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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The megageomorphology of the radar rivers of the eastern Sahara

The Eastern Sahara is devoid of surface drainage; this unusual characteristic distinguishes its morphology from that of most other desert regions where running water dominates landscape development. A map derived from SIR-A/B and LANDSAT images and the literature, shows the major presently known paleodrainages in the Eastern Sahara. This compilation permits consideration of the key questions: Where did the radar rivers come from and where did they go? Analysis of SIR-A data led McCauley et al. to suggest that the radar rivers, because of their southwestward trends, once flowed into the Chad basin. This key North African feature is a regional structural low formed in the Early Cretaceous in response to initial opening of the South Atlantic. The problem of the origin of headwaters for the radar rivers was less tractable. The idea that the source areas of the radar rivers might originally have been the same as those later captured by the Nile was proposed tentatively. A more extensive review of the Cenozoic tectonic history of North Africa reveals no reason now to suppose that the Central African tributaries of the present Nile were ever connected to the large alluvial valleys in southwestern Egypt and northwestern Sudan. formed in the Early Cretaceous in response to initial opening of the South Atlantic. The problem of the origin of headwaters for the radar rivers was less tractable. The idea that the source areas of the radar rivers might originally have been the same as those (The Ethiopian Highlands) later captured by the Nile was proposed tentatively. A more extensive review of the Cenozoic tectonic history of North Africa reveals no reason now to support that the Central African tributaries of the present Nile were ever connected to the large alluvial valleys in southwestern Egypt and northwestern Sudan.

Mccauley, John F.↗
NASA NTRS1988

Uplift of the Central Andean Plateau and bending of the Bolivian orocline

Topographic data are combined with data on structure magmatism, seismicity, and paleomagnetism to support a simple kinematical model for the late Cenozoic evolution of the central Andes. The model interrelates Andean uplift, a changing geometry of the subducted Nazca plate, and a changing outline of the leading edge of the South American plate. It is argued that the late Cenozoic uplift of the Andes is a result of thermal thinning of the lithosphere and crustal thickening produced by crustal shortening.

Isaks, Bryan L.↗
NASA NTRS1988

Volcanic ash layers in blue ice fields (Beardmore Glacier Area, Antarctica): Iridium enrichments

Dust bands on blue ice fields in Antarctica have been studied and have been identified to originate from two main sources: bedrock debris scraped up from the ground by the glacial movement (these bands are found predominantly at fractures and shear zones in the ice near moraines), and volcanic debris deposited on and incorporated in the ice by large-scale eruptions of Antarctic (or sub-Antractic) volcanoes. Ice core studies have revealed that most of the dust layers in the ice cores are volcanic (tephra) deposits which may be related to some specific volcanic eruptions. These eruptions have to be related to some specific volcanic eruptions. These eruptions have to be relatively recent (a few thousand years old) since ice cores usually incorporate younger ice. In contrast, dust bands on bare blue ice fields are much older, up to a few hundred thousand years, which may be inferred from the rather high terrestrial age of meteorites found on the ice and from dating the ice using the uranium series method. Also for the volcanic ash layers found on blue ice fields correlations between some specific volcanoes (late Cenozoic) and the volcanic debris have been inferred, mainly using chemical arguments. During a recent field expedition samples of several dust bands found on blue ice fields at the Lewis Cliff Ice Tongue were taken. These dust band samples were divided for age determination using the uranium series method, and chemical investigations to determine the source and origin of the dust bands. The investigations have shown that most of the dust bands found at the Ice Tongue are of volcanic origin and, for chemical and petrological reasons, may be correlated with Cenozoic volcanoes in the Melbourne volcanic province, Northern Victoria Land, which is at least 1500 km away. Major and trace element data have been obtained and have been used for identification and correlation purposes. Recently, some additional trace elements were determined in some of the dust band samples, including Ir. Iridium determinations were made using INAA, with synthetical and natural (meteorite) standards. These findings are discussed.

