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At least 523 records · Page 29

Utah FORGE: Reports on Northwestern Nevada Well Doublet Drilling and Testing by Fervo Energy

These reports review Fervo Energy's construction of a commercial enhanced geothermal system (EGS). Fervo has qualified full functionality of the system through production testing at commercially relevant operating conditions. The project site is located in a nearfield setting adjacent to an operating geothermal power station in north-central Nevada and is designed to deliver an uplift in high-temperature geothermal flow rates to increase the power capacity at the facility. The project involved drilling a first-of-a-kind EGS horizontal doublet well system consisting of an injection and production well pair within a high-temperature hard-rock geothermal formation. The lithology of the target reservoir is characterized as a mixed metasedimentary and igneous formation, comprised of phyllite, quartzite, diorite, and granodiorite, representative of the geology across the most prospective geothermal areas throughout the western US. This work included a 16-stage plug-and-perforate stimulation treatment which was the first of its kind in a high-temperature mixed metasedimentary and granitic formation in a fully horizontal doublet geothermal well.

15 GEOTHERMAL ENERGY↗

The ferroan-anorthositic suite and the extent of primordial lunar melting

The Apollo highlands rock collection includes more than 100 'pristine' fragments that survived the intense meteoritic bombardment of the ancient lunar crust with unmixed, endogenously igneous compositions. The geochemical anomaly manifested by the 'ferroan-anorthositic suite' (FAS) appears to reflect a geochemical, and probably also a genetic, bimodality among the ancient lunar cumulates. Early models that purported to account for this bimodality as a product of a single magma have been discredited. The model of the present paper implies that the Mg-suite rocks formed by a comparatively normal variety of basaltic fractional crystallization (FC) shortly after the era of magma ocean (MO) crystallization and FAS genesis.

Warren, Paul H.↗

Two contrasting metamorphosed ultramafic-mafic complexes from greenstone belts, the northern Kaapvaal Craton and their significance in Archaen tectonics

The character of Archaean ultramafic-mafic complexes can, given their prominance in greenstone belts, provide critical clues to help deduce the tectonic setting of these belts. Here are described two contrasting, metamorphosed, ultramafic-mafic complexes, the first a partially serpentinized dunitic body with associated chromite from Lemoenfontein, one of several peridotitic bodies occurring as discrete lenses and pods in granulite facies gneisses of the northern Kaapvaal craton. The second, the Rooiwater complex is a major layered igneous body, now metamorphosed in the amphibolite facies, but without pervasive deformation, which crops out in the northern Murchison greenstone belt. The Lemoenfontein chromites and associated ultramafic rocks are lithologically and chemically similar to their Phanerozoic equivalents of ophiolitic origin, interpreted as obducted oceanic crust. The Lemoenfontein complex is a remnant of Archaean oceanic material. In contrast, the Rooiwater complex is, despite the lack of exposed intrusive contacts, similar to layered igneous complexes such as Ushushwana or Bushveld. These complexes are intrusive in continental environments. It is concluded that contrasting ultramafic-mafic complexes represent a heterogeneity in greenstone belts with either oceanic or continental environments involved.

Smit, C. A.↗

The magma ocean from the Fra Mauro shoreline - An overview of the Apollo 14 crust

Petrographic and mineralogical studies of coarse grained, polymineralic, texturally monominct igneous clasts from the Apollo 14 breccias show troctolite and troctolitic anorthosite to be the most abundant rock types. The second most abundant group consists of plagioclase cumulates with more evolved mineral compositions than the Mg-rich trend anorthosite cumulates. Coarse grained ilmenite gabbros and mineralogically evolved monzonoritic and granitic clasts are widespread in occurrence, but not abundant. The present data provide further support for widespread regional heterogeneities within the early lunar crust.

