{"title":"Effects of thermal intrusion on biomarker distributions in the Alum Shale from south-central Sweden","authors":"","doi":"10.1016/j.coal.2024.104643","DOIUrl":null,"url":null,"abstract":"<div><div>The middle (Miaolingian) to upper (Furongian) Cambrian Alum Shale Formation in the DBH15/73 core from south-central Sweden was exposed to local heat from a diabase intrusion, providing an opportunity to investigate the molecular geochemical response to thermal stress. Organic petrological observations and biomarker analyses were conducted to study changes in maturity-indicating parameters and the distribution of high molecular weight polycyclic aromatic hydrocarbons (PAHs) during the maturation process. The DBH15/73 samples exhibit a maturity gradient, ranging from immature at the base to mature in the upper part of the Alum Shale Formation. Multiple maturity-based biomarker parameters were analyzed, and Ts/(Ts + Tm), M<sub>30</sub>/(M<sub>30</sub> + H<sub>30</sub>), and Hopane H<sub>32</sub>: 22S/(22S + 22R) of saturated hydrocarbon parameters are found to be more reliable. Ratios of alkylnaphthalenes, alkylphenanthrenes, and alkyldibenzothiophenes (MNR, DNR, TMNr, TeMNr, MPI-1, MPR, MDR, and DMDR) also showed consistent correlations with thermal maturity. Thermal maturation impacted the macromolecular structure, resulting in the aromatization and demethylation, leading to MPy/Py, MChy/Chy, and the sum of unsubstituted 5-ring/4-ring PAH ratios changes with maturity. The influence of thermal maturation outweighs that of uranium radiation in this study, and maturity varies mainly with depth.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Coal Geology","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166516224002003","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
The middle (Miaolingian) to upper (Furongian) Cambrian Alum Shale Formation in the DBH15/73 core from south-central Sweden was exposed to local heat from a diabase intrusion, providing an opportunity to investigate the molecular geochemical response to thermal stress. Organic petrological observations and biomarker analyses were conducted to study changes in maturity-indicating parameters and the distribution of high molecular weight polycyclic aromatic hydrocarbons (PAHs) during the maturation process. The DBH15/73 samples exhibit a maturity gradient, ranging from immature at the base to mature in the upper part of the Alum Shale Formation. Multiple maturity-based biomarker parameters were analyzed, and Ts/(Ts + Tm), M30/(M30 + H30), and Hopane H32: 22S/(22S + 22R) of saturated hydrocarbon parameters are found to be more reliable. Ratios of alkylnaphthalenes, alkylphenanthrenes, and alkyldibenzothiophenes (MNR, DNR, TMNr, TeMNr, MPI-1, MPR, MDR, and DMDR) also showed consistent correlations with thermal maturity. Thermal maturation impacted the macromolecular structure, resulting in the aromatization and demethylation, leading to MPy/Py, MChy/Chy, and the sum of unsubstituted 5-ring/4-ring PAH ratios changes with maturity. The influence of thermal maturation outweighs that of uranium radiation in this study, and maturity varies mainly with depth.
期刊介绍:
The International Journal of Coal Geology deals with fundamental and applied aspects of the geology and petrology of coal, oil/gas source rocks and shale gas resources. The journal aims to advance the exploration, exploitation and utilization of these resources, and to stimulate environmental awareness as well as advancement of engineering for effective resource management.