| 冲绳海槽岩浆作用的区域性差异 |
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| 引用本文： | 宗统,翟世奎,于增慧.冲绳海槽岩浆作用的区域性差异[J].地球科学,2016,41(6):1031-1040. |
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| 作者姓名： | 宗统 翟世奎 于增慧 |
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| 作者单位： | 1.中国海洋大学海底科学与探测技术教育部重点实验室，山东青岛 266100 |
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| 基金项目： | 国家重大基础研究发展计划(973计划)项目2013CB29702 |
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| 摘 要： | 冲绳海槽位于西太平洋活动大陆边缘，是一个目前正处于弧后扩张作用早期的、年轻的弧后盆地，张性断裂发育，火山活动强烈.岩石类型分布和岩石地球化学特征表明冲绳海槽中部和南部的岩浆作用存在明显差异，但迄今为止人们对于导致该差异的原因尚不清楚.对已有的冲绳海槽玄武岩的资料进行了综合对比分析，并依据冲绳海槽岩浆岩的Pb同位素组成特征，指出冲绳海槽及其所在的沟弧盆体系之下的地幔属于印度洋型地幔，相对于海槽中部的玄武岩岩浆，海槽南部的玄武岩岩浆来自地幔更高程度的熔融；冲绳海槽玄武岩岩浆受到了俯冲板块物质加入的影响，且南部玄武岩岩浆受影响的程度要高于中部，这可能受控于俯冲板块的深度(南部:100~150 km；中部:约200 km)；冲绳海槽玄武岩部分属于MORB型，这应是冲绳海槽早期扩张的重要特征和证据之一.在上述分析工作的基础上，提出了今后对冲绳海槽岩浆作用的研究应主要集中在以下几个方面:冲绳海槽基底岩石类型的甄别与分布；岩浆源区地幔的类型及特征；板块俯冲对冲绳海槽岩浆作用的贡献及制约机制；冲绳海槽岩浆作用与海底热液活动的内在联系等.
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| 关 键 词： | 冲绳海槽 玄武岩 岩浆作用 板块俯冲 熔融程度 构造地质 |
| 收稿时间： | 2015-11-18 |
Regional Differences of Magmatism in the Okinawa Trough |
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| Abstract: | Okinawa Trough is a young and active back-arc basin located at active continental margin in the western Pacific, which is in the initial stage of spreading and characterized by widespread extensional faults and intense volcanic activities. Distribution and geochemistry of rocks show distinct differences of magmatism in the central and southern Okinawa Trough, but the reason is unclear so far. To explore this issue, we study comprehensively published petrologic and geochemical data, combined with Pb isotopic composition of basalts in Okinawa Trough in this paper. It is found that mantle source beneath Okinawa Trough and the trench-arc-basin system in which the Okinawa Trough is located belongs to Indian Ocean-type mantle, and basalts derived from southern Okinawa Trough are products of higher degree of mantle melting relative to basalts from middle Okinawa Trough. Basalts derived from Okinawa Trough are affected by the subduction component and extent of the effect of subduction component on magma source in the southern Okinawa Trough is higher than that in the middle Okinawa Trough, and the cause may be subducted depth of plate (southern: 100-150 km; middle: about 200 km); only a few basalts are similar to MORB-type, which is considered to be an important characteristic and evidence of spreading in the Okinawa Trough. On the basis of the above analysis, we suggest that the studies of magmatism in the Okinawa Trough shall be focused on the following aspects in the future: identification and distribution of basement rocks, the types and characteristics of magmatic mantle source, the restriction mechanism and contribution of subduction to magmatism, and the internal relation between magmatism and hydrothermal activities. |
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