The spatial-temporal development of Cenozoic reactivation along Mesozoic suture zones in the Tibetan Plateau are first-order parameters needed for assessing models of plateau growth.The Ganzi-Litang suture,in the east...The spatial-temporal development of Cenozoic reactivation along Mesozoic suture zones in the Tibetan Plateau are first-order parameters needed for assessing models of plateau growth.The Ganzi-Litang suture,in the eastern Tibetan Plateau,developed in the Late Triassic because of subduction and closure along the eastern branch of the Paleo-Tethys Ocean.Near the city of Litang,the Ganzi-Litang suture is defined by a melange sequence with faultbound,synorogenic nonmarine strata along the western and eastern flanks,suggesting post-Triassic structural reactivation.We present detrital zircon U-Pb geochronology and field data to determine the timing and style of reactivation along the Ganzi-Litang suture,as well as sedimentary provenance of nonmarine strata.A reverse fault placing melange rock on top of nonmarine strata along the eastern flank of the Ganzi-Litang suture indicates a contractional deformational regime during reactivation.Conglomerate clast counts indicate a local sediment source of recycled Ganzi-Litang suture and Yidun terrane rock.Detrital zircons indicate a localized provenance consisting of recycled material from Triassic Yidun Arc plutons and Triassic Yidun Group turbidite rock.A weighted mean average of Cenozoic zircon grains(n=10) establishes a maximum depositional age of41.5 ± 1.2 Ma for nonmarine strata in the Ganzi-Litang suture.We interpret the maximum depositional age of the nonmarine strata to represent the upper-limit for structural reactivation along the Ganzi-Litang suture while undeformed Neogene strata in the suture zone represent the lower-limit;thereby bracketing structural reactivation from ca.42-25 Ma.Our results provide enhanced spatial-temporal resolution for Cenozoic deformation in the eastern Tibetan Plateau.展开更多
基金supported by U.S.National Science Foundation grants EAR-1119266(Robinson)and EAR-1119219(Weislogel)。
文摘The spatial-temporal development of Cenozoic reactivation along Mesozoic suture zones in the Tibetan Plateau are first-order parameters needed for assessing models of plateau growth.The Ganzi-Litang suture,in the eastern Tibetan Plateau,developed in the Late Triassic because of subduction and closure along the eastern branch of the Paleo-Tethys Ocean.Near the city of Litang,the Ganzi-Litang suture is defined by a melange sequence with faultbound,synorogenic nonmarine strata along the western and eastern flanks,suggesting post-Triassic structural reactivation.We present detrital zircon U-Pb geochronology and field data to determine the timing and style of reactivation along the Ganzi-Litang suture,as well as sedimentary provenance of nonmarine strata.A reverse fault placing melange rock on top of nonmarine strata along the eastern flank of the Ganzi-Litang suture indicates a contractional deformational regime during reactivation.Conglomerate clast counts indicate a local sediment source of recycled Ganzi-Litang suture and Yidun terrane rock.Detrital zircons indicate a localized provenance consisting of recycled material from Triassic Yidun Arc plutons and Triassic Yidun Group turbidite rock.A weighted mean average of Cenozoic zircon grains(n=10) establishes a maximum depositional age of41.5 ± 1.2 Ma for nonmarine strata in the Ganzi-Litang suture.We interpret the maximum depositional age of the nonmarine strata to represent the upper-limit for structural reactivation along the Ganzi-Litang suture while undeformed Neogene strata in the suture zone represent the lower-limit;thereby bracketing structural reactivation from ca.42-25 Ma.Our results provide enhanced spatial-temporal resolution for Cenozoic deformation in the eastern Tibetan Plateau.
