The detrital zircon geochronological record of Permian−Triassic clastic rocks of the Beishan region in the southern Central Asian orogenic belt indicates a pattern of cyclical, successive Paleozoic accretion events. Comparison of zircon age spectra derived from two individual arc terranes reveals similar age patterns offset by 30−40 m.y. Detrital samples with a provenance interpreted as the southern arc terrane indicate magmatic peaks at 275, 370, and 430 Ma with a 50 m.y. hiatus from 350 to 300 Ma. Samples with a provenance interpreted as the northern arc terrane exhibit a similar pattern yet with consistently earlier component peaks at 310, 400, and 445 Ma with a 40 m.y. hiatus from 380 to 340 Ma. This is interpreted to reflect that subduction developed successively between terranes and progressed until Silurian−Devonian sequential docking of the arcs along separate suture zones. Detrital geochronology of accreted sediments (single peak at 445 Ma) within the northern suture, with coincident tuff and pillow basalt U-Pb zircon ages of 409 ± 2.9 and 416.6 ± 15.0 Ma, respectively, may redefine a principal phase of amalgamation as Devonian, over previously interpreted ages in the Carboniferous−Permian. Initiation and cessation of arc magmatism are shown to correlate with regional phases of ophiolite generation and emplacement, respectively. This supports regional models that ophiolite belts in the Central Asian orogenic belt correlate with suture zones developed from multiple contemporaneous subduction systems between arcs. We explore whether a pericratonic archipelago of crustal slivers around the Tarim craton may have initiated successive arc formation.
Successive arc accretion in the southern Central Asian orogenic belt, NW China: Evidence from two Paleozoic arcs with offset magmatic periods
Nathan R. Cleven, Shoufa Lin, Wenjiao Xiao, Donald W. Davis, Bill Davis; Successive arc accretion in the southern Central Asian orogenic belt, NW China: Evidence from two Paleozoic arcs with offset magmatic periods. GSA Bulletin doi: https://doi.org/10.1130/B31434.1
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