Koeberl, Christian↗
NASA NTRS1988

Accretion rate of extraterrestrial matter: Iridium deposited over the last 70 million years

In order to quantify the accretion rate of extraterrestrial matter during the Cenozoic, Ir concentrations were measured in a continuous series of 450 samples across most of the length of piston core LL44-GPC3. LL44-GPC3 is a 25-meter-long, large-diameter piston core of abyssal clay from the central North Pacific. This core contains a nearly continuous record of sedimentation over the last 70 Ma, as this site migrated from a region near the Equator in the late Cretaceous to its present position north of Hawaii. The first-cut survey across the core is nearing completion, and all of the conclusions of the earlier study, in which was reported the concentrations of Ir, Co, and Sb across 9 meters of this core, remain unchanged. The only strongly enhanced Ir concentrations occur at the Cretaceous-Tertiary (K-T) boundary and outside the K-T boundary Ir correlates well with Co, a terrestrial element which is largely present in hydrogenous ferromanganese oxide precipitates from seawater. Concentrations of both elements appear to be inversely correlated with the sedimentation rate. Although the K-T Ir anomaly is unique in magnitude in this core, there are several small bumps in the Ir profile which may reflect smaller accretionary events. The most promising Ir enhancement was observed in a 30 cm section approximately 1 m below the K-T boundary. Preliminary data suggest deposition of an excess across this interval at a time estimate to be approximate 1 Ma before the K-T impact event, but there is insufficient evidence at present to prove that this reflects enhanced accretion of extraterrestrial matter. A detailed model is being prepared of the chemical record of sedimentation in this core using a combined database of 39 elements in approximately 450 samples across the Cenozoic. Preliminary working model indicates that the only sedimentary sources which contribute significantly to the Ir budget in this core are the hydrogenous precipitates and extraterrestrial particulates.

Kyte, Frank T.↗
NASA NTRS1993

Effect of subglacial volcanism on changes in the West Antarctic Ice Sheet

Rapid changes in the West Antarctic Ice Sheet (WAIS) may affect future global sea-level changes. Alley and Whillans note that 'the water responsible for separating the glacier from its bed is produced by frictional dissipation and geothermal heat,' but assume that changes in geothermal flux would ordinarily be expected to have slower effects than glaciological parameters. I suggest that episodic subglacial volcanism and geothermal heating may have significantly greater effects on the WAIS than is generally appreciated. The WAIS flows through the active, largely asiesmic West Antarctic rift system (WS), which defines the sub-sea-level bed of the glacier. Various lines of evidence summarized in Behrendt et al. (1991) indicate high heat flow and shallow asthenosphere beneath the extended, weak lithosphere underlying the WS and the WAIS. Behrendt and Cooper suggest a possible synergistic relation between Cenozoic tectonism, episodic mountain uplift and volcanism in the West Antarctic rift system, and the waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time. A few active volcanoes and late-Cenozoic volcanic rocks are exposed throughout the WS along both flanks, and geophysical data suggest their presence beneath the WAIS. No part of the rift system can be considered inactive. I propose that subglacial volcanic eruptions and ice flow across areas of locally (episodically?) high heat flow--including volcanically active areas--should be considered possibly to have a forcing effect on the thermal regime resulting in increased melting at the base of the ice streams.

Behrendt, John C.↗
NASA NTRS1993

Did surface temperatures constrain microbial evolution?

The proposition that glaciation may not have occurred before the Cenozoic--albeit not yet a consensus position--nevertheless raises for reconsideration the surface temperature history of the earth. Glacial episodes, from the Huronian (2.3 billion years ago; BYA) through the late Paleozoic (320 to 250 million years ago; MYA) have been critical constraints on estimation of the upper bounds of temperature (Crowley 1983, Kasting and Toon 1989). Once removed, few if any constraints on the upper temperature limit other than life remain. Walker (1982) recognized that life provides an upper limit to temperature in the Precambrian. We propose a more radical concept: the upper temperature limit for viable growth of a given microbial group corresponds to the actual surface temperature at the time of the group's first appearance. In particular, we propose here that two major evolutionary developments--the emergence of cyanobacteria and aerobic eukaryotes--can be used to determine surface temperature in the Precambrian, and that only subsequent cooling mediated by higher plants and then angiosperms permitted what may possibly be the earth's first glaciation in the late Cenozoic.

