Deep crustal and mantle inputs to North Sister Volcano, Oregon High Cascade Range

The Central Oregon High Cascade Range is an anomalously mafic segment of the Cascade Arc due to ongoing intra-arc extension, which allows most magmas to traverse the crust without stalling and evolving to more evolved compositions. North Sister, a composite volcano in this arc segment, has produced a seemingly monotonous basaltic andesite (52.5-54.0% SiO₂) that is depleted in incompatible elements from [aprroximately] 320 ka until 15 ka. This dissertation addresses the volcanic development of North Sister Volcano and deep crustal processes that produced its basaltic andesite. Stratigraphic variation signaling changes in eruptive style, unconformable contacts, ⁴⁰Ar/³⁹ dating, and geochemical correlations divide North Sister's eruptive history into four stages: (1) the early shield, (2) the subglacial stage, (3) the upper shield stage, and (4) the stratocone stage. Lastly, the north-striking, >1 11-km Matthieu Lakes Fissure (MLF) transected North Sister in three splays. North Sister's eruptive stages correspond to four compositional groups that record a general decrease in compatible elements such as Ni (112 to 35 ppm), while incompatible elements are constant or generally decrease (e.g. Ba 302 to 247 ppm) through time. Isotopic variations at North Sister are small, but systematic; Sr and Nd isotopic ratios become more mantle-like with time. Petrologic modeling places the generation of North Sister's basaltic andesite in the deep crust by a) deciphering upper crustal re-equilibration; b) mixing a primitive, low K tholeiite (LKT) with a silicic, Al-rich partial melt of 5-30 million year old crust; and c) high recharge rates by mantle-derived LKTs and interaction with a refractory crust. The Sr and Nd isotopic ratios of primitive basalts from the Cascade Range define four segments of the arc that reflect separate isotopic reservoirs and mantle melting regimes and correlate with major crustal domains. These segments are 1) north, Mt. Meager to Glacier Peak; 2) Columbia, Mt. Rainier to Mt. Jefferson; 3) central, the North Sister to Medicine Lake, and 4) south, Mt. Shasta to Mt. Lassen. The central segment has Basin and Range in the backarc and is the most restricted in bulk and isotopic composition

Linking Home Plate and Algonquin Class Rocks through Microtextural Analysis: Evidence for Hydrovolcanism in the Inner Basin of Columbia Hills, Gusev Crater

Examining the his-tory of a rock as the summed history of its constituent grains is a proven and powerful strategy that has been used on Earth to maximize the information that can be gleaned from limited samples. Grain size, sorting, roundness, and texture can be observed at the handlens scale, and may reveal clues to transport regime (e.g. fluvial, glacial, eolian) and transport distance. Diagenetic minerals may be of a form and textural context to allow identification, and to point to dominant diagenetic processes (e.g. evaporitic concentration, intermittent dissolution, early vs. late diagenetic emplacement). Handlens scale features of volcaniclastic particles may be diagnostic of primary vs recycled (by surface processes) grains and may provide information about eruptive patterns and processes. When the study site is truly remote, such as Mars, and when there are severe limitations on sample return or sample analysis with other methods, examination at the hand lens scale becomes critical both for extracting a maximum of information, and for best utilizing finite analytical capabilities

Structure and stratigraphy of Home Plate from the Spirit Mars Exploration Rover

Home Plate is a layered plateau observed by the Mars Exploration Rover Spirit in the Columbia Hills of Gusev Crater. The structure is roughly 80 m in diameter, and the raised margin exposes a stratigraphic section roughly 1.5 m in thickness. Previous work has proposed a pyroclastic surge, possibly followed by aeolian reworking of the ash, for the depositional origin for these beds. We have performed a quantitative analysis of the structure, stratigraphy, and sedimentology at this location. Our results are consistent with an explosive volcaniclastic origin for the layered sediments. Analysis of bedding orientations over half of the circumference of Home Plate reveals a radially inward dipping structure, consistent with deposition in the volcanic vent, or topographic draping of a preexisting depression. Detailed observations of the sedimentology show that grain sorting varies significantly between outcrops on the east and west sides. Observations on the western side show a well-sorted population of sand sized grains which comprise the bedrock, while the eastern margin shows a wider range of grain sizes, including some coarse granules. These observations are consistent with primary deposition by a pyroclastic surge. However, aeolian reworking of the upper stratigraphic unit is not ruled out. Identification of explosive volcanic products on Mars may implicate magma interaction with subsurface hydrologic reservoirs in the past

