Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production

Research Article| November 01, 2010 Detrital zircon provenance from three turbidite depocenters of the Middle–Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production A.L. Weislogel; A.L. Weislogel † 1Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA †E-mail: aweislogel@geo.ua.edu Search for other works by this author on: GSW Google Scholar S.A. Graham; S.A. Graham 1Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA Search for other works by this author on: GSW Google Scholar E.Z. Chang; E.Z. Chang 1Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA §Deceased Search for other works by this author on: GSW Google Scholar J.L. Wooden; J.L. Wooden 2Stanford-U.S. Geological Survey Micro Analysis Center, 367 Panama Street, Room 89, Stanford, California 94025, USA Search for other works by this author on: GSW Google Scholar G.E. Gehrels G.E. Gehrels 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2010) 122 (11-12): 2041–2062. https://doi.org/10.1130/B26606.1 Article history received: 31 Dec 2008 rev-recd: 22 Jul 2009 accepted: 13 Aug 2009 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation A.L. Weislogel, S.A. Graham, E.Z. Chang, J.L. Wooden, G.E. Gehrels; Detrital zircon provenance from three turbidite depocenters of the Middle–Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production. GSA Bulletin 2010;; 122 (11-12): 2041–2062. doi: https://doi.org/10.1130/B26606.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (<0.07) Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south- to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south- to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are inter preted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan shear zone that bounds the Dabie terrane to the north. The central depocenter deposits reflect a later influx of bimodally distributed Precambrian zircon, signifying either a decrease in the influx of Paleozoic zircon grains due to stalled UHP exhumation and/or dilution of the same influx of Paleozoic zircons by spilling of Precambrian zircon from the northeastern depocenter into the central depocenter basin, perhaps due to infilling and bypass of sediment from the northern depocenter or due to initial collapse and constriction of the eastern Songpan-Ganzi complex basin. The southeastern depocenter of the eastern Songpan-Ganzi complex bears significant Paleozoic, Neoproterozoic, and Paleoproterozoic zircon populations derived from the South China block and Yidun arc complex, likely recording nascent uplift of the Longmenshan deformation belt due to impingement of the Yidun arc complex upon the western margin of the South China block. 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