Petrology, geochronology, and geophysical characterization of Mesoproterozoic rocks in central Illinois, USA

• Published in: Di xue qian yuan. Vol. 11; no. 2; pp. 581 - 596
• Main Authors: Freiburg, Jared T., McBride, John H., Malone, David H., Leetaru, Hannes E.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.03.2020; Elsevier Science Ltd; Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 E. Peabody Drive, Champaign, IL 61820, USA; University of Greifswald, Institute of Geography and Geology, Friedrich-Ludwig-Jahn Str. 17a, D-17489 Greifswald, Germany%Department of Geological Sciences, Brigham Young University, Provo, UT, 84602, USA%Department of Geography, Geology, and the Environment, Campus Box 4400, Illinois State University, Normal, IL, 61790-4400, USA%Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 E. Peabody Drive, Champaign, IL 61820, USA; Elsevier
• Subjects: Age; Carbon sequestration; Carbon storage; Coring; Eastern granite-rhyolite province; Gabbro; Gallium; Geochronology; Geology; Geophysics; GEOSCIENCES; Granite; Heterogeneity; Illinois; Intrusion; Lithology; Mesoproterozoic; Petrology; Radiometric dating; Reflection; Reflection seismology; Rhyolite; Rocks; Seismic surveys; Volcanic activity; Zircon U-Pb geochronology; United States > US; Illinois; CCS2; EGRP; FWR; CCS1; Zircon U-Pb geochronology; Carbon storage; IBDP; FMI log; ICCS; WMA; Reflection seismology; Eastern granite-rhyolite province; VW2; 3D; VW1; 2D; Illinois; MSWD; LA-ICPMS; Mesoproterozoic; MCR
• ISSN: 1674-9871; 2588-9192
• DOI: 10.1016/j.gsf.2019.07.004

The Precambrian basement rocks of the Eastern Granite-Rhyolite Province (EGRP) in central Illinois (midcontinent region of North America) exhibit a complex history of early volcanism, granite emplacement, and intrusion of mafic rocks. A comprehensive suite of dedicated petrographic analyses, geophysical logs, and drill core from four basement-penetrating wells, two-dimensional and three-dimensional seismic reflection data, and U-Pb age data from the Illinois Basin–Decatur Project (IBDP) and Illinois Carbon Capture Storage (ICCS) Project site provide new constraints for interpreting the Precambrian basement of the Illinois Basin. These new data reveal the basement to be compositionally and structurally complex, having typical EGRP felsic volcanic rocks intruded by the first reported gabbro in the Precambrian basement in Illinois. Zircons (n ​= ​29) from rhyolite give a U-Pb weighted mean average age of 1467 ​± ​9 ​Ma. Zircons (n ​= ​3) from a gabbro dike that intrudes the rhyolite yield a concordia age of 1073 ​± ​12 ​Ma, which corresponds to Grenville-age extension and represents the first Grenville-age rock in Illinois and in the EGRP. A high-resolution three-dimensional seismic reflection volume, coincident with the four wells, provides a context for interpreting the petrological data and implies a high degree of heterogeneity for basement rocks at the IBDP–ICCS site, as also shown by the drill cores. The occurrence of Grenville-age gabbro is related to a prominent bowl-like structure observed on local two-dimensional seismic reflection profiles and the three-dimensional volume that is interpreted as a deep-seated mafic sill complex. Furthermore, heterogeneities such as the brecciated EGRP rhyolite and later gabbro intrusion observed in the basement lithology at the IBDP–ICCS may reflect previously unknown distal elements of the 1.1 ​Ga Midcontinent Rift in the EGRP and more likely Grenville-age extension. [Display omitted] •Grenville or Midcontinent Rift-age intrusives in EGRP rocks.•Intrusives associated with a major structure observed on seismic.•Archean-age zircon xenocrysts found in intrusives.•Evidence of extension and crustal thinning in the Midcontinent.