Static Temperature Survey At Long Valley Caldera Geothermal Area (Farrar, Et Al., 2003)
Exploration Activity: Static Temperature Survey At Long Valley Caldera Geothermal Area (Farrar, Et Al., 2003)
|Exploration Activity Details|
|Location||Long Valley Caldera Geothermal Area|
|Exploration Technique||Static Temperature Survey|
|Activity Date||1998 - 2002|
- The wells located on the Resurgent Dome east and southeast of LVEW (wells 13-21 and 13-26)
- The west moat (wells RDO-8 and 44-16)
- The south moat (Unocal Mammoth-1 well at Casa Diablo).
This thermal regime differs significantly from the dominantly conductive temperature gradients averaging about 35 °C/km, observed in the Bishop Tuff in the upper interval of LVEW, and throughout the Clay Pit-1 well. This contrasts sharply with the temperature profile in the underlying metamorphic basement, in which temperatures in LVEW become isothermal below 2000 m depth. This isothermal temperature interval is inferred to be related to a major permeable fracture zone intersected by LVEW at 2600 m depth that contains a 103°C fluid, which must be flowing more-or-less vertically outside the wellbore to produce constant temperatures observed across the ~600 m depth interval. The authors of the original study postulate that this fracture zone penetrated by LVEW may be the Eastern Graben Fault that bounds the eastern side of the caldera's medial graben. The Eastern Graben Fault is a steeply dipping normal fault thought to represent an extension of the northwest-trending Hilton Creek Fault, a major frontal fault of the Sierra Nevada Mountains to the south.Other, shallower wells drilled on or around the Resurgent Dome (wells Unocal Mammoth-1, 13-21, and 13-26) also exhibit isothermal intervals in the Bishop Tuff at about 100°C approaching the bottom of the wellbores. Of these wells, only (Unocal) Mammoth-1 penetrates metamorphic basement, in which the isothermal interval continues to the bottom of the well, similar to LVEW.
- Christopher D. Farrar, Michael L. Sorey, Evelyn Roeloffs, Devin L. Galloway, James F. Howle, Ronald Jacobson (2003) Inferences On The Hydrothermal System Beneath The Resurgent Dome In Long Valley Caldera, East-Central California, USA, From Recent Pumping Tests And Geochemical Sampling
- Christopher D. Farrar,Michael L. Sorey,Evelyn Roeloffs,Devin L. Galloway,James F. Howle,Ronald Jacobson. 2003. Inferences On The Hydrothermal System Beneath The Resurgent Dome In Long Valley Caldera, East-Central California, USA, From Recent Pumping Tests And Geochemical Sampling. Journal of Volcanology and Geothermal Research. 127(3-4):305-328.