Electrical anisotropic crust and mantle conductor: a 3-D conductivity model of the Western Junggar, NW China

摘要

The Central Asian Orogenic Belt (CAOB) is the largest orogeny in the world which comprises island arcs,rnseamounts, accretionary wedges, oceanic plateau and, possibly, microcontinents accreted during the closurernof the Paleo-Asian Ocean. The Kazakhstan orocline is the most prominent feature of CAOB, which hasrnbecome the international hot spot in recent years. The western Junggar situated in the southwest of CAOB,rnwhich is also the link part of the Kazakhstan orocline core, has the vast occurrences of granitoids andrnvolcanoes rocks, especially the ophiolitic. Therefore, the western Junggar is regarded as an ideal naturalrnlaboratory to decipher the tectonic evolution and crustal growth of the CAOB.rnDuring summer 2013 we deployed three about 100-km-long profiles, which extend approximately NNW-SSE,rnorthogonal to the Darbut fault belt. The profiles consist of 126 broadband magnetotelluric sounding sites inrntotal, using six GMS07e systems running for at least 20 hours for every setup. On the base of phase tensorsrnand vertical magnetic transfer functions a three dimensional model of the electric conductivity is developedrnand discussed. Highly conductive sediments of the Junggar basin with thickness stair-step changing fromrnwest to east, have a significant impact on the induction arrows and phase tensors. The pattern of the phaserntensors at long periods matches the structure very well.