Two Types of Neoproterozoic Granitoids Reveal the Multi‐Stage Tectonic Evolution of the South Altyn Tagh, Spanning From Rodinia's Disintegration to Palaeozoic Continental Deep Subduction

ABSTRACT The South Altyn Tagh (SAT) is renowned for hosting high‐pressure to ultrahigh‐pressure (HP–UHP) rocks indicative of continental deep subduction. Nevertheless, its geodynamic evolution remains enigmatic due to uncertainty regarding protolith origins and the intricate relationships between HP–UHP rocks and their coeval, unmetamorphosed or low‐grade metamorphic counterparts. This study presents novel LA–ICP–MS zircon U–Pb ages, zircon Lu–Hf isotopic compositions and whole‐rock geochemical analyses of both HP–UHP felsic gneiss and unmetamorphosed to low‐grade metamorphic Neoproterozoic granite samples from the SAT, northwestern China. Our findings indicate that both felsic gneiss and granite samples share protolith ages ranging from 920 to 898 Ma, displaying a high K 2 O content and low CaO and Na 2 O contents, characteristic of S‐type granites. The presence of inherited zircons with ages of 1.79–1.40 Ga, along with ε Hf ( t ) values of –5.32 to +4.03 and T DM2 ages of 2.00–1.54 Ga for ~900 Ma zircons, suggests that both felsic gneisses and granite samples originated from the partial melting of Mesoproterozoic metasedimentary rocks. Zircon grains of felsic gneiss samples exhibit a metamorphic age cluster at 505–498 Ma, consistent with the ~500 Ma continental deep subduction event in the SAT. Conversely, granite samples lack ~500 Ma metamorphic age records; a few granite samples record a younger anatectic age cluster at 455–452 Ma, indicating the influence of a ~450 Ma post‐collisional extension event in the SAT. Integrating petrological and geochemical investigations of both felsic gneisses and Neoproterozoic granite samples in the SAT and adjacent orogens, we propose that: (1) both the felsic gneisses and Neoproterozoic granites in the region formed during the late syn‐collision to extensional collapse of the Rodinia supercontinent, (2) the rifting of Rodinia (860–623 Ma) resulted in the development of the Proto‐Tethys ocean and the isolation of granite plutons along margins of different continental blocks, (3) the early‐Palaeozoic continental collision (~500 Ma) subjected the Neoproterozoic granite in the subduction plate to continental deep subduction and led to the coexistence of HP–UHP felsic gneiss and non‐subducted Neoproterozoic granite in the SAT after the exhumation process. These results demonstrate that HP–UHP felsic gneisses and Neoproterozoic granites preserve a complex tectono‐metamorphic history spanning Rodinia's fragmentation, the Proto‐Tethys ocean's evolution and the Early Palaeozoic orogeny.