| Ludong-Wucaiwan area, to the south of Kalamaili suture zone in north Xinjiang, was selected to study in this dissertation. Through geological and geochemical study of volcanic rocks in Batamayineishan Formation, including rock types, lithofacies, elemental and isotopic geochemistry, and the reservoir quality, the author has analysed the tectonic setting at early Carboniferous and the major controlling factors of volcanic reservoirs, and further discussed the mechanism and duration of post-collisional volcanism around Kalamaili suture zone, as well as the controlling on volcanic reservoirs by post-collisional tectono-magmatism.Carboniferous volcanic rocks were widespread and regionally different in Ludong-Wucaiwan area. After the observation of cores and slides, the volcanic rocks were divided into four types:lavas, volcaniclastic rocks, welded pyroclastic rocks, and volcanogenitic sedimentary rocks. The corresponding lithofacies were explosive facies, extrusive facies, transient facies between explosive and extrusive, and volcanogenitic sedimentary facies. Sedimentary tuff, tuffaceous siltstone and pelyte developed at the intervals of eruptions. The volcanic rocks generally evolved from basic to acidic. The volcanism was mainly extrusive eprutions, as well as explosive ones accidently. The explosive centers distributed along the major faults, since the explosive volcaniclastic rocks distributed mostly along them.According to the major elements, the Carboniferous volcanic rocks from Ludong-Wuwaican area had relatively high contents of total alkali, and were mainly belong to calc-alkaline series, while several samples were low-K tholeiitic series, and the acidic rocks were mainly high-K calc-alkaline series. The lavas were mainly intermediate-mafic, with several acidic. The MgO contents were interrelated with those of other major elements in Harker diagrams, indicating the characteristics of fractional crystallization. The Mg# values (38～57) indicated the characteristics of evolved magmas.As to the characteristics of rare Earth elements(REE), the intermediate-mafic samples had relatively high REE contents, and LREEs were relatively enriched in chondrite normalized REE patterns, with slight fractionation of HREEs. LILEs and LREEs of these volcanic samples were enriched while HFSEs and HREEs were relatively depleted in primitive mantle normalized incompatible element diagrams, but the contents of HFSEs were relatively high. These volcanic rocks were from depleted source, since the initial 87Sr/86Sr and 143Nd/144Nd ratios andεNd(t) values were 0.70278～0.70365,0.512517～0.512648 and+5.69～+8.24 respectively.Although the volcanic rocks from Ludong-Wucaiwan area indicated some characteristics of intraplate and island arc magmas, they were produced in post-collisional setting rather than intraplate or island arc, since the geochemical characteristics were identical with those of post-collisional lavas, such as high TiO2, Zr, Nb contents and Zr/Y, Nb/Y ratios.Extensive volcanism developed around Kalamaili suture zone from the middle stage of early Carboniferous to early Permian, and massive volcanic rocks were produced along the suture zone from central Luliang uprise in the west, Ludong-Wucaiwan area in the middle, and Santanghu basin in the east. Previous data from other authors was re-analysed in this dissertation since the previous understandings were confused. In general, these volcanic rocks were all produced in post-collisional period, without any contemporary subduction of oceanic crust.The collision of bilateral landmasses around Kalamaili oceanic basin was soft-collision, and the bilateral landmasses were subsequently untightly connected. Although the lithosphere was finitely thickened, the gravitational unbalance and extensive mantle convection could cause intense crust-manlte interaction and further extensive volcanism along Kalamaili suture zone in post-collisional period. The sources of volcanic rocks were depleted mantle materials and juvenile continental crust. Although mantle convection could be the major mechanism of this volcanism, several other mechanisms such as partial melting of residual oceanic crust, anatexis of thickened lithosphere could also cause post-collisional volcanism in specific regions and times.The bilateral landmasses around Kalamaili suture zone had experienced two extension-compression cycles after the soft-collision, extension (rift) at C13～C21 and compression (uprise) at C21-2, and extension (rift) at C23-P1 and compression (uprise) at P2-P3, indicating the characteristics of continent-continent superposition orogeny after soft-collision, and extensive volcanism developed at extension stage of each cycle. The principal volcanism migrated from west to east, indicating that the