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A D Fowler - One of the best experts on this subject based on the ideXlab platform.
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an archean submarine pyroclastic flow due to submarine dome collapse the hurd Deposit harker township ontario canada
Geophysical monograph, 2013Co-Authors: C R Scott, D Richard, A D FowlerAbstract:The Hurd Volcaniclastic Deposit lies within the Kinojevis Assemblage, a group of submarine volcanic rocks dominated by Mg-and Fe-rich metamorphosed pillow-basalt. The Volcaniclastic Deposit can be subdivided into two facies, a lower unorganized massive facies and an upper imbricated facies. The lower facies is composed of cm-to-m-scale flow-banded dacite blocks interspersed with angular to curved-to-blocky and equant mm-to-cm-scale fragments of altered glass; it has a sharp but undulatory basal contact with underlying massive to lobate dacitic lavas. Some blocks are partly composed of in-situ breccia, and agglomerations or curvilinear arrays of spherulites. This lithofacies contains well-developed columnar joints that terminate at the sharp contact with the ∼2m thick upper imbricated facies. With the exception of numerous large imbricated tabular clasts, the imbricated facies is dominated by blocky to angular mm-to-cm-scale fragments. The presence of pillows, chert, jig-saw fit breccias, and microscopic quench textures are evidence of a subaqueous environment of Deposition. Similarly, the presence of columnar joints, plastically deformed clasts, quench breccias, and possible gas escape structures indicate hot emplacement, perhaps by a gas-supported pyroclastic flow. Together, the massive and imbricated facies represent one flow unit that was quickly emplaced. The lower facies was Deposited by a high-density flow isolated from the aqueous environment by the development of a steam carapace, whereas the overlying facies was emplaced by a turbulent, aqueous flow. The onset of magmatic fragmentation may have been the result of sudden decompression possibly triggered by the gravitational collapse of a submarine dacite dome.
C R Scott - One of the best experts on this subject based on the ideXlab platform.
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an archean submarine pyroclastic flow due to submarine dome collapse the hurd Deposit harker township ontario canada
Geophysical monograph, 2013Co-Authors: C R Scott, D Richard, A D FowlerAbstract:The Hurd Volcaniclastic Deposit lies within the Kinojevis Assemblage, a group of submarine volcanic rocks dominated by Mg-and Fe-rich metamorphosed pillow-basalt. The Volcaniclastic Deposit can be subdivided into two facies, a lower unorganized massive facies and an upper imbricated facies. The lower facies is composed of cm-to-m-scale flow-banded dacite blocks interspersed with angular to curved-to-blocky and equant mm-to-cm-scale fragments of altered glass; it has a sharp but undulatory basal contact with underlying massive to lobate dacitic lavas. Some blocks are partly composed of in-situ breccia, and agglomerations or curvilinear arrays of spherulites. This lithofacies contains well-developed columnar joints that terminate at the sharp contact with the ∼2m thick upper imbricated facies. With the exception of numerous large imbricated tabular clasts, the imbricated facies is dominated by blocky to angular mm-to-cm-scale fragments. The presence of pillows, chert, jig-saw fit breccias, and microscopic quench textures are evidence of a subaqueous environment of Deposition. Similarly, the presence of columnar joints, plastically deformed clasts, quench breccias, and possible gas escape structures indicate hot emplacement, perhaps by a gas-supported pyroclastic flow. Together, the massive and imbricated facies represent one flow unit that was quickly emplaced. The lower facies was Deposited by a high-density flow isolated from the aqueous environment by the development of a steam carapace, whereas the overlying facies was emplaced by a turbulent, aqueous flow. The onset of magmatic fragmentation may have been the result of sudden decompression possibly triggered by the gravitational collapse of a submarine dacite dome.
Boyd, Ariana Sterling - One of the best experts on this subject based on the ideXlab platform.
