Petrologic and stable isotopic evidence for reaction-enhanced fluid flow during metamorphism of Precambrian-Cambrian sedimentary rocks, Lone Mountain, Nevada
Conference
·
· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5690287
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geochemical Sciences
Upper Precambrian to Cambrian sedimentary rocks, regionally metamorphosed during the Mesozoic to produce marbles and calc-silicate rocks, were contact metamorphosed at the end of the Cretaceous by the Lone Mountain granitic pluton. Mineral assemblages within the calc-silicates were in equilibrium with H[sub 2]O-rich fluids, while the marbles were in equilibrium with more CO[sub 2]-rich fluids. Mineralogical variation between two different calc-silicate lithologies is the result of differences in bulk rock chemical composition, which also results in differences in isotopic composition between the calc-silicate lithologies. delta O-18 and delta C-13 values show differences of greater than 6 and 4 per mil respectively across lithologic boundaries between interlayered calc-silicates and between interlayered marbles and calc-silicates. The absence of any systematic variation between delta O-18 and delta C-13 values in the calc-silicates suggests that isotopic variation due to decarbonation reactions was limited. The differences in mineralogy and isotopic composition indicate that permeability was enhanced by reaction, permitting the focused flow of fluid through the calc-silicates. Calculated mass balance variations in delta O-18 based on reaction space analysis and Rayleigh decarbonation cannot explain the observed variations of delta O-18, requiring infiltration of externally derived fluids, while the delta C-13 compositions in the calc-silicates can be explained by Rayleigh decarbonation alone.
- OSTI ID:
- 5690287
- Report Number(s):
- CONF-921058--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
- Country of Publication:
- United States
- Language:
- English
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