摘要:
1∶25万玉门镇幅(K47C004001)区域地质调查项目的主要进展如下:敦煌岩群总体为一套孔兹岩系组合,时代厘定为古元古代,从中新解体出了一套浅变质火山岩组合和浅变质细碎屑岩及碳酸盐岩组合,获得了大量微古化石,分别厘定为长城纪铅炉子沟群和蓟县纪平头山组、野马街组.对区内韧性剪切带进行了详细剖析,创新了有限应变测量的技术方法,识别出了敦煌岩群的5次变形事件.通过对昌马洪积扇不同沉积物粒度的统计分析,识别出7次粒度变粗事件,结合大量ESR测年数据,揭示了沉积物粒度突变事件与高原隆升期的必然联系.查明了区内侵入岩的时空分布和演化序列,将侵入岩划分为同源、异源、构造混杂、变质混杂4种类型.
Abstract:
The regional geological survey project of 1∶250 000 Yumenzhen sheet (K47C004001) has got some progress and achievements. In this project,we have found that the Dunhuang Group was mainly composed of a series of Paleoproterozoic khondalite rocks,and a set of epimetamorphic volcanic rocks,epimetamorphic fine clastic rocks and carbonate rocks. Combining with a large number of microfossil evidence,we confirmed that the three rock units were corresponding to the Qianluzigou group of Changcheng period,the Pingtoushan and Yema formation of Jixian,respectively. By using the innovative technology of finite strain measurement,five deformation events in the Dunhuang Group were identified on the basis of a detailed analysis of the ductile shear zone in this region. Through the statistics of the sedimentary grains,seven grain coarsening events in Changma alluvial fan were identified. Combining with a large number of ESR dating data,we suggested that the sediment grain size abrupt event and uplift of the plateau had a positive connection. In addition,we also found out the spatial-temporal distribution and evolution sequence of intrusive rocks in this region,and divided these intrusions into four types: homologous,heterologous,tectonic melange,and metamorphic.
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