Cenozoic reactivation along the Late Triassic Ganzi-Litang suture, eastern Tibetan Plateau

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 class 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 of 41.5 +/- 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.