In the central Himalaya,the Greater and Lesser Himalayan tectonostratigraphic zones can be distinguished from each other by combining detrital zircon U-Pb ages and whole-rock Nd isotopic data.In the Hazara-Kashmir syn...In the central Himalaya,the Greater and Lesser Himalayan tectonostratigraphic zones can be distinguished from each other by combining detrital zircon U-Pb ages and whole-rock Nd isotopic data.In the Hazara-Kashmir syntaxis of northern Pakistan,rock units in the Kaghan valley have been variously assigned to the Tethyan,Greater,and Lesser Himalayan zones.To determine which tectonostratigraphic zones are represented,we sampled across the Batal thrust in the northern Kaghan valley because this structure is identified in some research as the Main Central thrust.Samples from the footwall yield Paleo-to Mesoproterozoic maximum depositional ages(-1.8-1.1 Ga)and an averageεNd(0)value of-14.3.Samples from the hanging wall yield Neoproterozoic maximum depositional ages(~1000-600 Ma)andεNd(0)values of-17.3.The contrasting detrital zircon ages show that the Batal thrust in the Kaghan valley is a major structural division.However,these data lack the characteristic detrital zircon age spectra andεNd(0)values of Greater and Lesser Himalayan rocks north and south of the Main Central thrust in the central Himalaya,respectively.Therefore,either the Batal thrust is not the Main Central thrust,or the Main Central thrust in the Kaghan valley cuts a different structural level and carries rock units not seen outside the Hazara-Kashmir syntaxis.展开更多
Permian sedimentary successions,widely distributed in the eastern Junggar Basin,may record key details on the closure of the Paleo-Asian Ocean in this region.Results of boreholes show that Permian strata is mainly com...Permian sedimentary successions,widely distributed in the eastern Junggar Basin,may record key details on the closure of the Paleo-Asian Ocean in this region.Results of boreholes show that Permian strata is mainly composed of mudstone,sandy mudstone,siltstone,sandstone,sandy conglomerate,dolomite,and limestone.Detrital zircon U-Pb dating results of three sandstone samples yielded the calculated maximum ages of 296 Ma,278 Ma and 293 Ma,indicating they possibly deposited during the Early Permian.Permian strata in the eastern Junggar Basin show similar rock associations and detrital zircon age data distribution patterns.Our new and compiled age data for sandstone samples in the eastern Junggar Basin and Bogda region yield predominant Paleozoic ages,close to their sedimentary ages.Such detrital zircon age data distribution patterns support the hypothesis that these Early Permian meta-clastic rocks in the eastern Junggar Basin and Bogda region were deposited in a subduction-related basin,and indicate an Early Permian Ocean prevented Precambrian detritus from the Central Tianshan block from depositing in the eastern Junggar Basin and Bogda region.展开更多
Many aspects of the disassembly of Neoproterozoic supercontinent Rodinia remain poorly constrained. Current models for the breakup along western Laurentia (present coordinates) do not fully reconcile stratigraphic obs...Many aspects of the disassembly of Neoproterozoic supercontinent Rodinia remain poorly constrained. Current models for the breakup along western Laurentia (present coordinates) do not fully reconcile stratigraphic observations regarding the timing and mechanisms of continental rifting. Latest Neoproterozoic to Cambrian stratigraphic units exposed along the North American Cordillera from southwestern Canada to the southwestern United States contain Neoproterozoic and Cambrian zircons interpreted to be sourced from rift-related igneous rocks generated during the fragmentation of Rodinia. Two discrete magmatic episodes distinguished by a ca. 50 Myr period of apparent magmatic quiescence are identified using the detrital record: (1) Tonian and Cryogenian to earliest Ediacaran magmatism (mantle plume events followed by rifting);and (2) latest Ediacaran to late Cambrian magmatism. The detrital zircon record of the first episode supports a 660–650 Ma rift-to-drift transition followed by passive margin sedimentation of the upper Windermere Supergroup. After a period of apparent magmatic quiescence from 630–580 Ma, detrital zircon dates of 580–520 Ma from central-western Laurentia provide evidence for renewed rift magmatism preceding the initiation of the lower Paleozoic passive margin. These new U-Pb dates are used to present a refined model of Rodinia disassembly with improved timing constraints suggesting that its final breakup and the Sauk I transgression occurred ca. 520 Ma, in accordance with recent revisions to the timing of the Sauk transgressions in southwestern Laurentia.展开更多
基金This work was made possible by funding support from National Academy of Sciences Prime Cooperative Agreement No.AID-391-A-17-00001 to Dr.RobinsonPakistan-U.S.Science and Technology Cooperation Program Phase-VII No.HEC/R&D/PAK-US/2017/360 to Dr.Faisal+1 种基金Additional funding was provided by Graduate Student Research Grant 13308-21 from the Geological Society of America to Joel SchifferLogistical support in the field was provided by faculty and students at the National Centre of Excellence in Geology,University of Peshawar,Pakistan.Mineral separations,sample preparation,and analytical services were carried out with the help of GeoSep Services,the Arizona LaserChron Center,and students at the RadIs Laboratory,University of Alabama.
