Isotopically zoned carbonate cements in Early Paleozoic sandstones of the Illinois Basin: δ¹⁸O and δ¹³C records of burial and fluid flow

Journal Article · Mon Nov 20 00:00:00 EST 2017 · Sedimentary Geology

DOI:https://doi.org/10.1016/j.sedgeo.2017.09.004· OSTI ID:1661874

Denny, Adam C. ^[1]; Kozdon, Reinhard ^[2]; Kitajima, Kouki ^[1]; Valley, John W. ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)
2. Columbia Univ., Palisades, NY (United States). Lamont-Doherty Earth Observatory

SEM/SIMSimaging andanalysis of δ¹⁸O and δ¹³C in sandstonesfrom a transect through the Illinois Basin(USA) show systematic μm-scale isotopic zonation of up to 10‰ in both carbonate and quartzcements of the middle-Ordovician St. Peter and Cambrian Mt. Simonformations. Quartz δ¹⁸O values are broadly consistent with the model of Hyodo et al. (2014), wherein burial and heating in the Illinois Basinis recorded insystematically zonedquartz overgrowths. Observations of zoned dolomite/ankerite cements indicate that they preserve a more extended record of temperature and fluid compositionsthan quartz, including earlydiagenesis before orduring shallow burial,and late carbonates formed after quartzovergrowths. Many carbonate cements show innermostdolomite withδ¹⁸O values (21-25‰ VSMOW) that are too low to have formed by depositionat low temperatures from ancient seawater(δ¹⁸O>-3‰)and most likelyreflect mixing with meteoric water. A sharp increase in Fe content is commonly observed in zoned carbonate cements to be associated with a drop in δ¹⁸O and an abrupt shift in δ¹³C to higher or lower values. These changes are interpreted to record the passage of hot metal-richbrinesthrough sandstone aquifers,that wasassociated with Mississippi-Valley Type (MVT) Pb-Zn deposits (ca. 270 Ma) of the Upper Mississippi Valley. Local variability and individual trends in δ¹³Care likely controlled by the sources of carbon and the degree to which carbonis sourced fromadjacent carbonate units or thermal maturation of organic matter. Quartz overgrowths in sandstones provide an excellent record of conditions during burial, heating, and pressure-solution, whereas carbonate cements in sandstonespreserve a more-extendedrecord includinginitial pre-burial conditions and punctuated fluid flowevents.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG02-93ER14389
• OSTI ID: 1661874
• Alternate ID(s): OSTI ID: 1549977
• Journal Information: Sedimentary Geology, Vol. 361; ISSN 0037-0738
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

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