摘要
在对冲绳海槽及邻区构造地质学和热液地质学调查研究成果进行全面总结的基础上,将深部地球动力学机制、冲绳海槽形成演化、岩浆作用过程、热液系统结构、流体循环模式和成矿作用特征等多方面的问题,纳入到统一的框架下,探讨了冲绳海槽构造地质过程对热液活动和成矿作用的控制机理。分析认为,区域中尺度地幔流引起了东亚大陆边缘岩石圈向东的蠕散,并驱动了菲律宾海板块沿琉球海沟向欧亚板块之下的俯冲。在弧后小尺度地幔对流、岩石圈减薄、板片反卷和俯冲后退的共同作用下,冲绳海槽发生弧后张裂。张裂作用在岩石圈内形成了网状破裂系统,为岛弧和弧后岩浆上涌提供了通道,并且引起了不同来源岩浆的干扰和混合。侵位到地壳浅部的岩浆为热液活动提供了热源和主要成矿物质来源,是影响热液活动分布的主要因素。沉积层覆盖改变了流体的浅部循环结构和原始流体成分。热液区内普遍存在的流体相分离过程,导致了广域成矿作用的发生。
On the basis of comprehensive reviewing previous works and results on the tectonic geology and hydrothermal geology of Okinawa Trough, we discussed the tectonic constraints of the hydrothermal activities and mineralization through incorporating the deep geodynamics, tectonic evolution history, magmatism, structures of hydrothermal systems, hydrothermal fluid circulation and polymetallic mineralization. The regional middle-scale mantle flow was suggested to have driven the eastward creeping of the Eurasian marginal lithosphere and the westward subduction of the Philippine Sea Plate, which further induced the small scale mantle flow in the back-arc region. The back-arc opening of the Okinawa Trough was promoted by the combined action of lithosphere thinning, slab roll-back and trench retreat. The lithospheric fracture networks formed by the back-arc extension act as the plumbing system for the arc and back-arc magmatism, and caused the mixing and exchange of magmas from different sources. The shallow intruded magma provides the heat source and predominant metallogenic materials for the hydrothermal system and thus determined the distribution hydrothermal fields. The sedimentary cover altered the shallow circulation structure and the composition of the original hydrothermal fluid produced by the water-rock reaction. The phase separation and segregation of the hydrothermal fluid are pervasive and caused the diverse range of mineralization in hydrothermal fields of Okinawa Trough.
引文
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