| Authors |
Makovsky, Kyle A.; Pezzopane, Silvio; Culp, Lynn; Mink, Leland Roy; Hand, Daniel; Silveria, Daniel; Colahan, Erin; Douglas, Mark; Johnson, Kim |
| Abstract |
Volcanism along the northwest margin of the Basin and Range and K/Mg Giggenbach methods has shown that for several wells in the Paisley area, temperatures could range between 95-127 °C. Preliminary stable isotope data of water from the potential production well shows that it may be from meteoric sources, with mean ?D and ?18O values of -120.066 and -14.307 (n=3), respectively. province started in the early Eocene, and after a short hiatus, reinitiated in the late Oligocene (28 Ma) to early Miocene and continued through the mid Miocene (17 Ma). This second volcanic event is thought to have been the result of hinge rollback of the shallowly subducting Farallon plate in the Oligocene. After volcanism ceased, tectonic extension offset these early-mid Cenozoic units, with extension in this locality occurring at a younger age than the central and southern Basin and Range province. Two main trends in fault orientation have developed due to this extension, with the dominant trend striking NE-SW and dip-slip as the main kinematic feature. Minor faults trending NW-SE also occur and most likely accommodate strain with oblique-slip to strikeslip motion. These two trends may play a key role in the surface manifestation of geothermal anomalies in southeast Oregon. The structural framework of this area provides a unique view into young extensional terranes, where high angle normal faults and crustal blocks dominate. The combination of volcanism followed by regional extension has led to numerous geothermal anomalies in southern Oregon. Geologic mapping near Paisley, Oregon has indicated that Cenozoic, mostly Oligocene and Miocene, ash-flow tuffs, dacite to rhyolite lava flows, and other volcaniclastic rocks are the major lithologies of the region. Most of these rocks are potentially excellent reservoirs due to the highly fractured nature of welded tuffs and lava flows and the unconsolidated nature of ash flow deposits. Mapping has also indicated that faults created during mid-Miocene extension have offset volcanic strata of late Oligocene-early Miocene age. 2 meter survey data also shows high heat flow near the surface, ranging from 55-80 °F. The range and temporal change in the 2 m data suggests there is a flux of heat flow in the subsurface. A preliminary Complete Bouguer Gravity Anomaly map has also been created for the study area. A range of +18 to +23 mgals has been observed, with higher gravity values attributed to denser bedrock, adjacent to unconsolidated basin fill. This study was aimed at identifying the orientation of a range front fault that could play a major role in transport of hot fluids. Geothermometry using the Na/K |