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- Kleine, Barbara I., 1987-
(författare)
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How do metamorphic fluids move through rocks? : An investigation of timescales, infiltration mechanisms and mineralogical controls
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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- Kleine, Barbara I., et al.
(författare)
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Mineralogical controls on metamorphic fluid flow in metabasaltic sills from Islay, Scotland
- 2016
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937 .- 1872-6143. ; 248, s. 22-39
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Tidskriftsartikel (refereegranskat)abstract
- In this study we show that mineralogy was the primary control of metamorphic fluid flow in the well-studied metabasaltic sills in the 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. Although deformation set the stage for metamorphic fluid flow in the SW Scottish Highlands by causing the preferred alignment of mineral grains, metamorphic fluid flow was not coupled with active deformation but occurred later utilizing the pre-existing mineral alignment as a means of accessing the sill interiors. The sills which were studied were partially carbonated with well-preserved reaction fronts. They were selected because (atypically for the SW Scottish Highlands) they are mineralogically heterogeneous making them ideal for a study of mineralogical controls of metamorphic fluid flow. Their mineralogical heterogeneity reflects chemical heterogeneity arising from magmatic flow differentiation and spilitization, which occurred before greenschist facies metamorphism. Magmatic flow differentiation resulted in parts of the sill containing large crystals with no preferred alignment. Large (up to 3 cm) plagioclase phenocrysts were concentrated in the sill interior whereas large (up to 1 cm) amphibole (after pyroxene) grains formed cumulate layers close to the sill margins. These large randomly oriented crystals were replaced by an interface-coupled dissolution-precipitation mechanism. Replacement is constant volume and with hydration and carbonation affecting the cores of these minerals while the rims are remained intact and unaltered. This finding points to intro-granular metamorphic fluid flow. In contrast inter-granular metamorphic fluid flow was facilitated by mineral alignment on different scales. Pre-metamorphic spilitization, produced layers of epidote called segregations, whereas regional deformation caused preferred alignment mainly of amphibole and chlorite. Epidote undergoes a series of volume changes during greenschist facies metamorphism. This created porosity which produced preferred pathways for metamorphic fluids affecting the advancement of fluid-driven reaction fronts. Preferred alignment of amphibole and chlorite also affected the advancement of reaction fronts. In this case, fluid flow was preferentially parallel to the foliation. In both cases, inter-granular metamorphic fluid flow utilized a pre-existing fabric albeit on different scales. These results show intra-granular metamorphic fluid flow in unfoliated rock and inter-granular metamorphic fluid flow in foliated rock. In both cases metamorphic fluid flow occurred after deformation controlled by pre-existing mineralogical heterogeneities, such as grain composition and shape anisotropy as well as preferred alignment of mineral grains.
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- Kleine, Barbara Irene, et al.
(författare)
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Pre-metamorphic controls on the propagation of fluid-driven reaction fronts at greenschist-facies metamorphic conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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- Kleine, Barbara I., et al.
