Epidote in Geothermal Systems

Bird, Dennis K.; Spieler, Abigail R.

doi:10.2138/gsrmg.56.1.235

Cited by 106 publications

(68 citation statements)

References 282 publications

(498 reference statements)

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“…EMP analyses of epidote from drill cuttings in wells RN-8 and RN-9 in the Reykjanes geothermal system and wells in the nearby Svartsengi geothermal system show no systematic changes in major element concentration with depth or proximity of aquifers, despite documentation of many grains having complex zoning patterns (Lonker et al, 1993; Bird and Spieler, 2004). There are no systematic changes in X Fe of epidote with depth or temperature in RN-17 cuttings (Freedman et al, 2009;.…”

Section: Epidote Compositionmentioning

confidence: 90%

“…The Fe content of epidote is highly sensitive to small fluctuations in fCO 2 in H 2 O-rich fluids with overall low fCO 2 , although again, the relationship is strongly dependent on the buffering mineral assemblage (Arnason and Bird, 1993). The Fe 3+ content of epidote appears to be directly related to fO 2 ; oxidized mineral assemblages contain the most Fe-rich epidote, while reduced assemblages contain the most Fe-poor epidote (Holdaway, 1972;Bird and Helgeson, 1981;Liou et al, 1983;Arnason and Bird, 1993;Bird and Spieler, 2004).…”

Section: Epidote Compositionmentioning

confidence: 99%

“…The Reykjanes geothermal fluid is seawater, chemically modified due to boiling and fluid/rock interaction (Tómasson and Kristmannsdóttir, 1972;Arnórsson, 1978;Ólafsson and Riley, 1978;Arnórsson, 1995;Bird and Spieler, 2004;Friðleifsson and Elders, 2005;. Compared to seawater, hydrothermal fluids in the Reykjanes geothermal system have similar concentrations of Na and Cl; increased concentrations of K, Ca, SiO 2 , Fe, and Al; and decreased concentrations of SO 4 and Mg indicating that mineral precipitation, and significant water rock interaction have occurred (Lonker et al, 1993;Arnórsson, 1995;Pope et al, 2009).…”

Section: Geological Settingmentioning

confidence: 99%

“…Epidote zoned with respect to Fe 3+ -Al 3+ is commonly formed in hydrothermal systems hosted in a variety of geological settings (Bird et al, 1984;Arnason and Bird, 1992;Bird and Spieler, 2004). Fluid flux, permeability, temperature, oxygen fugacity (fO 2 ), carbon dioxide fugacity (fCO 2 ), fluid pH, whole rock composition, and aqueous speciation of Al 3+ and Fe 3+ are important variables controlling epidote composition (Arnason and Bird, 1993;Bird and Spieler, 2004).…”

Section: Epidote Compositionmentioning

confidence: 99%

“…Fluid flux, permeability, temperature, oxygen fugacity (fO 2 ), carbon dioxide fugacity (fCO 2 ), fluid pH, whole rock composition, and aqueous speciation of Al 3+ and Fe 3+ are important variables controlling epidote composition (Arnason and Bird, 1993;Bird and Spieler, 2004). Temperature, fCO 2 , and fO 2 are the most important intensive variables controlling epidote composition, however elucidation of the key variable is generally not possible (Arnason and Bird, 1993).…”

Section: Epidote Compositionmentioning

confidence: 99%

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Evolution of fluid–rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

