麻粒岩相金红石微量元素体系

麻粒岩是研究地壳演化最重要的变质岩类，金红石作为麻粒岩中常见的副矿物之一，深入探究其微量元素体系特点，可为大陆地壳演化研究提供新的视角.根据麻粒岩金红石的基础数据（显微结构、微量元素、离子替换方式）以及地壳常见造岩矿物的微量元素特点，初步探讨了麻粒岩变质过程中微量元素行为和扩散效应.麻粒岩金红石Zr含量可记录不同阶段的变质温度，但次生锆石和钛铁矿可对其Zr含量有较大影响，作为孤立体系（不与锆石和石英平衡）的金红石不能用于温度计算；金红石Nb、Ta、Cr和V不仅受全岩成分控制，还与变质过程中黑云母、钛铁矿、蓝晶石等矿物的形成和分解紧密相关；金红石与富Fe矿物之间有强烈的Fe扩散效应.深入理解麻粒岩变质过程中金红石微量元素行为，可为限定大陆地壳变质演化和动力学过程提供重要的矿物学信息. 

Trace Element Systematics of Granulite-Facies Rutile

Granulite is the most important metamorphic rock type for the study of crust evolution. As a common accessary mineral in granulite, rutile provides a new research window for the evolution of the continental crust. Based on fundamental information for granulite-facies rutile (microtextures, trace elements, and cation substitution) and related trace elements in major rock-forming minerals in the crust, this paper discusses the potential trace element behaviors and diffusion effects during granulite-facies metamorphism, which have received much less attention than eclogite ones during the last decades. The Zr contents in granulite-facies rutile may reflect metamorphic temperatures of different metamorphic stages; however, the formation of secondary zircon and/or ilmenite would significantly affect the Zr contents of former rutile via diffusion effects. The isolated rutile that is not equilibrated with zircon and quartz (e.g., rutile boundaries close to the secondary zircon and ilmenite, orientated rutile needles in garnet) cannot be used to calculate temperatures by Zr-in-rutile thermometer. The Nb, Ta, Cr and V contents of granulite-facies rutile are largely influenced by bulk-rock composition and by the formation and breakdown of biotite, ilmenite and kyanite. In addition, the Fe contents of rutile adjacent to garnet may be significantly modified due to the fast diffusion rate of Fe. Understanding the behaviors of rutile trace elements during granulite-facies metamorphism can provide important mineral constraints for the metamorphic evolution and dynamic processes of the continental crust.