Geothermal play fairway analysis, part 1: Example from the Snake River Plain, Idaho

The western Snake River Plain (SRP) is a southeast-northwest–trending complex graben bounded on the SW by the Owyhee Front. This graben, which merges with the central SRP at its southeast end near Bruneau Canyon, is a subsidiary tectonic feature that resulted from southwest-northeast extension as the main SRP–Yellowstone hotspot trend evolved. Silicic volcanism during the late Miocene along the Owyhee Front and in the central SRP resulted in large welded-tuff and rhyolite lava flows being erupted; these are well exposed southwest of the western Snake River Plain (WSRP) and in the western Mount Bennett Hills, northeast of where the western and central SRP merge. As the WSRP graben developed, it held a large lake, into which some of the rhyolite units flowed. At various stops described in this field guide, the characteristics of rhyolite lavas versus rheomorphically deformed welded tuffs, and of subaerially deposited versus subaqueously deposited rhyolite units, are displayed. During Pliocene and Pleistocene time, basaltic volcanism partially filled the WSRP graben and developed a basalt plateau across much of the central SRP. At various stops described in this field guide, the characteristics of subaerial versus subaqueous basalt flows, and of phreatomagmatic vent complexes, are displayed. Altogether, the stops described provide a guide to the wide variety of rhyolitic and basaltic volcanism phenomena in the western SRP, Owhyee Front, western Mount Bennett Hills, and Bruneau Canyon areas.

Project HOTSPOT, the Snake River Scientific Drilling Project (International Continental Scientific Drilling Program), tested for deep geothermal resources and examined the petrology of volcanic rocks with three drillholes in the central and western Snake River Plain (western USA). The MH-2 drillhole targeted fractured crystalline and hydrothermally altered basalt in the area of the Mountain Home Air Force Base (Idaho) to a total depth of 1821 m. At 1745 m depth the drillhole encountered flowing artesian hydrothermal fluids of at least 150 °C. We integrate geological analyses of core, image log, and borehole geophysical data, and in situ stress analyses to describe the structural environment that produces permeability for artesian flow. The rocks in the lower 540 m of the drillhole consist of basalt flows as much as 30 m thick, altered basalt, and thin sedimentary horizons. The mechanical stratigraphy is defined by nine mechanical horizons that are in three ranges of rock strength on the basis of experimentally determined strength data, core logging, and geophysical log signatures. Hydrothermal alteration products and mineralization in the core are associated with three highly faulted sections; the lowermost section is associated with the zone of flowing thermal water. Shear slip indicators on faults observed in core indicate slip ranging from pure strike slip to normal failure mechanisms in the stronger horizons. The borehole breakouts indicate that the maximum horizontal stress, SH, is oriented 047° ± 7°, and drilling-induced tensile fractures indicate that SH is oriented at 67° ± 21°. The in situ stress orientations exhibit little variation over the depth of the measured interval, but the SH magnitude varies with depth, and is best explained by an oblique normal fault stress regime. The geomechanical model indicates that if pore pressures at depth are elevated above the normal hydrostatic gradient, as observed here, the system has the potential to deform by mixed normal and strike-slip failure. Our observations and interpretations suggest that the MH-2 borehole was drilled into oblique normal faults that intersect a buried 300°-trending fault block masked by the basaltic volcanic complex. These data indicate that the transition from the central to western Snake River Plain is characterized by complex structures developed in response to a transitional stress state related to Snake River Plain and western Basin and Range stress regimes. Furthermore, the western Basin and Range stress and tectonic regime may extend from northern Nevada into western Idaho and may enhance the potential for geothermal resources by creating interconnected fracture and fault-related permeability at depth.

