<p>Table S1: Summary of the Middle Triassic unconformities in the North Qiangtang basin. Table S2: Major element compositions of the bauxite from the upper Nayixiong Formation in the Kaixinling area (wt%). Table S3: U-Pb isotopic ratios and ages of the samples from the Nayixiong Formation and Jiapila Formation in the Kaixinling area. Table S4: Compilations of the geochronological data of the closure of the Paleo-Tethys Ocean.</p> <p><br></p>
Detailed high-resolution images of the crust–mantle and lithosphere–asthenosphere boundaries (the Moho and the LAB, respectively) have been well observed by applying an S-receiver function technique to data collected by the Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere During Mountain Building) experiment. The Moho depth variation in the range of ∼50–70 km is in good agreement with that from previous P-receiver function results. The significant variation in the LAB depth indicates that the subducting Indian lithosphere drops northwards from a depth of ∼80 km beneath the Himalayas to ∼130 km just north of the Bangong–Nujiang suture at ∼33.0°N, and undergoes a transition from low angle to flat subduction beneath the Yarlung–Zangbo suture. Our findings provide new seismic constraints on the 3-D subducting configuration of the Indian lithosphere beneath Tibet.
Abstract We present detailed lithospheric images of the NE Tibetan Plateau by applying the depth migration technique to S receiver functions derived from 113 broadband stations. Our migrated images indicate that the lithosphere‐asthenosphere boundary (LAB) lies at depths of 105–120 km beneath the Qilian terrane and reaches depths of 126–140 km below the Alxa and Ordos blocks. The most prominent variation in the LAB depth is the presence of LAB steps of no less than 20 km in the transition zone between the active NE Tibetan Plateau and the surrounding cratonic Alxa and Ordos blocks, which conflicts with the model of southward subduction of the Alxa and Ordos blocks. Furthermore, the marked LAB steps occur at 130 ± 10 km away from the southern surficial boundary faults between the NE Tibetan Plateau and the surrounding tectonic provinces, corresponding to the North Qilian fault and the Liupanshan fault, respectively. Therefore, we propose that these scenarios of LAB can be attributed to the delamination of fragmented mantle lithosphere in the transition zone between the NE Tibetan Plateau and the surrounding Alxa and Ordos blocks, triggered by lateral asthenospheric flow. In addition, our observations of a thin lithosphere with thickness of 107–115 km beneath the Songpan‐Ganzi terrane and the west Qinlin orogen greatly facilitate the process of underlying lateral asthenospheric flow. The isostatic uplift of the plateau caused by the delamination of fragmented mantle lithosphere, together with increased horizontal compressive stress, may have led to the outward growth of the NE Tibetan Plateau.
In our country as the lower frequency of land and shallow water exploration for oil and gas,deep water oil and exploration is playing more important role.Big reservoir body becomes the target of deepwater oil and exploration,because the deepwater oil and exploration has some characteristics,such as greater risks and higher investment.Central canyon,which comes from Yinggehai basin and pass through Qiongdongnan basin and enter into the xisha trough,lies in the deepwater area of Qiongdongnan basin and is mainly formed at 10.5 Ma,5.5 Ma and 4.2 Ma.With an area of more than 50 000 km2,central canyon can be a target of deepwater oil and exploration. In the central canyon,levee-overbank sediments are abundant.Deepwater levee-overbank has received considerable attention in the petroleum industry because of having good reservoirs.In order to conduct the prospect for central canyon,this article has analyzed the shape and control factors of levee-overbank deposited in the central canyon by using 3D seismic profile and RMS attribute.After that,the sediment model is summed up and the foreground of prospect is analyzed.The result has shown below:1.levee-overbank sediments in the central canyon developed at least eight times,and have many micro facies such as crevasse splay,overflow splay and levee.In the cross seismic profiles,levee-overbank sediments represent wedge shape with strong amplitude,intermediate frequency and mid-good continuity,and combining with channel has shown gull-wing shape.In the plane,the overall shape of levee-overbank sediments is elongate and trends roughly parallel to the channel.Its area of single sand body could reach 17 km2. 2.In the central canyon,levee-overbank sediments is mainly controlled by province and ancient physiognomy.The grain size whether sand-rich or mud-rich is mainly decided by province.The position is mainly decided by ancient physiognomy.The pond accommodate space is afforded for levee-overbank to be deposited in the area where has fluctuation variation.On the opposite,in the incline area,there is no accommodation and levee-overbank cannot deposit. 3.Levee-overbank sediments which has many deposition time and large single sand body can be ideal stratigraphic traps and it could accumulate oil and if it cooperate with fault or gas chimney.Levee-overbank sediments have well foreground for prospect.
Abstract We present the results of a seismic wide-angle reflection/refraction profile across the central Qaidam basin, the largest basin within the Qinghai-Tibetan plateau. The 350-km‐long profile extends from the northern margin of the East-Kunlun Shan to the southern margin of the Qilian Shan. The P- and S-wave velocity structure and Poisson's ratio data provide constraints on composition. The crust here consists of a near-surface sedimentary layer and a four-layered crystalline crust having several significant features. (1) The sedimentary fill of the Qaidam basin reaches a maximum thickness of 8 km, and the basin shape mirrors the uplifted Moho. (2) Within the four layers of the crystalline crust, P- (S-) wave velocities increase with depth and fall within the following velocity ranges: 5.9–6.3 km/s (3.45–3.65 km/s), 6.45–6.55 km/s (3.7 km/s), 6.65 km/s (3.8 km/s), and 6.7–6.9 km/s (3.8–3.9 km/s), respectively; (3) low-velocity zones with a 3–5% reduction in seismic velocity are detected in the lower half of the crust beneath the Qaidam basin and its transition to the Qilian Shan. (4) The crystalline crust is thickest beneath the northern margin of the basin towards the Qilian Shan (58–62 km) and thinnest beneath the center of the basin (52 km). Variations in crustal thickness are caused most pronouncedly by thickness variations in the lowermost layer of the crust. (5) Poisson's ratio and P-wave velocity values suggest that the Qaidam crust has an essentially felsic composition with an intermediate layer at its base. Based on the crustal structure reported here, we suggest that late Cenozoic convergence is accommodated by thick-skinned tectonic deformation with thickening involving the entire crust across the Kunlun–Qaidam–Qilian system.
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