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| 冲绳海槽西南部火山岩熔体包裹体的均一温度及对岩浆混合的指示意义 |
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李雪丽1,2,3, 曾志刚1,2,3, 李晓辉1,3,4, 陈祖兴1,3,4, 张玉祥1,3,4, 齐海燕1,2,4
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1.中国科学院海洋研究所, 山东 青岛 266071;2.中国科学院大学, 北京 100049;3.青岛海洋科学与技术试点国家实验室 海洋矿产资源评价与探测技术功能实验室, 山东 青岛 266071;4.中国科学院海洋大科学研究中心, 山东 青岛 266071
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| 摘要: |
| 冲绳海槽西南部流纹岩（R10-H3）和安山岩（R11-H1）中斜长石发育大量玻璃质熔体包裹体，安山岩（R11-H1）斜长石中熔体包裹体的均一温度较高（1 050~1 200℃），而流纹岩（R10-H3）斜长石中熔体包裹体存在两个明显不同的均一温度峰值段（900~1 000℃，1 150~1 200℃），呈“双峰”式均一温度特征。流纹岩（R10-H3）和安山岩（R11-H1）中斜长石熔体包裹体呈现的均一温度特征与该斜长石的环带结构及An值变化特征一致，表明安山岩（R11-H1）中斜长石主要在高温阶段结晶，而流纹岩（R10-H3）中斜长石经历了两个不同的结晶阶段。结合流纹岩（R10-H3）中斜长石存在明显的环带结构及两种差异较大的An值特征，作者认为熔体包裹体的“双峰”式均一温度特征指示该地区发生了不同期次岩浆的混合作用。岩浆携带早期高温阶段结晶（1 150~1 200℃）的高An值偏基性斜长石向上运移，注入浅部较低温岩浆中（900~1 000℃），发生岩浆混合作用，偏基性的斜长石在进入浅部岩浆房后被重新吸收，形成具有较高均一温度熔体包裹体的核部（高An值），然后继续结晶出具有较低均一温度熔体包裹体的边部（低An值），进一步证实冲绳海槽西南部浅部岩浆房内存在着复杂的岩浆混合作用。 |
| 关键词: 斜长石 熔体包裹体 均一温度 岩浆混合 |
| DOI：10.11759/hykx20201125001 |
| 分类号:P736.3 |
| 基金项目:国家自然科学基金（91958213）；全球变化与海气相互作用专项（GASI-GEOGE-02）；中国科学院国际合作局对外合作重点项目（133137KYSB20170003）；大洋“十三五”深海资源潜力评估项目（DY135-G2-1-02）；泰山学者工程专项（ts201511061）；国家重点基础研究发展计划（973计划）项目（2013CB429700） |
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| Homogeneous temperature study of melt inclusions in volcanic rocks from the southwestern Okinawa Trough: Insights into magma mixing processes |
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LI Xue-li1,2,3, ZENG Zhi-gang1,2,3, LI Xiao-hui1,3,4, CHEN Zu-xing1,3,4, ZHANG Yu-xiang1,3,4, QI Hai-yan1,2,4
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1.Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2.University of Chinese Academy of Sciences, Beijing 100049, China;3.Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266071, China;4.Center for Ocean-Mega Science, Chinese Academy of Sciences, Qingdao 266071, China
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| Abstract: |
| A large number of vitreous melt inclusions are developed in plagioclase phenocrysts of rhyolite and andesite from the southwestern Okinawa Trough. The homogeneous temperature of the melt inclusions in plagioclase phenocrysts of andesite is higher (1 050~1 200℃), while that of rhyolite has two distinct peaks (900~1000℃ and 1 150~1 200℃), depicting a "double-peak" homogeneous temperature characteristic. The zonal structure and An value variation characteristics of plagioclase phenocrysts in rhyolite and andesite are consistent with the homogeneous temperature characteristics of the melt inclusions, indicating that plagioclase phenocrysts in andesite mainly crystallize in the high temperature stage, whereas in rhyolite they crystallize in two different stages. Combining the zonal structure of rhyolite plagioclase with the two different An value characteristics, the author believes that the "double-peak" homogeneous temperature characteristics of the melt inclusions indicate that different magmas were mixed in this area. The deeper magma carries the basic plagioclase phenocrysts crystallized in the early high temperature stage (1 150~1 200℃), migrates upwards, and is injected into the shallow lower temperature acidic magma chamber (900~1 000℃). The basic plagioclase phenocrysts are reabsorbed to form the cores (high An) containing higher temperature melt inclusions after entering the acidic magma chamber, then continue crystallizing to grow to form edges (low An) containing lower temperature melt inclusions, signifying that a complex magma mixing process occurs in the shallow magma chamber beneath the southwestern Okinawa Trough. |
| Key words: plagioclase melt inclusion homogeneous temperature magma mixing |