Large 18O and 13C depletions in greenschist facies carbonate rocks, western Arizona

Saved in:
Online Access: Get full text
doi: 10.1130/0091-7613(1997)025<0943:LOACDI>2.3.CO;2
Authors:Guerrera, Antonio, Jr.; Peacock, Simon M.; Knauth, L. Paul
Author Affiliations:Primary:
Arizona State University, Department of Geology, Tempe, AZ, United States
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 25(10), p.943-946. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1997
Note:In English. 31 refs.; illus., incl. geol. sketch map
Summary:Strongly deformed greenschist facies carbonate rocks in western Arizona exhibit large 18O and 13C depletions relative to unmetamorphosed correlative rocks in northeastern Arizona. Unmetamorphosed Permian Kaibab Formation carbonates on the Colorado Plateau yield δ13C values of +1 per mil to +5 per mil and δ18O values of +28 per mil to +37 per mil. In contrast, greenschist facies Kaibab Formation in the Little Harquahala and Granite Wash Mountains yields δ13C values of -6 per mil to +4 per mil and δ18O values of +9 per mil to +24 per mil. The magnitude of the observed 13C and 18O depletions cannot be explained by decarbonation reactions and requires extensive exchange with low δ13C and δ18O fluids. The 13C depletions may reflect isotopic exchange with lower δ13C carbonate in the underlying Paleozoic section and exchange with CO2 derived from oxidation of methane via reaction with hematite or sulfate in interbedded rocks. These data demonstrate that large 13C and 18O depletions can occur in strongly deformed terranes during very low-grade metamorphism. Depletions in 13C and 18O observed in some high-grade metamorphic terranes may be inherited from much lower metamorphic grades. [P.B.L.]
Subjects:C-13/C-12; Carbon; Carbonaceous composition; Facies; Geochemistry; Greenschist facies; Isotope ratios; Isotopes; Kaibab Formation; Low-grade metamorphism; Metamorphic rocks; Metamorphism; Metasedimentary rocks; O-18/O-16; Oxygen; Paleozoic; Permian; Regional metamorphism; Stable isotopes; Arizona; Coconino County Arizona; Colorado Plateau; Grand Canyon; La Paz County Arizona; United States; Granite Wash Mountains; Little Harquahala Mountains; Western Arizona
Coordinates:N334000 N335000 W1132500 W1134500
N360000 N360000 W1120000 W1120000
Abstract Numbers:98M/2864
Record ID:1997071761
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Tags: Add Tag
No Tags, Be the first to tag this record!