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Gry Hoffmann Barfod

Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland

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Standard

Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. / Zierenberg, R. A.; Schiffman, P.; Barfod, G. H.; Lesher, Charles; Marks, N. E.; Lowenstern, J. B.; Mortensen, A. K.; Pope, E. C.; Bird, D. K.; Reed, M. H.; Frioleifsson, G. O.; Elders, W. A.

I: Contributions to Mineralogy and Petrology, Bind 165, Nr. 2, 02.2013, s. 327-347.

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

Harvard

Zierenberg, RA, Schiffman, P, Barfod, GH, Lesher, C, Marks, NE, Lowenstern, JB, Mortensen, AK, Pope, EC, Bird, DK, Reed, MH, Frioleifsson, GO & Elders, WA 2013, 'Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland', Contributions to Mineralogy and Petrology, bind 165, nr. 2, s. 327-347. https://doi.org/10.1007/s00410-012-0811-z

APA

Zierenberg, R. A., Schiffman, P., Barfod, G. H., Lesher, C., Marks, N. E., Lowenstern, J. B., ... Elders, W. A. (2013). Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. Contributions to Mineralogy and Petrology, 165(2), 327-347. https://doi.org/10.1007/s00410-012-0811-z

CBE

Zierenberg RA, Schiffman P, Barfod GH, Lesher C, Marks NE, Lowenstern JB, Mortensen AK, Pope EC, Bird DK, Reed MH, Frioleifsson GO, Elders WA. 2013. Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. Contributions to Mineralogy and Petrology. 165(2):327-347. https://doi.org/10.1007/s00410-012-0811-z

MLA

Vancouver

Zierenberg RA, Schiffman P, Barfod GH, Lesher C, Marks NE, Lowenstern JB o.a. Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. Contributions to Mineralogy and Petrology. 2013 feb;165(2):327-347. https://doi.org/10.1007/s00410-012-0811-z

Author

Zierenberg, R. A. ; Schiffman, P. ; Barfod, G. H. ; Lesher, Charles ; Marks, N. E. ; Lowenstern, J. B. ; Mortensen, A. K. ; Pope, E. C. ; Bird, D. K. ; Reed, M. H. ; Frioleifsson, G. O. ; Elders, W. A. / Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. I: Contributions to Mineralogy and Petrology. 2013 ; Bind 165, Nr. 2. s. 327-347.

Bibtex

@article{04ecc7b796b44df49efb40c8d69707e8,
title = "Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland",
abstract = "The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 {\%} SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 A degrees C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (similar to 16 MPa) and below lithostatic (similar to 55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 aEuro degrees, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation.",
keywords = "Krafla, Iceland, Geothermal, Rhyolite, Basalt partial melting, Stable isotope, Strontium isotope, ISOTOPIC EVIDENCE, SPIRIT MOUNTAIN, CENTRAL VOLCANO, TH-ISOTOPES, O-ISOTOPES, MANTLE, OXYGEN, CONSTRAINTS, SYSTEMATICS, BASALTS",
author = "Zierenberg, {R. A.} and P. Schiffman and Barfod, {G. H.} and Charles Lesher and Marks, {N. E.} and Lowenstern, {J. B.} and Mortensen, {A. K.} and Pope, {E. C.} and Bird, {D. K.} and Reed, {M. H.} and Frioleifsson, {G. O.} and Elders, {W. A.}",
year = "2013",
month = "2",
doi = "10.1007/s00410-012-0811-z",
language = "English",
volume = "165",
pages = "327--347",
journal = "Contributions to Mineralogy and Petrology",
issn = "0010-7999",
publisher = "Springer",
number = "2",

}

RIS

TY - JOUR

T1 - Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland

AU - Zierenberg, R. A.

AU - Schiffman, P.

AU - Barfod, G. H.

AU - Lesher, Charles

AU - Marks, N. E.

AU - Lowenstern, J. B.

AU - Mortensen, A. K.

AU - Pope, E. C.

AU - Bird, D. K.

AU - Reed, M. H.

AU - Frioleifsson, G. O.

AU - Elders, W. A.

PY - 2013/2

Y1 - 2013/2

N2 - The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 A degrees C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (similar to 16 MPa) and below lithostatic (similar to 55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 aEuro degrees, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation.

AB - The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 A degrees C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (similar to 16 MPa) and below lithostatic (similar to 55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 aEuro degrees, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation.

KW - Krafla

KW - Iceland

KW - Geothermal

KW - Rhyolite

KW - Basalt partial melting

KW - Stable isotope

KW - Strontium isotope

KW - ISOTOPIC EVIDENCE

KW - SPIRIT MOUNTAIN

KW - CENTRAL VOLCANO

KW - TH-ISOTOPES

KW - O-ISOTOPES

KW - MANTLE

KW - OXYGEN

KW - CONSTRAINTS

KW - SYSTEMATICS

KW - BASALTS

U2 - 10.1007/s00410-012-0811-z

DO - 10.1007/s00410-012-0811-z

M3 - Journal article

VL - 165

SP - 327

EP - 347

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 2

ER -