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  • 1
    Publication Date: 2024-03-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Heat flow is estimated at eight sites drilled int the Guaymas Basin, Gulf of California, during the International Ocean Discovery Program Expedition 385. The expedition sought to understand the thermal regime of the basin and heat transfer between off‐axis sills intruding the organic‐rich sediments of the Guaymas Basin, and the basin floor. The distinct sedimentation rates, active tectonics, and magmatism make the basin interesting for scientific discoveries. Results show that sedimentation corrected heat flow values range 119–221 mW/m〈sup〉2〈/sup〉 in the basin and 257–1003 mW/m〈sup〉2〈/sup〉 at the site of a young sill intrusion, denominated Ringvent. Thermal analysis shows that heat in the Guaymas Basin is being dissipated by conduction for plate ages >0.2 Ma, whereas younger plate ages are in a state of transient cooling by both conduction and advection. Drilling sites show that Ringvent is an active sill being cooled down slowly by circulating fluids with discharge velocities of 10–200 mm/yr. Possible recharge sites are located ca. 1 km away from the sill's border. Modelling of the heat output at Ringvent indicates a sill thickness of ca. 240 m. A simple order‐of‐magnitude model predicts that relatively small amounts of magma are needed to account for the elevated heat flow in non‐volcanic, sediment‐filled rifts like the central and northern Gulf of California in which heating of the upper crust is achieved via advection by sill emplacement and hydrothermal circulation. Multiple timescales of cooling control the crustal, chemical and biological evolution of the Guaymas Basin. Here, we recognize at least four timescales: the time interval between intrusions (ca. 10〈sup〉3〈/sup〉 yr), the thermal relaxation time of sills (ca. 10〈sup〉4〈/sup〉 yr), the characteristic cooling time of the sediments (ca. 10〈sup〉5〈/sup〉 yr), and the cooling of the entire crust at geologic timescales.〈/p〉
    Description: Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California http://dx.doi.org/10.13039/501100003089
    Description: German Research Center for Geosciences
    Description: https://web.iodp.tamu.edu/LORE/
    Description: https://mlp.ldeo.columbia.edu/logdb/scientific_ocean_drilling/
    Keywords: ddc:551.1 ; Guyamas Basin ; Heat Flow ; Heat Transfer ; IODP Expedition 385
    Language: English
    Type: doc-type:article
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  • 2
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    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (12). pp. 5244-5262.
    Publication Date: 2018-02-28
    Description: Large volumes of magma emplaced within sedimentary basins have been linked to multiple climate change events due to release of greenhouse gases such as CH4. Basin-scale estimates of thermogenic methane generation show that this process alone could generate enough greenhouse gases to trigger global incidents. However, the rates at which these gases are transported and released into the atmosphere are quantitatively unknown. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release and transport of methane and to evaluate flow patterns within these systems. Our results show that the methane generation potential in systems with fluid flow does not significantly differ from that estimated in diffusive systems. The values diverge when vigorous convection occurs with a maximum variation of about 50%. The fluid migration pattern around a cooling, impermeable sill alone generates hydrothermal plumes without the need for other processes such as boiling and/or explosive degassing. These fluid pathways are rooted at the edges of the outer sills consistent with seismic imaging. Methane venting at the surface occurs in three distinct stages and can last for hundreds of thousands of years. Our simulations suggest that although the quantity of methane potentially generated within the contact aureole can cause catastrophic climate change, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales (〈 10,000 years).
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    Nature Research
    In:  In: Physical Geology of Shallow Magmatic Systems. , ed. by Breitkreuz, C. and Rocchi, S. Advances in Volcanology . Nature Research, Cham, Switzerland, pp. 119-130.
    Publication Date: 2019-01-14
    Description: Subvolcanic systems are characterized by complex combinations of intrusive units (dykes, sills, saucer-shaped sills, cone sheets, etc.) for which genetic relationships are unclear. This chapter explains how whole-rock geochemistry may be used to resolve the genetic relationships of such subvolcanic (and volcanic) systems. We start with a short introduction of the geochemical fingerprinting method with particular emphasis on the statistical refinement method called Forward Stepwise-Discriminant Function Analysis (FS-DFA). Combined with field mapping and structural analysis, geochemical fingerprinting based on major and trace elements and isotope ratios, is a very powerful tool to distinguish between igneous units (lavas, sills, dykes) with subtle (or not so subtle) geochemical differences. Different geochemical fingerprinting or signatures indicate derivation from distinct magma batches. The results from FS-DFA analyses may be used to reveal genetic relationships between geological units, or lack of such, which again may be used to throw light on subvolcanic plumbing systems, the feeding system in sill-dyke complexes, as well as other problems. The method is illustrated by studies of the Golden Valley Sill Complex in the Karoo Basin (South Africa).
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 4
    Publication Date: 2022-06-28
    Description: We document the geometry of a massive sill at the root of an approximately 20-m high and 800m-wide ring of hydrothermal formations, termed Ringvent, located 28.5 km off-axis on the northwestern flanking regions of the actively rifting Guaymas Basin (Gulf of California). Using petrophysical data collected during the IODP Expedition 385 and processed 2D seismic profiles, we present evidence on the mechanics of sill emplacement and how the related hydrothermal vent conduits were constructed. The currently active moderate-temperature hydrothermal vent field indicates that, despite being cold and crystallized, the magma plumbing system, is tapping into a deeper geothermal source of the basin. The vent system roots at the vertical end of the magma plumbing system with the top of the sill located at a depth range of 80 to 150 m below the seafloor. Our research aims at constraining how far deep the geothermal fluids are coming from, and identifying how close the hydrothermal system is from a steady-state condition, to draw implications for how frequently such a system may arise in nascent ocean basins.
    Type: Conference or Workshop Item , NonPeerReviewed
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