific mantle boundary has been stationary in the western Pacific at least since the Cretaceous.
机译：使用Pb-Nd-Hf同位素检查了太平洋板块西半部玄武质海洋地壳的源幔。结果表明，俯冲的伊萨纳吉-太平洋海岭（IPR）由太平洋（180-类似于80 Ma）和印度（类似于80-70 Ma）地幔形成。西太平洋板块向西变年轻，被认为是由IPR形成的。该山脊是沿日本-日本-南开-琉球（KJNR）海沟在60-55 Ma俯冲的，太平洋板块的前沿目前停滞在地幔过渡带。相反，整个太平洋板块的东半部则由沿着东太平洋上升带和胡安·德富卡海岭的同位素截然不同的太平洋地幔形成，大部分仍保留在海底。所获得的IPR无法访问;因此，关于哪个地幔可能对太平洋板块西半部形成负责的问题仍存在争议。了解IPR玄武岩的来源，可以洞悉新生代之前的印度太平洋地幔边界。西太平洋钻孔岩心（165-130 Ma）的玄武岩的同位素组成表明，表层洋壳起源于太平洋地幔。然而，沿KJNR海沟增生的棱柱体中增生的海床玄武岩（类似于80-70 Ma）具有印度地幔特征。这表明年轻的西太平洋IPR板块部分地由印度地幔形成，并且至少自白垩纪以来，印度太平洋的地幔边界一直稳定在西太平洋。

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