Spring temperatures in the Sagehen Basin, Sierra Nevada, CA: implications for heat flow and groundwater circulation (original) (raw)
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Tectonophysics, 1983
Twenty-five new heat-flow measurements are presented for the San Juan Basin and the Four Corners area of the Colorado Plateau in the southwestern United States. Temperature gradients at most sites are calculated from temperature logs at depths between 1 km and 2 km. Resulting heat-flow values appear to be locally less variable than shallower data. These new data develop smooth, uniform trends consistent with the regional geology. As such, it is reasonable to suggest that these data may be somewhat less influenced by near surface perturbations to heat flow than are shallower data in the area; i.e., local hydrologic movement, weathered conductivity samples, topographic variations, and paleoclimate effects. Heat-flow increases going from the Four Comers area into the northern San Juan Basin; a trend consistent with other geophysical studies. Heat flow also increases as the San Juan Basin is traversed south to north, approaching the San Juan volcanic field. This observation suggests a unique thermal anomaly associated with the San Juan volcanics. Heat flow in areas of the San Juan Basin, quite away from extensive volcanics, is 70 mW/m*; suggesting a small but statistically valid difference between regional heat flow in the non-volcanic regions of the San Juan Basin and in some of the other non-volcanic regions of the Colorado Plateau where the mean heat flow is 65 mW/m*. Again, this conclusion seems consistent with other geophysical data.
Terrestrial heat flow in eastern Arizona: A first report
Journal of Geophysical Research, 1979
Fifteen heat-flow measurements are presented for eastern Arizona and neighboring areas. In the Gila Mountains of southeastern Arizona a heat flow of 1.9 HFU (the approximate average for the Basin and Range Province) is estimated from the best measurements. In the eastern part of the Safford Valley, just south of the Gila Mountains, subsurface temperature gradients were measured at one site to 1050 m. Heat-flow data from this site, considered with the reported hydrogeology and hot spring activity of the valley fill deposits, suggest complex hydrothermal phenomena in the valley. Several hundred km to the north, high heat flows (_>2.5 HFU) are observed within the Mogollon Slope of the Colorado Plateau. These high heat flows, about 100 km from the southern boundary of the Colorado Plateau, are believed to result from the sources of extensive Quaternary volcanics in the region. Still farther into the interior of the Colorado Plateau the Black Mesa Basin has an estimated heat flow of 1.5-1.8 HFU and a uniform geothermal character (1 HFU = 41.8 mW/m2). REGIONAL GEOLOGY AND GEOPHYSICS Arizona is divided by a northwest-southeast trending transition zone which defines the boundary between the Basin and Range province to the southwest and the Colorado Plateau province to the northeast [Wilson and Moore, 1959]. The Colorado Plateau is an elevated crustal block with large structural basins and broad uplifts separated by monoclinal flexures. As compared to the Basin and Range, the Colorado Plateau appears to demonstrate large scale lithologic continuity; however, a number of igneous dikes and laccolithic intrusives are noted [Eardley, 1962]. Roller [1965] determines a crustal thickness of 43 km and a Pn velocity of 7.8 km/s in northeast Arizona near Chinle. Warren [1969] reports a fiat M discontinuity at 40 km depth under the Mogo!lon Slope in the southern Colorado Plateau with a Pn velocity of 7.85 km/s. Published heat-flow values for the Colorado Plateau [
Anomalous Hydrothermal Activity in Hot Creek Gorge Area, Long Valley Caldera, California, USA
2006
ABSTRACT Hot Creek Gorge is the area of greatest natural discharge of thermal water from the Long Valley Caldera hydrothermal system. A large number of subaerial and subaqueous thermal springs discharge about 240 L/s of alkaline water near ambient boiling temperatures (about 93°C). The USGS has measured thermal fluid discharge from Hot Creek and water levels in the 100-meter deep well CH-10b, about 1 km south of the gorge. Thirteen temperature profiles measured in CH-10b since 1988 indicate continuous and gradual warming of the well with a rather sharp increase following a period of intense seismic activity in 1997. In May 2006, after many years of relative stability in the locations of spring vents and thermal water discharge volumes, an abrupt change took place. The pressure in three subaqueous springs increased sufficiently to cause cyclical fountaining up to 2 m above the water surface of Hot Creek, and sometimes accompanied by audible popping sounds as the gas-charged water erupts. The intense thermal activity forced the closure of the creek for swimming. The maximum temperature in the well was 99.3°C in 2004 and has risen to 100.7°C following the onset of intense activity. However, no significant increase in spring discharge or fluid level in the well has been noted in the two months following the increased vigor of the springs. The trigger for the onset of thermal activity and the warming of water in the well is unknown; no unusual deformation or earthquakes were detected in the months before the anomalous thermal activity, but the winter of 2005-2006 had one of the highest snowpacks on record in the adjacent Sierra Nevada. High snowmelt-runoff and ground-water recharge could be factors contributing to the unusual behavior of the springs. In July 2006 we deployed a system that records the water temperatures every 30 minutes at 10 depths in the well. The goal of this system is to examine a possible correlation between thermal spring discharge and temperatures in the well as well as to track temperature transients and quantify hydrothermal flow rates.