Ninety-eight K-Ar dates for lavas of the Snake River Plain (SRP) and vicinity provide calibration for the stratigraphic framework discussed by Malde and Powers (1962). The Idavada Volcanics, predominantly silicic volcanic rocks, are 9 to 13 m.y. old in the western SRP. Rocks of similar type and comparable stratigraphic position are 8 to 10 m.y. old in the central SRP and as young as 4 to 5 m.y. old in the eastern SRP. This time-transgressive silicic volcanic assemblage merges in the east with the silicic volcanic units erupted during the last 2 m.y. from Island Park, Yellowstone, and related volcanic centers. The Idaho Group, consisting of intercalated basalt flows and sedimentary deposits in the western half of the SRP, ranges in age from about 0.6 to 11.5 m.y. (71 refs.)

The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other Cordilleran extensional structures and structurally from the down-warped lava plain of the eastern Snake River Plain. To investigate mechanisms driving extension and topographic evolution, we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the mountainous flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. AHe cooling dates from seventeen samples range from 7.9 ± 1.4 Ma to 55 ± 10 Ma. Most cooling dates from Cretaceous plutons adjacent to the WSRP are Eocene, while Eocene intrusions from within the Middle Fork Boise River canyon ~35 km NE of the WSRP yield Miocene cooling dates. The AHe dates provide evidence of exhumation of the Idaho batholith during the Eocene, supporting a high relief landscape at that time, followed by decreasing relief. The Miocene AHe dates show rapid cooling along the Middle Fork Boise River that we take to indicate focused river incision due to base level fall in the WSRP. Eocene AHe dates limit magnitudes of exhumation and extension on the flanks of the WSRP during Miocene rift formation. This suggests extension was accommodated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. We favor a model where WSRP extension was related to Columbia River Flood Basalt eruption and enhanced by later eruption of the Bruneau-Jarbidge and Twin Falls volcanic fields, explaining the apparent difference with other Cordilleran extensional structures.

<p>Southwest Idaho has experienced substantial topographic changes over the Cenozoic that are reflections of complex tectonic and mantle processes. The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other western Cordilleran extensional structures. It also differs in orientation and structural style from the down warped lava plain of the eastern Snake River Plain that follows the path of the Yellowstone hotspot (YHS). Potential magmatic drivers for WSRP formation include the ~12-10 Ma Bruneau-Jarbidge eruptive center of the YHS or the ~17-16 Ma Columbia River Basalt (CRB) large igneous province. To better constrain the timing and style of rifting in the region we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. We present new AHe dates from seventeen samples, with cooling dates ranging range from 7 Ma to 55 Ma. The majority of cooling dates for the Cretaceous plutons are Eocene, and the Eocene intrusions yield Miocene dates. The AHe dates provide thermochronological evidence of rapid cooling and exhumation of the Idaho batholith during the Eocene. This supports the presence a high relief landscape in Idaho associated with regional uplift due to Farallon slab rollback and Challis magmatism. We also find evidence for a post-Eocene decrease in relief, seen in the negative slope on date-elevation relationships in the southwest flank of the WSRP. Our AHe dates indicate limited exhumation on the flanks of the WSRP during Miocene rift formation. We interpret this to be evidence of extension dominated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. Miocene AHe dates show rapid exhumation along the Middle Fork Boise River that had begun by ~17 Ma. We take this to indicate focused incision along the river due to base level fall in the WSRP and the timing suggests that CRB activity was responsible for initiation of WSRP formation</p>

Snake River Plain Play Fairway Analysis - Phase 1 CRS Raster Files. This dataset contains raster files created in ArcGIS. These raster images depict Common Risk Segment (CRS) maps for HEAT, PERMEABILITY, AND SEAL, as well as selected maps of Evidence Layers. These evidence layers consist of either Bayesian krige functions or kernel density functions, and include: (1) HEAT: Heat flow (Bayesian krige map), Heat flow standard error on the krige function (data confidence), volcanic vent distribution as function of age and size, groundwater temperature (equivalue interval and natural breaks bins), and groundwater T standard error. (2) PERMEABILTY: Fault and lineament maps, both as mapped and as kernel density functions, processed for both dilational tendency (TD) and slip tendency (ST), along with data confidence maps for each data type. Data types include mapped surface faults from USGS and Idaho Geological Survey data bases, as well as unpublished mapping; lineations derived from maximum gradients in magnetic, deep gravity, and intermediate depth gravity anomalies. (3) SEAL: Seal maps based on presence and thickness of lacustrine sediments and base of SRP aquifer. Raster size is 2 km. All files generated in ArcGIS.

