柴达木北缘宗务隆构造带形成及演化过程OA

The Zongwulong tectonic belt constitutes a significant tectonic unit in the northern segment of the North Qaidam margin and underwent pronounced tectonothermal activity during the Mesozoic.However,the genesis and evolutionary history of this belt remain controversial.This study presents field investigations,petrographic analyses,and zircon U-Pb geochronology of the Zongwulong Group,diabase dykes,granitic intrusions,and mylonites from deformation zones in the Ma'ergou area of the eastern Zongwulong belt,aiming to further constrain its formation and tectonic evolution.Detrital zircons from quartz schists within the Zongwulong Group exhibit a unimodal age distribution centered at ca.822 Ma,indicating a relatively homogeneous provenance derived predominantly from the crystalline basement of the North Qaidam margin.Biotite-quartz schists from a ductile shear zone in the southern part of the belt yield a metamorphic or protolith age of ca.440 Ma,suggesting that this region was likely involved in the Early Paleozoic subduction-collision processes along the North Qaidam margin.Granitic intrusions in the southern Zongwulong Mountains yield zircon U-Pb ages clustering around 236 Ma.Additionally,late-stage diabase dykes intruding the Zongwulong Group display a unimodal detrital zircon peak at ca.831 Ma and a youngest concordant zircon age of ca.230 Ma,collectively implying that the basement of the Zongwulong belt shares affinities with that of the North Qaidam margin and experienced magmatic reworking during the Early Mesozoic.These new geochronological data collectively indicate that the Zongwulong tectonic belt likely possesses a basement composition similar to that of the Qaidam block.It was incorporated into the North Qaidam subduction-collision system during the Early Paleozoic,subsequently underwent aborted rifting in the Late Paleozoic,and finally experienced intracontinental orogenesis in the Early Mesozoic following the closure of the failed rift-culminating in the characteristic Mesozoic intracontinental orogenic event observed in the Zongwulong belt.