中国科学院青藏高原研究所吴晨及其课题组人员报道了西藏北部二叠纪-三叠纪榴辉岩的发现。2023年6月28日出版的《地质学》杂志发表了这项成果。
锆石 U-Pb 定年和温压法表明，榴辉岩相变质作用在峰值压力约为2.5 GPa 时，发生在约 ca. 262-240 Ma。继承的锆石和地球化学显示，榴辉岩源自上盘大陆原岩，它必须经历俯冲侵蚀才能将原岩镁铁质岩体运送达到榴辉岩形成的条件。东侧的大别榴辉岩经历了类似的历史，课题组人员表明，这两个同期的榴辉岩出露是由上盘俯冲侵蚀和沿同一条3000km长的北倾二叠纪-三叠纪俯冲杂岩深沟埋藏形成。研究结果揭示，由于ca. 260Ma峨眉山地幔柱的撞击，沿俯冲带走向的榴辉岩化的同步性受加速的板块聚合所驱动。
据悉，出露在西藏各地的榴辉岩体记录了青藏高原生长之前俯冲—碰撞事件的历史。解读榴辉岩生成的时空模式，有助于我们了解西藏新生代造山运动的先决条件和更广泛的榴辉岩形成和/或发掘过程。
附：英文原文
Title: Discovery of Permian–Triassic eclogite in northern Tibet establishes coeval subduction erosion along an ~3000-km-long arc
Author: Chen Wu, Andrew V. Zuza, Drew A. Levy, Jie Li, Lin Ding
Issue&Volume: 2023-06-28
Abstract: Eclogite bodies exposed across Tibet record a history of subduction-collision events that preceded growth of the Tibetan Plateau. Deciphering the time-space patterns of eclogite generation improves our knowledge of the preconditions for Cenozoic orogeny in Tibet and broader eclogite formation and/or exhumation processes. Here we report the discovery of Permo-Triassic eclogite in northern Tibet. U-Pb zircon dating and thermobarometry suggest eclogite-facies metamorphism at ca. 262–240 Ma at peak pressures of ～2.5 GPa. Inherited zircons and geochemistry show the eclogite was derived from an upper-plate continental protolith, which must have experienced subduction erosion to transport the protolith mafic bodies to eclogite-forming conditions. The Dabie eclogites to the east experienced a similar history, and we interpret that these two coeval eclogite exposures formed by subduction erosion of the upper plate and deep trench burial along the same ～3000-km-long north-dipping Permo-Triassic subduction complex. We interpret the synchroneity of eclogitization along the strike length of the subduction zone to have been driven by accelerated plate convergence due to ca. 260 Ma Emeishan plume impingement.
DOI: 10.1130/G51223.1
Geology：《地质学》，创刊于1973年。隶属于美国地质学会，最新IF：6.324
官方网址：https://pubs.geoscienceworld.org/geology
投稿链接：https://geology.msubmit.net/cgi-bin/main.plex