Provenance of the Hangu Formation, Lesser Himalaya, Pakistan: Insight from the detrital zircon U-Pb dating and spinel geochemistry

Abstract

Clastic rich Hangu Formation of the Early Paleocene exposed at the apex of Hazara-Kashmir syntaxis, is significant in providing evidence of the regional Mesozoic–Cenozoic unconformity and nature of detritus supplied. The current study focuses on U-Pb age dating of the detrital zircons along with spinel geochemistry to interpret tectonic implications on provenance. The Hangu Formation is composed of coarse grained sandstone, arenaceous limestone, carbonaceous shale and laterite around the Paras region and rests unconformably over Mesozoic Samana Suk Formation. The probability density plots of the detrital zircons of the Hangu Formation exhibit strong similarity to the Tethyan Himalayan detrital record. The younger Mesozoic detrital zircons exhibit resemblance to Tethyan Himalayan as well as ophiolitic detrital suites, but are very few compared to their coeval Stumpata, Jidula and Denggeng/Sangdanlin formations. The quantitative comparison reflects strong resemblance to the Tethyan Himalaya, whereas, the ophiolitic component relationship is quite poor. Comparison of spinel geochemical data with Northwestern ophiolites (Chilas Ophiolites) and Tethyan Himalaya exhibits mixed source regime of the Hangu sediments. However, the combined U-Pb dating, sandstone petrography and spinel geochemical data suggest that the detritus of the Hangu Formation is mainly derived from the Tethyan Himalayan source (Indian source). The absence of ophiolitic signature in petrography and U-Pb geochronology may suggest that the northern ophiolites were not exposed to provide detritus to the Early Paleocene Hangu Formation. This may also be interpreted that the ophiolites were emplaced during the Late Cretaceous on the northern Indian margin but uplifted and eroded later with the final India–Eurasia collision, which is clearly recorded in various studies all along the Indian margin. This fact also intimates the ophiolite emplacement as a possible cause of the regional Mesozoic–Cenozoic unconformity.