Possible contribution of a metal-rich magmatic fluid to a sea-floor hydrothermal system

Nature ◽  
1996 ◽  
Vol 383 (6599) ◽  
pp. 420-423 ◽  
Author(s):  
Kaihui Yang ◽  
Steven D. Scott
Keyword(s):  
Hydrothermal System ◽  
Magmatic Fluid ◽  
Sea Floor

scholarly journals Volcanic Unrest at Hakone Volcano after the 2015 phreatic eruption — Reactivation of a Ruptured Hydrothermal System?

2020 ◽  
Author(s):  
Kazutaka Mannen ◽  
Yuki Abe ◽  
Yasushi Daita ◽  
Ryosuke Doke ◽  
Masatake Harada ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Seismic Activity ◽  
Low Frequency ◽  
Magmatic Fluid ◽  
Volcanic Unrest ◽  
Hakone Volcano ◽  
Seismic Swarms ◽  
Cap Rock ◽  
Sealing Zone ◽  
Eruptive Period

Abstract Since the beginning of the 21st century, volcanic unrest has occurred every 2–5 years at Hakone volcano. After the 2015 eruption, unrest activity changed significantly in terms of seismicity and geochemistry. In this paper, characteristics of the post-eruptive volcanic unrest that occurred in 2017 and 2019 are described, and changes in the hydrothermal system of the volcano caused by the eruption are discussed. Like the pre- and co-eruptive unrest, each post-eruptive unrest episode was detected by deep inflation below the volcano (~ 10 km) and deep low frequency events, which can be interpreted as reflecting supply of magma or magmatic fluid from depth. The seismic activity during the post-eruptive unrest episodes also increased; however, seismic activity beneath the eruption center during the unrest episodes was significantly lower, especially in the shallow region (~2 km), while sporadic seismic swarms were observed beneath the caldera rim, ~3 km away from the center. The 2015 eruption established routes for steam from the hydrothermal system (≥ 150 m deep) to the surface through the cap-rock, allowing emission of super-heated steam (~ 160 ºC), which was absent before the eruption. This steam showed an increase in magmatic/hydrothermal gas ratios (SO2/H2S and HCl/H2S) in the 2019 unrest, which may be interpreted as magmatic intrusion at shallow depth; however, no indicative seismic and geodetic signals were observed. Net SO2 emission during the post-eruptive unrest episodes, which remained within the usual range of the post-eruptive period, is also inconsistent with shallow intrusion. We consider that the post-eruptive unrest episodes were also triggered by newly derived magma or magmatic fluid from depth; however, the breached cap-rock was unable to allow subsequent pressurization of the hydrothermal system beneath the volcano center and suppressed seismic activity significantly. The heat released from the newly derived magma or fluid dried the vapor-dominated portion of the hydrothermal system and inhibited scrubbing of SO2 and HCl to allow a higher magmatic/hydrothermal gas ratio. The 2015 eruption could have also breached the sealing zone near the brittle–plastic transition and the subsequent self-sealing process seems not to have completed based on the observations during the post-eruptive unrest episodes.

scholarly journals Lithium isotope traces magmatic fluid in a seafloor hydrothermal system

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Dan Yang ◽  
Zengqian Hou ◽  
Yue Zhao ◽  
Kejun Hou ◽  
Zhiming Yang ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Magmatic Fluid ◽  
Lithium Isotope ◽  
Seafloor Hydrothermal System

scholarly journals Volcanic unrest at Hakone volcano after the 2015 phreatic eruption: reactivation of a ruptured hydrothermal system?

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Kazutaka Mannen ◽  
Yuki Abe ◽  
Yasushi Daita ◽  
Ryosuke Doke ◽  
Masatake Harada ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Seismic Activity ◽  
Low Frequency ◽  
Magmatic Fluid ◽  
Volcanic Unrest ◽  
Hakone Volcano ◽  
Eruption Center ◽  
Brittle Ductile Transition ◽  
Seismic Swarms ◽  
Cap Rock

