Feldspar Alteration and Diagenetic Characteristics of the Parsora Sandstones, Son Basin, India |
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Authors: | Babar Ali Shah DN Bandyopadhyay |
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Institution: | aDepartment of Geological Sciences, Jadavpur University, Kolkata - 700 032, India |
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Abstract: | Moderate to poorly sorted immature Parsora sandstones rich in K-feldspar show much of the feldspar during early diagenesis transformed to kaolinite after prolonged interaction with acidic pore solutions. The kaolinitic epimatrix formed and was later partially or wholly converted as an orthomatrix producing chert-phyllosilicate assemblage. Ferric oxide, bleached biotite, kaolinite and quartz cement denote an oxy-acidic early diagenetic environment. Late diagenesis involved neoformation of primary or secondary matrix, illitisation of montmorillonite and muscovite authigenesis. The high pressure-temperature regime required for these transitions resulted from tectonic activity during Triassic-Jurassic times. Carbonate-chlorite appeared late in the sediments denoting an alkaline-reducing condition at the late part of the diagenesis. Finally, the secondary porosity developed through carbonate dissolution was later filled up with allochemical ferric iron cement receiving ions from the percolating meteoric water. |
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Keywords: | Parsora sandstone diagenesis kaolinisation pore filling kaolinite neoformation |
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