NASA Program Exobiology↗
DOE OSTI2023

Organic matter sulfurization and organic carbon burial in the Mesoproterozoic

Throughout the Proterozoic Era, sedimentary organic carbon burial helped set the pace of global oxygenation and acted as a major modulator of atmospheric CO 2 and climate. Although Proterozoic rocks generally contain low concentrations of organic matter (OM), there are key exceptions to this rule, including the relatively OM-rich Arctic Bay shales from Baffin Island, Canada (Bylot Supergroup, Borden Basin, ~1.05 Ga). The mechanisms driving elevated OM concentrations in these and other Proterozoic shales remain poorly understood. In the Mesozoic and Cenozoic, organic matter sulfurization can be a major driver of enhanced OM burial across a range of redox conditions comparable to those inferred for many Proterozoic environments. Therefore, in this study, we evaluate the role of sulfurization in driving OM preservation in the Mesoproterozoic Borden Basin and discuss its relevance to Proterozoic systems in general. We present the first evidence for syngenetic-to-early-diagenetic OM sulfurization in a Proterozoic basin, which begins to fill a several-billion-year gap in our record of organic S across Earth history. We find that OM sulfurization was particularly extensive in shales from a relatively shallow-water section (Alpha River) but less extensive in shales deposited in deeper water (Shale Valley), which is consistent with models that infer sulfidic ‘wedges’ or O 2 -minimum-zone-type structures on shelf margins at least intermittently at this time. At the shallower site, organic S and pyrite are similarly 34 S-depleted and thus likely formed at roughly the same time near the sediment–water interface under conditions previously interpreted to have been ferruginous to intermittently sulfidic. In contrast, at the deeper-water site, large S-isotope differences between pyrite and organic S along with low apparent OM sulfurization intensities indicate that pyrite formation was favored over OM sulfurization during early sedimentation under variable but primarily ferruginous conditions. Although Mesoproterozoic biomass can be substantially sulfurized, indicators of sulfurization intensity are not correlated with OM concentrations, and therefore sulfurization does not appear to have been the primary driver of enhanced OM concentrations in Arctic Bay Formation shales. The link between sulfurization and total OM preservation may have been modulated during the deposition of Arctic Bay Formation shales by differences in iron availability, nutrient cycling, and particle dynamics in the Mesoproterozoic.

58 GEOSCIENCES↗
DOE OSTI2024

The Kalahari sediments and hominins in southern Africa

In this study, the temporal coupling of the structural evolution of the Kalahari Basin and the accumulation of the Kalahari Group sediments has been an accepted paradigm leading to the assumption that the Kalahari group sediments have been accumulating gradually since the mid-Cretaceous. Here we review the first actual ages for the Kalahari Group based on cosmogenic ages from six geological localities. These results demonstrate that Kalahari Basin infill was a more dynamic process than previously thought and that the Kalahari Group sediments are mostly Plio-Pleistocene in age (~4 Ma to 1–2 Ma). The hiatus between the initial structural subsidence of the basin, during the Cretaceous, and the general young age of the investigated sediments, implies a dynamic landscape in which significant phases of erosion occurred during the Mesozoic and Cenozoic. The magnitude of erosion is manifested by the fact that in many locations Kalahari Neogene to Quaternary sediments overlie Precambrian basement. The age of the present infill of the Kalahari thus falls within the temporal range of the genus Homo. In light of this new understanding, we provide a review of the archaeological evidence from the Kalahari Basin and along its southern fringe. Initial hominin presence is found at Wonderwerk Cave during the Olduvai Event and there is subsequent high-density occupation along the southern fringe of the Kalahari Basin during the Acheulean and the Fauresmith. Middle Stone Age occupation is limited to localities of limited size and small artifact counts and it appears that the focus of human occupation, particularly in the later stages of the Middle Stone Age, shifts southward, including along the coastal regions.

