Three-dimensional Density Distributions Of The Asian Lithosphere By Using Gravity Data

The continent of Asian formed by a series of plates and blocks converged rapidly in the latePaleozoic(about 200~300Ma).The Indian subcontinent collided with Eurasian continent, whichis causing the crust shorted and uplifted and forming the highest plateau of Qinghai-Tibet,Pamir, and the orogens of Himalayan and Hindu Kush in the late Mesozoic to Paleocene epoch.Asian lithosphere from Indian subcontinent to Tibet, Xinjiang, Mongolia and Baikal regions, isthe most representative place in the world. The research of three-dimensional densitydistributions in Asia including China and its adjacent regions is great significant to realize theinner structure of the earth.The goal of this paper is to construct a three-dimensional (3-D) density model of the Asianlithosphere and relate this model to geologic structure by using gravity data. The study area isAsian region (60°~150°E and 15°~60°N). Firstly, the gravity anomaly, which is caused byMoho discontinuity and sedimentary layer discontinuity, is calculated by Parker formula.Secondly, the gravity anomaly of the spherical harmonics with the 2-40 order for the lowermantle is calculated, which is based on the model of EGM96. Thirdly, The residual gravityanomaly, which eliminated the gravity effect of Moho discontinuity, the sedimentary layerdiscontinuity and the spherical harmonics with the 2-40 order from the Bouguer gravityanomaly, is considered to be caused by density anomaly in lithosphere. Finally, on the basic ofvelocity data, the three-dimensional crustal density distribution of Asian lithosphere isdetermined by using Algebra Reconstruction Techniques(ART)inversion method. Based onthe theoretical studies above, we have a further research about the three-dimensional densitydistribution of the Asian lithosphere with the newly gravity and terrain data in this paper.A series of the discrete density models were set up in order to invert the three-dimensionaldensity distribution of the Asian lithosphere. The partition of the model grid should be inaccord with the velocity model grid.The density anomalies of the lithosphere show that the density distribution of the Asianlithosphere has some connection with the tectonic structure. There is a significant difference indifferent tectonic units. Oceanic plate corresponds to the high-density areas, and continentalplate and island arcs correspond to low density areas, the fault zone are the densityanomaly suddenchange belt. The minimum value of density lies in the North of Philippines, Hainan province and line follows the southeast coast of China , Okinawa Trough and the Eastsea. China -Russia's Siberia region showing the north-east to the ribbon low-density anomalycharacteristics, Qinghai-Tibet Plateau shows low-density anomaly characteristics, HimalayanOrogen show a strong high-density anomaly characteristics.