(författare)
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Preservation of blueschist-facies minerals along a shear zone by coupled metasomatism and fast-flowing CO2-bearing fluids
- 2014
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Ingår i: Journal of Petrology. - : Oxford University Press (OUP). - 0022-3530 .- 1460-2415. ; 55:10, s. 1905-1939
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Tidskriftsartikel (refereegranskat)abstract
- Two types of blue halo (types I and II) composed of blueschist-facies minerals are centered around a brittle, normal shear zone in greenschist-facies rocks on the island of Syros, Aegean Sea, Greece. The shear zone is steeply dipping and cuts a near-horizontal layer of greenschist-facies rocks (albite + epidote + actinolite + chlorite + quartz). Type I and II blue haloes are 0.3 m and c. 1m wide respectively, and are seen on both sides of the shear zone. The inner type I haloes are composed of nearly pure glaucophane schist and were formed by metasomatic addition of Na2O and SiO2, and to a lesser extent of K2O and large ion lithophile elements (LILE), coupled with loss of CaO, Al2O3 and MnO. The outer type II haloes consist of a carbonated blueschist-facies assemblage (glaucophane + calcite + phengite + epidote + garnet + quartz).These experienced only slight metasomatic changes (i.e. addition of K2O and LILE), which cannot alone explain halo formation.We present petrological, geochemical and thermodynamic evidence that this assemblage was preserved at greenschist-facies conditions because XCO2 was elevated by flow of a CO2-bearing fluid along the shear zone, which was approximately contemporaneous with greenschist-facies hydration in the surrounding rocks. We further note that the flux of CO2-bearing fluid along the shear zone was rapid with respect to the fluid flux in the surrounding rocks. Mass-balance calculations reveal that the fluid flux within the shear zone was at least 100-2000 times greater than the fluid flux within the surrounding rocks. Mineral textures show greenschist-facies minerals replacing blueschist minerals in the type II haloes, supporting our interpretation that the blueschist-facies minerals were preserved during greenschist-facies retrogression. A simplified P-T vs XCO2 pseudosection confirms that preservation of carbonated blueschist can occur at greenschist-facies conditions in the presence of a CO2-bearing fluid.
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- Kleine, Barbara I., et al.
(författare)
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RAPID FLUID FLOW ALONG FRACTURES AT GREENSCHIST FACIES CONDITIONS ON SYROS, GREECE
- 2016
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Ingår i: American Journal of Science. - : American Journal of Science (AJS). - 0002-9599 .- 1945-452X. ; 316:2, s. 169-201
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Tidskriftsartikel (refereegranskat)abstract
- Brittle fractures cut through greenschist facies metavolcanic rocks at Delfini on Syros, Greece. An equation for one-dimensional transport by advection along a single fracture and transverse diffusion outwards from this fracture was used to calculate time-averaged fluid velocities and the duration of fluid flow along the brittle fractures. These quartz and carbonate filled fractures are surrounded by symmetrical dark reaction halos. These reaction halos were formed by diffusion of CO2 outwards from the fracture in a hydrous fluid which caused carbonation of the country rock. Changes in concentration of relatively mobile elements (for example K, Na, Cs, Ba, Pb and Sr) occurred. However, little to no changes in most of the major elements and less mobile trace elements were observed. This implies that carbonation was largely isochemical with respect to most non-volatile components. The Sr/Ca ratio was used to model time-averaged fluid velocities and the duration of fluid flow along the fractures. Fluid flow along narrower fractures with discernibly tapering haloes was found to be rapid (10(-6) - 10(-5) ms(-1)) and short lived (0.1-400 years). These are time-averaged values and can therefore alternatively record a series of even shorter and faster pulses, perhaps associated with fracture propagation and associated seismicity. Within the widest fractures with constant halo widths (ca. 60 cm) fluid flow was slower (10(-8) to 10(-6) ms(-1)) and longer lived (100-15000 years). We suspect that the constant width of these haloes reflects a steady state having been reached at which halo width was controlled by the relative rates of fluid flow along the fracture and in the surrounding rock.
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- Kleine, Barbara Irene, et al.