Terrestrial heat flow in Arizona
Journal of Geophysical Research, 1981
New heat flow data in Arizona suggest that the southern Basin and Range has recently undergone less extension than other areas of the Basin and Range province. Heat flow-heat production data imply that magmatism and hydrothermal circulation in the crust and upper mantle beneath southern Arizona and northwestern Mexico may be less extensive than along the Rio Grande rift. A heat flow transition between the Basin and Range and the Colorado Plateau occurs within a lateral distance of 60 km in central Arizona. Predicted steady state temperatures suggest that the M discontinuity may be nearly coincident with an isotherm along this transition. The new heat flow measurements from depths greater than 650 m suggest that the mean value for the Arizona Basin and Range is 1.94 :!: 0.12 HFU, indicating as little as 0.3 to 0.4 HFU difference between the Colorado Plateau and the Arizona Basin and Range. This difference could be attributed primarily to widespread magmatic intrusion in the Basin and Range. REGIONAL GEOLOGY AND GEOPHYSICS The southwestern half of Arizona is within the Basin and Range province, a region of extensional faulting beginning about 15 to 20 m.y.B.P. [Coney, 1978]. Atwater [1970] suggests that the Basin and Range is a wide, structurally weak boundary between the Pacific and North American plates and has developed as an oblique shear zone with the growth of the San Andreas transform fault system. Eaton [1979] further suggests that the southern Basin and Range of Arizona is relatively inactive at present. Throughout the Basin and Range of Arizona, the predominant orientation of the late Tertiary structure is north-northwest [Earalley, 1962; Rehrig and Heidrick, 1976]. A compositional change in volcanism occurred in the Basin and Range about 17 m.y.B.P. Volcanic rocks younger than 17 m.y. are predominantly basalt or bimodal ba-•Now at Research and Development,
Heat flow on the southern Colorado Plateau
Tectonophysics, 1991
Heat-flow data from the study area in the southern Colorado Plateau indicate a pattern of local anomalies having relatively high heat flow superimposed on a regional, intermediate heat-flow setting. While many of the conventional heat-flow data are relatively shallow and may be perturbed by groundwater circulation, bottom-hole temperature data from two relatively deep petroleum exploration drill holes near the southern plateau periphery yield intermediate heat-flow estimates. The mean heat flow within the volcanically active Jemez zone does not appear to be significantly greater than the mean heat flow for the remainder of the study area. This is due to the presence of high heat-flow values outside the Jemez zone. Sites with relatively high heat flow located towards the plateau interior and away from recent volcanic activity of the Jemez zone may reflect magma intrusion and/or groundwater movement along crustal zones of weakness associated with Laramide deformation (monoclines). The heat-flow data are consistent with coal maturation data, which suggest that any regional post-Cretaceous thermal events that may be associated with the southern Plateau boundary have been initiated relatively recently, or are occurring at relatively great depths, or are occurring south of the Jemez lineament.
The thermal environment of Cascadia Basin
Geochemistry, Geophysics, Geosystems, 2012
1] Located adjacent to the NE Pacific convergent boundary, Cascadia Basin has a global impact well beyond its small geographic size. Composed of young oceanic crust formed at the Juan de Fuca Ridge, igneous rocks underlying the basin are partially insulated from cooling of their initial heat of formation by a thick layer of pelagic and turbidite sediments derived from the adjacent North American margin. The igneous seafloor is eventually consumed at the Cascadia subduction zone, where interactions between the approaching oceanic crust and the North American continental margin are partially controlled by the thermal environment. Within Cascadia Basin, basement topographic relief varies dramatically, and sediments have a wide range of thickness and physical properties. This variation produces regional differences in heat flow and basement temperatures for seafloor even of similar age. Previous studies proposed a north-south thermal gradient within Cascadia Basin, with high geothermal flux and crustal temperatures measured in the heavily sedimented northern portion near Vancouver Island and lower than average heat flux and basement temperatures predicted for the central and southern portions of the basin. If confirmed, this prediction has implications for processes associated with the Cascadia subduction zone, including the location of the "locked zone" of the megathrust fault. Although existing archival geophysical data in the central and southern basin are sparse, nonuniformly distributed, and derived from a wide range of historical sources, a substantial N-S geothermal gradient appears to be confirmed by our present compilation of combined water column and heat flow measurements.
