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.
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 …
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 ...
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 ...
DOI: 10.1016/J.JVOLGEORES.2008.06.032 Corpus ID: 129005077; Zeolitization of intracaldera sediments and rhyolitic rocks in the 1.25 Ma lake of Valles caldera, New Mexico, USA @article{Chipera2008ZeolitizationOI, title={Zeolitization of intracaldera sediments and rhyolitic rocks in the 1.25 Ma lake of Valles caldera, New Mexico, USA}, …
intra-caldera samples, and of equivalent unaltered extra-caldera rocks, we are able to characterise the mineralogical, elemental and isotopic changes brought about by …
Potassium fertilizers (potash) are mined in a handful of countries in the Northern Hemisphere. Potash is either expensive or unavailable to the farmers of the Southern Hemisphere. Alkaline alteration of K-feldspar rock (ultrapotassic syenite) in autoclave in the presence of Ca2+ generates a mixture of K-bearing calcium-aluminum …
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) …
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 …
The low temperature, shallow-water hydrothermal system was discovered by the venting of Fe-rich fluids that produced a seafloor draped by extensive Fe …
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 ...
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 …
Quantitative X-ray diffraction analysis of about 80 rhyolite and associated lacustrine rocks has characterized previously unrecognized zeolitic alteration throughout the Valles caldera resurgent dome. The alteration assemblage consists primarily of smectite-clinoptilolite-mordenite-silica, which replaces groundmass and fills voids, especially in the tuffs and …
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Low-Temperature Hydrothermal Alteration of Intra-Caldera Tuffs, Miocene Tejeda Caldera, Gran Canaria, Canary Islands E. 1DONOGHUE V.R. TROLL1 C. 2HARRIS A. O' HALLORAN1 T.R. WALTER3 F.J. PÉREZ TORRADO4 1 Department of Geology, Trinity College, Dublin, Ireland; [email protected] 2 Department of Geological Sciences, …
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 …
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 …
Hydrothermal manifestations are notably absent in the western caldera moat (Bailey and others, 1976); however, detailed mapping (Suemnicht and Varga, 1988) and remote sensing studies of the western caldera (Martini, 2002) identify many high-temperature alteration mineral assemblages <100,000 years old that are related to vigorous …
The time of the hydrothermal alteration is determined by a lower intercept age of a U-Pb SHRIMP discordia of 17.9 (2σ) Ma, which is in good agreement with an apatite fission track age of 22.2 (2σ) Ma. The hydrothermal alteration event occurred contemporaneously with the main rifting phase of the Red Sea and widespread low- …
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 …
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 …
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 ...
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 …
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 ...
Low-temperature hydrothermal alteration of basement from Site 801 was studied through analyses of the mineralogy, chemistry, and oxygen isotopic compositions of the rocks. The more than 100-m ...
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 at least ~15.7 Ma ago (8). During this interval, intracaldera magmat-ic resurgence resulted in minor volcanism and uplift of the
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).
The relative age relationships and stable isotopic geochemistry indicate the intermediate argillic alteration assemblage represents the flux of magmatic-derived hydrothermal fluid that mixed with external fluid and thus represents either the last fluid pulse in the porphyry Cu deposit or a younger, temporally distinct hydrothermal fluid.
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
Illite concentrations measured in situ range from ~1.3 to 2.4 weight % of Li within fluorine-rich illitic claystones. 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.
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In Gran Canaria Island, low-temperature steam fumaroles produced epithermal alteration during the Miocene, with clay minerals, zeolites, and adularia …