58 GEOSCIENCES↗
DOE OSTI2024

North‐East Peri‐Tethyan Water Column Deoxygenation and Euxinia at the Paleocene Eocene Thermal Maximum

Abstract The Paleocene–Eocene Thermal Maximum (PETM) is associated with climatic change and biological turnover. It shares features with the Oceanic Anoxic Events (OAEs) of the Mesozoic, such as transient global warming and biogeochemical perturbations. However, the PETM experienced a more muted expansion of marine anoxia compared to the Mesozoic OAEs (especially OAE2), with geographically limited evidence for photic zone euxinia (PZE). We explore the extent and drivers of marine deoxygenation during the PETM using biomarkers for water column euxinia and anoxia as well as an intermediate complexity Earth system model (cGEnIE). These reveal that the water column in the North‐East Peri‐Tethys became anoxic, with euxinic conditions reaching the photic zone (PZE) during the PETM. Our model shows that euxinia developed due to a global increase in the ocean nutrient inventory with concomitant oxygen consumption, similar to findings for OAE2. The particularly strong regional response in the NE Peri‐Tethys appears to arise from a combination of global CO 2 ‐weathering forcing, regionally restricted circulation and upwelling of sulphidic thermocline waters. Unlike OAE2, anoxia and PZE do not become widespread in our PETM simulations, consistent with new and existing geochemical and biological proxy data. This globally muted response could result from reduced biogeochemical feedbacks to climate forcing relative to the mid‐Cretaceous climate. Our observations suggest that similar mechanisms operated in response to disparate Cenozoic (PETM) and Mesozoic (OAEs) transient global warming events, while also highlighting that background conditions are crucial in modulating the sensitivity of Earth's system to them.

Behrooz, L.↗
DOE OSTI2023

Preservation of corneous β-proteins in Mesozoic feathers

Fossil proteins are valuable tools in evolutionary biology. Recent technological advances and better integration of experimental methods have confirmed the feasibility of biomolecular preservation in deep time, yielding new insights into the timing of key evolutionary transitions. Keratins (formerly α-keratins) and corneous β-proteins (CBPs, formerly β-keratins) are of particular interest as they define tissue structures that underpin fundamental physiological and ecological strategies and have the potential to inform on the molecular evolution of the vertebrate integument. Reports of CBPs in Mesozoic fossils, however, appear to conflict with experimental evidence for CBP degradation during fossilization. Further, the recent model for molecular modification of feather chemistry during the dinosaur–bird transition does not consider the relative preservation potential of different feather proteins. Here we use controlled taphonomic experiments coupled with infrared and sulfur X-ray spectroscopy to show that the dominant β-sheet structure of CBPs is progressively altered to α-helices with increasing temperature, suggesting that (α-)keratins and α-helices in fossil feathers are most likely artefacts of fossilization. Our analyses of fossil feathers shows that this process is independent of geological age, as even Cenozoic feathers can comprise primarily α-helices and disordered structures. Critically, our experiments show that feather CBPs can survive moderate thermal maturation. Importantly, as predicted by our experiments, analyses of Mesozoic feathers confirm that evidence of feather CBPs can persist through deep time.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Landscape responses to intraplate deformation in the Kalahari constrained by sediment provenance and chronology in the Okavango Basin

The structural depression that occupies the Okavango Basin in southern Africa comprises a depo-centre within the intracratonic Kalahari Basin where sediments of the Cenozoic Kalahari Group have accumulated. The Okavango Basin has been formed due to stretching and subsidence at an area of diffused deformation, southwestwards to the main East African Rift System (EARS). Sediments from two full Kalahari Group sequences, located on opposite sides of the Gumare Fault that forms a major fault within the Okavango Basin, were studied to determine their provenance and chronology. Terrestrial Cosmogenic Nuclide (TCN) 26 Al/ 10 Be burial dating was used to constrain a chronostratigraphical framework, and Pb, Sr, and Nd isotopic ratios combined with geochemical and sedimentological analyses were applied to track the source areas of the sediments.Results indicate the following sequence of basin filling: (a) Accumulation between ca. 4–3 Ma during which the currently downthrown (southern) block received a mixture of sediments mostly from the Choma-Kalomo, Ghanzi-Chobe, and Damara terranes, and possibly from the Lufilian Belt and/or Karoo basalts during earlier stages of deposition. Simultaneously, the upthrown (northern) block received sediments from more distant Archean sources in the Zimbabwe and/or Kasai cratons, (b) Hiatus in sedimentation occurred at both sites between ca. 3–2 Ma, (c) Sediments on both sides of the Gumare Fault share a similar source (Angolan Shield) with minor distinct contributions to the downthrown block from the Kasai Craton and local sources input to the upthrown block, and (d) Regional distribution of aeolian sand since at least 1 Ma. The change in source areas is attributed to rearrangements of the drainage systems that were probably linked to vertical crustal movements on the margins of the Okavango Basin. The tectonically induced morphodynamics controlled the landscape evolution of the endorheic basin where vast lakes, wetlands and salt pans have developed through time.

