| 俯冲带深部流体:来自超高压变质锆石晶内结构和包裹物的证据 |
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| 引用本文： | 刘嵘,陈能松,何谋春,肖平.俯冲带深部流体:来自超高压变质锆石晶内结构和包裹物的证据[J].地学前缘,2006,13(2):205-212. |
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| 作者姓名： | 刘嵘 陈能松 何谋春 肖平 |
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| 作者单位： | 1. 中国地质大学(武汉)地球科学学院,湖北,武汉,430074
2. 中国地质大学(武汉)资源学院,湖北,武汉,430074 |
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| 摘 要： | 利用阴极发光和激光拉曼研究了大别山俯冲带超高压基性和长英质变质岩中的锆石。超高压变质增生锆石环带或新生锆石颗粒从不同角度反映了俯冲带地幔深度流体作用信息。其一,在超高压变质锆石生长域中存在微米级流体包裹体。由于其十分细小,组成往往难以测定。但是在变基性岩中检测到富CO2的负晶形包裹体。其二,在超高压锆石生长域中较普遍地发现富含挥发份的多硅白云母和磷灰石包裹体,其与典型的超高压变质矿物———柯石英稳定共生。副矿物研究表明,即使是在新鲜的弱退变质的榴辉岩中,富含挥发份的矿物相———磷灰石仍是含量较高的矿物,说明在俯冲带的深部(>100km),流体仍可以稳定地保存在高挥发份的矿物晶体格架中。其三,超高压变质增生锆石环带的边界呈蚕食状或港湾状,指示流体参与了锆石的变质生长过程,即通过流体与锆石之间的相互作用导致原有锆石的溶解和新生锆石的沉淀结晶。考虑到如此高的锆溶解度,认为在地幔俯冲深度,流体的成分复杂,并不是简单的富水体系,其化学组成与深熔融体相似,且赋存状态应为含水融体相。
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| 关 键 词： | 俯冲作用 变质流体 锆石 形貌学 大别山造山带 |
| 文章编号： | 1005-2321（2006）02-0205-08 |
| 收稿时间： | 2005-12-10 |
| 修稿时间： | 2006-01-04 |
Fluids in deep subduction zone: evidence from internal morphology and inclusions within ultra-high pressure metamorphic zircon domains |
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| LIU Rong,CHEN Neng-song,HE Mou-chun,XIAO Ping.Fluids in deep subduction zone: evidence from internal morphology and inclusions within ultra-high pressure metamorphic zircon domains[J].Earth Science Frontiers,2006,13(2):205-212. |
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| Authors: | LIU Rong CHEN Neng-song HE Mou-chun XIAO Ping |
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| Institution: | 1. Faculty of Earth Science, China University of Geosciences, Wuhan 430074, China; 2. Faculty of Resources, China University of Geosciences , Wuhan 430074, China |
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| Abstract: | Zircons from ultra-high pressure (UHP) metamorphic metabasite and metafelsic rock in Dabie orogen were investigated by cathodoluminescence and Laser Raman spectrometry. Zircon overgrowth domains or neo-crystals under UHP eclogite facies provide evidences for fluid activity in mantle depth subduction zone. Firstly, microscale fluid inclusions are entrapped in UHP zircon domains. It is usually hard to detect fluid composition because of size limitation,but CO_2-rich vapor inclusion is determined in metabasite.Secondly, within ultrahigh-pressure metamorphic domains of zircon the volatile-rich phases of phengite and apatite are found as stable phases coexisting with typical UHP metamorphic coesite. In addition, apatite content is relatively high even in fresh eclogite, suggesting that fluid can be preserved in crystal lattice of volatile-rich minerals even during subduction to a depth greater than 100 km.Thirdly, the interfaces between UHP overgrowth zone domains and the previous zircon cores or succedent rims show irregular gulf-like contours, implying partial dissolution of the precursor and forming of the UHP zircon through dissolution-reprecipitation mechanism. Considering such high zircon solubility, the fluid in mantle depth subduction zone is assumed to be similar to felsic melt, but with more or less water,i.e.,“wet”melt rather than water-rich systems. |
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| Keywords: | subduction metamorphic fluids zircon morphology Dabieshan orogen |
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