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SAND Deposit MAPPING AND AEOLIAN MORPHOLOGIES AS CLUES FOR IDENTIFYING ORIGINS OF DARK SAND IN AEOLIS DORSA, MARS
TRACE: Tennessee Research and Creative Exchange, 2018Co-Authors: Boyd, Ariana SterlingAbstract:Dark sand Deposits occur at all latitudes on the Martian surface. Sand sources in some regions have been inferred via paleo-wind indicator analyses, sand and source mineralogy comparisons, and climate modeling. However, all known sources are sedimentary, leaving outstanding the question of primary igneous origin(s) of these dark sand Deposits. One hypothesis addressing this question is that Volcaniclastic Deposits are a primary origin of Martian sand. Terrestrial analogs of Volcaniclastic units sourcing sand support this hypothesis. However, sand generation has yet to be observed or inferred from any such Martian Deposit. This thesis tests this hypothesis via a case study in Aeolis Dorsa, Mars, a locality where sand overlies bedrock consisting of a hypothesized Volcaniclastic Deposit, the Medusae Fossae Formation (MFF). In addition to the MFF, additional potential external sand sources exist: Elysium Mons, the Cerberus Plains lavas, and the Southern Highlands.To identify likely sand source(s) in Aeolis Dorsa, sand Deposits were mapped to address geospatial sand distribution, scour mark orientations were mapped and analyzed to reveal dominant paleo-wind directions, and instances of apparent erosion of bedrock to dark sediment were recorded. Hierarchical clustering analysis of sand distribution revealed preferential sand Deposition on the peripheries of the MFF and in the southern depression (where bedrock may be remnant southern highlands material). Hierarchical cluster analysis of scour mark distribution revealed spatial groups of scour marks with consistent paleo-wind directions within groups. Such paleo-wind directions provide no evidence for long-distance sand transport from potential external source regions, but instead provide support for paleo-winds controlled by local topography. Apparent erosion of bedrock to dark sediments occurs in both the MFF (in ~20 localities) and in the southern depression (in over 100 localities), suggesting that both the MFF and bedrock in the southern depression have the potential to generate dark sand. The implication that the MFF has the potential to produce dark sand raises two important possibilities: first, that elsewhere along the Martian equator the MFF may have produced dark sand, and second, that other friable layered Deposits (of which the MFF is one) may also serve as sources of Martian sand
D Richard - One of the best experts on this subject based on the ideXlab platform.
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an archean submarine pyroclastic flow due to submarine dome collapse the hurd Deposit harker township ontario canada
Geophysical monograph, 2013Co-Authors: C R Scott, D Richard, A D FowlerAbstract:The Hurd Volcaniclastic Deposit lies within the Kinojevis Assemblage, a group of submarine volcanic rocks dominated by Mg-and Fe-rich metamorphosed pillow-basalt. The Volcaniclastic Deposit can be subdivided into two facies, a lower unorganized massive facies and an upper imbricated facies. The lower facies is composed of cm-to-m-scale flow-banded dacite blocks interspersed with angular to curved-to-blocky and equant mm-to-cm-scale fragments of altered glass; it has a sharp but undulatory basal contact with underlying massive to lobate dacitic lavas. Some blocks are partly composed of in-situ breccia, and agglomerations or curvilinear arrays of spherulites. This lithofacies contains well-developed columnar joints that terminate at the sharp contact with the ∼2m thick upper imbricated facies. With the exception of numerous large imbricated tabular clasts, the imbricated facies is dominated by blocky to angular mm-to-cm-scale fragments. The presence of pillows, chert, jig-saw fit breccias, and microscopic quench textures are evidence of a subaqueous environment of Deposition. Similarly, the presence of columnar joints, plastically deformed clasts, quench breccias, and possible gas escape structures indicate hot emplacement, perhaps by a gas-supported pyroclastic flow. Together, the massive and imbricated facies represent one flow unit that was quickly emplaced. The lower facies was Deposited by a high-density flow isolated from the aqueous environment by the development of a steam carapace, whereas the overlying facies was emplaced by a turbulent, aqueous flow. The onset of magmatic fragmentation may have been the result of sudden decompression possibly triggered by the gravitational collapse of a submarine dacite dome.
Danielsen Jacob - One of the best experts on this subject based on the ideXlab platform.
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Phreatomagmatic Eruption Deposits on the Seafloor Record Cataclysmic Caldera Formation on Axial Seamount, Juan de Fuca Mid-Ocean Ridge
SJSU ScholarWorks, 2019Co-Authors: Danielsen JacobAbstract:The physical and compositional characteristics of a unique ash-rich hydrothermal sediment, hydrothermal muddy tuff (HMT), on Axial Seamount, Juan de Fuca Ridge, suggest that it formed by phreatomagmatic eruptions during caldera formation. Deposit thickness trends away from the seamount summit and the presence of 68% primary volcaniclasts and 32% secondary lithics suggest a source from along caldera ring-faults deep in the crust. Lithic geothermometry indicates that the source was subject to low-temperature (\u3c150 \u3e°C) alteration, consistent with a provenance as deep as 600 – 800 m below the seafloor. At this depth, just above the critical point of seawater, the brittle fragmentation of magma upon interaction with deep-circulating hydrothermal fluids triggered molten fuel coolant interaction (MFCI) and the production of highly angular and very fine grained (100 µm) glass shards. The resulting phreatomagmatic eruption was dispersed over 3.5 km away from the caldera by eruption plume fall-out, ocean bottom currents, and dilute gravity-flows. The result is a unique Volcaniclastic Deposit that has never been described in mid-ocean ridge settings. This study provides the framework for future studies to further explore fragmentation and dispersal mechanisms within the context of deep-marine volcanic setting
