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Geochemistry of the sandstone of Jurassic Loralai Formation, Sulaiman Fold- Thrust Belt, Pakistan: Implications for provenance and source area weathering.

Byline: Razzaq Abdul Manan Durrani, Akhtar Muhammad Kassi, Henrik Friis and Aimal Khan Kasi

The Jurassic Loralai Formation is part of the Sulaiman Fold-Thrust Belt, Pakistan, which is predominantly composed of limestone with minor shale, marl and sandstone. Sandstone succession has been discovered in the Feroz-e-Kan and Ziarat Morh sections, southwest of the town of Muslim Bagh. Geochemical analyses of these sandstones were carried out in order to classify and understand the source area weathering and provenance. Geochemically, the sandstone is classified as litharenite. Compared to the Upper Continental Crust (UCC), the sandstones are depleted in SiO2, and Al2O3, and enriched in K2O and MgO. The Chemical Index of Alteration (CIA) (range: 71.08-83.68) reflects moderate weathering of the source area, and the Chemical Index of Weathering (CIW) (range: 73.87-94.56) indicates high level of weathering. Trace elements analyses indicate depletion of the Large-ion Lithophile elements (LILE), as compared to the UCC.

Enrichment of the Zr in the sandstone samples indicates derivation from the zircon-rich source rocks. The Ferromagnesian Trace Elements (FTE), however, show depletion, which suggest very minor input from the mafic and ultramafic source. Plots of the sandstone samples in the tectonic discrimination diagrams indicate derivation from the passive margin setting having quartzose sedimentary and intermediate igneous provenance. We propose that igneous and metamorphic rocks were the major contributors, which were recycled. Therefore, terrigenous detritus of the sandstone has been derived from the Indian Craton, situated to the east-southeast of the study area of the Sulaiman Fold-Thrust Belt.

Centre of Excellence in Mineralogy, University of Balochistan, Quetta, Pakistan

Department of Geology, University of Balochistan, Quetta, Pakistan

Department of Earth Sciences, Aarhus University, Denmark

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Publication:Journal of Himalayan Earth Sciences
Date:Dec 31, 2012
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