| LI Xiaohui,ZENG Zhigang,CHEN Shuai,MA Yao,YANG Huixin,ZHANG Yuxiang. 2018. Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge, the middle Okinawa Trough: implications for petrogenesis and a mantle source. Acta Oceanologica Sinica, 37(1):73－88 |
| Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge, the middle Okinawa Trough: implications for petrogenesis and a mantle source |
| 冲绳海槽中部伊平屋脊火山岩地球化学和Sr-Nd-Pb同位素组成：对岩石成因和地幔源区的指示 |
| Received:June 19, 2017 |
| DOI：10.1007/s13131-017-1118-8 |
| Key words:basic to intermediate-acid rocks fractional crystallization subduction sediment components Iheya Ridge Okinawa Trough |
| 中文关键词: 基性到中酸性岩 分离结晶 俯冲沉积组分 伊平屋脊 冲绳海槽 |
| 基金项目: |
| Author Name | Affiliation | E-mail | | LI Xiaohui | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | ZENG Zhigang | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China | zgzeng@ms.qdio.ac.cn | | CHEN Shuai | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | | | MA Yao | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | | | YANG Huixin | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | | | ZHANG Yuxiang | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
University of Chinese Academy of Sciences, Beijing 100049, China | |
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| Abstract: |
| As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-Nd-Pb isotopic composition data are presented for volcanic rocks from the Iheya Ridge (IR), the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in 87Sr/86Sr (0.703 862-0.704 884), 144Nd/143Nd (0.512 763-0.512 880) and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle (DM) but extends to the enriched mantle (EMII), indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%-2.0% subduction sediment components and 98.0%-99.2% mantle-derived melts. |
| 中文摘要: |
| 作为活动的弧后盆地，冲绳海槽位于中国东海的最南端并受到菲律宾板块俯冲的强烈影响。我们报道了冲绳海槽中部伊平屋脊火山岩的主量元素、微量元素和Sr-Nd-Pb同位素数据。伊平屋脊火山岩的主量元素变化范围大且呈现出玄武岩到流纹岩的岩石变化序列。相似的微量元素分配模式和相近的87Sr/86Sr (0.703862-0.704884), 144Nd/143Nd (0.512763-0.51288)及Pb同位素比值表明伊平屋脊岩石具有近似相同的地幔源区。橄榄石、单斜辉石、斜长石、角闪石以及副矿物的分离结晶可以合理的解释伊平屋脊岩石的成分变化。模拟显示演化的玄武质岩浆分别发生60%和75%左右的分离结晶将会产生与该区域中性岩和酸性岩类似的微量元素组成。Sr-Nd-Pb同位素显示伊平屋脊岩石源区接近亏损地幔（DM）并向富集地幔（EMII）延伸，说明源区可能存在DM和EMII的混合。模拟计算表明伊平屋脊火山岩源区可能是由0.8-2%的俯冲沉积组分和98-99.2%的地幔来源物质组成。 |
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