58 GEOSCIENCES↗
DOE OSTI2024

Rapid in situ diversification rates in Rhamnaceae explain the parallel evolution of high diversity in temperate biomes from global to local scales

Summary The macroevolutionary processes that have shaped biodiversity across the temperate realm remain poorly understood and may have resulted from evolutionary dynamics related to diversification rates, dispersal rates, and colonization times, closely coupled with Cenozoic climate change. We integrated phylogenomic, environmental ordination, and macroevolutionary analyses for the cosmopolitan angiosperm family Rhamnaceae to disentangle the evolutionary processes that have contributed to high species diversity within and across temperate biomes. Our results show independent colonization of environmentally similar but geographically separated temperate regions mainly during the Oligocene, consistent with the global expansion of temperate biomes. High global, regional, and local temperate diversity was the result of high in situ diversification rates, rather than high immigration rates or accumulation time, except for Southern China, which was colonized much earlier than the other regions. The relatively common lineage dispersals out of temperate hotspots highlight strong source‐sink dynamics across the cosmopolitan distribution of Rhamnaceae. The proliferation of temperate environments since the Oligocene may have provided the ecological opportunity for rapid in situ diversification of Rhamnaceae across the temperate realm. Our study illustrates the importance of high in situ diversification rates for the establishment of modern temperate biomes and biodiversity hotspots across spatial scales.

Plant Sciences↗
DOE OSTI2021

The Indian Ocean, its supra-subduction history, and implications for ophiolites

We report Ophiolite complexes represent fragments of ocean crust and mantle formed at spreading centers and emplaced on land. The setting of their origin, whether at mid-ocean ridges, back-arc basins, or forearc basins has been debated. Geochemical classification of many ophiolite extrusive rocks reflect an approach interpreting their tectonic environment as the same as rocks with similar compositions formed in various modern oceanic settings. This approach has pointed to the formation of many ophiolitic extrusive rocks in a supra-subduction zone (SSZ) environment. Paradoxically, structural and stratigraphic evidence suggests that many apparent SSZ-produced ophiolite complexes are more consistent with mid-ocean ridge settings. Compositions of lavas in the southeastern Indian Ocean resemble those of modern SSZ environments and SSZ ophiolites, although Indian Ocean lavas clearly formed in a mid-ocean ridge setting. These facts suggest that an interpretation of the tectonic environment of ophiolite formation based solely on their geochemistry may be unwarranted. New seismic images revealing extensive Mesozoic subduction zones beneath the southern Indian Ocean provide one mechanism to explain this apparent paradox. Cenozoic mid-ocean-ridge–derived ocean floor throughout the southern Indian Ocean apparently formed above former sites of subduction. Compositional remnants of previously subducted mantle in the upper mantle were involved in generation of mid-ocean ridge lavas. The concept of historical contingency may help resolve the ambiguity on understanding the environment of origin of ophiolites. Many ophiolites with “SSZ” compositions may have formed in a mid-ocean ridge setting such as the southeastern Indian Ocean.

