青海乌拉斯太地区万宝沟群火山岩地球化学特征及构造环境分析

Analysis on Geochemical Characteristics and Tectonic Environment of Volcanic Rocks of Wanbaogou Group in Wulasitai Area in South of Dongkunlun

摘要:

分布于东昆仑南部乌拉斯太地区的万宝沟群是一套灰绿色变玄武岩夹灰灰白色白云石大理岩的岩石组合，综合室内岩石学、地球化学、同位素年龄研究，将该岩群划为中新元古代万宝沟群。区内万宝沟群出露以基性变火山岩夹大理岩的岩性组合为特征，原岩恢复为火山岩夹碳酸盐岩的沉积建造。其主量元素特征表明万宝沟群火山岩具从洋中脊拉斑玄武岩→岛弧拉斑玄武岩→板内钙碱性玄武岩演化的趋势；稀土元素特征显现出与岛弧拉斑玄武岩略相似；微量元素特征具有板内玄武岩拉斑碱性过渡类型特征，与过渡型拉斑质玄武岩更为接近。万宝沟群变火山岩的成岩环境为洋中脊环境岛弧环境板内环境。

Abstract:

Wanbaogou group in Wulasitai area in south of Dongkunlun is a set of gray green metabasalt clip ash—gray dolomite marble rock combination. Combining with petrology, geochemistry and isotope age study, the rock group is classified into Mesoproterozoic-Neoproterozoic Wanbaogou group. The layers in Wanbaogou group is a combination of basic meta-volcanics with marble lithologic assemblage, and original rock recovery is a sedimentary formation of volcanic rock with carbonate rock. The characteristics of major elements show that the volcanic rocks of Wanbaogou group has the evolution trend of mid ocean ridge tholeiite→ island arc tholeiite →intraplate calc alkaline basalt. Characteristics of rare earth elements are similar to island arc tholeiite slightly. Characteristics of trace elements are intraplate basalt→alkaline transition type. It is closer with transitional tholeiitic basalt. The diagenesis environment of volcanic rocks in Wanbaogou group is mid ocean ridge environment → island arc environment→intraplate environment.