Reports of significant hydrocarbon discoveries and the current tender offering in the Tarim Basin have focused worldwide attention on the basins of the Xinjiang Uygur Autonomous Region. Regional information has been synthesized to analyze and evaluate these complex, multiphase basins. The Tarim, Junggar and Qaidam Basins have unique basin histories, but share common attributes linked to plate convergence and sequential amalgamation onto Eurasia beginning in middle Paleozoic time. Basement rocks surrounding these basins include continental crust, ophiolites, blueschists, arc terranes and metasediments. A general outline of tectonic events is as follows: the Junggar "block" was consolidated out of island arcs, oceanic fragments and accretionary material and was sutured onto the southern margin of Eurasia in the mid-Paleozoic. In contrast, the Tarim plate likely rifted away from a southern hemispheric landmass in the late Precambrian, then traveled northward as a microcontinent, with a thick platformal section. Tarim collided with the Central Tian Shan microcontinental block, in low northern paleolatitudes, during the Late Devonian/Early Carboniferous. This collision is marked by a widespread angular unconformity, by Devonian red beds, and by a Carboniferous flexural foredeep located along the northwestern margin of the Tarim Basin. The resultant Tarim/Central Tian Shan Block later collided diachronously with volcanic arcs in the North Tian Shan/Bogda Shan region in the Late Carboniferous, uplifting a paleo-Tian Shan Range which shed sediments into both the southern Junggar and northern Tarim basins. Meso-Cenozoic collisions added the North China, Qiangtang, South China, Lhasa, and Indian continental blocks. The latter collision and continued convergence drives vigorous uplift of basin-bounding ranges, flexural subsidence of adjacent depocenters and extensive strike-slip deformation. This deformation has resulted in over 20 km vertical structural relief over a distance of only 200 km between the southwest Tarim basin and the adjacent Kunlun Mountains.

Structural features, subsidence histories, and strata of the western China basins demonstrate strong linkages between their tectonic evolution and the timing and distribution of exploration play elements. Episodic block collisions produced regionally variable, repeated, tectonostratigraphic responses in these basins, locally affecting the development or demise of hydrocarbon systems. The collisions can be tied to episodes of both basement-involved and detached contraction, and to the inversion of Precambrian to early Cambrian normal faults. In addition to trap generation, the depositional, burial and diagenetic histories of source, reservoir, and seal units were also affected. For example, the lower Paleozoic section of the northern and central Tarim Basin was repeatedly uplifted, tilted and eroded, as indicated by a series of regional angular unconformities and by reverse faults. The generally low reservoir quality of these carbonate rocks was locally enhanced by collision-related fracturing, and by subaerial leaching or karsting. Rich, thick, Upper Permian, lacustrine source rocks (up to 34% TOC) were deposited and preserved in the Junggar Basin after the Tarim/Tian Shan and Junggar blocks were amalgamated. The paleo-Tian Shan may have enhanced lake formation by providing an orographic effect on local climate, resulting in higher rainfall on the Junggar side. In the Qaidam Basin, Paleozoic strata were deformed during collision along the south margin of Tarim, limiting their potential as reservoirs. Post-Paleozoic, non-marine, organically-rich rocks are found in at least four western China basins. Widespread Jurassic coaly shales may reflect synchronous flexural subsidence responses to regional tectonic events in these basins, all lying within a warm, temperate climate. Repeated Mesozoic and Cenozoic episodes of subsidence and clastic sedimentation, especially along basin margins, provided maturation for Paleozoic/Mesozoic hydrocarbon systems. However, Lower Paleozoic source rocks are presently overmature in the deepest portions of the Tarim Basin.

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