Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Pre-metamorphic controls on the propagation of fluid-driven reaction fronts at greenschist-facies metamorphic conditions
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this study we show that pre-metamorphic mineralogical and chemical heterogeneities control fluid flow and fluid-driven propagation of reaction fronts during regional metamorphism. The study was undertaken at Port Ellen, Islay, in SW Scottish Highlands. Here, basaltic sills have been partially carbonated by H2O-CO2 fluids at greenschist-facies conditions. This has led to mineral zonation with carbonate poor sill interiors separated from carbonate-rich sill margins by reaction fronts. The sills which were studied are partially carbonated and reaction fronts are well-preserved. These sills are unique for the Scottish Highlands in that they show excellent evidence of 1) extensive magmatic flow differentiation and 2) spilitization having occurred before greenschist-facies metamorphism. Magmatic flow differentiation concentrated large (up to 3 cm) phenocrysts of plagioclase in the sill interior and spilitic alteration produced layers of segregated epidote and caused albitization of these plagioclase phenocrysts resulting in their preservation throughout greenschist-facies metamorphism. Coupled with this pre-metamorphic mineralogical zonation, sill margins where enriched in Ti, Fe, P, HFSEs and REEs whereas the sill interiors were enriched in Al, Na and LILEs. In this study, we show spatial correlation of metamorphic reaction fronts with pre-metamorphic mineralogical zonation produced by magmatic flow differentiation (plagioclase phenocrysts size distributions) and epidote segregations produced by spilitization. We infer a pre-metamorphic mineralogical and chemical control on the positions of fluid-driven metamorphic reaction fronts. Based on mineralogical and chemical profiles across these sills and reaction textures preserved within them, we conclude that availability of reactant minerals and mechanical factors, such as volume change in epidote and foliation development due to chlorite formation are primary controls of fluid-driven reaction front propagation during metamorphism. We further suggest that elevated oxygen fugacity in the sill margins may have further promoted carbonation.

Keyword [en]
Carbonation, fluid-rock interaction, magmatic flow differentiation, metamorphic fluid flow, spilitization
National Category
Geology
Research subject
Geology
Identifiers
URN: urn:nbn:se:su:diva-115171OAI: oai:DiVA.org:su-115171DiVA: diva2:795881
Available from: 2015-03-17 Created: 2015-03-17 Last updated: 2016-01-29Bibliographically approved
In thesis
1. How do metamorphic fluids move through rocks?: An investigation of timescales, infiltration mechanisms and mineralogical controls
Open this publication in new window or tab >>How do metamorphic fluids move through rocks?: An investigation of timescales, infiltration mechanisms and mineralogical controls
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis aims to provide a better understanding of the role of mountain building in the carbon cycle. The amount of CO2 released into the atmosphere due to metamorphic processes is largely unknown. To constrain the quantity of CO2 released, fluid-driven reactions in metamorphic rocks can be studied by tracking fluid-rock interactions along ancient fluid flow pathways. The thesis is divided into two parts: 1) modeling of fluid flow rates and durations within shear zones and fractures during greenschist- and blueschist-facies metamorphism and 2) the assessment of possible mechanisms of fluid infiltration into rocks during greenschist- to epidote-amphibolite-facies metamorphism and controlling chemical and mineralogical factors of reaction front propagation.

On the island Syros, Greece, fluid-rock interaction was examined along a shear zone and within brittle fractures to calculate fluid flux rates, flow velocities and durations. Petrological, geochemical and thermodynamic evidence show that the flux of CO2-bearing fluids along the shear zone was 100-2000 times larger than the fluid flux in the surrounding rocks. The time-averaged fluid flow velocity and flow duration along brittle fractures was calculated by using a governing equation for one-dimensional transport (advection and diffusion) and field-based parameterization. This study shows that fluid flow along fractures on Syros was rapid and short lived.

Mechanisms and controlling factors of fluid infiltration were studied in greenschist- to epidote-amphibolite-facies metabasalts in SW Scotland. Fluid infiltration into metabasaltic sills was unassisted by deformation and occurred along grain boundaries of hydrous minerals (e.g. amphibole) while other minerals (e.g. quartz) prevent fluid infiltration. Petrological, mineralogical and chemical studies of the sills show that the availability of reactant minerals and mechanical factors, e.g. volume change in epidote, are primary controls of reaction front propagation.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University, 2015. 35 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 356
Keyword
Metamorphic fluid flow, fluid-rock interaction, fluid infiltration mechanisms, fluid flux rates, thermodynamic modeling, reaction front propagation, fluid flux calculation
National Category
Geology
Research subject
Geology
Identifiers
urn:nbn:se:su:diva-115172 (URN)978-91-7649-120-1 (ISBN)
Public defence
2015-04-28, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

 

Available from: 2015-03-31 Created: 2015-03-17 Last updated: 2015-06-18Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Kleine, Barbara IrenePitcairn, Iain K.Skelton, Alasdair D. L.
By organisation
Department of Geological Sciences
Geology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 115 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf