Detrital Zircon and Geochemical Constraints on the Proto‐Tethys Subduction Polarity and the Independent Precambrian Origin of the South Kunlun Block, Western Kunlun Orogenic Belt

ABSTRACT The Western Kunlun Orogenic Belt (WKOB) records the evolution of the Proto‐Tethys Ocean from Neoproterozoic rifting through Early Palaeozoic subduction to final closure. However, the origin of the South Kunlun Block and the polarity of Proto‐Tethys subduction remain debated. This study presents detrital zircon U–Pb geochronology and whole‐rock geochemistry of metasedimentary and magmatic rocks from the Sailajiazitage Group and Xihexiu Group in the North Kunlun and the Pushou Group in the South Kunlun. Maximum depositional ages (MDAs) of 788 Ma for the Sailajiazitage Group confirm its deposition on the Neoproterozoic Tarim margin. The Xihexiu Group yields MDAs of 422 Ma, and together with active‐margin geochemistry and Tarim‐affinity detrital zircons (peak at ~1405 Ma), identifies this unit as a Silurian‐Devonian forearc‐to‐accretionary wedge formed during northward subduction of the Proto‐Tethys beneath Tarim. The Pushou Group yields MDAs of 409 Ma and exhibits arc‐affinity geochemical signatures with mixed detrital zircon age populations derived from Gondwana‐Tarim detrital components (~760–877 Ma and ~1846 Ma), indicating Devonian forearc deposition during southward Proto‐Tethys subduction beneath the South Kunlun Block. A 905 Ma orthogneiss within the Pushou Group displays a within‐plate granite geochemical signature, recording intraplate magmatism during Rodinia fragmentation. Critically, the absence of ~800 Ma detrital zircons that are characteristic of the Tarim margin demonstrates that the South Kunlun Block is an independent Precambrian microcontinent that rifted from Rodinia concurrently with, but separately from, the Tarim Block at 905 Ma. The South Kunlun is therefore interpreted as a composite arc block, comprising a 905 Ma Precambrian microcontinent core overprinted by Cambrian‐Devonian arc magmatism and accretionary assemblages generated during Proto‐Tethys subduction, prior to its final amalgamation with the Tarim Plate following Proto‐Tethys closure at 409 Ma.