58 GEOSCIENCES↗
DOE OSTI2025

Zinc isotope constraints on the cycling of carbon in the Bermuda mantle source

Volatile recycling and storage in the mantle transition zone (MTZ) is important for the refertilization of the upper mantle and is associated with the generation of high-µ (HIMU, where µ is 238 U/ 204 Pb) mantle. One way to probe the MTZ and the processes associated with mantle convection is to sample lavas that originate from the shallow mantle and were contaminated by upwelling from the MTZ, such as at the previously proposed shallow plume of Bermuda. Here we present the first δ 66 Zn isotopic compositions of Bermuda silica-undersaturated and silica-saturated lavas to explore the origin of the carbon-rich lithologies and the genesis of the large seamount found in the western North Atlantic Ocean. Contrasting with global δ 66 Zn data sets, our results (δ 66 Zn between 0.24 ± 0.04 and 0.41 ± 0.04) do not support direct sampling of recycled marine carbonates in the Bermuda HIMU mantle. Instead, we show that δ 66 Zn fractionation toward higher values is associated with magmatic processes and incorporation of carbon sourced from deep fluids associated with the formation of carbonatites. These carbon-rich fluids are likely sourced from the metasomatic reactions between the subducted cold slab of the Iapetus oceanic lithosphere ca. 500 Ma and the thickened continental lithospheric mantle of Pangea. Melting of this metasomatized mantle was triggered by the arrival of the Farallon slab to the eastern North American margin in the late Cenozoic via shallow convection.

Mazza, Sarah E. [Smith College, Northampton, MA (U↗
DOE OSTI2022

Opening-mode fracturing and cementation during hydrocarbon generation in shale: An example from the Barnett Shale, Delaware Basin, West Texas

Relative timing of fracturing is a key input for predictive fracture models, but timing information for fractures is commonly difficult to obtain. In this study, we used crosscutting relations and fluid inclusion assemblage temperatures from fracture cements from a few well-documented sampled fractures, combined with a one-dimensional burial history model, to establish timing for three generations of opening-mode fractures in a Barnett Shale core from the southern part of the Delaware Basin, Pecos County, West Texas. A burial history model is presented for the cored well and matched to measured vitrinite reflectance in samples from the core, and bottomhole temperature in the well. Here, the earliest fractures (group 1) likely formed due to early fluid-expulsion events (ca. 300 Ma) and were folded during host-rock compaction. Later group 2 fractures are sealed with fibrous barite containing primary, liquid hydrocarbon inclusions (mean homogenization temperature [T h ] = –9°C) and aqueous fluid inclusions (mean T h = 108.1°C). Group 2 fractures likely formed in response to fluid overpressure associated with cracking of type II kerogen to oil. Group 3 vertical fractures are up to 2 m in height with kinematic apertures ranging from less than 0.05 to 1.4 mm, partly open, and strike dominantly 010°–020°. Sequentially trapped aqueous fluid inclusions in fracture-spanning quartz cement bridges (mean T h = 110°C in crack-seal texture and 128°C in post-crack-seal fracture cement) record fracture opening under increasing temperature, inferred to reflect increasing burial, with continued overpressuring during the Triassic to Late Cretaceous. Some group 3 fractures may have continued to fill during Cenozoic uplift.

02 PETROLEUM↗
DOE OSTI2024

Adjoint Waveform Tomography for Crustal and Upper Mantle Structure of the Middle East and Southwest Asia for Improved Waveform Simulations Using Openly Available Broadband Data

