S-N profile of Receive function image across Qiangtang, Northern Tibet

Huge thicken Triassic and Jurassic sediments widely outcorp within Qiangtang, tens of oilstones outcorped within Qiangtang showed that Qiangtang have a good advantage in exploring oil and gas. So, the basement beneath Qiangtang and its structures have become the key for us to look for oil and gas accumulations. Within tectonic settings of Qiangtang, the center uplift of Qiangtang (abbr. CUQT) and its developments have become the great barrier to understand the basement and its structures within the basin. Because of complicated structure relief and blueschist and ophiolite outcorps within the CUQT, there was the paradox for lots of geologist to understand how the CUQT developed. One was that it formed under the extension environment. On the contrary, CUQT was ever paleo-Tethys suture zone, because CUQT had the belt of blueschists and ophiolite. So, different opinions to CUQT resulted in the different viewpoints in the basin beneath Qiangtang terrane. Surveying deep structure beneath the CUQT was the key to understand the basement under Qiangtang. In past two years, we have deployed 40 portable broadband seismic stations along E88°to across the whole Qiangtang from Bangong-Nujiang Suture, southern side of Qiangtang terrane, to northern margin of Qiangtang terrane. The temporary network collected a lot of farm waveform data, which is helpful to know about the more finest deep structure beneath the CUQT and its two sides basin. We used P-to-S receiver functions methods to get deep structure image beneath the profile. The preliminary results showed: (1) Within the crust, the velocity structure beneath southern Qiangtang basin is higher than beneath northern Qiangtang basin. (2) Sedimental layer within southern Qiangtang basin is thichen than within northern Qiangtang basin. Combined with other geophysical information, CUQT is an important lithosphere-level boundary fault belts, and southern Qiangtang basin have great difference with northern Qiangtang basin, in velocity structure, basement depth, although during Qiangtang terrane had been strongly reconstructed laterly, especiall in Cenozoic uplift of the Tibetan plateau. The above-mentioned evidences showed that Qiangtang terrance in present-day tectonic study should be divided by CUQT into two parts which includes south Qiangtang terrane in sourthern side and north Qiangtang terrrane in northern side. Because CUQT and Qiangtang terrane were traditionally named, tectonic settings within the Tibetan plateau had to be remarked renewedly . This project was financially supported together by Natural Science Foundations of China (40774051, 40974060), the basic outlay of scientific research work from Ministry of Science and Technology, China in 2009 ( J0915 ), China National Probing Project (SinoProbe-02).