Zhong Q.,The Institute of Geophysical and Geochemical Exploration IGGE |
Zhong Q.,The Geophysical Electromagnetic Detection Technology Key Laboratory of Ministry of Land and Resources |
Fang H.,The Institute of Geophysical and Geochemical Exploration IGGE |
Fang H.,The Geophysical Electromagnetic Detection Technology Key Laboratory of Ministry of Land and Resources |
And 8 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015
The boundary between lithosphere and asthenosphere is called the lithosphere asthenosphere boundary (LAB), which is one of the most important interfaces of earth layer structure. The internal structure of continental lithosphere of China is very complex after a long evolution. Studies on the structure and properties of LAB of the continental lithosphere can provide important information for understanding the structure of lithosphere and crust mantle interaction. According to the upper mantle high conductive layers based on the magnetotelluric sounding results, the spatial distribution of electric lithospheric LAB can be given. However most scholars are concentrated in a certain area by now, there are only few studies on the overall development status and distribution of the high conductive layers in the upper mantle of continental lithosphere of China. According to the magnetotelluric sounding survey results of China before 1994, one of the authors of this paper Li Li had compiled the top surface depth map of high conductive layer in the upper mantle of continental lithosphere of China to analyze the electrical characteristics of the continental lithosphere of China. Based on this work, we add the results of high conductive layers in the upper mantle from 1995 to 2010, including the inversion results of magnetotelluric sounding data from our field works and publications, and the depth in the upper mantle from the heat flow data in the gap zones. For a 1 by 1 degree network, we calculate the average depth of the grid data of all upper mantle high conductive layers, then finish the new top surface depth map of the upper mantle high conductive layers of China. The depth of the upper mantle high conductive layers changes greatly in China, it appears as zones in northern-southern direction, and blocks in eastern-western direction. Overall, in the northern and eastern China the depths of upper mantle high conductive layers are relatively shallow, and in the southern and western China are relatively deep. The shallowest place is located in Songliao basin, about 50~60 km, the deepest place is located at Changsha-Guilin belt, about 230 km, and the average depth of upper mantle high conductive layers is about 100~120 km. According to the distribution of upper mantle high conductive layers, Chinese continent can be divided into 27 uplift units, the top surface depth map of upper mantle high conductive layers reflects the overall characteristics of the lithospheric thickness in Chinese continent. Comparing its distribution and the distribution of metallic ore, oil and gas fields in China, we have found that there are great correlations between the distribution of Mesozoic endogenous metallic ore deposit and the upper mantle high conductive layers uplift and depression pattern in China, about 80% of the metallic ore deposit are located in the upper mantle high conductive layers uplift areas. In eastern China, most of the petroliferous basins are located in the upper mantle high conductive layers areas, and most of the oil and gas field are above the uplift area or on the transitional zones of the edge; In Western China, most of the petroliferous basins are located in the mantle depression areas, the main oil and gas fields are located in the gradient belt of the transition areas; In Central China, only the interior of petroliferous basins are corresponding to the mantle depression areas, oil and gas fields are mainly located in the uplift areas. In general, there are space correlations between the distribution of endogenous metal ore deposit or the distribution of oil and gas fields and the asthenosphere upwelling areas, most of the endogenous metal ore deposits are distributed in the side of the upper mantle uplift area close to the orogenic belt, while most of the oil and gas fields are distributed in the upper mantle uplift near the basin side, formed “metallic ore surrounding petroleum” pattern in the space. The extensional faults generated by the uplift of the upper mantle high conductive layers is the main passageway of earth interior material and energy migrating to the upper crust, not only provided ore-forming materials and energy for the formation of endogenous metal mineral deposit, but also brought the catalyst for hydrocarbon generation, heat, inorganic oil and gas for petroliferous basin. The existence of supercritical fluid in deep earth may play an important role for the formation of upper mantle conductive layers and ore-forming material migration. ©, 2015, Science Press. All right reserved.