Triassic Intracontinental Crustal Reworking of the Eastern Tianshan: New Insights From Late Triassic Adakitic and Low‐Sr/Y Granitoids in the Bogda Range

Abstract Continental intraplate magmatism remains a fundamental challenge in Plate Tectonics. Triassic magmatism represents a critical phase in the evolution of the Central Asian Orogenic Belt and continues to provoke debate about its tectonic setting. This study presents an integrated analysis of field, petrographic, geochronologic, geochemical, and isotopic data from two newly identified Triassic granitoids in the Bogda Range: an adakitic porphyry and a low‐Sr/Y granite porphyry. Zircon U‐Pb dating yields nearly coeval crystallization ages of 221–220 Ma and 219–217 Ma, respectively. Both granitoids are characterized by high SiO 2 and K 2 O content, low MgO (Mg # ) and Ni content, and elevated K 2 O/Na 2 O and Th/Nb ratios. They have also depleted whole‐rock Sr‐Nd and zircon Hf isotopic compositions, indicative of juvenile crustal sources. The adakitic porphyry exhibits high Sr/Y and (La/Yb) N ratios, low Rb/Sr ratios, and weak Eu anomalies, suggesting derivation from garnet‐stable mafic lower crust. In contrast, the granite porphyry displays low Sr/Y and (La/Yb) N ratios, consistent with a plagioclase‐stable source. By integrating these results with regional data, we propose that the diversity of Triassic magmatism in the Eastern Tianshan is due to the reworking of juvenile and ancient crust at different depths and temperatures, resulting in arc‐like geochemical signatures. This process was associated with transcurrent tectonics and variable mantle contributions in a continental intraplate setting.