AbstractSince the beginning of the twenty-first century, volcanic unrest has occurred every 2–5 years at Hakone volcano. After the 2015 eruption, unrest activity changed significantly in terms of seismicity and geochemistry. Like the pre- and co-eruptive unrest, each post-eruptive unrest episode was detected by deep inflation below the volcano (~ 10 km) and deep low frequency events, which can be interpreted as reflecting supply of magma or magmatic fluid from depth. The seismic activity during the post-eruptive unrest episodes also increased; however, seismic activity beneath the eruption center during the unrest episodes was significantly lower, especially in the shallow region (~ 2 km), while sporadic seismic swarms were observed beneath the caldera rim, ~ 3 km away from the center. This observation and a recent InSAR analysis imply that the hydrothermal system of the volcano could be composed of multiple sub-systems, each of which can host earthquake swarms and show independent volume changes. The 2015 eruption established routes for steam from the hydrothermal sub-system beneath the eruption center (≥ 150 m deep) to the surface through the cap-rock, allowing emission of super-heated steam (~ 160 ºC). This steam showed an increase in magmatic/hydrothermal gas ratios (SO2/H2S and HCl/H2S) in the 2019 unrest episode; however, no magma supply was indicated by seismic and geodetic observations. Net SO2 emission during the post-eruptive unrest episodes, which remained within the usual range of the post-eruptive period, is also inconsistent with shallow intrusion. We consider that the post-eruptive unrest episodes were also triggered by newly derived magma or magmatic fluid from depth; however, the breached cap-rock was unable to allow subsequent pressurization and intensive seismic activity within the hydrothermal sub-system beneath the eruption center. The heat released from the newly derived magma or fluid dried the vapor-dominated portion of the hydrothermal system and inhibited scrubbing of SO2 and HCl to allow a higher magmatic/hydrothermal gas ratio. The 2015 eruption could have also breached the sealing zone near the brittle–ductile transition and the subsequent self-sealing process seems not to have completed based on the observations during the post-eruptive unrest episodes.

scholarly journals Ar–Ar dating for hydrothermal quartz from the 2.4 Ga Ongeluk Formation, South Africa: implications for seafloor hydrothermal circulation

2018 ◽  
Vol 5 (9) ◽  
pp. 180260
Author(s):  
Takuya Saito ◽  
Hua-Ning Qiu ◽  
Takazo Shibuya ◽  
Yi-Bing Li ◽  
Kouki Kitajima ◽  
...  
Keyword(s):  
South Africa ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Hydrothermal System ◽  
Magmatic Fluid ◽  
Crustal Fluid ◽  
Hydrothermal Quartz ◽  
Argon Isotopes ◽  
Stepwise Crushing ◽  
Binary Mixing

Fluid inclusions in hydrothermal quartz in the 2.4 Ga Ongeluk Formation, South Africa, are expected to partially retain a component of the ancient seawater. To constrain the origin of the fluid and the quartz precipitation age, we conducted Ar–Ar dating for the quartz via a stepwise crushing method. The obtained argon isotopes show two or three endmembers with one or two binary mixing lines as the crushing proceeds, suggesting that the isotopic compositions of these endmembers correspond to fluid inclusions of each generation, earlier generated smaller 40 Ar- and K-rich inclusions, moderate 40 Ar- and 38 Ar Cl (neutron-induced 38 Ar from Cl)-rich inclusions and later generated larger atmospheric-rich inclusions. The K-rich inclusions show significantly different 40 Ar/ 38 Ar Cl values compared to the 38 Ar Cl -rich inclusions, indicating that it is difficult to constrain the quartz formation age using only fluid inclusions containing excess 40 Ar. The highest obtained 40 Ar/ 36 Ar value from the fluid inclusions is consistent with an expected value of the Ongeluk plume source, suggesting that the quartz precipitation was driven by Ongeluk volcanism. Considering the fluid inclusion generations and their compositions, the hydrothermal system was composed of crustal fluid and magmatic fluid without seawater before the beginning of a small amount of seawater input to the hydrothermal system.

Hydrodynamics of magmatic and meteoric fluids in the vicinity of granitic intrusions

1996 ◽  
Vol 87 (1-2) ◽  
pp. 251-259 ◽  
Author(s):  
R. Brooks Hanson
Keyword(s):  
Hydrothermal System ◽  
Numerical Models ◽  
Fluid Pressure ◽  
Granitic Magma ◽  
Magmatic Fluid ◽  
Metamorphic Fluid ◽  
Magmatic Fluids ◽  
Fluid Production ◽  
Granitic Intrusions ◽  
Fluid Release

