Magmatic-Hydrothermal Fluids

Elements ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 401-406 ◽  
Author(s):  
Andreas Audétat ◽  
Marie Edmonds
Keyword(s):  
Metal Content ◽  
Fluid Phase ◽  
Volcanic Eruptions ◽  
Hydrothermal Systems ◽  
Ore Deposits ◽  
Hydrothermal Fluids ◽  
Geological Processes ◽  
Mineral Growth ◽  
Fluid Saturation ◽  
Fluid Phase Equilibria

Magmatic-hydrothermal fluids play a key role in a variety of geological processes, including volcanic eruptions and the formation of ore deposits whose metal content is derived from magmas and transported to the site of ore deposition by means of hydrothermal fluids. Here, we explain the causes and consequences of fluid saturation in magmas, the corresponding fluid-phase equilibria, and the behavior of metals and ligands during the transition from magma to an exsolved hydrothermal fluid. Much of what we know about magmatic-hydrothermal systems stems from the study of fluid inclusions, which are minute droplets of fluids trapped within minerals during mineral growth.

Seawater dissolved gases associated with hydrothermal fluids in convergent margins (Brandsfield-South Shetland, Antarctica) and mid-ocean ridge and intraplate settings (Azores, Portugal)

2020 ◽  
Author(s):  
María Asensio-Ramos ◽  
Cecilia Amonte ◽  
Esther Santofimia ◽  
Gladys V. Melián ◽  
Enrique López ◽  
...  
Keyword(s):  
Water Column ◽  
Sea Water ◽  
Volcanic Eruptions ◽  
Isotopic Signature ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Convergent Margins ◽  
Dissolved Gases ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

<p>The occurrence of hydrothermal emissions implies the existence of heat sources related to magma reservoirs both in convergent margins (Bransfield-South Shetland) and in mid-ocean ridge and intra-plate settings (Azores). The importance of these systems lies in (a) producing important mineralizations,  (b) favouring extremophilic ecosystems, (c) being precursors of underwater volcanic eruptions, (d) playing a major role they play in the matter and energy exchange between the geosphere and the hydrosphere and (d) their impact on the geochemistry of the oceans. In subduction margins, rifts, transforming faults or volcanic buildings in hot spots, emissions of hot fluids related to magmas and/or circulation in hydrothermal systems can occur. The fluids associated with magmas are fundamentally gases (CO<sub>2</sub>, H<sub>2</sub>O, H<sub>2</sub>, SO<sub>2</sub>, H<sub>2</sub>S, He, etc.). Hydrothermal fluids constitute a complex system where seawater percolates through fissures and fractures in sediments and rocks at different depths and heats up upon contact with magmas and hot volcanic rocks, leaching a large amount of chemical elements. The identification of acoustic plumes in the water column is the first step in the exploration of unknown underwater emissions. The new acoustic detection technologies, which operate with a wide frequency range, are one of the most innovative tools for detecting gas plumes and other fluids in the water column, especially in deep waters. Once detected, physical-chemical parameters (temperature, salinity, turbidity, cations, anions, dissolved gases, isotopic signature, etc.) that allow their characterization and classification will be determined. This type of studies is particularly useful when it is not possible to collect free gases, fumarolic and/or bubbling gases, as in the case of submarine activity. In this work, we show the results obtained regarding the chemical composition of dissolved gases (He, H<sub>2</sub>, CO<sub>2</sub> (aq), O<sub>2</sub>, N<sub>2</sub>, CH<sub>4</sub> and He) and isotopic signature of the dissolved CO<sub>2</sub> (δ<sup>13</sup>C-CO<sub>2</sub>) in sea water sampled in sites of hydrothermal interest. With this purpose, we carried out two oceanographic surveys (EXPLOSEA1 and EXPLOSEA2) in 2019: the first in Antarctica aboard the Spanish Research Vessel (RV) Hespérides and the second in North Atlantic Ocean aboard the Spanish RV Sarmiento de Gamboa. To do so, 13 and 10 water vertical profiles were studied in the RV Hespérides and the RV Sarmiento de Gamboa, respectively, using a SBE 911plus CTD system where there was evidence of acoustic plumes or where appropriate, emission buildings of fluids were present. Water samples were kept in glass bottles for subsequent analysis. The establishment of the physicochemical characteristics of volcanic hydrothermal fluids and the characterization of the nature and origin of the different types of fluid emissions will help to classify the hydrothermal fluids in order to understand the phenomena that take place in them and their surroundings.</p>

scholarly journals 3.5-Ga hydrothermal fields and diamictites in the Barberton Greenstone Belt—Paleoarchean crust in cold environments

