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Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hovedøya Case, Oslo Rift, Norway. / Poppe, Sam; Galland, O.; de Winter, N. J.; Goderis, S.; Claeys, Philippe; Debaille, V.; Boulvais, P.; Kervyn, M.

In: Geochemistry, Geophysics, Geosystems, Vol. 21, No. 3, e2019GC008685, 2020, p. 1-22.

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@article{76635ea91bfc41169b1c669709cb72d3,
title = "Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hoved{\o}ya Case, Oslo Rift, Norway",
abstract = "Abstract Two end-member conceptual models are used to describe deformation of the Earth's crust induced by magma intrusion. ?Mode I? fracturing assumes tensile or opening-mode, elastic deformation, while ?Mode II? fracturing assumes plastic shear-mode deformation around a viscous indenter. Field observations of both mechanisms exist, but it remains unclear which mechanism dominates in which conditions. We describe intrusion geometries, host rock deformation, and geochemical magma-host rock interactions around 53 exceptionally preserved, tephrite-basanite Permian dike segments of 0.5- to 30-cm thickness. These thin dikes, that is, ?dikelets,? intruded Late-Ordovician carbonate-rich sedimentary rocks on Hoved?ya island, Oslo Rift, Norway. Dikelets emplaced in preexisting fractures dominantly created cavities ahead of their narrow, tapering tips and are associated with bent host rock, broken bridges, and stepped segmented geometries. Other tips are blunt with dense brittle fracturing around them. Also, cross-sectional intrusion segment opening profiles deviate from parabola-shaped profiles typical for elastic media. The observations demonstrate that dominant opening-mode host rock deformation can coexist with shear-mode deformation locally. Alignment of most dikelet segments along the dominant host rock fracture directions highlights the control of local structural orientations on magma emplacement. Analysis of bulk major and trace element compositions, in situ micro-XRF sample analysis and carbon and oxygen stable isotope compositions, suggests that thermochemical interactions between magma and the carbonate-rich host rock produced a low-viscosity mixture of magma, pore water, and gas. We propose that such low-viscosity hybrid fluid may assist in the intrusion of magma in sedimentary rocks by filling the cavity ahead of propagating sheet intrusion tips.",
keywords = "magma, intrusion, structural deformation, Oslo Rift, geochemistry, stable isotopes",
author = "Sam Poppe and O. Galland and {de Winter}, N. J. and S. Goderis and Philippe Claeys and V. Debaille and P. Boulvais and M. Kervyn",
note = "doi: 10.1029/2019GC008685",
year = "2020",
doi = "10.1029/2019GC008685",
language = "English",
volume = "21",
pages = "1--22",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "3",

}

RIS

TY - JOUR

T1 - Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hovedøya Case, Oslo Rift, Norway

AU - Poppe, Sam

AU - Galland, O.

AU - de Winter, N. J.

AU - Goderis, S.

AU - Claeys, Philippe

AU - Debaille, V.

AU - Boulvais, P.

AU - Kervyn, M.

N1 - doi: 10.1029/2019GC008685

PY - 2020

Y1 - 2020

N2 - Abstract Two end-member conceptual models are used to describe deformation of the Earth's crust induced by magma intrusion. ?Mode I? fracturing assumes tensile or opening-mode, elastic deformation, while ?Mode II? fracturing assumes plastic shear-mode deformation around a viscous indenter. Field observations of both mechanisms exist, but it remains unclear which mechanism dominates in which conditions. We describe intrusion geometries, host rock deformation, and geochemical magma-host rock interactions around 53 exceptionally preserved, tephrite-basanite Permian dike segments of 0.5- to 30-cm thickness. These thin dikes, that is, ?dikelets,? intruded Late-Ordovician carbonate-rich sedimentary rocks on Hoved?ya island, Oslo Rift, Norway. Dikelets emplaced in preexisting fractures dominantly created cavities ahead of their narrow, tapering tips and are associated with bent host rock, broken bridges, and stepped segmented geometries. Other tips are blunt with dense brittle fracturing around them. Also, cross-sectional intrusion segment opening profiles deviate from parabola-shaped profiles typical for elastic media. The observations demonstrate that dominant opening-mode host rock deformation can coexist with shear-mode deformation locally. Alignment of most dikelet segments along the dominant host rock fracture directions highlights the control of local structural orientations on magma emplacement. Analysis of bulk major and trace element compositions, in situ micro-XRF sample analysis and carbon and oxygen stable isotope compositions, suggests that thermochemical interactions between magma and the carbonate-rich host rock produced a low-viscosity mixture of magma, pore water, and gas. We propose that such low-viscosity hybrid fluid may assist in the intrusion of magma in sedimentary rocks by filling the cavity ahead of propagating sheet intrusion tips.

AB - Abstract Two end-member conceptual models are used to describe deformation of the Earth's crust induced by magma intrusion. ?Mode I? fracturing assumes tensile or opening-mode, elastic deformation, while ?Mode II? fracturing assumes plastic shear-mode deformation around a viscous indenter. Field observations of both mechanisms exist, but it remains unclear which mechanism dominates in which conditions. We describe intrusion geometries, host rock deformation, and geochemical magma-host rock interactions around 53 exceptionally preserved, tephrite-basanite Permian dike segments of 0.5- to 30-cm thickness. These thin dikes, that is, ?dikelets,? intruded Late-Ordovician carbonate-rich sedimentary rocks on Hoved?ya island, Oslo Rift, Norway. Dikelets emplaced in preexisting fractures dominantly created cavities ahead of their narrow, tapering tips and are associated with bent host rock, broken bridges, and stepped segmented geometries. Other tips are blunt with dense brittle fracturing around them. Also, cross-sectional intrusion segment opening profiles deviate from parabola-shaped profiles typical for elastic media. The observations demonstrate that dominant opening-mode host rock deformation can coexist with shear-mode deformation locally. Alignment of most dikelet segments along the dominant host rock fracture directions highlights the control of local structural orientations on magma emplacement. Analysis of bulk major and trace element compositions, in situ micro-XRF sample analysis and carbon and oxygen stable isotope compositions, suggests that thermochemical interactions between magma and the carbonate-rich host rock produced a low-viscosity mixture of magma, pore water, and gas. We propose that such low-viscosity hybrid fluid may assist in the intrusion of magma in sedimentary rocks by filling the cavity ahead of propagating sheet intrusion tips.

KW - magma

KW - intrusion

KW - structural deformation

KW - Oslo Rift

KW - geochemistry

KW - stable isotopes

U2 - 10.1029/2019GC008685

DO - 10.1029/2019GC008685

M3 - Article

VL - 21

SP - 1

EP - 22

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 3

M1 - e2019GC008685

ER -

ID: 50039139