塔里木盆地北部坳陷震旦纪—奥陶纪大陆裂谷性质及其演化

THE CHARACTERISTICS AND EVOLUTION OF SINIAN-ORDOVICIAN CONTINENTAL RIFT IN THE NORTHERN TROUGH OF TARIM BASIN

塔里木盆地北部坳陷是在前震旦纪结晶基底之上发育起来的大陆裂谷盆地 ,始于早震旦世 ,结束于晚奥陶世。裂谷的轴部自西向东由阿瓦提凹陷、满加尔凹陷、英吉苏凹陷 (包括库鲁克塔格南区 )组成 ,向东延伸到罗布泊以东地区。裂谷轴部与地幔隆起带和高磁异常带相对应。裂谷东部主要以半深海 -深海相的浊积岩、放射虫硅质岩和笔石页岩为特征 ,裂谷西部和翼部则以浅水盆地相和台地相的碳酸盐为特征。裂谷早期的火山岩主要分布于中东部的切谷内 ,具有双峰式火山岩的特征 ,玄武岩属低硅高钛富碱型。据区域动力学背景、沉积特征、沉降速率 ,将裂谷演化划分为幼年期 ,成年期和衰亡期

The northern trough of Tarim basin is a continental rift zone that was devoloped on the presinian crystalline basemet. It begen at the early Sinian period and ended at the late Ordovician period The axial part of the trough is composed of Awati subsidence,Manjiaer subsidence,Yingjisu subsidence and the east subsidence of Luobupo from the west to the east The axial part of the rift zone correspond with the mantal uplift zone and the zone of highmagnetic anomaly. The turbidite,radiolarite and graptolite that formed from half-deep-sea to deep sea facies are developed widely in the east of the rift zone. In the west part of the rift zone,it is characterized by carbonate deposit of plateform facies in shallow sea Volcanic rocks at the early period in the rift zone are mainly distributed in the east part and characterized by bimodal valcanic rocks Basalt is belong to the type with lower silicium,higher titanium and alkali According to the regional dynamic setting,the characteristics of sedimentury and the variation of subsidence rate,the evolution of the rift was divided into the three stages: the younth, the mature and the extinction