Kalamaili suture zone gradually evolved into post-collisional period from west to east, which reflected that the oceanic basin might be closed gradually from west to east. Therefore, Kalamaili suture zone shared the same characteristics with total north Xinjiang as successive, cyclic, periodical and orientational.The oil and gas exploration of Junggar basin has focused on volcanic reservoirs in recent years. The primary pores of Carboniferous volcanic rocks in Ludong-Wucaiwan area, including gas pores and pipes, intra-crystal pores, inter-crystal pores, inter-grain pores, condensational shrinking fissures, were less developed than the secondary pores, which included solution pores and fissures and tectonic fissures, and were more significative to oil and gas reservoirs. The superposition of secondary pores on primary ones significantly improved the reservoir quality of volcanic rocks, and the development of primary and secondary pores and the assemble types of reservoir pore space were regionally different.The reservoir quality of volcanic rocks in Ludong-Wucaiwan area was affected by weathering and leaching, hydrothermal fluids, tectonism and environment of eruption rather than burial and welding, and was closely related to the lithologies and lithofacies. The formation and evolvement of volcanic reservoir space had experienced the following stages:the development of primary pores, the modification by faults, weathering and leaching by uprising, deep-buried hydrothermal activities, the filling of oil and gas. The latter stages could modify the reservoir space produced by the early stages. In general, the more intensive of tectonism and weathering as well as secondary solution, the better reservoir quality of the volcanic rocks. The reservoir quality of Carboniferous volcanic rocks in Ludong-Wucaiwan area were regionally different. Almost all the volcanic rocks with favorable reservoir quality lied in the weathered crust at the top of Carboniferous.In general, the favorable factors controlling volcanic reservoir formation for oil and gas were as follows:close to the depression of hydrocarbon generation from Carboniferous and Permian source rocks, favorable quality of volcanic reservoirs, overlying compact mudstones and silty mudstones, good capping quality of clay deposition at the top of weathered crust and ultra-high pressure of rock stratums, favorable pathway for vertical and lateral migration of oil and gas by faults and unconformities respectively, favorable pointing zones for oil and gas as successive paleo-uprise and positive reversion structures. Besides some inner-volcanic reservoirs, the majority of Carboniferous volcanic reservoirs in Ludong-Wucaiwan area were related to unconformities, and their reservoir formation models were mainly two types, new bed generating and old bed preserving reservoirs, self-generating and self-preserving reservoirs. Oil and gas exploration in recent years revealed plentiful oil and gas resources in post-collisional volcanic rocks around Kalamaili suture zone, and several large oil and gas fields were discovered, such as Shixi oil field, Kelameili gas field and Santanghu oil field. Post-collisional tectono-magmatism of Kalamaili suture zone had controlled the volcanic reservoir formation obviously:underplating of mantle-derived magmas and post-collisional volcanism had promoted the thermal evolution of organic matters; the magmatism and igneous rocks could be directly involved in the generation of hydrocarbons; the distribution of Carboniferous hydrocarbon source rocks was controlled by post-collisional setting and volcanism; compact volcanic rocks and the clay deposition at the top of weathered crust of volcanic rocks could be the favorable capping rocks in the accumulation and reservoir formation processes of oil and gas.The reservoir formation mechanism and exploration techniques of volcanic reservoirs for oil and gas were different from those of regular ones, and it's worthy of strengthening the interrelated research and investment. Therefore, it's urgent to deepen the study on reservoir formation mechanisms and exploration on oil and gas reservoirs in volcanic rocks even the bedrocks, and to enlarge the new fields on volcanic reservoirs for oil and gas exploration. They are favorable to both the understanding of disciplines of accumulation and reservoir formation in volcanic rocks, and the stable increase of oil and gas output.Though the controlling of post-collisional tectono-magmatism on volcanic reservoirs had been analysed in this dissertation taking Kalamaili suture zone as an example, the study on the controlling of tectono-magmatism on volcanic reservoirs were weak, and need to be strengthened in further works.
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