Here we present a new model of radially anisotropic seismic wavespeeds for the crust and upper mantle of a broad region of the Middle East and Southwest Asia (MESWA) derived from adjoint waveform tomography. The new model enables fully 3D simulations of complete three-component waveforms and provides improved fits that were not possible with previous models. We inverted over 32,000 waveforms from 192 earthquakes recorded by over 1000 openly available broadband seismic stations from permanent and temporary networks in the region with highly uneven coverage. Inversion iterations proceeded from the period band 50–100 s in six stages and 54 total iterations reducing the minimum period to 30 s. Our final model, MESWA, improves waveform fits compared to the starting and other models for both the data used in the inversion and an independent validation set of 66 events. Restitution tests indicate that the model resolves features in the central part of the model to depths of about 150 km. The new model reveals tectonic features imaged by other studies and methods but in a new holistic model of anisotropic shear and compressional wavespeeds (V S and V P , respectively) covering a larger domain with smaller scale length and amplified features. Examples include low crustal V S in the Tethyan belt and low mantle VS following divergent (Gulf of Aden, Red Sea) and transform (Dead Sea fault) margins of the Arabian plate. Low V S is imaged below Cenozoic volcanic centers of the Mecca–Madina–Nafud Line, Arabian Peninsula, and the Türkiye–Iran border region. Elevated V S tracks Makran subduction under southeast Iran with near vertical dip. MESWA could be used as a starting model for further improvements, say, using waveforms from in-country seismic networks that are not currently openly available and/or smaller-scale studies targeting a shorter period. The model could be used to improve earthquake hazard studies and nuclear explosion monitoring.

58 GEOSCIENCES↗
DOE OSTI2021

Discovering Blind Geothermal Systems in the Great Basin Region: An Integrated Geologic and Geophysical Approach for Establishing Geothermal Play Fairways: All Phases

Most geothermal resources in the Great Basin region of the western USA are blind, and thus the discovery of new commercial-grade systems requires synthesis of favorable characteristics for geothermal activity. The geothermal play fairway concept involves integration of multiple parameters indicative of geothermal activity to identify promising areas for new development. This project integrated multiple datasets to apply the play fairway concept and assess geothermal potential in a large region of the Great Basin in Nevada. It is therefore referred to as the Nevada play fairway project. This project was a strong collaborative effort between several organizations, led by the Nevada Bureau of Mines and Geology at the University of Nevada, Reno, but with key support from the U.S. Geological Survey, ATLAS Geosciences, Inc,, Hi-Q Geophysical, Inc., Lawrence Berkeley National Laboratory, Utah Geological Survey, and Innovative Geothermal Ltd. In Budget Period 1 of this project, available data for nine geologic, geochemical, and geophysical parameters were initially synthesized to produce a new detailed geothermal potential map of 96,000 km2 from west-central to eastern Nevada. These parameters were grouped into subsets and individually weighted to delineate rankings for local permeability, intermediate permeability, regional permeability, and thermal potential, which collectively defined geothermal play fairways (i.e., most likely locations for significant geothermal fluid flow). This initial work was aimed at reducing the risks in regional exploration and therefore facilitating discovery of new commercial-grade systems in blind settings, as well as in areas with surface expressions of geothermal activity. Budget Period 2 of the project involved detailed analysis of some of the most promising areas identified in Phase 1. Twenty-four highly prospective areas, including both known undeveloped systems and previously undiscovered potential blind systems, were identified for further analysis. After reconnaissance of these areas, five of the most promising sites were selected for detailed studies. Multiple techniques were employed in the detailed studies, including geologic mapping, shallow temperature surveys, gravity surveys, Lidar, geochemical studies, seismic reflection analysis, and 3D modeling. The goal of the detailed studies was to identify specific areas with the highest likelihood for high permeability and thermal fluids, such that drill sites could be targeted. Three main sets of predictive maps were generated for each detailed study area: 1) play fairway maps, 2) play fairway error maps, and 3) direct evidence maps. Local- and intermediate-scale permeability models were revised to reflect results of the detailed geologic, geophysical, and geochemical analyses. Budget Period 3 of the project involved more detailed geophysical analyses and temperature-gradient (TG) drilling in southeastern Gabbs Valley and northern Granite Springs Valley, deemed the two most promising sites, with the goal of providing preliminary validation of the play fairway methodology. In southeastern Gabbs Valley, the collocation of a favorable structural setting (displacement transfer zone and fault intersections), Quaternary faults, intersecting and terminating gravity gradients, magnetic low, shallow (2 m) temperature anomaly, low resistivity anomaly, and promising geothermometry from nearby water wells provided evidence for a blind system. Drilling of six TG holes defines an apparent geothermal system at this locality with temperatures as high as 124°C at 152 m. This system is blind, with no surface hot springs, fumaroles, or paleo-geothermal deposits. For northern Granite Springs Valley, a favorable structural setting (termination of a major Quaternary normal fault), terminating gravity gradient, magnetic gradient, newly discovered sinter deposits, nearby warm water wells, previously drilled TG holes in the vicinity, and promising geothermometry suggest a hidden system. Drilling of six new TG holes yields temperatures of ~96°C at ~250 m, suggesting the presence of a geothermal system. Major lessons learned in the course of this project include: 1) initially identified sites commonly include multiple favorable structural settings at a finer scale; 2) promising sites in Cenozoic basins cannot be recognized without detailed geophysical surveys; and 3) play fairway analysis should be refined as the exploration program vectors into the most promising sites and finer-scale data are acquired. In addition to producing copious amounts of data, this project resulted in 16 published papers, 10 abstracts, more than 40 presentations across the U.S. and abroad (including several keynote addresses), 2 Masters theses, and 7 media reports.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Adjoint Waveform Tomography for Crustal and Upper Mantle Structure the Middle East and Southwest Asia for Improved Waveform Simulations Using Openly Available Broadband Data