文摘In the central Himalaya,the Greater and Lesser Himalayan tectonostratigraphic zones can be distinguished from each other by combining detrital zircon U-Pb ages and whole-rock Nd isotopic data.In the Hazara-Kashmir syntaxis of northern Pakistan,rock units in the Kaghan valley have been variously assigned to the Tethyan,Greater,and Lesser Himalayan zones.To determine which tectonostratigraphic zones are represented,we sampled across the Batal thrust in the northern Kaghan valley because this structure is identified in some research as the Main Central thrust.Samples from the footwall yield Paleo-to Mesoproterozoic maximum depositional ages(-1.8-1.1 Ga)and an averageεNd(0)value of-14.3.Samples from the hanging wall yield Neoproterozoic maximum depositional ages(~1000-600 Ma)andεNd(0)values of-17.3.The contrasting detrital zircon ages show that the Batal thrust in the Kaghan valley is a major structural division.However,these data lack the characteristic detrital zircon age spectra andεNd(0)values of Greater and Lesser Himalayan rocks north and south of the Main Central thrust in the central Himalaya,respectively.Therefore,either the Batal thrust is not the Main Central thrust,or the Main Central thrust in the Kaghan valley cuts a different structural level and carries rock units not seen outside the Hazara-Kashmir syntaxis.
基金supported by China Petroleum&Chemical Corporation Key Scientific and Technological Projects(P22078,P22128,and 22079).
文摘Permian sedimentary successions,widely distributed in the eastern Junggar Basin,may record key details on the closure of the Paleo-Asian Ocean in this region.Results of boreholes show that Permian strata is mainly composed of mudstone,sandy mudstone,siltstone,sandstone,sandy conglomerate,dolomite,and limestone.Detrital zircon U-Pb dating results of three sandstone samples yielded the calculated maximum ages of 296 Ma,278 Ma and 293 Ma,indicating they possibly deposited during the Early Permian.Permian strata in the eastern Junggar Basin show similar rock associations and detrital zircon age data distribution patterns.Our new and compiled age data for sandstone samples in the eastern Junggar Basin and Bogda region yield predominant Paleozoic ages,close to their sedimentary ages.Such detrital zircon age data distribution patterns support the hypothesis that these Early Permian meta-clastic rocks in the eastern Junggar Basin and Bogda region were deposited in a subduction-related basin,and indicate an Early Permian Ocean prevented Precambrian detritus from the Central Tianshan block from depositing in the eastern Junggar Basin and Bogda region.
基金conducted at the Calgary Geo-and Thermochronology Research Group and Laboratory(formerly the Centre for Pure and Applied Tectonics and Thermochronology)at the University of Calgary,a LA-ICP-MS thermochronology , geochronology laboratory funded by the Canadian Foundation for Innovation(CFI project 30696),Samples of the Tapeats Sandstone from the Grand Canyon were collected under Scientific Collection Permit#GRCA-2017-SCI-0024 under Study#GRCA-00578 issued to Dr.Karl Karlstrom.
文摘Many aspects of the disassembly of Neoproterozoic supercontinent Rodinia remain poorly constrained. Current models for the breakup along western Laurentia (present coordinates) do not fully reconcile stratigraphic observations regarding the timing and mechanisms of continental rifting. Latest Neoproterozoic to Cambrian stratigraphic units exposed along the North American Cordillera from southwestern Canada to the southwestern United States contain Neoproterozoic and Cambrian zircons interpreted to be sourced from rift-related igneous rocks generated during the fragmentation of Rodinia. Two discrete magmatic episodes distinguished by a ca. 50 Myr period of apparent magmatic quiescence are identified using the detrital record: (1) Tonian and Cryogenian to earliest Ediacaran magmatism (mantle plume events followed by rifting);and (2) latest Ediacaran to late Cambrian magmatism. The detrital zircon record of the first episode supports a 660–650 Ma rift-to-drift transition followed by passive margin sedimentation of the upper Windermere Supergroup. After a period of apparent magmatic quiescence from 630–580 Ma, detrital zircon dates of 580–520 Ma from central-western Laurentia provide evidence for renewed rift magmatism preceding the initiation of the lower Paleozoic passive margin. These new U-Pb dates are used to present a refined model of Rodinia disassembly with improved timing constraints suggesting that its final breakup and the Sauk I transgression occurred ca. 520 Ma, in accordance with recent revisions to the timing of the Sauk transgressions in southwestern Laurentia.