Geochemical properties of rocks and soils in Gusev Crater, Mars: Results of the Alpha Particle X-Ray Spectrometer from Cumberland Ridge to Home Plate

Geochemical diversity of rocks and soils has been discovered by the Alpha Particle X-Ray Spectrometer (APXS) during Spirit’s journey over Husband Hill and down into the Inner Basin from sol 470 to 1368. The APXS continues to operate nominally with no changes in calibration or spectral degradation over the course of the mission. Germanium has been added to the Spirit APXS data set with the confirmation that it occurs at elevated levels in many rocks and soils around Home Plate. Twelve new rock classes and two new soil classes have been identified at the Spirit landing site since sol 470 on the basis of the diversity in APXS geochemistry. The new rock classes are Irvine (alkaline basalt), Independence (low Fe outcrop), Descartes (outcrop similar to Independence with higher Fe and Mn), Algonquin (mafic-ultramafic igneous sequence), Barnhill (volcaniclastic sediments enriched in Zn, Cl, and Ge), Fuzzy Smith (high Si and Ti rock), Elizabeth Mahon (high Si, Ni, and Zn outcrop and rock), Halley (hematite-rich outcrop and rock), Montalva (high K, hematite-rich rock), Everett (high Mg, magnetite-rich rock), Good Question (high Si, low Mn rock), and Torquas (high K, Zn, and Ni magnetite-rich rock). New soil classes are Gertrude Weise (very high Si soil) and Eileen Dean (high Mg, magnetite-rich soil). Aqueous processes have played a major role in the formation and alteration of rocks and soils on Husband Hill and in the Inner Basin

Elemental Composition and Chemical Evolution of Geologic Materials in Gale Crater, Mars: APXS Results From Bradbury Landing to the Vera Rubin Ridge

The Alpha Particle X-ray Spectrometer (APXS) on the rover Curiosity has analyzed the composition of geologic materials along a >20-km traverse in Gale crater on Mars. The APXS dataset after 6.5 Earth years (2,301 sols) includes 712 analyses of soil, sand, float, bedrock, and drilled/scooped fines. We present the APXS results over this duration and provide stratigraphic context for each target. We identify the best APXS measurement of each of the 22 drilled and scooped samples that were delivered to the instruments Chemistry and Mineralogy (CheMin; X-ray diffractometer) and Sample Analysis at Mars (SAM; mass spectrometer and gas chromatograph) during this period. The APXS results demonstrate that the basaltic and alkali-rich units in the Bradbury group (sols 0-750) show minimal alteration indicating an arid climate. In contrast, the Murray formation of the Mount Sharp group (sols ∼750-2,301) has compositions indicating pervasive alteration. Diagenetic features are common and show fluid interaction with the sediment after (and possibly during) lithification. A sandstone unit, the Stimson formation, overlies part of the Murray formation. This has a composition similar to the basaltic sand and soil, suggesting a shared source. Cross-cutting, fracture-associated haloes are evidence of late-stage fluid alteration after lithification of the sediment. The APXS dataset, evaluated in concert with the full science payload of Curiosity, indicates that Gale crater was habitable, and that liquid water was stable for extended periods.We are indebted to NASA-JPL, the Canadian Space Agency, and Australian Research Council (DP150104604) for supporting our work and the MSL mission. A portion of this study was conducted at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration

