Detrital mode and whole-rock geochemistry of the Miocene-Pliocene fluvial succession, Pishin Belt, Pakistan: implication
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ORIGINAL PAPER
Detrital mode and whole-rock geochemistry of the Miocene-Pliocene fluvial succession, Pishin Belt, Pakistan: implications on provenance and source area weathering in peripheral foreland basins Aimal Khan Kasi 1 & Akhtar Muhammad Kassi 2 & Henrik Friis 3 & Muhammad Umar 4 & Mohibullah Mohibullah 2 & Muhammad Ishaq Kakar 1
Received: 17 July 2015 / Accepted: 26 February 2016 # Saudi Society for Geosciences 2016
Abstract Detrital mode and geochemical composition of sandstones and mudstones of the Miocene Dasht Murgha Group (DMG) and Pliocene Malthanai Formation (MF) of the Pishin Belt, northwestern Pakistan, have been examined to identify their provenance and source area weathering. Sandstones of the Dasht Murgha Group and Malthanai Formation are lithic to sublitharenites, rich in quartz, and metamorphic and sedimentary lithic fragments, indicating a recycled orogenic source. LmLvLs plots show that the Dasht Murgha Group is rich in sedimentary and metamorphic lithic fragments (Lm35Lv18Ls47), while samples of the Malthanai Formation are overwhelmingly rich in sedimentary fragments (Lm14Lv10Ls76). Eocene Nisai Formation and Oligocene Khojak Formation within the Pishin Belt were mainly providing the sedimentary/metasedimentary detritus. High content of monocrystalline quartz (DMG 28.21 %; MF 30.7) and higher SiO2/Al2O3 ratios in sandstones (DMG 9.86; MF 11.98) also indicate high maturity of sandstones due to recycling of source terrain in collision orogens. High Cr/Ni
(DMG 5.23; MF 6.17) and moderate Cr/V (DMG 3.96; MF 3.88) ratios suggest significant contributions from mafic and ultramafic detritus derived from Muslim Bagh-Zhob Ophiolite. Malthanai Formation has higher CIA and CIW values (68.96 and 77.53) than Dasht Murgha Group (63.87 and 70.93); however, they both indicate low to moderate weathering intensities. Dasht Murgha Group and Malthanai Formation have higher ICV values which indicate abundance of aluminous silicates, hence, showing moderate weathering of the source area. In A-CN-K diagrams, the samples make linear trend towards illite which suggests that the sediments were derived from a tectonically active source going through non-steady-state weathering, where the detritus has been derived from different zones of weathering profiles. Keywords Detrital modes . Geochemistry . Provenance . Neogene succession . Pishin Belt . Western Pakistan
Introduction Electronic supplementary material The online version of this article (doi:10.1007/s12517-016-2415-9) contains supplementary material, which is available to authorized users. * Henrik Friis [email protected]
1
Centre of Excellence in Mineralogy, University of Balochistan, Quetta, Pakistan
2
Department of Geology, University of Balochistan, Quetta, Pakistan
3
Department of Geoscience, Aarhus University, Aarhus, Denmark
4
Department of Environmental Sciences, COMSATS Institute of Technology, Abbottabad, Pakistan
Peripheral foreland basins (Dickinson, 1974) are large wedgeshaped sedimentary bodies developed on both sides of continent
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