A note on terrestrial heat flow in the Colorado Plateau
Geophysical Research Letters, 1983
The mean of deep heat-flow measurements in the interior of the Colorado Plateau (temperature measurements to depths >750 m) is about 5 mWm-2 greater than the mean of shallow data. Although these data sets have remarkably similar means considering the experimental difficulties in measuring heat flow, the means never the less appear statistically different (59 mWm-2 vs 64 mWm-Z). If various lithospheric heating models are used to explain the uplift of the Colorado Plateau, a 5 mWm-2 difference in surface heat flow will make the time of lithospheric heating very different. Deep heat-flow data in the Colorado Plateau typically lack the large spatial variability that shallow data show. The deeper data should therefore relate better to regional geothermal trends caused by mantle thermal conditions and by crustal radioactivity. The deep heat-flow data, where present, in the Colorado Plateau interior suggest a rather uniform heat flow and therefore rather constant mantle temperatures and crustal radioactivity. Continued concern with experimental data will be necessary to appreciate the uncertainties in the heat-flow data and the resulting thermal models.
Heat flow in the Ozark Plateau, Arkansas and Missouri: relationship to groundwater flow
Journal of Volcanology and Geothermal Research, 1991
Heat flow values were calculated from direct measurements of temperature and thermal conductivity at thirteen sites in the Arkansas-Missouri Ozark Plateau region. These thirteen values are augmented by 101 estimates of heat flow, based on thermal conductivity measurements and temperature gradients extrapolated from bottom-hole temperatures. The regional heat flow profile ranges from 9 mW m−2 to over 80 mW m−2, but at least two distinct thermal regimes have been identified. Seven new heat flow determinations are combined with three previously published values for the St. Francois Mountains (SFM), a Precambrian exposure of granitic and rhyolitic basement rocks, average 47 mW m−2. Radioactive heat production of 76 samples of the exposed rocks in the SFM averages 2.4 μW m−2 and a typical continental basement contribution of 14 mW m−2 is implied. Conversely, the sedimentary rock sequence of the plateau is characterized by an anomalously low heat flow, averaging approximately 27 mW m−2. Groundwater transmissivity values that are based on data from 153 wells in deep regional aquifers demonstrate an inverse relationship to the observed heat flow patterns. The areas of high transmissivity that correspond to areas of low total heat flux suggest that the non-conservative vertical heat flow within the Ozark sedimentary sequence can be attributed to the effects of groundwater flow.
Heat flow from a scientific research well at Cajon Pass, California
Journal of Geophysical Research, 1992
The long-standing "stress/heat flow paradox" was the primary scientific motivation for the Cajon Pass borehole. For nearly two decades, the absence of a fault-centered heat flow anomaly from measurements to relatively shallow (-200 m) depths had indicated low average shear stresses (-<20 MPa) on the San Andreas fault, while laboratory data on rock strength and in situ stress determinations to about a kilometer had indicated high stress (-100 MPa). Initial results from an unsuccessful 1.7-km-deep oil well at the site gave a high heat flow (-90 mW m -2) consistent with a strong San Andreas fault; however, the late Cenozoic geologic history of the Cajon Pass area suggested that the anomalous heat flow was the transient effect of rapid erosion. Theoretical studies predicted that the -•30% surface anomaly would be substantially reduced at depths of 3-5 km. The research borehole reached a total depth of 3.5 km. Below a superficial covering of Tertiary sedimentary rocks, it penetrated gneissic rocks with composition ranging from gabbroic to granodioritic. Core recovery amounted to only about 3% of the total depth, necessitating the use of drill cuttings to characterize thermal conductivity. This, in turn, resulted in much higher uncertainties in average conductivity (+_ 10-15%) than would have occurred with a continuously cored hole (_+3-5%). From a time series of temperature logs, equilibrium temperature gradients were established over selected intervals of 250-500 m to within 95% confidence limits of 2%. These gradients were combined with harmonic mean thermal conductivities having larger uncertainties to give interval heat flows, which vary systematically from 100 _+ 5 mW m -2 in the uppermost 400 m to 75 _+ 3 mW m -2 in the lowermost 300 m. Thus, at the Cajon Pass site, heat flow is decreasing with depth at a mean rate of more than 7 mW m -2 per kilometer, consistent with a frictionless fault and with theoretical predictions based on local erosional history.
Temperature Profiles and Hydrologic Implications from the Nevada Test Site
2005
Groundwater temperature is sensitive to the competing processes of heat flow from below and the advective transport of heat by groundwater flow. Because groundwater temperature is sensitive to conductive and advective processes, groundwater temperature may be utilized as a tracer to further constrain the uncertainty of predictions of advective radionuclide transport models constructed for the Nevada Test Site (NTS). Since heat transport, geochemical, and hydrologic models for a given area must all be consistent, uncertainty can be reduced by excluding those models that do not match estimated heat flow. temperature profiles from Bechtel geophysical log archives at the NTS. The author would also like to acknowledge Jackie Kenneally, Brad Lyles, and Todd Mihevc, for providing temperature profiles from various boreholes at the NTS, obtained during previous investigations; and to Chuck Russell and Marjory Jones for their review and comments on the manuscript. Dee Donithan and Scott Campbell were instrumental in obtaining the temperature profiles conducted specifically for this investigation. The author would also like to thank the U.S. Department of Energy (DOE) and the DOE Underground Test Area project manager, Bob Bangerter, for providing funding to accomplish the work described herein.