Hunter, R. H.↗

Ge abundances in the lunar mantle and implications for the origin of the Moon

Regardless of the origin of the Moon, metal segregation must have occurred within the moon in order to account for its low siderophile element abundances relative to the Earth or chondrites. Germanium is a strongly siderophile element whose bulk distribution coefficient indicates that it is not fractionated during igneous processes on the Moon. The variability in absolute Ge abundances in mare basalts and pristine highland rocks, rather than elemental ratios, can be used to infer lunar mantle abundances and processes. Literature data have been compiled for Ge abundances in mare basalts and pristine highland rocks. For some landing sites, samples with 12 ppb Ge were considered to be extreme outliers and are not included. The Apollo 15 samples are enriched in Ge by a factor of 2.5 over the Apollo 12, 16 and 17 samples. Other siderophile element variations have been found in the Moon. Based on this data, best estimate of the average Ge abundance in the silicate portion of the Moon is 3.52 ppb. The Moon is depleted, relative to chondritic abundances, by a factor of 38,000 normalized to Si. Two possible explanations for the observed variations in Ge abundance in the Moon are: (1) more metal may have segregated from some regions of the Moon than from others; or Ge-bearing material may been been added later in the evolution of the Moon.

Dickinson, T.↗

Weathering and Sedimentation in Basaltic Terrains On Earth; Implications For the Paleoclimate of Gale Crater, Mars

In the Early Hesperian period, rivers transported detritus from igneous source terrains to a downstream lake within Gale crater, Mars, creating a stratified stack of fluviolacustrine rocks that is currently exposed along the slopes of Mount Sharp[e.g., 1-2]. Debate still exists regarding the paleo climate that supported overland flow of liquid water at Gale crater, in large part because little is known about how chemical and mineralogical paleoclimate indicators from mafic-rock dominated source-to-sink systems are translated into the rock record. Here, we present the findings from Thorpe et al., (2021), where we compiled data from basaltic terrains with varying climates on Earth in order to provide a reference frame for the conditions that may have prevailed during the formation of the sedimentary strata in Gale crater, particularly focusing on the Sheepbed and Pahrump Hills members.

M T Thorpe↗

Petrology of brecciated ferroan noritic anorthosite 67215

A petrologic study of breccia 67215 is presented, showing that the rock has the bulk composition of a ferroan noritic anorthosite and is a polymict breccia containing several lithic clast types within a crushed, cataclastic matrix. The dominant lithic clasts contained in breccia 67215 are found to be igneous and metamorphic low- and high- Ca pyroxenes and olivine. Other clasts include granulated and sheared clasts, coarse-grained anorthosite with relatively Fe-rich augite, aphanitic, feldspathic microporphyritic melt breccias, and an impact-melt rock with strongly zoned relatively Mg-rich pyroxene. It is concluded that this rock type is relatively common in the highlands regolith excavated by the North Ray Crater.

Mcgee, James J.↗

Petrology and geochemistry of the high-pressure Nilgiri Granulite Terrane, Southern India

The Nilgiri granulite terrane in Southern India is predominantly composed of late Archaean medium- to coarse-grained enderbitic to charnockitic rocks. The dominant regional foliation strikes N60 to 70E with generally steep dips. Tight minor isoclinal folds have been observed in places. Granoblastic polygonal micro-structures are common and indicate thorough post-kinematic textural and chemical equilibration at conditions of the granulite facies (2.5 Ga ago). Late compressional deformation in connection with the formation of the Moyar and Bhavani shear zones to the north and south of the Nilgiri block, resulted in wide-spread development of weakly to strongly strained fabrics and was accompanied by minor rehydration. Enderbites and charnockites range from tonalitic to granodioritic in composition. A magmatogenic origin of the protoliths is inferred from their chemical characteristics which resemble those of the andesitic to dacitic members of Cordillera-type calc-alkaline igneous suites. A significant lithological feature of the Nilgiri granulite terrane are numerous extended bodies, lenses and pods of gabbroic and pyroxenitic rocks which are aligned conformable to the foliation of the enderbite-charnockite complex and which have also been deformed and metamorphosed at granulite facies conditions.

Srikantappa, C.↗

The Black Pearl mine, Arizona - Wolframite veins and stockscheider pegmatite related to an albitic stock

Wolframite-bearing quartz veins flanked by greisen alteration occur at and near the Black Pearl mine, Yavapai County, Arizona. The veins are genetically related to a small albitite stock, and cut a series of Proterozoic metasedimentary and intrusive rocks. The largest vein, the only one mined, is located at the apex of the stock. Field relations imply that this stock is a late-stage differentiate of time 1.4-Ga anorogenic Lawler Peak batholith, which crops out about 3 km to the south. The albitites are of igneous origin and have suffered only minor deuteric alteration. A thin (1 to 2 m) pegmatite unit ('stockscheider') occurs at the contact of the Black Pearl Albitite stock with the country rocks. Directional indicators and other evidence suggest that the pegmatite was formed in the presence of a volatile-rich fluid phase close to the time of magma emplacement. The sudden change from coarse-grained microcline-rich pegmatite to fine-grained, albite-rich albitite suggests pressure quenching, possibly due to escape of fluids up the Black Pearl vein. Stockscheider-like textures typically occur near the apical contacts of productive plutons. The presence or absence of this texture is a useful guide in prospecting for lithophile metal deposits.