Fowler

Zierenberg

Schiffman

et al. 2015

Journal of Volcanology and Geothermal Research

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We describe the lithology and present spatially resolved geochemical analyses of samples from the hydrothermally altered Iceland Deep Drilling Project (IDDP) drill core RN-17B. The 9.3 m long RN-17B core was collected from the seawater-dominated Reykjanes geothermal system, located on the Reykjanes Peninsula, Iceland. The nature of fluids and the location of the Reykjanes geothermal system make it a useful analog for seafloor hydrothermal processes, although there are important differences. The recovery of drill core from the Reykjanes geothermal system, as opposed to drill cuttings, has provided the opportunity to investigate evolving geothermal conditions by utilizing in-situ geochemical techniques in the context of observed paragenetic and spatial relationships of alteration minerals. The RN-17B core was returned from a vertical depth of~2560 m and an in-situ temperature of~345°C. The primary lithologies are basaltic in composition and include hyaloclastite breccia, fine-grained volcanic sandstone, lithic breccia, and crystalline basalt. Primary igneous phases have been entirely pseudomorphed by calcic plagioclase + magnesium hornblende + chlorite + titanite + albitized plagioclase + vein epidote and sulfides. Despite the extensive hydrothermal metasomatism, original textures including hyaloclastite glass shards, lithic clasts, chilled margins, and shell-fragment molds are superbly preserved. Multi-collector LA-ICP-MS strontium isotope ratio ( 87 Sr/ 86 Sr) measurements of vein epidote from the core are consistent with seawater as the dominant recharge fluid. Epidote-hosted fluid inclusion homogenization temperature and freezing point depression measurements suggest that the RN-17B core records cooling through the two-phase boundary for seawater over time to current in-situ measured temperatures. Electron microprobe analyses of hydrothermal hornblende and hydrothermal plagioclase confirm that while alteration is of amphibolite-grade, it is in disequilibrium and the extent of alteration is dependent upon protolith type and water/rock ratio. Alteration in the RN-17B core bares many similarities to that of Type II basalts observed in Mid-Atlantic Ridge samples.

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Section: Epidote Compositionmentioning

confidence: 90%

Section: Epidote Compositionmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Epidote Compositionmentioning

confidence: 99%

Section: Epidote Compositionmentioning

confidence: 99%

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Evolution of fluid–rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

Fowler

Zierenberg

Schiffman

et al. 2015

Journal of Volcanology and Geothermal Research

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Complex Bedrock Fracture Patterns: A Multipronged Approach to Resolve Their Evolution in Space and Time

Scheiber

Viola

2018

Tectonics

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The complex fault and fracture patterns commonly observed in metamorphic terranes are the cumulative expression of repeated episodes of brittle deformation. The temporal sequence of deformation remains, however, often obscure due to the general lack of systematic overprinting relationships and absolute geochronological constraints. Here we present a multipronged approach combining remote sensing, field work, structural analysis, and paleostress inversion with mineralogical characterization and K‐Ar dating of brittle features to develop an evolutionary model for one such complex fracture pattern. We applied this methodological approach to pervasively fractured Early to Middle Ordovician intrusive rocks in the northern Bømlo islands, SW Norway. The local brittle structural record is interpreted as reflecting a sequence of six deformation stages, three ascribable to the Caledonian orogenic cycle and three to the rift evolution of the North Sea. The Caledonian structures are assigned to (1) Late Ordovician NNW‐SSE transpression, (2) Silurian ESE‐WNW compression, and (3) Devonian NW‐SE transtension. The rift‐related structures formed during (4) Permian to Middle Triassic ENE‐WSW extension (~ 290–245 Ma), (5) Late Triassic to Late Jurassic E‐W extension (~ 210–160 Ma), and (6) Early Cretaceous ESE‐WNW extension (~ 125 Ma). The reconstructed gradual rotation of the extensional stress field during the Mesozoic might reflect the continuous northward migration of the rift activity from the North Sea toward the mid‐Norwegian margin. Our multipronged approach may be applied to the unraveling of complex and commonly long brittle histories stored in exhumed metamorphic terranes elsewhere.

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The Hydrothermal Minerals

Cioni

Marini²

2020

Springer Geochemistry

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Epidote in Geothermal Systems

Cited by 106 publications

References 282 publications

Evolution of fluid–rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

Evolution of fluid–rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

Complex Bedrock Fracture Patterns: A Multipronged Approach to Resolve Their Evolution in Space and Time

The Hydrothermal Minerals

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