羌塘地区榴辉岩中矿物出溶体及其成因机制探讨

西藏羌塘地区榴辉岩石榴子石和磷灰石中均发育矿物出溶体,结合电子探针和扫描电镜分析及能谱分析,确定了石榴子石中的出溶体有金红石、石英和角闪石,指示其可能经历了高压/超高压变质作用。本研究在磷灰石中发现了金红石出溶,并认为其可能是在高压/超高压条件下元素相互置换的结果,置换方式为Ti~(4+)(Fe~(2+)、Si~(4+))=2Ca~(2+),这些出溶体的形成为榴辉岩曾经历高压/超高压变质作用提供了矿物学证据。

Mineral Exsolution and its Genetic Significance of the Songduo-Qiangtang Eclogite in Qinghai-Tibet

Recent studies have shown that garnet and apatite with needle-like exsolution lamellae are widely found in the eclogites from the central Qiangtang metamorphic belt. Needle-like exsolution lamellae of rutile, quartz and amphibole are identified in garnet and apatite by electron microprobe (EPMA), scanning electron microscope (SEM) and X-ray energy-dispersive (EDS) analyses. The garnet may have experienced HP/UHP metamorphism. We find for the first time apatite with exsolution of rutile that may have been formed by the replacement of Ti4+(Fe2+, Si4+)=2Ca2+ under high pressure or ultra-high pressure conditions. These exsolution lamellae in garnet and apatite imply that the Qiangtang eclogite may have experienced HP/UHP metamorphism.