| 北祁连清水沟红帘石变硅质岩矿物学、原岩特征及地质意义 |
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| 引用本文： | 郭晶,张建新,李云帅,武亚威,李国倩,周开,郭祺,毛小红.北祁连清水沟红帘石变硅质岩矿物学、原岩特征及地质意义[J].岩石矿物学杂志,2024,43(2):238-249. |
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| 作者姓名： | 郭晶 张建新 李云帅 武亚威 李国倩 周开 郭祺 毛小红 |
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| 作者单位： | 天津商业大学 管理学院, 天津 300134;自然资源部大陆动力学重点实验室, 中国地质科学院 地质研究所, 北京 100037;自然资源部大陆动力学重点实验室, 中国地质科学院 地质研究所, 北京 100037;天津大学 地球系统科学学院, 表层地球系统科学研究院, 天津 300072 |
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| 基金项目： | 国家自然科学基金（U2344214，42072237）；自然资源部大陆动力学重点实验室开放课题基金（J2306） |
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| 摘 要： | 北祁连早古生代大洋俯冲带以发育早古生代的蛇绿（混杂）岩带及高压低温变质带为特征。在清水沟高压低温混杂岩片中出露蛇纹岩以及榴辉岩、蓝片岩、红帘石硅质岩和多硅白云母石英片岩等典型高压低温变质岩石。本文对北祁连清水沟含红帘石的变硅质岩进行了详细的岩相学、矿物化学及地球化学分析， 发现该岩石主要由石英、多硅白云母、红帘石、石榴子石、蓝闪石、单斜辉石以及砷硅锰矿、赤铁矿等矿物组成， 结合矿物化学及围岩变质条件， 推测该岩石可能也经历了高压低温榴辉岩相变质作用。全岩地球化学分析结果表明， 北祁连清水沟含红帘石变硅质岩的原岩为远洋环境沉积的含泥硅质岩， 由于热液活动的参与， 使得Fe、Mn富集沉积， 进而与大陆活动边缘或大陆岛弧物质被卷入到俯冲带中， 共同经历了高压低温变质作用。变硅质岩中红帘石、砷硅锰矿以及石榴子石中大量的赤铁矿包裹体表明该岩石形成于高氧逸度条件， 而石榴子石中的Fe3+从核部到边部的降低趋势， 也表明俯冲变质过程中氧逸度的变化， 这一过程释放的氧所形成的流体对于探究岩石圈地幔氧逸度变化、岛弧岩浆生成以及俯冲带氧循环等方面具有重要的意义。
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| 关 键 词： | 红帘石 富锰变硅质岩 高氧逸度 榴辉岩相变质 北祁连 |
| 收稿时间： | 2023/12/18 0:00:00 |
| 修稿时间： | 2024/1/22 0:00:00 |
Mineralogy, protolith and geological implication of piemontite-bearing metacherts in Qingshuigou, North Qilian |
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| GUO Jing,ZHANG Jian-xin,LI Yun-shuai,WU Ya-wei,LI Guo-qian,ZHOU Kai,GUO Qi,MAO Xiao-hong.Mineralogy, protolith and geological implication of piemontite-bearing metacherts in Qingshuigou, North Qilian[J].Acta Petrologica Et Mineralogica,2024,43(2):238-249. |
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| Authors: | GUO Jing ZHANG Jian-xin LI Yun-shuai WU Ya-wei LI Guo-qian ZHOU Kai GUO Qi MAO Xiao-hong |
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| Institution: | School of Management, Tianjin University of Commerce, Tianjin 300134, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;School of Earth System Science, Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China |
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| Abstract: | The North Qilian is characterized by the early Paleozoic ophiolite and high-pressure/low-temperature metamorphic rocks, such as serpentinite, eclogite, blueschist and metasedimentary rocks. In this study, a detailed petrographic, mineral-chemical, and geochemical analysis is presented on the piemontite-bearing metacherts in Qingshuigou, North Qilian. The piemontite-bearing metacherts are mainly composed of quartz, phengite, piemontite, garnet, glaucophane, clinopyroxene, ardennite, and hematite. Based on the mineral assemblage, mineral chemistry, and the p-T conditions of the country rocks, the piemontite-bearing metacherts may have undergone low-temperature and high-pressure eclogite-facies metamorphism. Whole-rock geochemistry suggested that the protolith of the piemontite-bearing metacherts was argilliferous cherts deposited in the oceanic environment with the participation of hydrothermal activities which resulted in the deposition of Fe and Mn. They were involved in the subduction zone with the materials from the continental active margin or continental island arc, and then experienced low-temperature and high-pressure metamorphism. The piemontite, ardennite, spessartite, and many inclusions of hematite in garnet indicated that the piemontite-bearing metacherts experienced a condition of high oxygen fugacity, which also recorded by the decreases of the Fe3+ from core to rim of the garnet. Oxygen released in this process played a significant role in the exploration of oxygen fugacity in the lithosphere mantle, the generation of island arc magma, and the oxygen cycle in a subduction zone. |
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| Keywords: | piemontite Mn-rich metachert high oxygen fugacity eclogite-facies metamorphism North Qilian |
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