柴北缘早古生代滩间山群火山岩形成的构造环境

Tectonic Environment of the Tanjianshan Group on the Northern Margin of the Qaidam Basin

柴北缘早古生代滩间山群火山岩由下部火山碎屑岩组(Oh1-2)和上部熔岩次火山岩组(Oy3)构成,其成岩背景长期存在争议。火山岩岩石学、岩石化学及地球化学研究结果表明,下部火山岩总体表现出大陆裂谷环境特征,上部火山岩显示出类岛弧环境特征,由下而上显示本区经历了一个由开(裂开)→合(闭合)的过程。结合柴北缘及其邻区构造演化史,认为柴北缘是在早古生代古大陆基础上发生和发展而来的裂谷环境,不同于洋壳俯冲的典型活动陆缘岛弧环境,应是演化阶段更高级和更复杂的微陆块间的"开-合构造"。

The Tanjianshan Group distributed on the northern margin of the Qaidam basin is an important vol- canic-sedimentary formation of the Early Palaeozoic. ingeous petrological, petrochemical, and geochemical research show that the under stratum of Tanjianshan group（ Oh1-2 ） is formed in an intracontinental rift setting,the upper stra- rum （ 0y3 ） has the characteristic of a formation with the island-arc setting, Volcanic facies range from Bimodal vol- canic sequences to cal-alkaline igneous sequences with minor intermediate and oceanic ridges basalt. Conbined with the evolution history of this region, the author considered that the North Qaidam undergone a break-make course during Eopleozoic, So it is different to the marginal island arc environment.