湘东北文家市蛇绿混杂岩带的发现及意义

在湘东北文家市首次识别出蛇绿岩套残片 ,它由变沉积岩、变玄武岩、变辉绿岩、变辉长岩、变辉石岩类及变硅质岩组成。综合其地质学、岩石学、地球化学和同位素年代学的资料 ,提出文家市蛇绿岩可能形成于有限小洋盆的构造环境。文家市蛇绿混杂岩带、前陆盆地、磨拉石建造和“S”型花岗岩等构造岩石组合记录了碰撞造山的全过程 ,证实了江南雪峰古陆属元古宙造山带。这一发现为华南前寒武纪的大地构造格架和地壳演化提供了依据 ,同时该地区也将成为研究早期华南大陆地壳演化———武陵运动的关键地带。

DISCOVERY OF THE WENJIASHI OPHIOLITIC MELANGE BELT IN NORTHEASTERN HUNAN AND ITS IMPLICATIONS

This is the first report on the ophiolite suite, which consists of metasediment, meta-basalt, metadiabase, metagabbro, metapyroxene and metasilicith, in the Wenjiashi area, northeastern Hunan. Based on geology, petrology, geochemistry and isotope chronologic data issued in this work, it is suggested that the Wenjiashi ophiolite be developed under the tectonic setting of a restricted small ocean basin. Tectono-rock assemblages such as ophiolite mélange belt, foreland basin, molasse formation and "S-type" granitoid recorded the whole process of collisional orogenesis of Wuling epoch and confirm that the Jiangnan-Xuefeng Block should belong to Proterozoic orogens. The discovery of the ophiolitic mélange belt in the Wenjiashi area provides information about the Precambrian geotectonic framework and crust evolution of South China, and therefore, this area would become one of key areas to study the early evolution (the Wuling Movement) of South China continental crust.