Hydrothermal origin of halogens at Home Plate, Gusev Crater

In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered clastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X-Ray Spectrometer (APXS), Mössbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini- TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however, has higher abundances of Cl, Br, Zn, and Ge with comparable SO3 to the Irvine basalts. Nanophase ferric oxide (np ox) and volcanic glass were detected in the Barnhill class rocks by Mössbauer and Mini-TES, respectively, and imply greater alteration and cooling rates in the Barnhill than in the Irvine class rocks. The high volatile elements in the Barnhill class agree with volcanic textures that imply interaction with a briny groundwater during eruption and (or) by later alteration. Differences in composition between the Barnhill and Irvine classes allow the fingerprinting of a Na-Mg-Zn-Ge-Cl-Br (±Fe ± Ca ± CO2) brine with low S. Nearby sulfate salt soils of fumarolic origin may reflect fractionation of an acidic S-rich vapor during boiling of a hydrothermal brine at depth. Persistent groundwater was likely present during and after the formation of Home Plate

SchmidtMariekE2006.pdf

The Central Oregon High Cascade Range is an anomalously mafic segment of the Cascade Arc due to ongoing intra-arc extension, which allows most magmas to traverse the crust without stalling and evolving to more evolved compositions. North Sister, a composite volcano in this arc segment, has produced a seemingly monotonous basaltic andesite (52.5-54.0% SiO₂) that is depleted in incompatible elements from [aprroximately] 320 ka until 15 ka. This dissertation addresses the volcanic development of North Sister Volcano and deep crustal processes that produced its basaltic andesite. Stratigraphic variation signaling changes in eruptive style, unconformable contacts, ⁴⁰Ar/³⁹ dating, and geochemical correlations divide North Sister's eruptive history into four stages: (1) the early shield, (2) the subglacial stage, (3) the upper shield stage, and (4) the stratocone stage. Lastly, the north-striking, >1 11-km Matthieu Lakes Fissure (MLF) transected North Sister in three splays. North Sister's eruptive stages correspond to four compositional groups that record a general decrease in compatible elements such as Ni (112 to 35 ppm), while incompatible elements are constant or generally decrease (e.g. Ba 302 to 247 ppm) through time. Isotopic variations at North Sister are small, but systematic; Sr and Nd isotopic ratios become more mantle-like with time. Petrologic modeling places the generation of North Sister's basaltic andesite in the deep crust by a) deciphering upper crustal re-equilibration; b) mixing a primitive, low K tholeiite (LKT) with a silicic, Al-rich partial melt of 5-30 million year old crust; and c) high recharge rates by mantle-derived LKTs and interaction with a refractory crust. The Sr and Nd isotopic ratios of primitive basalts from the Cascade Range define four segments of the arc that reflect separate isotopic reservoirs and mantle melting regimes and correlate with major crustal domains. These segments are 1) north, Mt. Meager to Glacier Peak; 2) Columbia, Mt. Rainier to Mt. Jefferson; 3) central, the North Sister to Medicine Lake, and 4) south, Mt. Shasta to Mt. Lassen. The central segment has Basin and Range in the backarc and is the most restricted in bulk and isotopic composition

Segmentation of the Cascade Arc as indicated by Sr and Nd isotopic variation among diverse primitive basalts.

