Provenance and Tectonic Implications of Early Paleozoic Sedimentary Rocks in the Central Altyn Tagh Terrane, Southeast of the Tarim Craton

Considerable controversy concerns the consumption and closure processes of the North and South Altyn Oceans resulting in the formation of the North Altyn Tagh subduction-accretion belt and the South Altyn Tagh subduction-collision belt in the Altyn Tagh orogen in southeastern Tarim. This study focused on U–Pb ages and Hf isotopes of detrital zircons from early Paleozoic sedimentary rocks in the Central Altyn Tagh terrane. Our dating results revealed that the studied sedimentary rocks were deposited at ca. 467–429 Ma. The predominant early Paleozoic detrital zircons demonstrate negative εHf(t) values, highlighting their derivation from the coeval intermediate-felsic magmatic rocks sourced from ancient supracrustal materials with enriched isotopes. These inferred, enriched intermediate-felsic magmatic rocks were probably generated in different consumption and closure processes of the North and South Altyn Oceans, based on geochronology and geochemistry of the early-middle Paleozoic intermediate-felsic magmatic rocks in the Altyn Tagh orogen. A number of ca. 520–490 Ma detrital zircons were primarily derived from the coeval, enriched intermediate-felsic magmatic rocks in the local Central Altyn Tagh terrane and the adjacent North Altyn Tagh subduction-accretion belt associated with the advancing subduction of the North Altyn Ocean. The ca. 490–470 Ma detrital zircons are most prominent and suggest a derivation from the coeval, enriched magmatic rocks subject to the rollback of the North Altyn Ocean. These inferred magmatic rocks might have once existed in the region but have been intensely exhumed to be source material for the studied sedimentary rocks. A few ca. 450 Ma detrital zircons indicate a provenance from the North Altyn Tagh subduction-accretion belt during collision after the final closure of the North Altyn Ocean. In contrast, some ca. 470–460 Ma detrital zircons were probably derived from the coeval intermediate- to felsic-magmatic rocks in the Central Altyn Tagh terrane during the exhumation stage of the deep continental collision after the final closure of the South Altyn Ocean. Combination of provenance study and magmatic record provides potential to establish complicated orogenic evolution.