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摘要
Ningwu volcanic basin is an important part of the Middle-Lower Reaches of Yangtze metallogenic belt, which has been famous for porphyry-type iron deposit. To explore and discuss its deep structures and the process of geodynamic, three seismic reflection profiles crossing the Ningwu volcanic basin were completed in a number of key areas in Ningwu volcanic basin. They vary in length, NW01 is about 42km long, NW02 56.3km, NW03 27. 1km. Channel numbers are all 720. Sample interval is 2ms. Time length of record is 16s. Seismic reflection data of 4s are cut out to analysize structure characteristic under Ningwu volcanic basin. According to the interpretation results which, combined with other studies, provide new insight into the varied tectonic, fine structure of the upper crust, spatial distribution patterns of magma and fault systems are revealed. In addition, the lower layered reflectivity characteristics and Moho discontinuity imaged along the seismic profiles reveals that underplating and delamination occurs under the lower lithosphere under the Ningwu volcanic basin during approximately Mesozoic. Reflective upper crust can be related to geological structures at the surface; the thin-skinned tectonics implied has yet to be reconciled with the block tectonics of the crust. The Moho reflection has highly variable characteristics as imaged within transects and among different transects. Crustal and Moho reflectivity is caused by a wide range of features, including fault/shear zones, lithologic contacts, compositional layering. The work not only vertifies previous understandings to the basin, but present new understanding results. (1) NE and SW boundary faults of the basin are discoveried, which are not traditionally so-called Yangtze fault (NW) and Fangshan-Nanling fault (SE), but F1 (NW dipping) and F2 (SE dipping) fault, controlling the volcanic rock distribution of the Ning-Wu volcanic basin. (2) Maanshan-Xuelin fault is a key one which control spatial structure of SW-NE of the basin. The fault all detached toward NE direction so that SW part of the basin is all higher than NE. (3) Spatial form of magma chamber which provide source of heat and magma are illustrated through the three seismic reflection profiles. (4) Spatial distribution characteristics of magma chamber and fault systems, especially buried fault (BCF) which controls magmatic activity of Ningwu volcanic basin, are clearly ascertained. The findings provide evidence for understanding deep structures and metallogenic prediction and dynamic analysis.
- 出版日期2014-4
- 单位中国地质科学院矿产资源研究所
