Regional fluid flow as a factor in the thermal history of the Illinois basin: Constraints from fluid inclusions and the maturity of Pennsylvanian coals

摘要

Vitrinite reflectance measurements on Pennsylvanian coals in the Ilinois basin indicate significantly higher thermal maturity than can be explained by presen-day burial depths. An interval of additional sedimentary section, now removed by erosion, has been suggested to accout for the discrepancy. Although burial could indeed account for the observed maturity levels of organic matter, fluid-inclusion temperatures provide a stringent additional constraint. In this article, we combine measurements of coal maturity with fluid-inclusion temperatures from three sites to constrain the asin's thermal and burial history: the Fluorspar district at the Illinois basin's southern margin, the Upper Mississippi Valley zinc district at the basin's northern margin, and a north-central location.