Deep hot mantle upwelling is widely revealed around the Qiongdongnan Basin on the northwestern South China Sea margin. However, when and how it influenced the hyper-extended basin is unclear.To resolve these issues, a...Deep hot mantle upwelling is widely revealed around the Qiongdongnan Basin on the northwestern South China Sea margin. However, when and how it influenced the hyper-extended basin is unclear.To resolve these issues, a detailed analysis of the Cenozoic time-varying residual subsidence derived by subtracting the predicted subsidence from the backstripped subsidence was performed along a new seismic reflection line in the western Qiongdongnan Basin. For the first time, a method is proposed to calculate the time-varying strain rates constrained by the faults growth rates, on basis of which, the predicted basement subsidence is obtained with a basin-and lithosphere-scale coupled finite extension model, and the backstripped subsidence is accurately recovered with a modified technique of backstripping to eliminate the effects of later episodes of rifting on earlier sediment thickness. Results show no residual subsidence in 45–28.4 Ma. But after 28.4 Ma, negative residual subsidence occurred, reached and remained ca. -1000 m during 23–11.6 Ma, and reduced dramatically after 11.6 Ma. In the syn-rift period(45–23 Ma), the residual subsidence is ca. -1000 m, however in the post-rift period(23–0 Ma),it is positive of ca. 300 to 1300 m increasing southeastwards. These results suggest that the syn-rift subsidence deficit commenced at 28.4 Ma, while the post-rift excess subsidence occurred after 11.6 Ma.Combined with previous studies, it is inferred that the opposite residual subsidence in the syn-and post-rift periods with similar large wavelengths(>10^(2) km) and km-scale amplitudes are the results of transient dynamic topography induced by deep mantle upwelling beneath the central QDNB, which started to influence the basin at ca. 28.4 Ma, continued into the Middle Miocene, and decayed at ca.11.6 Ma. The initial mantle upwelling with significant dynamic uplift had precipitated considerable continental extension and faulting in the Late Oligocene(28.4–23 Ma). After ca. 11.6 Ma, strong mantle upwelling probably occurred beneath the Leizhou–Hainan area to form vast basaltic lava flow.展开更多
The northwestern Sichuan region has experienced multi-stage tectonic evolution including marine cratonic basin from the Sinian to the Middle Triassic and intra-continental basin from the Late Triassic to the Cenozoic....The northwestern Sichuan region has experienced multi-stage tectonic evolution including marine cratonic basin from the Sinian to the Middle Triassic and intra-continental basin from the Late Triassic to the Cenozoic. Several regional tectonic activities caused complicated stratigraphic distribution and structural deformations in the deep-buried layers. During the key tectonic periods, some characteristic sedimentary and deformation structures were formed, including the step-shaped marginal carbonate platform of Dengying Formation, the western paleo-high at the end of Silurian, and the passive continental margin of the Late Paleozoic–Middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the Late Triassic controlled the formation of complex thrusting structures surrounding and inside the northwestern basin. The northern Longmenshan fold-thrust belt has a footwall in-situ thrust structure,which is controlled by two sets of detachments in the Lower Triassic and Lower Cambrian and presents as a multi-level deformation structure with the shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. The thrust belt in front of the Micangshan Mountain shows a double-layer deformation controlled by the Lower Triassic salt detachment, which is composed by the upper monocline and deep-buried imbricate thrust structures. The interior of the basin is characterized by several rows of large-scale basement-involved folds with NEE strike direction. From the perspective of structural geology, the favorable exploration reservoirs and belts in northwestern Sichuan have obvious zoning characteristics. The favorable exploration layers of Dengying Formation of Upper Sinian are mainly distributed in the eastern and northern areas of the northwestern Sichuan Basin, in which the Jiulongshan structural belt, Zitong syncline and Yanting slope are the most favorable. The Lower Paleozoic was transformed by Caledonian paleo-uplift and late Cenozoic folding, and the midwest area such as the Zitong syncline is a potential area for hydrocarbon exploration. The favorable part of the Upper Paleozoic is mainly distributed in the northern Longmenshan belt and its frontal area, where the deep-buried thin-skin thrust structures in the footwall are the key exploration targets.展开更多
油砂是固态或半固态的砂和其岩石中包含油的混和物,是常规油气资源的重要补充(Liu et al.,2019)。准噶尔盆地西北缘是我国油砂资源最为丰富的地区之。目前,准西油砂的勘探程度较低,以往研究局限于单个矿区或单个层位,或延续对深层常规...油砂是固态或半固态的砂和其岩石中包含油的混和物,是常规油气资源的重要补充(Liu et al.,2019)。准噶尔盆地西北缘是我国油砂资源最为丰富的地区之。目前,准西油砂的勘探程度较低,以往研究局限于单个矿区或单个层位,或延续对深层常规油气成因的认识(单玄龙等,2007;万初发等,2019;王启予,2020),尚未对整个西北缘各层系油砂的储层特征和成矿规律进行过系统对比研究(代振龙等,2022;马小平等,2022)。展开更多
