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Peter W Lipman - One of the best experts on this subject based on the ideXlab platform.
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the fish canyon magma body san juan volcanic field colorado rejuvenation and eruption of an upper crustal batholith
Journal of Petrology, 2002Co-Authors: Olivier Bachmann, Michael A Dungan, Peter W LipmanAbstract:from >5·5–6 to 7·7–8·5 wt % Al2O3). Homogeneity in magma More than 5000 km of nearly compositionally homogeneous crystalcomposition at the chamber-wide scale, contrasting with extreme rich dacite (>68 wt % SiO2: >45% Pl + Kfs + Qtz + textural and chemical complexities at the centimeter–millimeter scale, Hbl + Bt + Spn + Mag + Ilm + Ap + Zrn + Po) is consistent with a dynamic environment, wherein crystals with a erupted from the Fish Canyon magma body during three phases: (1) variety of growth and resorption histories were juxtaposed shortly the pre-caldera Pagosa Peak Dacite (an unusual poorly fragmented before eruption by convective currents. Pyroclastic Deposit, >200 km); (2) the syn-collapse Fish Canyon Tuff (one of the largest known ignimbrites, >5000 km); (3) the post-collapse Nutras Creek Dacite (a volumetrically minor lava). The late evolution of the Fish Canyon magma is characterized by
Carlton C Allen - One of the best experts on this subject based on the ideXlab platform.
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complex explosive volcanic activity on the moon within oppenheimer crater
Icarus, 2016Co-Authors: K. A. Bennett, Briony Horgan, Paul O. Hayne, J F Bell, Benjamin T. Greenhagen, Lisa R Gaddis, Carlton C Allen, David Abbey PaigeAbstract:Abstract Oppenheimer crater is a floor-fractured crater located within the South Pole–Aitken basin on the Moon, and exhibits more than a dozen localized Pyroclastic Deposits associated with the fractures. Localized Pyroclastic volcanism on the Moon is thought to form as a result of intermittently explosive Vulcanian eruptions under low effusion rates, in contrast to the higher-effusion rate, Hawaiian-style fire fountaining inferred to form larger regional Deposits. We use Lunar Reconnaissance Orbiter Camera images and Diviner Radiometer mid-infrared data, Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra, and Clementine orbiter Ultraviolet/visible camera images to test the hypothesis that the Pyroclastic Deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. Mineralogically, we find that the Deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor, juvenile clinopyroxene, and juvenile iron-rich glass, and that the mineralogy of the Pyroclastics varies both across the Oppenheimer Deposits as a whole and within individual Deposits. We observe similar variability in the inferred iron content of Pyroclastic glasses, and note in particular that the northwest Deposit, associated with Oppenheimer U crater, contains the most iron-rich volcanic glass thus far identified on the Moon, which could be a useful future resource. We propose that this variability in mineralogy indicates variability in eruption style, and that it cannot be explained by a simple Vulcanian eruption. A Vulcanian eruption should cause significant country rock to be incorporated into the Pyroclastic Deposit; however, large areas within many of the Deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material. Thus, we propose that at least the most recent portion of these Deposits must have erupted via a Strombolian or more continuous fire fountaining eruption, and in some cases may have included an effusive component. These results suggest that localized lunar Pyroclastic Deposits may have a more complex origin and mode of emplacement than previously thought.
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taurus littrow Pyroclastic Deposit high yield feedstock for lunar oxygen
Lunar and Planetary Science Conference, 2015Co-Authors: Carlton C AllenAbstract:Future human habitation of the Moon will likely require the use of locally derived materials because of the high cost of transportation from Earth. Oxygen, extracted from oxides and silicates, is a potentially abundant lunar resource vital for life support and spacecraft propulsion. The anticipated costs of supplying all oxygen needs for a lunar base from Earth are high enough to warrant serious study of oxygen production from local resources.
