洛扎县幅地质调查新成果及主要进展  

New results and major progress in regional geological survey of the Lhozag County Sheet

作　　者：钟华明[1] 夏军[1] 童劲松[1] 鲁如魁[1] 李运怀[1] 徐生发[1] 

机构地区：[1]安徽省地质调查院,安徽合肥230001

出　　处：《地质通报》2004年第5期451-457,共7页Geological Bulletin of China

基　　金：中国地质调查局青藏高原1:25万洛扎县幅(H46C004001)地调项目成果。

摘　　要：在拉康组中发现了早白垩世小型特化类型菊石生物群,为确定该组时代和喜马拉雅地层区划提供了依据。分析结果显示,晚侏罗世—早白垩世早期亚(钙)碱性拉斑玄武岩系列火山岩和辉绿玢岩的岩石地球化学特征与大陆边缘裂谷型拉斑玄武岩相似,表明新特提斯洋在晚侏罗世晚期—早白垩世早期处于扩张阶段。初步确定晚白垩世宗卓组与下伏地层为不整合接触关系,为研究特提斯沉积盆地由被动陆缘盆地转变为“远缘前陆盆地”提供了依据,即沉积盆地性质转化的时间代表了新特提斯洋的闭合时代。在洛扎一带分布着以库拉抗日巨大岩基为代表的大量SP花岗岩,这些花岗岩是在喜马拉雅造山后碰撞作用阶段地壳快速隆升和大规模伸展拆离背景下地壳熔融的产物。An Early Cretaceous small specialized ammonite fauna is found in the Lakang Formation, which provides evidence for the determination of the age of this formation and the stratigraphic divisions of the Himalayas. Analysis shows that the geochemical characteristics of volcanic rocks and diabase-porphyrite of the Late Jurassic-early Early Cretaceous subalkaline (calc-alkaline) tholeiites series are similar to those of continental-margin rift-type tholeiites, suggesting that the Neo-Tethys Ocean was in a spreading stage during the late Late Jurassic-early Early Cretaceous. It is preliminarily confirmed that the Late Cretaceous Zongzhuo Formation has an unconformable contact with the underlying strata, which provides evidence for the study of the transformation of the Tethyan sedimentary basin from a passive continental-margin basin to a 'distal foreland basin', i.e. the time of transformation of the nature of the sedimentary basin represents the age of closing of the Neo-Tethys Ocean. Voluminous SP granites represented by the huge Kulakangri batholith are distributed in the vicinity of Lhozag. These granites are the product of melting of the crust in the settings of rapid uplift of the crust and large-scale extension and detachment in the post-collision stage of the Himalayas.

关 键 词：下白垩统拉康组 特提斯生物群 晚侏罗世至早白垩世 裂谷型拉斑玄武岩 角度不整合 盆-山转换 sP花岗岩 造山后碰撞作用 喜马拉雅 

分 类 号：P623.12[天文地球—地质矿产勘探]