摘要:
根据最新的重磁资料,反演了西湖凹陷北部的基底深度,推断解释了火成岩和断裂构造,结合相关地质和构造方面资料,对西湖凹陷北部基底性质和基底构造特征进行了分析,深化了对西湖凹陷北部基底构造特征的认识。研究认为,区内的断裂构造主要由NE向和NW向两组断裂构成。NE向的断裂主要为年代较老的大断裂,它们在构造上被NW向的断裂错断,并被NW向断层复杂化;西湖凹陷的火成岩比较发育,火成岩主要沿着大的断裂带以及断裂带的两侧分布,形成许多串珠状的火成岩带。岩浆岩的分布受断裂控制明显,尤其是在NE向断裂与NW向断裂交汇处,更是岩浆活动的主要地区;西湖凹陷北部的古新近系基底构造主体走向为NE向,但明显受NW向断裂的改造,形成东西分带、南北分块的构造特征。西湖凹陷基底构造起伏较大,绝大部分的基底深度都在5000m以下,总体上呈南高北低、凸凹相问分布,由东到西分别为保傲斜坡、三潭深凹、浙东中央背斜带、白堤深凹和天屏冲断带5个次级构造单元。
关键词:
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基底构造
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断裂
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火成岩
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重磁
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西湖凹陷
Abstract:
Based on the latest gravity and magnetic data, we inverted basement depth of north Xihu sag,deduced and explained its igneous rock and fault structure. Together with relevant geological and structural data, we also analyzed basement and structural characteristics of north Xihu sag in order to further under-stand basement characteristics of the sag. Study results show that faults in the study area are mainly of two kinds of striking directions:northeast and northwest. Faults with NE striking are regionally much older in ages,and with interveined by NW ones,they look more complicated in shape. Volcanic rocks are developed well in the Xihu sag, anti distributed along the large scale fault belts with a beaming shape in space. The distribution of volcanic rocks is clearly controlled by the faults, especially at the intersection area of the NE-and NW-striking faults. Tertiary basement structures in the north Xihu sag are mainly striking in NE direction, but significantly replaced by the NW striking faults,thus showing "zoning in E-W direction and blocking in S-N direction" macro-scale shaping characteristics. This basement undulated greatly with more than 5 000 m depth below the seafloor, and was generally higher in south than in north. From east to west, there are developed 5 substructrure units in the basement, namely, Baojiao slope, Santan deep-depression,east Zhejiang anticline belt, Baidi depression and Tianping faulting belt.
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