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taurus littrow Pyroclastic Deposit an optimum feedstock for lunar oxygen
Annual Meeting of the Lunar Exploration Analysis Group, 2014Co-Authors: Carlton C AllenAbstract:Future human habitation of the Moon will likely require the use of locally derived materials because of the high cost of transportation from Earth. Oxygen, extracted from oxides and silicates, is a potentially abundant lunar resource vital for life support and spacecraft propulsion. The anticipated costs of supplying all oxygen needs for a lunar base from Earth are high enough to warrant serious study of oxygen production from local resources. Over 20 different processes have been proposed for oxygen production on the Moon. Among the simplest and best studied of these processes is the reduction of oxides in lunar minerals and glass using hydrogen gas. Oxygen can be extracted from lunar soils and Pyroclastic glass beads by exposing the samples to flowing hydrogen at subsolidus temperatures (approx. 1050 C). Total oxygen yield is directly correlated to the sample's abundance of FeO, but is not correlated to the abundance of any other oxide. Oxygen is extracted predominantly from FeO, with lesser contributions from TiO2 and SiO2. Oxygen yield is independent of soil maturity. All major FeO-bearing phases contribute oxygen, with extraction from ilmenite and glass significantly more efficient than from olivine and pyroxene. This study demonstrates that the optimum location for a lunar resources demonstration mission can be identified, and that the oxygen yield can be predicted, using a combination of high-resolution imaging and thermal-infrared data. A mission to Taurus Littrow will encounter a Deposit at least 10 m in depth with few landing hazards, a uniform composition, and a predicted oxygen yield of approximately 3 wt. %, among the highest values on the Moon.
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Remote Analysis of Regional Lunar Pyroclastic Deposits - Consistency and Precision of LRO Diviner Estimates
2014Co-Authors: Carlton C Allen, Benjamin T. Greenhagen, David A. PaigeAbstract:Allen et al. recently published a new method of estimating the FeO abundances of lunar Pyroclastic Deposits. This method is derived from orbital thermal infrared measurements by the Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter (LRO) spacecraft. The present study utilizes Diviner data from the Taurus Littrow regional Pyroclastic Deposit to assess the consistency and precision of such estimates.
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Analysis of lunar Pyroclastic Deposit FeO abundances by LRO Diviner
Journal of Geophysical Research: Planets, 2012Co-Authors: Carlton C Allen, Benjamin T. Greenhagen, Kerri Donaldson Hanna, David A. PaigeAbstract:[1] Thermal infrared reflectance spectra of rock-forming minerals include a prominent minimum near 8μm, known as the “Christiansen feature” (CF). The inflection point wavelength is sensitive to the degree of polymerization of silicates, which is strongly influenced by major cations – notably iron – in the minerals. Laboratory spectra of lunar soils demonstrate that the CF location is closely correlated to the sample's bulk FeO abundance, across the full range of Apollo soil samples, including Pyroclastic glass. This correlation is the basis for estimating lunar surface FeO abundances using orbital thermal infrared measurements. The Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter includes three thermal infrared channels, selected to determine the CF positions for sites across the lunar surface. Diviner measurements are used to derive FeO abundances in the Aristarchus, Sulpicius Gallus, and Rima Fresnel Pyroclastic Deposits. The calculated FeO abundances for Aristarchus and Sulpicius Gallus lie within the compositional range of FeO-rich Pyroclastic glasses but outside the range of most mare soils, supporting the interpretations of these Deposits as glass rich. The calculated FeO abundance for the Rima Fresnel Deposit is close to that of mare soils, supporting a contention that this Deposit is dominated by basaltic fragments rather than glass. The Diviner measurements hold the potential to determine FeO abundances in many lunar Pyroclastic Deposits. A better understanding of these compositions will provide insight into the magmatic history and composition of the lunar interior, as well as an enhanced inventory of potential resources for future human exploration.
Olivier Bachmann - One of the best experts on this subject based on the ideXlab platform.