We present a new model of radially anisotropic seismic wavespeeds for the crust and upper mantle of a broad region of the Middle East and Southwest Asia (MESWA) derived from adjoint waveform tomography. We inverted waveforms from 192 Global Centroid Moment Tensor earthquakes (MW 5.5-7.0) recorded by over 1000 openly available broadband seismic stations from permanent and temporary networks in the region. Spatial coverage of the available data is highly uneven due to earthquakes clustered along plate boundaries and sparse coverage of open seismic networks in the region. We considered three possible starting models: the SPiRaL global model (Simmons et al., 2021); MEC-1 (Kaviani et al., 2020); and CSEM2.0 (Noe et al., 2023). Because the SPiRaL model provides good fits to the observed waveforms measured by the time-bandwidth product of selected windows in several period bands, provides all the necessary parameters and covers the entire domain we used it for the starting model with the period band 50-100 seconds. Inversion iterations proceeded using time-frequency phase misfits in six stages and 54 total iterations reducing the minimum period to 30 seconds. Our final model, MESWA, provides improved waveform fits compared to the starting model for both the data used in the inversion and an independent validation data set of 66 events. Two metrics of waveform fit (the time-frequency phase misfit used in the optimization and normalized L2 misfit) were both reduced by nearly 60% for both data sets and MESWA provides significantly larger misfit reductions relative to the SPiRaL model than the MEC-1 or CSEM models. We also find that MESWA provides a larger time-bandwidth product of selected windows indicating that more information content of the observed waveforms is explained by MESWA than the other models. Our new model reveals tectonic features imaged by other studies and methods but in a new holistic model of shear and compressional wavespeeds (v S and v P , respectively) with anisotropy covering the crust and uppermost mantle of a larger domain. MESWA has smaller scale-length features and tends to sharpen some features relative to the SPiRaL starting model. Examples include: low crustal v S in the TurkishIranian Plateau, Zagros Mountains, Afghan Central Blocks and Sulaiman Fold Belt; low mantle vSfollowing divergent (Gulf of Aden, Red Sea) and transform (Dead Sea Fault) margins of the Arabian Plate; low and high v S in the mantle beneath the Arabian Shield and Platform, respectively. Low vS is imaged below Cenozoic volcanic centers of the Arabian Peninsula, the so-called Mecca-Madina-Nafud (MMN) Line. Positive anisotropy (v SH > v SV ) is inferred for asthenospheric depths across the region except where up/downwelling may influence fabric alignment (e.g. Afar, Red Sea, Arabian Shield). Elevated vS tracks Makran subduction under southeast Iran. MESWA resembles the SPiRaL model in its long-wavelength structure, but enhances shorter wavelengths features on the order of 200 km and smaller. The resulting model could be used for as a starting model for further improvements, say using waveforms from in-country seismic networks that are not openly available or smaller-scale studies targeting shorter period waveforms. The model also could be used for source characterization and moment tensor inversion to improve earthquake hazard studies and nuclear explosion monitoring.

58 GEOSCIENCES↗