Miocene Tectonics of the Lake Mead Region, Central Basin and Range
Fluid flow, solution collapse, and massive dissolution at detachment faults, Mormon Mountains, Nevada
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Published:June 01, 2010
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CiteCitation
S.F. Diehl, R. Ernest Anderson, J.D. Humphrey, 2010. "Fluid flow, solution collapse, and massive dissolution at detachment faults, Mormon Mountains, Nevada", Miocene Tectonics of the Lake Mead Region, Central Basin and Range, Paul J. Umhoefer, L. Sue Beard, Melissa A. Lamb
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Dissolution has removed large volumes of rock at low-angle normal faults, i.e., detachment faults, in the Mormon Mountains and the Tule Springs Hills in the eastern Basin and Range Province, southeastern Nevada. Evidence for major dissolution includes widespread solution-collapse breccias, meter-scale stylolite structures, and high-angle accommodation faults that terminate at or merge with dissolution seams. Chemically reactive fluids moving along the fault zones led to a strong depletion of 18O in the detachment fault breccias (e.g., a δ18O decrease of 8‰ relative to the unaltered rocks). These strong chemical shifts, demonstrated by (1) negative oxygen isotope values and (2) steep compositional gradients marked by metal enrichment in elements such as Au, Ag, Ti, Pb, Zn, and Cu, are generally restricted to the narrow (<1 m to 8 m) microbreccia zones.
Extensional faulting and fracturing, accompanying regional uplift, opened conduits for the influx of meteoric waters from above and hydrothermal fluids from below. As the largest, most permeable structures that formed during uplift, detachment faults focused the fluid flow. In this deformation and hydrogeologic model, dissolution-caused stratal thinning is a major complement to detachment faulting and is an important process that resolves void space issues in the reconstruction of cross sections.
- Basin and Range Province
- breccia
- Clark County Nevada
- collapse structures
- detachment faults
- faults
- fluid dynamics
- geochemistry
- hydrothermal alteration
- isotope ratios
- isotopes
- Lincoln County Nevada
- low-angle faults
- metasomatism
- meteoric water
- Mormon Mountains
- Nevada
- normal faults
- North America
- O-18/O-16
- oxygen
- permeability
- solution
- stable isotopes
- structural controls
- thermal waters
- United States
- uplifts
- water-rock interaction
- southeastern Nevada