ABSTRACT:Numerical models that account for fluid flow, magmatic and metamorphic fluid production, topography and thermal expansion of the fluid following emplacement of a granitic magma in the upper crust reveal controls on the distribution of magmatic fluids during the evolution of a hydrothermal system. Initially, fluid pressures are close to lithostatic in and near an intrusion, and internally generated magmatic and metamorphic fluids are expelled. Later, fluid pressures drop to hydrostatic values and meteoric fluids circulate throughout the system. High permeabilities and low rates of fluid production accelerate this transition. Fluid production in the magma and wallrocks is the dominant mechanism elevating fluid pressures to lithostatic values. For granitic intrusions, about three to five times as much magmatic fluid is produced as metamorphic fluid. Continuous fluid release from a granitic magma with a vertical dimensions of 10 km produces a dynamic permeability of up to several tens of microdarcies.Near the surface, topography associated with a typical volcano acts to maintain a shallow meteoric flow system and drive fluids laterally. The exponential decay with depth of the influence of topography on fluid pressures results in a persistent zone of mixing at a depth of 1-2 km between these meteoric fluids and magmatic fluids despite variations in the strength of the magmatic hydrothermal system. However, in shallow systems where fluid release is episodic, dramatic changes in the region of mixing are still possible because fluid pressure is sensitive to variations in the rates of fluid production. At depth, high rates of metamorphic fluid production in the wallrocks and low permeabilities (< 1 μD) produce elevated fluid pressures, which hinder the lateral flow of magmatic fluids. Together, these patterns are consistent with the distribution and evolution of skarns and hydrothermal ore deposits around granitic magmas.

Remnants of an Early Archaean (>3.75 Ga) sea-floor, hydrothermal system in the Isua Greenstone Belt

2001 ◽  
Vol 112 (1-2) ◽  
pp. 27-49 ◽  
Author(s):  
Peter W.U Appel ◽  
Hugh R Rollinson ◽  
Jacques L.R Touret
Keyword(s):  
Hydrothermal System ◽  
Greenstone Belt ◽  
Sea Floor

scholarly journals Volcanic Unrest at Hakone Volcano after the 2015 phreatic eruption — Reactivation of a Ruptured Hydrothermal System?

2021 ◽  
Author(s):  
Kazutaka Mannen ◽  
Yuki Abe ◽  
Yasushi Daita ◽  
Ryosuke Doke ◽  
Masatake Harada ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Seismic Activity ◽  
Earthquake Swarm ◽  
Low Frequency ◽  
Magmatic Fluid ◽  
Volcanic Unrest ◽  
Hakone Volcano ◽  
Eruption Center ◽  
Seismic Swarms ◽  
Cap Rock

Abstract Since the beginning of the 21st century, volcanic unrest has occurred every 2–5 years at Hakone volcano. After the 2015 eruption, unrest activity changed significantly in terms of seismicity and geochemistry. Like the pre- and co-eruptive unrest, each post-eruptive unrest episode was detected by deep inflation below the volcano (~ 10 km) and deep low frequency events, which can be interpreted as reflecting supply of magma or magmatic fluid from depth. The seismic activity during the post-eruptive unrest episodes also increased; however, seismic activity beneath the eruption center during the unrest episodes was significantly lower, especially in the shallow region (~2 km), while sporadic seismic swarms were observed beneath the caldera rim, ~3 km away from the center. This observation and a recent InSAR analysis imply that the hydrothermal system of the volcano could be composed of multiple sub-systems, each of which can host earthquake swarm and show independent volume change. The 2015 eruption established routes for steam from the hydrothermal sub-system beneath the eruption center (≥ 150 m deep) to the surface through the cap-rock, allowing emission of super-heated steam (~ 160 ºC). This steam showed an increase in magmatic/hydrothermal gas ratios (SO2/H2S and HCl/H2S) in the 2019 unrest episode; however, no magma supply was indicated by seismic and geodetic observations. Net SO2 emission during the post-eruptive unrest episodes, which remained within the usual range of the post-eruptive period, is also inconsistent with shallow intrusion. We consider that the post-eruptive unrest episodes were also triggered by newly derived magma or magmatic fluid from depth; however, the breached cap-rock was unable to allow subsequent pressurization and intensive seismic activity within the hydrothermal sub-system beneath the eruption center. The heat released from the newly derived magma or fluid dried the vapor-dominated portion of the hydrothermal system and inhibited scrubbing of SO2 and HCl to allow a higher magmatic/hydrothermal gas ratio. The 2015 eruption could have also breached the sealing zone near the brittle–plastic transition and the subsequent self-sealing process seems not to have completed based on the observations during the post-eruptive unrest episodes.

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