2016 ◽  
Vol 2 (2) ◽  
pp. e1500368 ◽  
Author(s):  
Maarten J. de Wit ◽  
Harald Furnes
Keyword(s):  
South Africa ◽  
Sea Level ◽  
Volcanic Rocks ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Sea Floor ◽  
Cold Environments ◽  
Barberton Greenstone Belt ◽  
Mineral Growth ◽  
Hydrothermal Fields

Estimates of ocean temperatures on Earth 3.5 billion years ago (Ga) range between 26° and 85°C. We present new data from 3.47- to 3.43-Ga volcanic rocks and cherts in South Africa suggesting that these temperatures reflect mixing of hot hydrothermal fluids with cold marine and terrestrial waters. We describe fossil hydrothermal pipes that formed at ~200°C on the sea floor >2 km below sea level. This ocean floor was uplifted tectonically to sea level where a subaerial hydrothermal system was active at 30° to 270°C. We also describe shallow-water glacial diamictites and diagenetic sulfate mineral growth in abyssal muds. These new observations reveal that both hydrothermal systems operated in relatively cold environments and that Earth’s surface temperatures in the early Archean were similar to those in more recent times.

scholarly journals Analysis of Hydrothermal Systems Beneath Tayukeng through Long-Term Geochemical Signals of Hydrothermal Fluids in Tatun Volcano Group, Taiwan

2021 ◽  
Vol 18 (14) ◽  
pp. 7411
Author(s):  
Hsin-Fu Yeh ◽  
Hung-Hsiang Hsu
Keyword(s):  
Surface Temperature ◽  
Hydrothermal System ◽  
Hydrothermal Fluid ◽  
Thermal Water ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Geochemical Variations ◽  
Northern Taiwan

The Tatun Volcano Group (TVG) is located in northern Taiwan and consists of many springs and fumaroles. The Tayukeng (TYK) area is the most active fumarole site in the TVG. In this study, we analyzed the long-term geochemical variations of hydrothermal fluids and proposed a mechanism responsible for the variation in TYK. There are two different aquifers beneath the TYK area: a shallow SO42−-rich aquifer and a deeper aquifer rich in Cl−. TYK thermal water was mainly supplied by the shallow SO42−-rich aquifer; therefore, the thermal water showed high SO42− concentrations. After 2015, the inflow of deep thermal water increased, causing the Cl− concentrations of the TYK to increase. Notably, the inferred reservoir temperatures based on quartz geothermometry increased; however, the surface temperature of the spring decreased. We inferred that the enthalpy was lost during transportation to the surface. Therefore, the surface temperature of the spring does not increase with an increased inflow of deep hydrothermal fluid. The results can serve as a reference for understanding the complex evolution of the magma-hydrothermal system in the TVG.

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

1984 ◽  
Vol 48 (348) ◽  
pp. 311-322 ◽  
Author(s):  
A. P. Dickin ◽  
C. M. B. Henderson ◽  
F. G. F. Gibb
Keyword(s):  
Stable Isotope ◽  
Hydrothermal Alteration ◽  
Closed System ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Drill Core ◽  
Sr Isotope ◽  
Core Section ◽  
High Silica ◽  
Isotope Measurements

Abstract The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.

SEG Presidential Address: I Never Met a Rhyolite I Didn’t Like – Some of the Geology in Economic Geology

SEG Discovery ◽  
2004 ◽  
pp. 1-13
Author(s):  
Jonathan G. Price
Keyword(s):  
Public Policy ◽  
Decision Making ◽  
Economic Geology ◽  
Presidential Address ◽  
Policy Decision ◽  
Volcanic Eruptions ◽  
Hydrothermal Systems ◽  
Radioactive Elements ◽  
Alteration Processes ◽  
Policy Decision Making

ABSTRACT Rhyolites and their deep-seated chemical equivalents, granites, are some of the most interesting rocks. They provide good examples of why it is important to look carefully at fresh rocks in terms of fıeld relationships, mineralogy, petrography, petrology, geochemistry, and alteration processes. Because of their evolved geochemisty, they commonly are important in terms of ore-forming processes. They are almost certainly the source of metal in many beryllium and lithium deposits and the source of heat for many other hydrothermal systems. From other perspectives, rhyolitic volcanic eruptions have the capacity of destroying civilizations, and their geochemistry (e.g., high contents of radioactive elements) is relevant to public policy decision-making.

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