Geochemical signatures of potassium metasomatism in anthracite from the Himalayan fold-thrust belts of Sikkim,India
Santanu Ghosh1
Anwita Ojha2
Atul Kumar Varma2
1.Coal Geology and Organic Petrology Laboratory,Department of Applied Geology,Indian Institute of Technology(Indian School of Mines),Dhanbad,Jharkhand 826004,India;Department of Earth Sciences,Indian Institute of Technology Bombay,Powai,Mumbai,Maharashtra 400076,India2.Coal Geology and Organic Petrology Laboratory,Department of Applied Geology,Indian Institute of Technology(Indian School of Mines),Dhanbad,Jharkhand 826004,India
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 SiO2 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 Al2O3/TiO2(6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples)reveal the inter-mediate igneous source rock composition of the minerals.The ratio of the K2O/A12O3 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 field and are a bit offset from the weathering trend.This may imply the plausible influences of the potassium-metasomatism at post coalification stages,which is further supported by high K2O/Na2O ratio(29.88-80.13).The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the effect 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.
机标关键词：fromanthracitebeltsfold-thrustgeochemicalhimalayanindiametasomatism
论文发表日期：2022-04-28
在线出版日期：2025-08-15（本平台首次上网日期，不代表文献的发表时间）
页数：22( 48-69 )
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