The boundary between the Yangtze and Cathaysia blocks, south China, from gravity data
Abstract
The Yangtze and Cathaysian blocks, which are famous tectonic units in south China, are important because they are rich in mineral resources. These two blocks exhibit complicated mineral concentrations and metallogenic mechanisms, both in terms of spatial distributions and formation throughout geological time. The Jianshan—Shaoxing (JS) fault is the main boundary between the Yangtze and Cathaysian blocks. This fault occurs in the northern section of the Qinzhou—Hangzhou (QH) metallogenic belt, which straddles the boundary between the two blocks. The QH belt is an ancient subduction zone with mantle source materials involved in the formation of its ore deposits. Subsequent modification and superimposed mineralization during the Yanshan epoch have resulted in a Proterozoic-Mesozoic bimodal age of porphyry and associated ore deposits in the QH belt. A key to understanding this economically important region is that the location of the JS fault and the relative movement that has occurred across it be accurately defined. In this study, 3D inversions of gravity data from the northern end of the QH belt were performed to help determine the main tectonic structure of the area. The inversion results show that the JS fault begins at Pingxiang, passes through Jiangshan, and ends in Shaoxing. The inversion results, along with geological mapping and two deep seismic and MT profiles that cross the area, also show that the fault extends from the Earth's surface to the Moho, which is at a depth of roughly 40km. Over the Yangtze block to the north of the JS fault, gravity has a high to the north and a low closer to the JS fault. Over the Cathaysian block to the south of the JS fault, gravity is low. This is consistent with abundant basic—ultrabasic magma around 200 250 Ma, which is the result of lithosphere stretching, thinning and mantle upwelling.
Financial supports for this work were provided by China Geological Survey with the project (NO. DD20160082) and China Ministry of Science and Technology with the project (NO. 2016YFC0600201). We would like to thank China Scholarship Council for funding on this research.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.S51C0343L
- Keywords:
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- 0902 Computational methods: seismic;
- EXPLORATION GEOPHYSICSDE: 0925 Magnetic and electrical methods;
- EXPLORATION GEOPHYSICSDE: 7255 Surface waves and free oscillations;
- SEISMOLOGYDE: 7290 Computational seismology;
- SEISMOLOGY