http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1100 2025-10-30T07:13:41Z 2025-10-30T07:13:41Z Hauhnar, Malsawmtluangkima http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1103 2025-10-21T09:01:23Z 2018-01-01T00:00:00Z

Title: Petrography of Barail sandstone of ChamphaiMualkawi section in Champhai district, Mizoram: Implication on provenance and tectonic setting Authors: Hauhnar, Malsawmtluangkima Abstract: The area around Champhai district contains exposed Barail Group of rocks (Oligocene) which comprises of buff-coloured sandstones with alternating beds of shale and siltstone. This study focussed on the provenance and tectonic setting of the Barail sandstones with the help of detailed petrographic studies and quantitative and qualitative modal analysis by point counting technique. The general lithological units consist of sandstone, shale, crumpled shale, silty-shale and siltstone. A modal analysis of the 25 sandstone samples was carried out on selected detrital grains like quartz, feldspar and lithic fragments which indicated that quartz ranges between 69.75 to 82.25%, feldspar ranges between 1.80 to 6.91% and lithic fragments ranges between 13.82% to 29.43%. The sandstones belong to sublitharenite, litharenite and feldspathic litharenite indicating predominant presence of quartz in the sandstones with lesser components of feldspar and lithic fragments. Different variants of quartz such as undulatory monocrystalline quartz and polycrystalline quartz and other lithic fragments like schist and gneiss indicate metamorphic source rock. The common occurrence of micas in almost all the sandstone samples may also indicate the common occurrence of mica-bearing metamorphic schists or gneiss in the provenance. Various characteristics of feldspar like strong alteration in orthoclase, deformed twinning of plagioclase and presence of micas may be indicative of low to high grade metamorphic rocks and acidic to basic igneous rocks. On the basis of different tectonic discrimination diagram using QFL and QmFL, the tectono-provenance of the sandstones was found to be Quartzose Recycled Orogen. It is concluded that the source area might be the tectonically active continent-continent collision zone of eastern Himalaya and the Indo-Burmese belt and that the associated extrusive and intrusive igneous rocks are prone to weathering and erosion by various denudation processes.

2018-01-01T00:00:00Z Hauhnar, Malsawmtluangkima http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1102 2025-10-21T08:59:16Z 2020-09-29T00:00:00Z

Title: Geochemistry of Barail sandstone in Champhai, Mizoram: Implications on provenance and weathering history Authors: Hauhnar, Malsawmtluangkima Abstract: Mizoram is geologically young comprising entirely of sedimentary rocks. The Oligocene age of Barail group of sedimentary rocks, exposed near the Indo Myanmar mobile belt, i.e., Champhai area, Mizoram have been studied to infer the provenance and paleoweathering history. The significance of the work is that it will uncover and reconstruct origin of Barail sandstone and restore the tectonic and paleoclimatic conditions based on petrography and geochemistry of the sandstone. The geochemical classiBcation based on diagrams of log(SiO2/Al2O3) vs. log(Na2O/K2O) and log(SiO2/Al2O3) vs. log(Fe2O3/K2O) of the Barail sandstones indicated that the sandstones belong to litharenite and wacke. The geochemical characteristics of the rock are plotted in various binary and ternary diagrams and selected ratios of elements are interpreted in the light of source rock characteristics. The Chondrite normalised REE pattern show similar pattern to UCC (Taylor and McLennan 1985) with an enrichment of LREE and depletion of HREE. The ratio of Al2O3/TiO2 and the ternary diagram of La–Th–Sc indicate felsic to intermediate source. Similarly, the high LREE/HREE ratios and negative Eu anomaly (La/Lu)cn, ratios of Eu/Eu*, La/Sc, La/Co, Cr/Th, Th/Sc, Th/Co and Cr/V ratio indicate felsic source. The binary diagram between ratios of Zr/Sc vs. Th/Sc inferred volcanic source. The sediments are also found to be derived from recycled sedimentary rock which is proved by ratios of Zr/Sc and Th/U. The A–CN–K diagram and weathering indices such as CIA, PIA shows moderate to intense weathering in the source area. The investigated Barail sandstones are chemically mature as indicated by the ICV while the ratio of SiO2/Al2O3 indicated moderate sediment maturity.

2020-09-29T00:00:00Z