西藏改则县冈玛错地区发现榴辉岩

    Discovery of eclogite at Gangmacuo area from Gerze County, Tibet, China

    • 摘要: 青藏高原羌塘中部出露有一条东西长约500km的高压变质带,高压变质带中段片石山地区已有榴辉岩的报道,然而其他地区至今尚没有发现榴辉岩出露。首次在羌塘中部高压变质带西段冈玛错地区发现了典型的榴辉岩,岩石呈透镜状或块状,主要矿物成分为石榴子石、绿辉石、多硅白云母和角闪石。地质温压计估算结果表明,榴辉岩相变质作用发生的温度和压力条件为427~472℃和约2.3GPa。冈玛错榴辉岩是藏北羌塘地区第二例榴辉岩,它的发现进一步证明了该地区板块缝合带的存在,同时也暗示羌塘中部地区可能存在一条榴辉岩带,这对研究特提斯洋的闭合与青藏高原的早期演化具有重要意义。

       

      Abstract: A high pressure metamorphic (HP) belt is exposed from west to east with a length of about 500 km in central Qiangtang, northern Qinghai-Tibet Plateau. Eclogite presence has been reported in Pianshishan area in the middle of the belt. In this paper, we report another eclogite outcrop at Gangmacuo area in the western of this HP belt. The eclogite in Gangmacuo area occurs as lens or blocks and consists of garnet, omphacite, phengite and amphibole. Peak temperature of 427~472℃ and pressure of ~2.3GPa were obtained based on the geothermobarometer. The discovery of Gangmacuo eclogite further supports that a suture zone should exist in this area, which is very important for interpreting the evolution of Qinghai-Tibet Plateau and Tethys Ocean.

       

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