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.
Additional Publication Details
Magmatic intrusion west of Three Sisters, central Oregon, USA: The perspective from spring geochemistry