Geochemical signatures of potassium metasomatism in anthracite from the Himalayan fold‑thrust belts of Sikkim,India
作者机构：Coal Geology and Organic Petrology LaboratoryDepartment of Applied GeologyIndian Institute of Technology(Indian School of Mines)DhanbadJharkhand 826004India Department of Earth SciencesIndian Institute of Technology BombayPowaiMumbaiMaharashtra 400076India
出 版 物：《International Journal of Coal Science & Technology》 (国际煤炭科学技术学报（英文）)
年 卷 期：2022年第9卷第2期
页 面：48-69页
核心收录：
学科分类：0820[工学-石油与天然气工程] 0709[理学-地质学] 0819[工学-矿业工程] 07[理学] 070901[理学-矿物学、岩石学、矿床学]
基 金：the Department of Science and Technology(DST)India for financing the Department of Applied Geology IIT(ISM)Dhanbad India for acquiring modern facilities and instrument setups under the scheme of DST-FIST Level II
主 题：Himalayan fold-thrust belts Anthracite Potassium metasomatism Kaolinite to quartz-feldspar intensity ratio Montmorillonite stretching and bending intensities Illite-stretching frequency
摘 要：The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basins,as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim,India.The SiO_(2)content(48.05 wt%to 65.09 wt%and 35.92 wt%to 50.11 wt%in the bituminous and anthracite samples,respectively)and the ratio of Al_(2)O_(3)/TiO_(2)(6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples)reveal the intermediate igneous source rock composition of the minerals.The ratio of the K_(2)O/Al_(2)O_(3)in the ash yield of the bituminous coal samples(0.03 to 0.09)may suggest the presence of kaolinite mixed with montmorillonite,while its range in the ash yield of the anthracite samples(0.16 to 0.27)may imply the presence of illite mixed with kaolinite.The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions.The plot of the bituminous coal samples in the A–CN–K diagram depicts the traditional weathering trend of parent rocks,but the anthracite samples plot near the illite feld and are a bit ofset from the weathering trend.This may imply the plausible infuences of the potassium-metasomatism at post coalifcation stages,which is further supported by high K_(2)O/Na_(2)O ratio(29.88–80.13).The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the efect of the epigenetic potassium-metasomatism.The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.
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