Geochemistry and alteration facies associated with epithermal precious metal mineralization in an active geothermal system, northern Lesbos, Greece

1994 ◽  
Vol 29 (5) ◽  
pp. 430-433 ◽  
Author(s):  
E. Kontis ◽  
A. E. Kelepertsis ◽  
S. Skounakis
Keyword(s):  
Precious Metal ◽  
Geothermal System ◽  
Active Geothermal System

scholarly journals Copper–arsenic decoupling in an active geothermal system: A link between pyrite and fluid composition

2017 ◽  
Vol 204 ◽  
pp. 179-204 ◽  
Author(s):  
Daniele Tardani ◽  
Martin Reich ◽  
Artur P. Deditius ◽  
Stephen Chryssoulis ◽  
Pablo Sánchez-Alfaro ◽  
...  
Keyword(s):  
Geothermal System ◽  
Fluid Composition ◽  
System A ◽  
Active Geothermal System ◽  
Copper Arsenic

Opaque mineral alteration states correlated with temperature in an active geothermal system

Nature ◽  
1978 ◽  
Vol 272 (5650) ◽  
pp. 239-240 ◽  
Author(s):  
OSAMA Y. ABDEL-AAL ◽  
JAMES M. HALL
Keyword(s):  
Geothermal System ◽  
Opaque Mineral ◽  
Mineral Alteration ◽  
Active Geothermal System

scholarly journals Compaction of Hyaloclastite from the Active Geothermal System at Krafla Volcano, Iceland

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Guðjón H. Eggertsson ◽  
Jackie E. Kendrick ◽  
Joshua Weaver ◽  
Paul A. Wallace ◽  
James E. P. Utley ◽  
...  
Keyword(s):  
Effective Stress ◽  
Physical And Mechanical Properties ◽  
Geothermal System ◽  
Strength Increase ◽  
Yield Curves ◽  
Strength Differential ◽  
Brittle Ductile Transition ◽  
Porosity And Permeability ◽  
Active Geothermal System ◽  
Mean Stresses

Hyaloclastites commonly form high-quality reservoir rocks in volcanic geothermal provinces. Here, we investigated the effects of confinement due to burial following prolonged accumulation of eruptive products on the physical and mechanical evolution of surficial and subsurface (depths of 70 m, 556 m, and 732 m) hyaloclastites from Krafla volcano, Iceland. Upon loading in a hydrostatic cell, the porosity and permeability of the surficial hyaloclastite decreased linearly with mean effective stress, as pores and cracks closed due to elastic (recoverable) compaction up to 22-24 MPa (equivalent to ~1.3 km depth in the reservoir). Beyond this mean effective stress, denoted as P∗, we observed accelerated porosity and permeability reduction with increasing confinement, as the rock underwent permanent inelastic compaction. In comparison, the porosity and permeability of the subsurface core samples were less sensitive to mean effective stress, decreasing linearly with increasing confinement as the samples compacted elastically within the conditions tested (to 40 MPa). Although the surficial material underwent permanent, destructive compaction, it maintained higher porosity and permeability than the subsurface hyaloclastites throughout the experiments. We constrained the evolution of yield curves of the hyaloclastites, subjected to different effective mean stresses in a triaxial press. Surficial hyaloclastites underwent a brittle-ductile transition at an effective mean stress of ~10.5 MPa, and peak strength (differential stress) reached 13 MPa. When loaded to effective mean stresses of 33 and 40 MPa, the rocks compacted, producing new yield curves with a brittle-ductile transition at ~12.5 and ~19 MPa, respectively, but showed limited strength increase. In comparison, the subsurface samples were found to be much stronger, displaying higher strengths and brittle-ductile transitions at higher effective mean stresses (i.e., 37.5 MPa for 70 m sample, >75 MPa for 556 m, and 68.5 MPa for 732 m) that correspond to their lower porosities and permeabilities. Thus, we conclude that compaction upon burial alone is insufficient to explain the physical and mechanical properties of the subsurface hyaloclastites present in the reservoir at Krafla volcano. Mineralogical alteration, quantified using SEM-EDS, is invoked to explain the further reduction of porosity and increase in strength of the hyaloclastite in the active geothermal system at Krafla.

Water–rock interaction in the active geothermal system of Pantelleria, Italy

2001 ◽  
Vol 181 (1-4) ◽  
pp. 113-130 ◽  
Author(s):  
Giovanni Gianelli ◽  
Sergio Grassi
Keyword(s):  
Geothermal System ◽  
Rock Interaction ◽  
Active Geothermal System ◽  
Water Rock Interaction

Element redistribution during hydrothermal alteration of rhyolite in an active geothermal system: Yellowstone drill cores Y-7 and Y-8

1986 ◽  
Vol 50 (8) ◽  
pp. 1619-1631 ◽  
Author(s):  
Neil C. Sturchio ◽  
Karlis Muehlenbachs ◽  
Martin G. Seitz
Keyword(s):  
Hydrothermal Alteration ◽  
Geothermal System ◽  
Element Redistribution ◽  
Active Geothermal System ◽  
Drill Cores

scholarly journals Behavior of Nuclear Waste Elements During Hydrothermal Alteration of Glassy Rhyolite in an Active Geothermal System: Yellowstone National Park, Wyoming

1984 ◽  
Vol 44 ◽  
Author(s):  
Neil C. Sturchio ◽  
Martin G. Seitz
Keyword(s):  
Hydrothermal Alteration ◽  
Nuclear Waste ◽  
Yellowstone National Park ◽  
National Park ◽  
Thermal Waters ◽  
Geothermal System ◽  
Altered Rock ◽  
Active Geothermal System

AbstractThe behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm.d)u ring hydrothermal alteration of glassy rhyolite is investigated through geochemaical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant enrichments of U, Sr, Sb, Cs, and Ba are found in altered rock relative to unaltered rock. Excess Sr, Cs, and Ba are concentrated in zeolites in altered rock. Excess U is associated with titanomagnetite surfaces. Th, Zr, and Sm are relatively immobile during alteration, and are strongly concentrated in celadonite.

Fracture analysis, hydrothermal mineralization and fluid pathways in the Neogene Geitafell central volcano: insights for the Krafla active geothermal system, Iceland

2020 ◽  
Vol 391 ◽  
pp. 106502 ◽  
Author(s):  
Domenico Liotta ◽  
Andrea Brogi ◽  
Giovanni Ruggieri ◽  
Valentina Rimondi ◽  
Martina Zucchi ◽  
...  
Keyword(s):  
Fracture Analysis ◽  
Geothermal System ◽  
Central Volcano ◽  
Hydrothermal Mineralization ◽  
Active Geothermal System

Hydrothermal eruptions in the Waiotapu geothermal system, New Zealand; their origin, associated breccias, and relation to precious metal mineralization

1985 ◽  
Vol 80 (6) ◽  
pp. 1640-1668 ◽  
Author(s):  
Jeffrey W. Hedenquist ◽  
Richard W. Henley
Keyword(s):  
New Zealand ◽  
Precious Metal ◽  
Geothermal System
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