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A geochemical investigation of springs near Three Sisters volcanoes was conducted in response to the detection of crustal uplift west of the peaks. Dilute, low-temperature springs near the center of uplift show 3He/4He ratios ≥7RA (RA is the ratio in air), and transport in total ∼16 MW of heat and ∼180 g/s of magmatic carbon (as CO2). These anomalous conditions clearly reflect the influence of magma, but they seemingly predate the onset of the present uplift and derive from a previous event. Episodes of intrusion may thus be more common in this area than the age of eruptive vents would imply.
The dataset includes whole-rock geochemistry, phenocryst/mineral trace element compositions, zircon U–Pb geochronology, and zircon in situ Lu–Hf isotopes for intrusions associated with the Oligocene Platoro caldera complex of the San Juan volcanic locus in Colorado features numerous exposed plutons, both within the caldera and outside its margins, enabling investigation of the timing and evolution of postcaldera magmatism. Intrusion and , coupled with new document distinct pulses of magma derived from different depths beneath the caldera complex. Fourteen intrusions, the Chiquito Peak Tuff, and the dacite of Fisher Gulch were dated, showing intrusive magmatism began after the 28.8 Ma-eruption of the Chiquito Peak...
A geochemical investigation of springs near Three Sisters volcanoes was conducted in response to the detection of crustal uplift west of the peaks. Dilute, low-temperature springs near the center of uplift show 3He/4He ratios ≥7RA (RA is the ratio in air), and transport in total ∼16 MW of heat and ∼180 g/s of magmatic carbon (as CO2). These anomalous conditions clearly reflect the influence of magma, but they seemingly predate the onset of the present uplift and derive from a previous event. Episodes of intrusion may thus be more common in this area than the age of eruptive vents would imply.
    map background search result map search result map Petrologic data for 'Postcaldera intrusive magmatism at the Platoro caldera complex, Southern Rocky Mountains Volcanic Field, Colorado' Tertiary dikes in the Southern Piceance Basin, Colorado (psintrg) Petrologic data for 'Postcaldera intrusive magmatism at the Platoro caldera complex, Southern Rocky Mountains Volcanic Field, Colorado' Tertiary dikes in the Southern Piceance Basin, Colorado (psintrg)