Abstract In the central Oregon Cascades, extension of the arc has promoted eruption of primitive basalts that are of three types, calcalkaline (CAB), low K tholeiitic (LKT) and rare absarokitic (ABS) in the forearc. Based on a comparison with the distribution of primitive magma types and their 87 Sr/ 86 Sr and 143 Nd/ 144 Nd isotopic signature in the Cascades, we divide the arc into four segments that correspond to distinct tectonic settings and reflect mantle domains and melting regimes at depth. The segments are: 1) the North Segment from Mt. Meager to Glacier Peak; 2) the Columbia Segment from Mt. Rainier to Mt. Jefferson; 3) the Central Segment from the Three Sisters to Medicine Lake, and 4) the South Segment from Mt. Shasta to Lassen Peak. Calcalkaline basalts (CABs) are found all along the arc axis and are produced by fluxing of variable mantle domains by subduction-derived fluid. In the South Segment, the degree of fluxing and melting is greatest as indicated by high 87 Sr/ 86 Sr and Ba/ Ce of CABs relative to other types of ambient basalt and is consistent with the greater abundance of high-Mg basaltic andesite, relative to other segments. High flux and abundant melt is enhanced by the presence of a slab window and subduction of the altered and deformed Gorda Plate. In the northern part of the arc, small degrees of flux melting are coupled with the presence of an enriched mantle component to yield abundant high-field strength element-enriched (HFSE-rich) basalts. Extension and higher heat flow favors the production of abundant low potassium tholeiites LKT in the Central Segment. A distinct shift in 87 Sr/ 86 Sr of low LKTs occurs between the Columbia and Central Segments (0.7028 vs. 0.7034, respectively), which we interpret as juxtaposition of mantle of accreted oceanic terranes, including the enriched large igneous province Siletz Terrane, with encroaching mantle related to the adjacent Basin and Range Province. The latter, although depleted, carries an enrichment signature from an older subduction history. The segmentation presented here for the Cascade Arc provides a framework for testing the relative influences of the downgoing slab, mantle heterogeneity, and the tectonics and make up of the upper place

An overview of PIXL results obtained during the Perseverance rover’s exploration of crater floor lithologies at Jezero Crater, Mars

The Planetary Instrument for X-ray Lithochemistry (PIXL) is a micro-focus X-ray fluorescence spectrometer mounted on the robotic arm of NASA’s Perseverance rover (Allwood et al., 2021). As of the time of this writing, PIXL has acquired high spatial resolution observations of rock and regolith chemistry on the natural surfaces of two targets, named “Naltsos” and Beaujeu”. These targets represent rocks from the Jezero Floor map unit (Njf) of Sun and Stack (2020), and the scanned areas contained a mixture of variably weathered rock, dust, cemented dust-crust, and regolith, the latter collected in local topographic lows on the rock surfaces. On the target “Naltsos” a scan consisting of a single 30mm line with 0.25mm spacing between X-ray analysis points was collected on sol 125; details of the geochemical data associated with the scan of this target are discussed in Schmidt et al. (this meeting). On the target “Beaujeu”, three scans were collected: two identical scans consisting of 21mm by 21 mm grids with 1.5mm spacing between X-ray analysis points (sols 138 and 141), and a 3mm x 7mm map scan with contiguous X-ray analysis points (sol 139). The two grid scans were conducted before and after Beaujeau was scanned by the SuperCam LIBS instrument, with the intention of using the LIBS laser to clear the rock’s surface of loose dust. The PIXL instrument performed all these scans flawlessly, collecting the first high spatial resolution (120-micron beam size), fully quantitative, geochemical map ever collected on the surface of a rock on Mars, allowing texture, geochemistry, and derived mineralogy to be tied together at the sub-mm scale. Additional details of geochemical compositions (Liu et al., this meeting; Schmidt et al, this meeting), multispectral UV-VIS images derived from the PIXL camera and flood light illuminator subsystem (Henneke et al., this meeting), and optical fiducial subsystem performance (Pedersen et al., this meeting) are discussed elsewhere. We will focus on summarizing geochemical and petrologic results derived from PIXL scans collected on rock targets during the Mars 2020 Perseverance exploration of Jezero crater’s floor units, with discussion of the origin and modification history of rocks and soils that have been analyzed by the PIXL instrument

Regional Paleoenvironments Recorded in Sedimentary Rocks of the Western Fan-Delta, Jezero Crater, Mars

International audienceThe Mars 2020 Perseverance rover science team recently completed an investigation of the fan-delta sedimentary sequence [1] and has begun exploration of the crater margin. High resolution chemical, mineralogical, and morphological observations collected with the rover instrument payload provide powerful constraints on rock origins, contextualizing the suite of high-value samples collected as part of the Mars Sample Return campaign