大别—苏鲁超高压榴辉岩中富Si金红石的地球化学意义

发布时间：2018-03-17 18:13

本文选题：金红石　切入点：硅　出处：《地学前缘》2017年03期 　论文类型：期刊论文

【摘要】：本文对大别—苏鲁造山带的超高压榴辉岩中的富Si金红石进行了地球化学研究。通过对双河、东海等地区的金红石进行详细的岩相学以及激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)微量元素分析,结果显示不同地区、不同赋存状态(粒间颗粒和包裹体)的金红石均含有高达400×10~(-6)以上的Si。金红石中富含Si的现象普遍存在于大别—苏鲁不同地区的超高压变质岩中。纳米离子探针(NanoSIMS)面扫描分析显示,金红石中的Si均匀分布于金红石颗粒内部而非包裹体。这与前人报道的金红石中富含Si可能是硅酸盐包裹体所致这一结论不一致。据此,推测金红石中一定量的Si可能是以6次配位的形式存在,替代Ti的位置。这种类质同象置换通常在地壳范围的温、压条件下是不可能完成的,而陆壳物质深俯冲产生的高温、高压环境是Si进于金红石晶格的有利条件。因此,富Si金红石可能发展成为一种新的示踪超高压变质作用矿物学标准。同时,这一研究对揭示地球深部Si的赋存形态和指示陆壳物质俯冲深度具有重要的意义。
[Abstract]:Si-rich rutile in the ultrahigh pressure eclogite of the Dabie Sulu orogenic belt was studied in this paper. Rutile in the East China Sea and other areas were analyzed in detail by lithology and laser denudation inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results show that there are different regions. Rutile with different occurrence states (intergranular particles and inclusions) contains more than 400 脳 10 ~ (-1) Si. The phenomenon of rich in Si in rutile is commonly found in ultrahigh pressure metamorphic rocks in different areas of Dabie-Sulu. NanoSIMS is a nanoscale ion probe. Surface scan analysis shows that, The Si in rutile is uniformly distributed in rutile grains rather than inclusions, which is inconsistent with the conclusion that Si rich in rutile may be caused by silicate inclusions. It is inferred that a certain amount of Si in rutile may exist in the form of six coordination positions to replace the position of Ti. This isomorphous substitution is usually impossible under the conditions of crustal temperature and pressure, while the high temperature produced by deep subduction of continental crust material. High pressure environment is a favorable condition for Si entering rutile lattice. Therefore, Si-rich rutile may become a new mineralogical standard for tracing ultrahigh pressure metamorphism. This study is of great significance to reveal the occurrence of Si in the deep part of the earth and to indicate the depth of subduction of continental crust material.
【作者单位】：中国科学技术大学地球和空间科学学院中国科学院壳幔物质与环境重点实验室;成都理工大学地球化学系;中国科学院广州地球化学研究所中国科学院矿物与成矿重点实验室;
【基金】：国家自然科学基金项目(41273031)
【分类号】：P578.47;P588.3

【相似文献】