(PDF) Low-temperature hydrothermal alteration of intra …
The δ18O values of the altered intra-caldera tuffs are significantly higher than in unaltered extra- Canary Islands caldera ignimbrites, consistent with an overall low-temperature …
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The δ18O values of the altered intra-caldera tuffs are significantly higher than in unaltered extra- Canary Islands caldera ignimbrites, consistent with an overall low-temperature …
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Saponite- and celadonite-type alteration of the tholeiite section occurred at a normal mid-ocean ridge basalt spreading center at temperatures <20°C. Near- or off-axis intrusion of an alkali basalt magma at depth reinitiated hydrothermal circulation, and the Fe-Si hydrothermal deposit formed from cool (<60°C) distal hydrothermal fluids.
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Ancient intracaldera lacustrine beds commonly show extensive zeolitic alteration and intercalated volcanic rocks and spring deposits (Larsen and Crossey, 1996). In many cases, shallow zeolitic alteration of intracaldera sediments is difficult to distinguish from deeper, high-temperature hydrothermal alteration (Utada et al., 1999).
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The hydrothermal alteration event occurred contemporaneously with the main rifting phase of the Red Sea and widespread low-temperature mineralizations along the Red Sea coast. Abstract The chemical and structural alteration of metamict zircon crystals from a 619±17 (2σ) Ma old, post-tectonic granite in the southern part of the …
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Oxygen isotope compositions of intracaldera rocks: hydrothermal history of the Long Valley Caldera, California
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The low temperature, shallow-water hydrothermal system was discovered by the venting of Fe-rich fluids that produced a seafloor draped by extensive Fe …
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The intracaldera fill, exhibiting stratified units with a maximum thickness of 2 km, consists of at least four seismic units and a thick wedge of landslide debris derived from the caldera wall. ... The magnetization lows indicate sites of submarine hydrothermal vents that caused an alteration of magnetic minerals. Faults recognized on the outer ...
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The altered intra-caldera samples contain minerals characteristic of secondary fluid–rock interaction (clays, zeolites, adularia), and relics of the primary …
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The unique lithium enrichment of illite at Thacker Pass resulted from secondary lithium- and fluorine-bearing hydrothermal alteration of primary neoformed smectite-bearing sediments, a phenomenon ...
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The main inputs of Li to the ocean are river waters and high-temperature hydrothermal fluids, and the main sinks are low-temperature alteration of the oceanic crust and sediment diagenesis (Fig. 1).Estimates of both the size of the Li fluxes, and their isotopic compositions, vary substantially (Fig. 1) as do models for which of these is most …
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The unique lithium enrichment of illite at Thacker Pass resulted from secondary lithium- and fluorine-bearing hydrothermal alteration of primary neoformed smectite-bearing sediments, a phenomenon not previously identified. Post-caldera hydrothermal fluids altered smectite-bearing sediments to Li-rich illite, creating an exceptional lithium deposit.
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The altered intra-caldera samples contain minerals characteristic of secondary fluid-rock interaction (clays, zeolites, adularia), and relics of the primary …
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Over the past 40 years, two universally accepted maxims of geology dealing with zeolite minerals have been shown to be incorrect: the first is that zeolites occur primarily as cavity fillings in basaltic igneous rocks, and the second is that these zeolites crystallized from so-called hydrothermal solutions, i.e. thermal waters from depth. We recognize today that …
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Interaction and equilibration of the intra-caldera tuffs with ambient meteoric water at low temperature can only account for whole-rock δD values of around − 45‰, given that ∆D clay–water is ca. − 30‰ at 100 °C, and decreases in magnitude at higher …
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This study documents large and systematic variations in the K-isotope composition of oceanic crust that has been affected by seafloor hydrothermal alteration, and indicates that analytically resolvable 41K/39K effects arise in Oceanic crust as a result of hydroThermal alteration. Expand
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The hydrothermal alteration event occurred contemporaneously with the main rifting phase of the Red Sea and widespread lowtemperature mineralizations along the Red Sea coast. Discover the world's ...
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In Gran Canaria Island, low-temperature steam fumaroles produced epithermal alteration during the Miocene, with clay minerals, zeolites, and adularia …
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Overall, the results from the intra-caldera tuffs on Gran Canaria are consistent with low-temperature alteration in the shallow, epithermal part of a larger, fault-controlled …
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In many cases, shallow zeolitic alteration of intracaldera sediments is difficult to distinguish from deeper, high-temperature hydrothermal alteration (Utada et al., 1999). Recognition of the differences is important for generalized caldera investigations, for economic investigations, and, in the case of some zeolites (erionite), for health ...
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Low-temperature hydrothermal alteration of intra-caldera tuffs, Miocene Tejeda caldera, Gran Canaria, Canary Islands
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Hydrothermal alteration is an important sink for magnesium, sodium, sulfate and bicarbonate, and a net source of volatiles, iron and other nutrients to the deep ocean and vent ecosystems. Magmatic ...
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In addition, the extent of hydrothermal alteration in the intracaldera volcanic fill beneath the V.S. McConnell et al. /Journal of Volcanology and Geothermal Research 76 (1997) 83-109 87 resurgent dome requires higher temperatures than the present-day 50/km gradient measured in LVEW (Sass et al., 1991; Smith and …
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nogenic intracaldera sediments cov er ~70% of the ~1000-km. 2. McDermitt caldera (Fig. 2) and are locally more than 200 m thick (8, 10). ... Hydrothermal alteration of smectite to illite during ...
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1. Introduction. Production of molecular hydrogen (hereafter hydrogen or H 2) is a phenomenon that can occur naturally during water–rock interaction (Klein et al., 2020).Recently, this process has drawn increasing scientific attention owing to the central role that this molecule plays in supporting deep microbial subsurface ecosystems and in …
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Dacitic lava recovered from the immediate subsurface of the submarine PACMANUS hydrothermal vent field exhibits variable degrees of hydrothermal alteration resulting from the interaction of the glassy volcanic rocks with mineralizing hydrothermal fluids at relatively low temperatures. Transmission electron microscopic (TEM) …
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Zircon occurs in voids and cracks in phosphatic coprolites enclosed in siderite concretions in Mississippian shales near Edinburgh, Scotland. The zircon formed during hydrothermal alteration of early-diagenetic concretions and occurs as spherical aggregates of prismatic crystals, sometimes radiating. Vitrinite reflectance …
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The degassing intracaldera tuff (9) formed the floor of a massive paleo lake within the caldera, on which accumulated a thick (>200 m) sequence of tuffaceous lacustrine sediments until
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High-temperature hydrothermal alteration of oceanic crust is one of the two main sources of potassium (K) to the oceans, with modern flux estimates ranging roughly from ∼8 to 30 % of the K flux from rivers. Despite the role of high-temperature hydrothermal fluids in the global seawater K budget, little is known about its effect on …
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Before subduction into the mantle, the oceanic crust formed at mid-ocean ridges would undergo fluid-rock interaction on the seafloor and within the crust. Study in this regard can enhance our understanding of the seafloor hydrothermal system and crust-mantle recycling. Lithium (Li) is strongly mobilized by hydrous fluids and has significant isotopic …
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Lithium resources, which represent the total amount of Li extractable under current (reserves) plus potentially foreseeable economic conditions, occur primarily as pegmatites, brines, and clays ...
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Extra-caldera shield basalts (lower left) are unconformably overlain by steeply- to shallowly-dipping intra-caldera tuffs of upper-Mogán age to the top right. This sequence …
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