基金This research was supported by the Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology(NO.MMRKF201805)by CAS Youth Innovation Promotion Association+5 种基金by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0205)by Guangzhou Municipal Science and technology program(NO.201904010285)by K.C.Wong Education Foundation(NO.GJTD2018-13)by Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources(NO.KLMMR-2018-B-06)by Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences(NO.ISEE2018PY02)by National Natural Science Foundation of China(NO.42076077)。
文摘Deep hot mantle upwelling is widely revealed around the Qiongdongnan Basin on the northwestern South China Sea margin. However, when and how it influenced the hyper-extended basin is unclear.To resolve these issues, a detailed analysis of the Cenozoic time-varying residual subsidence derived by subtracting the predicted subsidence from the backstripped subsidence was performed along a new seismic reflection line in the western Qiongdongnan Basin. For the first time, a method is proposed to calculate the time-varying strain rates constrained by the faults growth rates, on basis of which, the predicted basement subsidence is obtained with a basin-and lithosphere-scale coupled finite extension model, and the backstripped subsidence is accurately recovered with a modified technique of backstripping to eliminate the effects of later episodes of rifting on earlier sediment thickness. Results show no residual subsidence in 45–28.4 Ma. But after 28.4 Ma, negative residual subsidence occurred, reached and remained ca. -1000 m during 23–11.6 Ma, and reduced dramatically after 11.6 Ma. In the syn-rift period(45–23 Ma), the residual subsidence is ca. -1000 m, however in the post-rift period(23–0 Ma),it is positive of ca. 300 to 1300 m increasing southeastwards. These results suggest that the syn-rift subsidence deficit commenced at 28.4 Ma, while the post-rift excess subsidence occurred after 11.6 Ma.Combined with previous studies, it is inferred that the opposite residual subsidence in the syn-and post-rift periods with similar large wavelengths(>10^(2) km) and km-scale amplitudes are the results of transient dynamic topography induced by deep mantle upwelling beneath the central QDNB, which started to influence the basin at ca. 28.4 Ma, continued into the Middle Miocene, and decayed at ca.11.6 Ma. The initial mantle upwelling with significant dynamic uplift had precipitated considerable continental extension and faulting in the Late Oligocene(28.4–23 Ma). After ca. 11.6 Ma, strong mantle upwelling probably occurred beneath the Leizhou–Hainan area to form vast basaltic lava flow.
基金Supported by the China National Science and Technology Major Project(2016ZX05003-001)PetroChina Science and Technology Project(2016E-0601,2016B-0501)
文摘The northwestern Sichuan region has experienced multi-stage tectonic evolution including marine cratonic basin from the Sinian to the Middle Triassic and intra-continental basin from the Late Triassic to the Cenozoic. Several regional tectonic activities caused complicated stratigraphic distribution and structural deformations in the deep-buried layers. During the key tectonic periods, some characteristic sedimentary and deformation structures were formed, including the step-shaped marginal carbonate platform of Dengying Formation, the western paleo-high at the end of Silurian, and the passive continental margin of the Late Paleozoic–Middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the Late Triassic controlled the formation of complex thrusting structures surrounding and inside the northwestern basin. The northern Longmenshan fold-thrust belt has a footwall in-situ thrust structure,which is controlled by two sets of detachments in the Lower Triassic and Lower Cambrian and presents as a multi-level deformation structure with the shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. The thrust belt in front of the Micangshan Mountain shows a double-layer deformation controlled by the Lower Triassic salt detachment, which is composed by the upper monocline and deep-buried imbricate thrust structures. The interior of the basin is characterized by several rows of large-scale basement-involved folds with NEE strike direction. From the perspective of structural geology, the favorable exploration reservoirs and belts in northwestern Sichuan have obvious zoning characteristics. The favorable exploration layers of Dengying Formation of Upper Sinian are mainly distributed in the eastern and northern areas of the northwestern Sichuan Basin, in which the Jiulongshan structural belt, Zitong syncline and Yanting slope are the most favorable. The Lower Paleozoic was transformed by Caledonian paleo-uplift and late Cenozoic folding, and the midwest area such as the Zitong syncline is a potential area for hydrocarbon exploration. The favorable part of the Upper Paleozoic is mainly distributed in the northern Longmenshan belt and its frontal area, where the deep-buried thin-skin thrust structures in the footwall are the key exploration targets.
文摘油砂是固态或半固态的砂和其岩石中包含油的混和物,是常规油气资源的重要补充(Liu et al.,2019)。准噶尔盆地西北缘是我国油砂资源最为丰富的地区之。目前,准西油砂的勘探程度较低,以往研究局限于单个矿区或单个层位,或延续对深层常规油气成因的认识(单玄龙等,2007;万初发等,2019;王启予,2020),尚未对整个西北缘各层系油砂的储层特征和成矿规律进行过系统对比研究(代振龙等,2022;马小平等,2022)。
