The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tect...The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.展开更多
The Qianjiadian uranium deposit is located in the Kailu Depression of Songliao Basin.It is a large-scale in-situ leachable uranium deposit of sandstone type and provides a typical case of the uranium deposits in the S...The Qianjiadian uranium deposit is located in the Kailu Depression of Songliao Basin.It is a large-scale in-situ leachable uranium deposit of sandstone type and provides a typical case of the uranium deposits in the Songliao Basin.Here we analyze the impact of oil and gas on reduction alteration,and factors including low grade mineralization.The Qianjiadian uranium deposit is characterized as a typical rolltype deposit with interlayers in oxidized zone.The occurrence of reductive low-permeability sandstone in uranium reservoirs controls the morphology of the uranium-rich orebody.We propose a metallogenic model involving multi-stage superposition characterized by“primary sediment enrichment-interlayer oxidation-superimposed transformation”.Our model would be helpful for formulating guidelines in the exploration for sandstone-type uranium deposits in the Songliao Basin.展开更多
基金supported by the National Key Research and Development Project (Grant No. 2017YFC0601405)the National Natural Science Foundation of China (Grant Nos. 41572189 & 41820104004)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB18030604)
文摘The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.
基金Financial support for this study was provided by New Energy Technology Development and Application Research(grant No.2019A-4809(JT)).
文摘The Qianjiadian uranium deposit is located in the Kailu Depression of Songliao Basin.It is a large-scale in-situ leachable uranium deposit of sandstone type and provides a typical case of the uranium deposits in the Songliao Basin.Here we analyze the impact of oil and gas on reduction alteration,and factors including low grade mineralization.The Qianjiadian uranium deposit is characterized as a typical rolltype deposit with interlayers in oxidized zone.The occurrence of reductive low-permeability sandstone in uranium reservoirs controls the morphology of the uranium-rich orebody.We propose a metallogenic model involving multi-stage superposition characterized by“primary sediment enrichment-interlayer oxidation-superimposed transformation”.Our model would be helpful for formulating guidelines in the exploration for sandstone-type uranium deposits in the Songliao Basin.
