Petrography, clay mineralogy and geochemistry of Lower Gondwana sandstones of Western Arunachal Pradesh Himalayas, India

Autor: Ranjan Kr. Sarmah, Hiruj Saikia, Ramesh Laishram, Tapos Kr. Goswami, Mousumi Gogoi, Bashab N. Mahanta, Bhaskar Oza
Rok vydání: 2021
Předmět:
Zdroj: Journal of Sedimentary Environments. 6:561-583
ISSN: 2447-9462
2662-5571
Popis: Extra-Peninsular Gondwana rocks of Arunachal Himalaya are an interbedded sequence between Sub-Himalayan Siwaliks and Lesser Himalayan Bomdila Group of rocks. This unit is restricted to the area between Sikkim and Arunachal Pradesh representing the only extra-peninsular Gondwana basin affected by the Himalayan orogeny and denotes a significantly different tectonic set up than other basins. This work aims to study the petrological and geochemical signatures of these Gondwana rocks and to decipher the provenance, tectonic setting, palaeoclimatic and weathering conditions in the period when these rocks were formed. The clay mineral identification and abundances also were studied based on relative intensities (I/I1) of different clay minerals. Petrologically, and geochemically the sandstones are classified as wacke to arkose type. The tectonic discrimination diagrams indicate that the sediments are derived from craton interior to quartzose recycled orogen terranes with more contribution from low-rank metamorphic rocks. In addition, geochemical characteristics obtained from the tectonic discrimination plots point to a passive margin basin configuration. The dominance of illite and smectites indicate towards a palaeoalkaline environment of deposition for Gondwana sediments. Major oxide study reveals a humid palaeoenvironment and medium to intense chemical weathering of source rocks. The high ratio between Light Rare Earth Elements (LREE) and Heavy Rare Earth Elements (HREE) (average 3.72), (La/Yb)N (average 9.01) and La/Th (average 2.29) values, together with negative Eu anomaly (Eu/Eu* is 0.44–0.90) also indicate a post-Archean granitic source rock for the detritus of Gondwana sandstones.
Databáze: OpenAIRE
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