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Strain Partitioning in Synthetic Accommodation Zones and Selected Geothermal Systems in Colorado Paul Morgan and Matthew Sares Colorado Geological Survey. Transfer Zones and Accommodations Zones. Cenozoic Volcanism.
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Strain Partitioning in Synthetic Accommodation Zones and Selected Geothermal Systems in Colorado Paul Morgan and Matthew Sares Colorado Geological Survey
Cenozoic Volcanism Upper Arkansas Valley, the northernmost classical valley of the Rio Grande rift. Abundant Oligocene-early Miocene magmatic activity. Miocene to recent tectonic activity.
Accommodation Zones in Upper Arkansas Valley North: Cottonwood/Charlotte Hot Springs Central: Mt Princeton/Hortense Hot Springs South: Poncha Hot Springs Map source: 1:500,000 CGS Geology (ArcMap)
Mt Princeton Accommodation Zone
Cottonwood Accommodation Zone Mt Princeton Accommodation Zone Poncha Springs Accommodation Zone
Poncha Springs Accommodation Zone
Spring temperatures Sources: Barrett and Pearl, Colo. Geol. Surv., Info. Ser. 6., 1976 Barrett and Pearl, Colo. Geol. Surv., Bull. 39, 1978
Mt. Princeton: 2009 Gradient Well ~65°C at 140 m
Mt. Princeton: 2009 Gradient Well Cold Water over 60°C warm water
Map of Elevation of top of 65°C Isotherm Sub-regional ‘65°C Aquifer’ feeds Mt Princeton Hot Springs – at least part rises from source ~1km SW of springs, not below springs. Hortense Hot Springs (82°C) separate system?
Detailed Geologic Map of Mt. Princeton Source: Scott et al., USGS MF-658, 1975.
Concluding Remarks I • A simple model of strain partitioning in synthetic accommodation zones suggests that extensional strain is greatest in the quadrants behind the tips of overlapping faults • Three major hot spring systems in the Upper Arkansas Valley of the northern Rio Grande rift in Colorado are in synthetic accommodation zones, suggesting that increased permeability associated with these accommodation zones may provide conduits for the ascent of hot fluids
Concluding Remarks II • Chemical geothermometers indicate that the springs are mixed waters with higher temperature deeper reservoirs. • Buoyancy calculations are consistent with the elevations of the hot springs being fed from deep circulation in the valley. • Detailed studies at Mt Princeton indicate that the surface expression of the springs may not coincide with their (sub-)vertical conduits, and complexities in the geology at each site result in inclusive tests of the simple model.
Thank you Chalk Cliffs at Mt. Princeton (hydrothermally altered qtz. monzonite)