摘要
岛弧从水下生长到水上其沉积环境也发生了演变 ,西藏东部三江地区中段的情况就是如此 ,厚度大于 1 2 1 0 m的上三叠统哇曲组 (T3w)由弧火山岩夹碳酸盐岩与碎屑岩组成 ,沉积相自下而上由海底扇发展到河流相。与此相对应的火山熔岩流形态也发生了变化 ,从下而上由块状向块体或枕状体的变化说明这是渐进的浅水环境。综合火山 -沉积物特征的研究 。
The surroundings are changed with arc growing from below water to above water, and so is the study area. The Upper Triassic Waqu (T 3 w ) consists of volcanic rocks intercalated with minor carbonate and debris rocks. Sedimentary facies developed from marine floor fan to river from bottom to top. A submarine fan consists of all kinds of the rhyolitic pyroclastic rocks formed by turbidity flow, with a complete set of outer, middle and inner fans from bottom to top. Massive rhyolitic megabreccia and brecciola showed below submarine both are debris flow sediments in a slope environment. The observed volcanic exoclastic rocks are normal sedimentary rocks or volcanic terrigenous detrital rocks which originated from weather and denude, and were transported and subsided by river. The well sorted quartz fine siltstones with compositional and textural maturity high formed in a shelf enviroment. At the same time, the shapes of volcanic lava flows also evolved, and differences from below massive to massive of pillow demonstrated a gradient shallow environment. It turns out that precontinental arc rose from below water to land surrounding by analyzing volcano sediments.
出处
《成都理工学院学报》
CSCD
2000年第2期166-171,共6页
Journal of Chengdu University of Technology
关键词
陆缘弧
火山-沉积物
熔岩流形态
沉积环境
古环
precontinental arc
volcano sediment
shape of lava flow
sedimentary environment