Geothermal resource exploration in South America using an innovative GIS-based approach: A case study in Ecuador

High-K alkali basalts of the Western Snake River Plain (Idaho): Abrupt transition from tholeiitic to mildly alkaline plume-derived basalts

Geothermal energy could be used to reduce or replace diesel for heating in remote northern communities. Geothermal development has primarily focused on shallow, high-temperature resources, but interest in low-temperature and deep geothermal resource exploration has increased as energy costs and climate change policy have evolved. Here, we evaluated the low-temperature geothermal favourability in southwestern Yukon by adapting Play fairway analysis to data-scarce regions. Play fairway analysis is a spatial statistical tool that uses a layered data approach to model favourability and risk assessments for resource exploration. Previous Play fairway analyses concentrate on the physical aspects of geothermal favourability: heat, permeability, and fluid availability. This study presents an overview of potential direct and indirect physical parameters that could be used in a geothermal Play fairway analysis in data-scarce regions and introduces the importance of considering socio-economic data in the exploration phase. The socio-economic controls are grouped into quantitative and qualitative parameters that describe population trends and community interests. The framework presented is then applied to a Play fairway analysis for southwestern Yukon. Based on the physical and socio-economic analysis, there is interest in exploring geothermal potential along the Denali fault near Duke River to support the community of Burwash Landing.

Geothermal plays in extensional and transtensional tectonic environments have long been a major target in the exploration of geothermal resources and the Dixie Valley area has served as a classic natural laboratory for this type of geothermal plays. In recent years, the interactions between normal faults and strike-slip faults, acting either as strain relay zones have attracted significant interest in geothermal exploration as they commonly result in fault-controlled dilational corners with enhanced fracture permeability and thus have the potential to host blind geothermal prospects. Structural ambiguity, complications in fault linkage, etc. often make the selection for geothermal exploration drilling targets complicated and risky. Though simplistic, the three main ingredients of a viable utility-grade geothermal resource are heat, fluids, and permeability. Our new geological mapping and fault kinematic analysis derived a structural model suggest a two-stage structural evolution with (a) middle Miocene N -S trending normal faults (faults cutting across the modern range), - and tiling Olio-Miocene volcanic and sedimentary sequences (similar in style to East Range and S Stillwater Range). NE-trending range-front normal faulting initiated during the Pliocene and are both truncating N-S trending normal faults and reactivating some former normal faults in a right-lateral fashion. Thus the two main fundamental differences to previous structural models are (1) N-S trending faults are pre-existing middle Miocene normal faults and (2) these faults are reactivated in a right-later fashion (NOT left-lateral) and kinematically linked to the younger NE-trending range-bounding normal faults (Pliocene in age). More importantly, this study provides the first constraints on transient fluid flow through the novel application of apatite (U-Th)/He (AHe) and 4He/3He thermochronometry in the geothermally active Dixie Valley area in Nevada.

The Snake River Plain (SRP), Idaho, hosts potential geothermal resources due to elevated groundwater temperatures associated with the thermal anomaly Yellowstone-Snake River hotspot. Project HOTSPOT has coordinated international institutions and organizations to understand subsurface stratigraphy and assess geothermal potential. Over 5.9km of core were drilled from three boreholes within the SRP in an attempt to acquire continuous core documenting the volcanic and sedimentary record of the hotspot: (1) Kimama, (2) Kimberly, and (3) Mountain Home. The Mountain Home drill hole is located along the western plain and documents older basalts overlain by sediment. Data submitted by project collaborator Doug Schmitt, University of Alberta