Schmitz, Christopher↗

North Massif lithologies and chemical compositions viewed from 2-4 mm particles of soil sample 76503

We identify the lithologic and compositional components of soil 76503 based on INAA of 243 2-4-mm particles and 72 thin sections from these and associated 1-2-mm particles (76502). We present a statistical distribution of the major compositional types as the first step of a detailed comparative study of the North and South Massifs. The soil sample was collected well away from any boulder and is more representative of typical North Massif material than any single large rock or boulder sample. So far, our examination of the 76503 particles has provided a better definition of precursor igneous lithologies and their petrogenetic relationships. It has enabled us to refine the nature of mixing components for the North Massif less than 1-mm fines. It has confirmed the differences in lithologies and their proportions between materials of the North and South Massifs; e.g., the North Massif is distinguished by the absence of a 72275-type KREEP component, the abundance of a highly magnesian igneous component, and the absence of certain types of melt compositions found in the South Massif samples.

Bishop, Kaylynn M.↗

A Mars 2020 Perseverance SuperCam Perspective on the Igneous Nature of the Máaz Formation at Jezero Crater, Mars

The Mars2020 Perseverance rover landed in Jezero crater in February 2020,and first encountered the Máaz formation (or Crater floor-fractured rough(Cf-fr) unit previously mapped based on orbital data[1]).In this study, we use data from the SuperCam instrument(SCAM) to show that the Máaz formation has an igneous origin. SuperCam is a remote-sensing instrument onboard Perseverance, and investigates the texture, mineralogy, and chemistry of rocks and soils, as well as atmospheric features [2,3]. SuperCam comprises the Remote Micro Imager (RMI) to provide high-resolution images, laser-induced breakdown spectroscopy (LIBS)to investigate the major and minor element chemistry of materials, Raman, and passive visible-near infrared (VISIR) spectroscopy to analyze the mineralogy of targets, and time-resolved luminescence spectroscopy (TRLS)to measure organic fluorescence and inorganic luminescence. In addition, the microphone (MIC) can constrain the rock hardness through measurements of the shockwave of LIBS shots. In this study, we use LIBS-based major-oxide compositions (MOC),quantified using the calibration in [2].

Mars 2020↗

Watson: A new link in the IIE iron chain

Watson, which was found in 1972 in South Australia, contains the largest single silicate rock mass seen in any known iron meteorite. A comprehensive study has been completed on this unusual meteorite: petrography, metallography, analyses of the silicate inclusion (whole rock chemical analysis, INAA, RNAA, noble gases, and oxygen isotope analysis) and mineral compositions (by electron microprobe and ion microprobe). The whole rock has a composition of an H-chondrite minus the normal H-group metal and troilite content. The oxygen isotope composition is that of the silicates in the IIE iron meteorites and lies along an oxygen isotope fractionation line with the H-group chondrites. Trace elements in the metal confirm Watson is a new IIE iron. Whole rock Watson silicate shows an enrichment in K and P (each approximately 2X H-chondrites). The silicate inclusion has a highly equilibrated igneous (peridotite-like) texture with olivine largely poikilitic within low-Ca pyroxene: olivine (Fa20), opx (Fs17Wo3), capx (Fs9Wo14)(with very fine exsolution lamellae), antiperthite feldspar (An1-3Or5) with less than 1 micron exsolution lamellae (An1-3Or greater than 40), shocked feldspar with altered stoichiometry, minor whitlockite (also a poorly characterized interstitial phosphate-rich phase) and chromite, and only traces of metal and troilite. The individual silicate minerals have normal chondritic REE patterns, but whitlockite has a remarkable REE pattern. It is very enriched in light REE (La is 720X C1, and Lu is 90X C1, as opposed to usual chonditic values of approximately 300X and 100-150X, respectively) with a negative Eu anomaly. The enrichment of whole rock K is expressed both in an unusually high mean modal Or content of the feldspar, Or13, and in the presence of antiperthite.

