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Was the Pamir salient built along a Late Paleozoic embayment on the southern Asian margin?
Earth and Planetary Science Letters ( IF 5.3 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.epsl.2020.116554 Yi-Peng Li , Alexander C. Robinson , Mustafo Gadoev , Ilhomjon Oimuhammadzoda
Earth and Planetary Science Letters ( IF 5.3 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.epsl.2020.116554 Yi-Peng Li , Alexander C. Robinson , Mustafo Gadoev , Ilhomjon Oimuhammadzoda
Abstract While the northward convex Pamir salient has been interpreted to be a Cenozoic feature, resulting from terranes of the Pamir experiencing ∼300 km of northward translation relative to Tibet and Afghanistan during the India-Asia collision, structural evidence for large magnitudes of translation is generally lacking. We focus on the geology of the Northern Pamir, which forms the outer margin of the salient, to argue that the Pamir salient has not experienced significant northward translation as has been suggested by several recent studies. We then present evidence based on new detrital zircon results that the Pamir salient may be an inherited feature from the Late Paleozoic southern margin of Asia. Kinematic endmember models of northward translation of the Pamir predict either ∼300 km of arc-parallel extension (radial thrusting model) or truncation of geologic terranes at the margins of the salient by strike-slip faults (transfer faulting model). However, both models are inconsistent with the regional geology and structural evolution, which shows minimal extension along outer arc of the Pamir (∼50 km) and no clear truncation or thinning of geologic terranes that make up the Northern Pamir. Regarding the origin of the Pamir salient, a pronounced change in detrital zircon age signature of the Northern Pamir from west to east suggests the regions were not directly connected (i.e. part of a continuous linear belt), and were sourced from distinct cratons. Further, an absence of Triassic arc/forearc flysch deposits and arc plutons along WNW portion of the Northern Pamir suggests the possibility of a transform boundary segment along the Triassic Paleo-Tethys oceanic subduction zone. Based on these observations, we suggest an embayment existed between Tarim and Karakum Cratons after their amalgamation to the southern margin of Asia in the Early Permian. During the Late Triassic, colliding Cimmerian Gondwanan terranes (Central-Southern Pamir) filled in the embayment, resulting in the northward deflection in the trace of the Paleotethyan suture zone and Gondwanan terranes and the current arcuate geometry of the Pamir. Subsequent Cenozoic northward translation of the Pamir is interpreted to be only ∼50 km, no more than ∼80-100 km, and may be coupled with northward translation of northwestern Tibet and northeastern Afghanistan.
更新日期：2020-11-01
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