Organic geochemical characteristics of coal deposits in Lampang Province

• Main Author: Patthapong Chaiseanwang
• Other Authors: Piyaphong Chenrai
• Format: Theses and Dissertations
• Language: English
• Published: Chulalongkorn University 2019
• Subjects: ถ่านหิน > ไทย > ลำปาง; ธรณีเคมี; Coal > Thailand > Lampang; Geochemistry
• Online Access: https://digiverse.chula.ac.th/Info/item/dc:36493
• Institution: Chulalongkorn University

Thirty-one rocks and coals were collected from Mae Teep and Mae Than coal mines located in Lampang Province, Northern Thailand in order to investigate their geochemical characteristics. The total organic carbon (TOC) contents of Mae Teep coal samples are slightly higher with the range of 30.12 - 73.71 wt. % compared to those from Mae Than samples ranging from 23.48 - 52.20 wt. %. Shales from Mae Teep and Mae Than coal mines exhibit similar values with 4.82 - 19.49 wt. % and 14.00 - 24.87 wt. %, respectively. The lowest TOC contents appear on mudstones, ranging from 0.88 to 4.92 wt. % in Mae Teep coal mine and from 0.59 to 5.98 wt. % in Mae Than coal mine. The extractable organic matter (EOM) from Mae Teep samples vary between 1,277 and 9,764 ppm, while Mae Than samples are higher in the range of 1,256 – 16,421 ppm. The TOC and EOM results indicate coals and shales are good to excellent hydrocarbon generation potential for source rocks, except some mudstone samples. Biomarker and non-biomarker parameters from GC-MS analysis are useful to interpret thermal maturity, organic matter input and depositional environment. The thermal maturity of coal samples from both coal mines are represented in the range of immature to early mature stage at the present day which is equivalent to lignite to high volatile bituminous C based on the American Society for Testing and Materials (ASTM). The distribution of n-alkanes showing the predominance of long-chain n-alkanes and the high CPI values in all samples indicate terrestrial higher plants input. The difference in redox conditions of depositional environments exhibits the different lithology. The coal formation in both basins requires high level of oxygen content, probably related to suboxic to oxic condition during sediment deposits. Local water table within the basins may be controlled the organic matter inputs and coal formation. Shale samples in this study are deposited under anoxic condition during high water level. Consequently, this condition provides algal input originated from blooms of planktonic algae settling to the bottom of the basin where is little to no oxygen content, resulting in the oil shale formation, particularly in Mae Teep basin. During the low productivity, mudstones can be occurred mostly under suboxic condition.