Olsen, Edward↗

Petrography of shock features in the 1953 Manson 2-A drill core

Drilling of Nx core in late 1953 into an anomalous zone of disturbed rocks northwest of Manson, Iowa disclosed presence of extensive breccias including crystalline rocks brought to the surface from depths of 4 km or more. Hole 2-A penetrated breccias dominated by leucocratic igneous and metamorphic lithologies, later interpreted to be part of a general ringed peak complex within a 35 km wide impact structure produced about 65 Ma ago. Proof of this origin was given in 1966 by NMS through recognition of shock metamorphic features in 2-A materials during a cursory examination of samples provided by R.A. Hoppin, University of Iowa. A detailed study of this material now underway has revealed that most breccia clasts in 2-A show abundant and varied evidence of shock damage, including extensive planar deformation features (PDF) in quartz, K-feldspar, plagioclase, and a pyroxene and varying degrees of isotropization and incipient melting in feldspars.

Short, N. M.↗

Compositional Constraints on Hematite-Rich Spherule (Blueberry) Formation at Meridiani Planum, Mars

Meridiani Planum was chosen as the landing site for the Mars Exploration Rover Opportunity partially based on Mars Global Surveyor Thermal Emission Spectrometer data indicating an abundance of hematite. Hematite often forms through processes that involve water, so the site was a promising one to determine whether conditions on Mars were ever suitable for life. Opportunity struck pay dirt; it s Miniature Thermal Emission Spectrometer (Mini-TES) and Mossbauer Spectrometer (MB) confirmed the presence of hematite in sulfate-rich sedimentary beds and in lag deposits. Meridiani Planum rocks contain three main components: silicate phases, sulfate and possibly chloride salts, and ferric oxide phases such as hematite. Primary igneous phases are at low abundance despite the basaltic origin of the protoliths. Jarosite, an alkali ferric sulfate, was identified by Mossbauer. Some of the hematite is contained in the spherules, and some resides in finer grains in outcrops. Mossbauer and Mini-TES data indicate that hematite is a dominant constituent of the spherules. Panoramic Camera (Pancam) and Microscopic Imager (MI) images of spherule interiors show that hematite is present throughout. The exact composition of the spherules is unknown. Mini-TES only identifies a hematite signature in the spherules; any other constituents have an upper limit of 5-10% .The MB data are consistent with the spherules being composed of only hematite.

Schneider, A. L.↗

Iron Redox Systematics of Martian Magmas

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite [1]. Morris et al. [1] propose that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks [2,3]. Magnetite stability in terrestrial magmas is well understood, as are the stability of FeO and Fe2O3 in terrestrial magmas [4,5]. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas we have undertaken an experimental study with two emphases. First we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition. Second, we determine the FeO and Fe2O3 contents of the same shergottite bulk composition at 1 bar and variable fO2 at 1250 C, and at variable pressure. These two goals will help define not only magnetite stability, but pyroxene-melt equilibria that are also dependent upon fO2.

Righter, K.↗

Unusual Iron Redox Systematics of Martian Magmas

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite. Morris et al. proposed that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks. Magnetite stability in terrestrial magmas is well understood, as are the stabilities of FeO and Fe2O3 in terrestrial magmas. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas, we have undertaken an experimental study with two emphases. First, we determine the FeO and Fe2O3 contents of super- and sub-liquidus glasses from a shergottite bulk composition at 1 bar to 4 GPa, and variable fO2. Second, we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition.

Danielson, L.↗

Mineralogy, Provenance, and Diagenesis of a Potassic Basaltic Sandstone on Mars: CheMin X-Ray Diffraction of the Windjana Sample (Kimberley Area, Gale Crater)

The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X-ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, approximately Or(sub 95)); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (approximately 25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X-ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations-like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser-Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K-rich targets have 5.6% K2O, approximately 1.8 times that of Windjana, implying a sediment component with greater than 40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K-rich sediment component is consistent with APXS and ChemCam observations of K-rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g.,mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar-age terranes on Earth.

Treiman, Allan H.↗