Seismological features of the lithospheric structure in Northeast China and dynamic controls on mineral resources
YANG Bao-jun, LIU Cai, LIU Wan-song, WANG Xi-chen, LIU Guo-xing, LIU Yang, HU Yan-fei (Department of Geophysics, Jilin University, Changchun, 130026, Jilin China)
A model of basic structure of the tectosphere and uniform layer in the study area is preliminarily constructed by using 3D VP (km/s) values with a grid of 1°×1°to the 400 km depth in Northeast China and selecting two representative sections perpendicular to each other and a structure model spectrum to the depth of the transition layer in the study area is depicted by using eight VP value sections along different longitudes and latitudes. Through further integration of the data, a 3D lithospheric structure model is obtained. Layer B″in Northeast China likely consists of three parts, the low-velocity zone in the lower part, alternating medium-velocity and low-velocity zone in the middle-upper part and accelerated velocity zone in the upper part. The lower boundary of layer B″is a stable indicator for distinguishing between B″and B″′. The velocity value of the accelerated zone in layer B″is close to the velocity value in the lower part in layer B′. According to the conventional view, the place near the zone is the position of the basal interface of the lithosphere. From the shape of the top interface, it is inferred that there probably exist loci of discontinuous or abrupt changes in layer B″in Northeast China. The wide boundary form and its change in the upper and middle parts of layer B″may reflect the corrosion and assimilation of Earth's material in the surroundings by the asthenosphere. The upwelling of the asthenospheric material provides the source for solid mineral resources and also accelerates the formation of petroleum resources. The lithospheric structure is the result of dynamic balance reached by crust-mantle interaction, which involves the effect of the asthenosphere on the overlying Earth's material and has a dynamic controlling effect on petroleum and solid mineral resources.