Mineral assemblages and tectono‐provenance of the Oligocene Barail sandstones in parts of Naga Hills of theAssam‐ArakanOrogenic Belt, North‐east India

Abstract

Oligocene Barail sandstones in parts of the Naga Hills, west of Kohima town, Nagaland, north-east India have been studied for their provenance and tectonic environments using mineral assemblages and heavy mineral contents. Moderate to well-sorted litharenite to sublith-arenite Barail sandstones are dominated by monocrystalline quartz and are represented by both undulose and non-undulose varieties.Of the two feldspars, plagioclase dominates over K-feldspar. Rock fragments are second in abundance and constituted of chert, siltstones, schist, and volcanic fragments.The heavy mineral assemblage of Barail sandstones is represented by euhedral, subhedral/subrounded, and well-rounded zircon, tourmaline, rutile, staurolite, sillimanite, and kyanite. Opaques are represented by rounded iron oxides. Detailed petrography coupled with heavy mineral assemblage points towards a mixed provenance dominated by a sedimentary source of recycled orogenic provenance in a foreland basinal set-up. Our study further reveals that sediments were mainly supplied from a northeast direction. However, at the higher stratigraphic levels, contributions were also made from the west. In response to changing plate interaction with time, contributions were made from the Indo-Myanmar Ranges, the Shillong Plateau and/or the Karbi-Anglong Massif, and also from the sediments formed under earlier tectonic regimes of the Assam-Arakan Orogenic Belt.

Study on Iron Source and Original Mineral Assemblage of Iron Formation in Paleoproterozoic Wuzhiling Formation in North China

“…Different from the green rust described by predecessors, the size of ' green rust ' in the iron formation samples of the Wuzhiling Formation is about 100μm, which is different from the green rust characteristics observed by predecessors. However, experiments have proved that the hexagonal crystal of green rust will gradually age and become larger over time [18], and the magnetite transformed from green rust is almost equilateral [19], which also excludes the biomineralization of magnetite by magnetotactic bacteria [20]. At the same time, hematite, which can appear in hexagonal form, can easily react with Fe 2+ -containing fluids to form magnetite [21].This process often forms self-faceted magnetite crystals (usually octahedron), so it is difficult to observe hexagonal hematite particles.…”

Depositional Environment and Reservoir Prospect Analysis of Barail Sandstone Exposed in the Northeastern Part of Bangladesh

“…K-feldspar is more prominent than plagioclase feldspar, mostly orthoclase and microcline (Hossain et al, 2010). The sources of sediments are mostly sedimentary and metamorphic rocks exposed to erosion by the orogenic uplift of the Himalayas (Borgohain et al, 2019;Srivastava and Kichu, 2022). A 4-meter thick laterite bed in the upper surface of the Barail Group indicates a major transgressive unconformity surface (Khanam et al, 2021).…”

Introduction, Part 2—Geodynamic evolution of Eastern Himalaya and Indo‐Myanmar orogenic belts: Advances through interdisciplinary studies

“…This Special Issue‐ Part 2 is a continuation of earlier Special Issue‐ Part 1 published in vol. 57 (2), of Geological Journal , which contained 26 research articles (Ao & Satyanarayanan, 2022; Baral et al, 2022; Bhowmik et al, 2022; Bora, Borah, et al, 2022; Bora, Mukherjee, et al, 2022; Deb & Ray, 2022; Devi & Singh, 2022; Devrani et al, 2022; Doley et al, 2022; Gogoi et al, 2022; Gupta et al, 2022; Hazarika & Kayal, 2021; Imtisunep et al, 2022; Liu et al, 2022; Luirei et al, 2022; Lukram & Tandon, 2022; Bidyananda et al, 2022; Majumdar, Gogoi, & Ghatak, 2022; Majumdar, Gogoi, Ghatak, Saikia, et al, 2022; Mukherjee et al, 2022; Pebam et al, 2021; Rashid et al, 2022; Saikia et al, 2022; Singh and Kshetrimayum, 2021; Singh, Guruaribam, Singh et al, 2022; Singh, Singh, Singh, et al, 2022; Srivastava, 2021; Srivastava & Kichu, 2021). Figure 2 displays the area of study of 29 papers included in this Special Issue 2.…”

“…57 (2), of Geological Journal, which contained 26 research articles (Ao & Satyanarayanan, 2022;Baral et al, 2022;Bhowmik et al, 2022;Bora, Mukherjee, et al, 2022;Deb & Ray, 2022;Devrani et al, 2022;Doley et al, 2022;Gogoi et al, 2022;Gupta et al, 2022;Hazarika & Kayal, 2021;Imtisunep et al, 2022;Liu et al, 2022;Luirei et al, 2022;Lukram & Tandon, 2022;Bidyananda et al, 2022;Majumdar, Gogoi, Ghatak, Saikia, et al, 2022;Mukherjee et al, 2022;Pebam et al, 2021;Rashid et al, 2022;Saikia et al, 2022;Singh and Kshetrimayum, 2021; F I G U R E 1 (a) Tectonic map of the peri-Indian region, showing the current plate boundaries and plate distributions, major continental blocks, suture zones, and salient fault systems. (b) Simplified regional geologic map of the Himalayan Orogen, Indo-Myanmar orogenic belt and adjoining areas (modified after Mitchell et al, 2007;Singh, 2013;Yin, 2006) Singh Srivastava, 2021;Srivastava & Kichu, 2021). Figure 2 displays the area of study of 29 papers included in this Special Issue 2.…”