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the fish canyon magma body san juan volcanic field colorado rejuvenation and eruption of an upper crustal batholith
Journal of Petrology, 2002Co-Authors: Olivier Bachmann, Michael A Dungan, Peter W LipmanAbstract:from >5·5–6 to 7·7–8·5 wt % Al2O3). Homogeneity in magma More than 5000 km of nearly compositionally homogeneous crystalcomposition at the chamber-wide scale, contrasting with extreme rich dacite (>68 wt % SiO2: >45% Pl + Kfs + Qtz + textural and chemical complexities at the centimeter–millimeter scale, Hbl + Bt + Spn + Mag + Ilm + Ap + Zrn + Po) is consistent with a dynamic environment, wherein crystals with a erupted from the Fish Canyon magma body during three phases: (1) variety of growth and resorption histories were juxtaposed shortly the pre-caldera Pagosa Peak Dacite (an unusual poorly fragmented before eruption by convective currents. Pyroclastic Deposit, >200 km); (2) the syn-collapse Fish Canyon Tuff (one of the largest known ignimbrites, >5000 km); (3) the post-collapse Nutras Creek Dacite (a volumetrically minor lava). The late evolution of the Fish Canyon magma is characterized by
Leon Bardot - One of the best experts on this subject based on the ideXlab platform.
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Emplacement temperature determinations of proximal Pyroclastic Deposits on Santorini, Greece, and their implications
Bulletin of Volcanology, 2000Co-Authors: Leon BardotAbstract:This paper presents the results of a study undertaken to determine emplacement temperatures of volcanic Deposits on the volcano of Santorini, Greece, using palaeomagnetic methods. Two types of breccia have been identified on Santorini, lithic lag breccias and ground breccias; they have been interpreted as Deposits from Pyroclastic flows. However, where the breccia Deposits are not intimately associated with ignimbrite, their origin is ambiguous. Emplacement-temperature determinations were carried out on lithic clasts within these Deposits to assess the origin and to place constraints on their emplacement mechanisms. The results of thermal demagnetization show that all the clasts display at present Earth's field component of magnetization. The Earth's field component indicates that these clasts have cooled from elevated temperatures within the Deposits. Therefore, these breccia Deposits were emplaced hot, verifying their origin as primary products of Pyroclastic eruption. Many of the Deposits display a wide range of emplacement temperatures, and the lowest temperature at any one location probably represents the equilibrium temperature of the Deposit. An emplacement temperature determination records the highest temperature experienced by the clast, before cooling in situ. These clasts may have been heated before, during or after the eruption. In estimating the emplacement temperature, it is important to understand at what stage the clasts were heated. Thermal modelling was carried out to assess the effects of heating of the clasts (a) during the eruption and subsequent transport by hot gases and juvenile pyroclasts within Pyroclastic flows, and (b) by an overlying hot Deposit such as a Pyroclastic Deposit or lava flow. Results from this study indicate that many of the clasts were hot before incorporation took place. This indicates that clasts were either derived from depth within the volcano or that there were abundant rocks at elevated temperature near or at the surface.
J K Russell - One of the best experts on this subject based on the ideXlab platform.
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mapping porosity variation in a welded Pyroclastic Deposit with signal and velocity patterns from ground penetrating radar surveys
Bulletin of Volcanology, 2001Co-Authors: Alison C Rust, J K RussellAbstract:Ground-penetrating radar (GPR) is used to both image and quantify porosity variations in a variably welded Pyroclastic flow Deposit. Characteristic radar signals for nonwelded (constant, high porosity) and welded (porosity lower and variable) zones are identified by comparison of radar signals to exposed stratigraphy. A moderate rate of change in porosity with depth generates abundant, unresolvable reflections. A relatively constant porosity results in a flat, zero-amplitude response. Lastly, a discrete jump or extremely high rate of change in porosity (abrupt at scale of radar wavelength) can produce a strong, distinct reflection. Common-midpoint (CMP) survey data are analyzed to determine relative radar velocity patterns in the Pyroclastic flow. Changes in radar velocity are linked to changes in relative porosities that are attributed to differential welding. Our analysis shows that welding causes substantial reductions in radar velocity. Moisture in subsurface stratigraphy also strongly affects velocity. Therefore, we advocate the interpretation of radar data in terms of relative changes in porosity. Our results also suggest that, in areas of rapid facies changes, multiple CMP surveys are required for accurate conversions of travel time to depth.