Northern Pakistan lies within the collision zone of the Indian and Asian plates comprising Himalaya, Kohistan, and Karakoram, with numerous hot springs associated with the Himalayan Geothermal Belt, extending 3000 km along the Himalayas. The magnitude of terrestrial heat flow and the characteristics of potential heat sources for the present geothermal systems in this belt are of great importance and interest in geoscientific disciplines. The geothermal exploration in this remote region is limited to a two-decade-old geochemical analysis of hot springs. At the same time, the rugged topography, limited road infrastructure, and harsh climate hinder any prospect of large-scale exploration. Despite the indication of high surface heat flow in neighboring Indian Kashmir, the absence of reliable geophysical data and petrophysical parameters prevents the establishment of the thermal state of the lithosphere, which is a prerequisite for geothermal modeling and evaluation. Moreover, high radiogenic heat production (RHP) and fast exhumation of the basement crystalline complexes and granitoid batholiths are assumed to contribute significantly to the upper crust's heat flow. The focus of the thesis was to understand and assess the geothermal resources of the Himalaya-Karakoram region of Pakistan on a reconnaissance scale and provide the baseline information and zones of interest as potential targets for future detailed exploration. To this end, it concentrated on the following objectives: 1) Identifying the areas with high lineament density, thermal anomalies, and hydrothermal alteration associated with active and paleo-geothermal zones. 2) Estimating the magnitude and variation of radiogenic heat production in different lithological units and understanding its role and contribution to overall heat flow and local geothermal systems. 3) Petrological, geochemical, and petrophysical characterization of outcrop analogs of subsurface reservoirs. 4) Creation of conceptual geological and geothermal models for understanding the geothermal play-types in the area and propose potential development scenarios. A multi-method and multi-scale approach is followed, which started from a regional level large-scale study through remote sensing, geological mapping, and literature review to analyze and understand the tectonic mechanism and structural features, surface temperature patterns, and hydrothermal alterations. A portable gamma spectrometer was used to measure radioelement concentration on the ground. Lab analysis (XRD, optical and cathodoluminescence microscopy, XRF, ICP-MS) of altered and unaltered samples were carried out to determine the mineralogical, petrological, geochemical, and petrophysical properties. The remote sensing results confirmed the presence of high lineament density, thermal anomalies, and hydrothermal alteration in the regions close to hot springs and suture zones. The hydrothermal alteration results from remote sensing, later confirmed by XRD analysis, provided base information for subsequent field investigation. The radiogenic heat production in the Nanga Parbat Massif – NPM (with > 4 μWm-3) is classified as high heat-producing, the Karakoram batholith – KB (with 2 – 4 μWm-3) as moderately heat-producing, and the Kohistan-Ladakh batholith – KLB (with < 2 μWm-3) as low heat producing. Geochemical results indicate that the gneisses and granites of the NPM are mostly peraluminous alkaline S-type, enriched in REEs and radioactive elements, indicating partial melting and high fractionation. The granitoids of the KB are syenitic to granitic in composition, with the presence of REE-rich allanites in syenite. The KLB granitoids are calc-alkaline I-type and show depletion of REEs and radiogenic elements. Low matrix porosities (0.6 – 3.5%) and higher fault zone alteration indicate hydrothermal fluids' feedback effect on the host rocks via alteration-induced permeability. The crustal-scale thermal models revealed that the surface radiogenic heat production cannot be extrapolated to mid-crustal depth in the case of a subducting or under-thrusting layer. This layer's magnitude of heat production and thickness mainly control surface heat flow. Exhumation transports hot rocks to the surface, resulting in higher surface heat flow, even in an upper crust with low RHP. However, the lateral influence of exhumation is limited compared to the RHP. The shape of the near-surface isotherms is greatly influenced by topography, which gets expanded under mountains and compressed in valleys. A conceptual model explaining the genetic mechanism for current hot springs considers increased concentrations of radiogenic elements and high exhumation for increasing the geothermal gradient, which is accessed by meteoric waters via deep faults. Finally, combining multi-scale and multi-method studies, the Nanga Parbat region, central Karakoram, and eastern Karakoram are potential geothermal targets identified for detailed and site-specific investigations. This thesis suggests the presence of hydrothermal and hot-dry rock geothermal play types in these identified areas. The findings presented in this work provide new key data for understanding of the region's geothermal regime on a larger scale and are fundamental for future geothermal exploration.

