Tectono-magmatic evolution of the Ambela granitic complex, Northwest Himalayas, Pakistan: Insights from LA-ICP-MS U–Pb zircon geochronology, Lu–Hf isotope, and trace element geochemistry

• U–Pb zircon ages (282–287 Ma) indicate Ambela Granitic Complex (AGC) emplacement during the Permian Cimmerian orogeny. • Trace element geochemistry of zircons indicates a crustal source with no recycled material. • AGC rocks generated in a within-plate tectonic setting. • Positive εHf(t) values (1.4–13.8) of the dated zircons suggest AGC granitoids generated from juvenile crust derived from a depleted mantle source. Ambela Granitic Complex (AGC) is a dominant alkaline magmatic body exposed in the Peshawar Plain Alkaline Igneous Province of the NW Himalaya. However, its petrogenetic source was not clear till data. This study aims to investigate petrogenetic source and magma origin of AGC using whole-rock geochemistry, zircon U–Pb/Lu–Hf isotope and trace element geochemistry. Oscillatory-zoned zircons in AGC yielded 206 Pb/ 238 U age spanning between 282 and 287 Ma, indicating granite emplacement during Permian. Positive εHf(t) values of + 1.4 to + 13.8 from zircons confirm mantle-derived juvenile material slightly mixed with continental crust.Whole-rock data show the studied rocks are ferroan, high-K calc-alkaline, and A-type granites. Chondrite-normalized REE patterns of zircon, characterized by LREE depletion, positive Ce and negative Eu anomalies, with elevated U/Yb, Sc/Yb and Nb/Yb ratios, indicate crystallization from an evolved, oxidized melt that underwent plagioclase fractionation in an anorogenic within-plate rift related setting. Zircon-saturation (722 to 858 °C) and Ti-in-zircon (692 to 820 °C) thermometry indicate high-temperature magmatism typical of granitic system. The petrogenetic sequence suggests that initial partial melting of lower crustal rocks was triggered by upwelling of the asthenosphere causing doming and crustal thinning, followed by magmatic differentiation that generated AGC rocks. The presence of mafic dykes in AGC, along with Panjal Trap basalts, represents bimodal magmatism, indicative of mantle plume input. The geochemical affinity and temporal overlap of AGC with the coeval widespread Permian magmatic episode in the Himalayan region suggest an intracontinental rifting related to the Cimmerian orogeny in the northern margin of Gondwana.