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对马里亚纳海槽弧后扩张脊上所采集的玄武岩样品进行了系统的 K- Ar定年和微量元素及稀土元素地球化学特征研究。指出马里亚纳海槽的张开及其与之相伴的玄武岩浆活动至今仍在进行 ,海槽的半扩张速率可能为 2 .0～ 2 .5 cm/ a。同时 ,海槽玄武岩年龄在空间上具有从南到北逐渐变新的演化规律。地球化学特征指示 ,地幔岩的部分熔融程度是控制海槽区玄武岩地球化学性质差异的主要机制。岩石学和微量元素地球化学特征及其随纬度的规律性变化 ,指示海槽区玄武岩的岩浆是由具有 N- MORB源区性质的热区地幔物质由南到北在不同深度经不同程度的部分熔融而形成的。同时 ,由南到北其岩浆源区受到了来自俯冲板块富含水及 L IL 流体的不断加深的交代作用影响。据此 ,推断该海槽的扩张演化可能受控于存在于该区的热区迁移及运动规律
The K-Ar dating and trace element and REE geochemical characteristics of basalt samples collected from the back-arc ridges of the Mariana Trough were studied. Pointed out that the opening of the Mariana Trough and its accompanying basaltic magmatism are still under way and the trough half-expansion rate may be 2.0-2.5 cm / a. At the same time, the age of trough basalts has a gradual new evolution in space from south to north. Geochemical characteristics indicate that the partial melting degree of mantle rocks is the main mechanism controlling the geochemical characteristics of basalts in the trough area. The petrological and trace element geochemical characteristics and their regularity change with latitude indicate that the magma in the basalts in the trough area is composed of the hot-zone mantle material with N-MORB source zone properties varying from south to north at different depths Melted and formed. At the same time, the magmatic source region from south to north is affected by the deepening metasomatism from the subducted plate-rich water and LIL fluid. Based on this, it is inferred that the expansion of the trough may be controlled by the migration and movement of hot zones existing in the area