The geothermal resources in the southwest section of the Mid-Spine Belt of Beautiful China are abundant, but the quantitative prediction and evaluation of geothermal resources are very difficult. Based on geographic information system (GIS) and remote sensing (RS) platforms, six impact factors, namely land surface temperature, fault density, Gutenberg–Liszt B value, formation combination entropy, distance to river and aeromagnetic anomaly were selected. Through the establishment of the certainty factor model (CF), weights of the information entropy certainty factor model (ICF) and weights of the evidence certainty factor model (ECF), the geothermal potential in the study area were predicted quantitatively. Based on the ECF results, the six main geothermal resource areas were delineated. The results show that (1) ECF had high prediction accuracy (success index is 0.00405%, area ratio is 0.867); (2) The geothermal resource areas obtained were Ganzi–Ya’an–Liangshan, Panzhihua–Liangshan, Dali–Chuxiong, Nujiang–Baoshan, Diqing–Dali, and Lijiang–Diqing. The results provide a basis for the effective development and utilization of geothermal resources in the southwest section of the mid-ridge belt.

Geothermal energy is an increasingly important component of green energy in the globe. A prerequisite for geothermal energy development is to acquire the local and regional geothermal prospects. Existing geophysical methods of estimating the geothermal potential are usually limited to the scope of prospecting because of the operation cost and site reachability in the field. Thus, explorations in a large-scale area such as the surface temperature and the thermal anomaly primarily rely on satellite thermal infrared imagery. This study aims to apply and integrate thermal infrared (TIR) remote sensing technology with existing geophysical methods for the geothermal exploration in Taiwan. Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) imagery is used to retrieve the land surface temperature (LST) in Ilan plain. Accuracy assessment of satellite-derived LST is conducted by comparing with the air temperature data from 11 permanent meteorological stations. The correlation coefficient of linear regression between air temperature and LST retrieval is 0.76. The MODIS LST product is used for the cross validation of Landsat derived LSTs. Furthermore, Landsat ETM+ multi-temporal brightness temperature imagery for the verification of the LST anomaly results were performed. LST Results indicate that thermal anomaly areas appear correlating with the development of faulted structure. Selected geothermal anomaly areas are validated in detail by field investigation of hot springs and geothermal drillings. It implies that occurrences of hot springs and geothermal drillings are in good spatial agreement with anomaly areas. In addition, the significant low-resistivity zones observed in the resistivity sections are echoed with the LST profiles when compared with in the Chingshui geothermal field. Despite limited to detecting the surficial and the shallow buried geothermal resources, this work suggests that TIR remote sensing is a valuable tool by providing an effective way of mapping and quantifying surface features to facilitate the exploration and assessment of geothermal resources in Taiwan.

ABSTRACTThe Kingdom of Saudi Arabia has rich geothermal energy resources. In Saudi Arabia, the studies on geothermal resources exploration were started in 1980. Saudi Arabia is among the most geothermally active countries in the Middle East. The geothermal power plants are not yet installed in Saudi Arabia. Some direct-use low-grade geothermal applications are already installed in the five last years. Some refreshment and swimming pools are already constructed in the Bani Malik-Jizan area. Geothermal energy can be utilized in various forms such as direct use, electricity generation, space heating, heat pumps, greenhouse heating, and industrial usage. The Kingdom of Saudi Arabia government has plans to become completely powered by difference forms of renewable energy such as solid waste, solar, geothermal, and wind.