Mantle process beneath Philippine Sea back‐arc spreading ridges: A synthesis of peridotite petrology and tectonics
Mantle process beneath Philippine Sea back‐arc spreading ridges: A synthesis of peridotite petrology and tectonics
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DOI：
10.1111/j.1440-1738.2006.00515.x
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发表时间：
2006-03
期刊：
影响因子：
1.5
通讯作者：
Y. Ohara
中科院分区：
文献类型：
--
作者：
Y. Ohara
摘要为了获得弧后盆地扩张脊下地幔过程的总体视图，对菲律宾海两个弧后盆地扩张脊的橄榄岩岩石学和构造产状的多样性进行了研究：Parece Vela裂谷和马里亚纳海槽。帕雷斯贝拉盆地扩张脊（帕雷斯贝拉裂谷）是一个物理上快速/中间扩张脊，尽管许多构造岩浆特征类似于慢速至超慢速扩张脊。帕雷塞船帆座裂谷的两个不寻常的特征进一步证明了海岭的独特性：大洋核杂岩的全轴发展和地幔橄榄岩在部分中点的暴露。帕雷斯贝拉裂谷产生了残留但仍然肥沃的二辉橄榄岩/辉橄榄岩、含斜长石的辉橄榄岩和纯橄榄岩的岩性组合;在罗曼什断裂带的赤道大西洋中脊以及印度洋和北冰洋的超低速扩张脊也报告了类似的组合。帕雷斯贝拉裂谷的构造-岩浆特征表明，扩散的多孔熔体流动和普遍的熔体-地幔相互作用是那里重要的地幔过程。在全球范围内，这种“多孔熔体流动型”地幔过程可能发生在具有厚岩石圈的脊的部分中点之下，通常是超低速扩张脊。相比之下，马里亚纳海槽是一个典型的缓慢扩张的海脊，在部分末端暴露地幔橄榄岩。马里亚纳海槽的岩性组合为残留辉橄榄岩和脉状辉橄榄岩，这是全球深海橄榄岩套中的一种常见组合。马里亚纳海槽的构造岩浆特征表明，由于段端较冷的围岩橄榄岩，通道熔体/流体流动和有限的熔体-地幔相互作用是重要的地幔过程。这种“通道熔体流型”地幔过程很可能发生在任何扩张脊段端部的浅岩石圈地幔中。
Abstract In order to obtain a general view of the mantle process beneath a back‐arc basin spreading ridge, the diversity of peridotite petrology and tectonic occurrences in two back‐arc basin spreading ridges from the Philippine Sea were examined: the Parece Vela Rift and the Mariana Trough. The Parece Vela Basin spreading ridge (Parece Vela Rift) was a physically fast/intermediate‐spreading ridge, although many tectono‐magmatic features resemble those of slow‐ to ultraslow‐spreading ridges. Two unusual features of the Parece Vela Rift further demonstrate the uniqueness of the ridge: full‐axial development of oceanic core complexes and exposure of mantle peridotite at segment midpoints. The Parece Vela Rift yields a lithological assemblage of residual but still fertile lherzolite/harzburgite, plagioclase‐bearing harzburgite and dunite; similar assemblages are reported from the equatorial Mid‐Atlantic Ridge at the Romanche Fracture Zone and the ultraslow‐spreading ridges from the Indian and Arctic Oceans. The tectono‐magmatic characteristics of the Parece Vela Rift suggest that diffuse porous melt flow and pervasive melt–mantle interaction were the important mantle processes there. Globally, this ‘porous melt flow‐type’ mantle process is likely to occur beneath a segment midpoint of the ridge having a thick lithosphere, typically an ultraslow‐spreading ridge. In contrast, the Mariana Trough is a typical slow‐spreading ridge, exposing mantle peridotite at segment ends. The Mariana Trough yields a lithological assemblage of residual harzburgite and veined harzburgite, a common assemblage among the global abyssal peridotite suite. The tectono‐magmatic characteristics of the Mariana Trough suggest that channeled melt/fluid flow and limited melt–mantle interaction are the important mantle processes there, because of the colder wall‐rock peridotite in the segment end. This ‘channeled melt flow‐type’ mantle process is likely to occur in the shallow lithospheric mantle at the segment ends of any spreading ridges.