(författare)
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Rapid fluid flow along fractures at greenschist-facies conditions on Syros, Greece
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Using an equation for one-dimensional transport by advection along a single fracture and transverse diffusion outwards from this fracture to model field, petrological and geochemical data we calculated time-averaged fluid velocities and constrain the duration of fluid flow along brittle fractures cutting through greenschist-facies metamorphosed quartz-mica schists at Delfini on Syros, Greece. These quartz and carbonate filled fractures are surrounded by symmetrical dark reaction halos. These reaction halos were formed by diffusion of CO2 outwards from the fracture in a hydrous fluid which caused carbonation of the country rock. Changes in concentration of relatively mobile elements (e.g. K, Na, Cs, Ba, Pb and Sr) occurred. However, little to no changes in most of the major elements and less mobile trace elements were observed. This implies that carbonation was largely isochemical with respect to most non-volatile components. The Sr/Ca ratio was used to model time-averaged fluid velocities and the duration of fluid flow along the fractures. Fluid flow along narrower fractures with discernibly tapering haloes was found to be rapid (10-6 to 10-5 ms-1) and short lived (0.1 to 400 years). These are time-averaged values and can therefore alternatively record a series of even shorter and faster pulses, perhaps associated with fracture propagation and associated seismicity. Within the widest fractures with constant halo widths (ca. 60 cm) fluid flow was slower (10-8 to 10-6 ms-1) and longer lived (100 to 15000 years). We suspect that the constant width of these haloes reflects a steady state having been reached at which halo width was controlled by the relative rates of fluid flow along the fracture and in the surrounding rock.
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- Kleine, Barbara I., et al.
(författare)
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The mechanism of infiltration of metamorphic fluids recorded by hydration and carbonation of epidote-amphibolite facies metabasaltic sills in the SW Scottish Highlands
- 2015
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Ingår i: American Mineralogist. - : Mineralogical Society of America. - 0003-004X .- 1945-3027. ; 100:11-12, s. 2702-2717
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigate a group of metabasaltic sills from the SW Scottish Highlands metamorphosed at epidote-amphibolite facies conditions that provide useful insight into the mechanisms and characteristics of fluid infiltration during metamorphism. The sills are amphibole and garnet bearing and exhibit a strong foliation in the sill margins that developed pre- to syn- peak metamorphism. Fluid infiltration caused hydration and carbonation in the sills, expressed as 1) replacement of garnet and amphibole by chlorite and calcite and 2) replacement of amphibole and epidote to form chlorite and calcite. Using garnet-amphibole and garnet-chlorite geothermometers we show that these reactions occurred after peak metamorphism at T = 290 to 400°C. Reaction textures show that the fluid infiltration into the sill that caused hydration and carbonation occurred in the absence of deformation. The fluid infiltration was mineralogically controlled with greater fluid access in areas of abundant fine-grained elongate minerals such as amphibole and chlorite. The replacement of garnet by chlorite most likely occurred by an interface-coupled dissolution-precipitation mechanism as evidenced by perfect pseudomorphic textures of garnet, porosity generation behind the reactive interface and fracturing ahead of this interface. Porosity generated in the product chlorite enhanced fluid access to the replacement front. The study shows that deformation was not required for extensive fluid infiltration and alteration during metamorphism. Fluid flow uses a pre-existing foliation to gain access to the rock, taking advantage of the anisotropic shape of the aligned minerals.
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- Lewerentz, Alexander, et al.
(författare)
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Fluid and carbon flux estimation of regional metamorphic fluid flow in Glen Esk, SE Scottish Highlands : The role of hydrodynamic dispersion for broadening of an isotopic front
- 2018
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Ingår i: American Journal of Science. - : American Journal of Science (AJS). - 0002-9599 .- 1945-452X. ; 318:4, s. 435-457
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Tidskriftsartikel (refereegranskat)abstract
- During metamorphism, large quantities of fluids are mobilized and transported through the crust. Such fluids may interact with surrounding rock and serve as a medium for chemical transport. In this study, we use coupled carbonation and oxygen isotope fronts to estimate fluid and carbon fluxes for metamorphic fluid flow in vein pathways in the Dalradian metasediments that crop out in Glen Esk, SE Scottish Highlands. Comparison of wall rock and vein oxygen Isotope ratios indicate that the Barrovian sequence in Glen Esk was infiltrated by at least two separate fluid flow events, where fluid flow from the North Esk Fault overprints an earlier fluid flow event, for which the syn-metamorphic magmatic intrusions north of Glen Esk are a probable fluid source. Advection is the dominating mode of fluid transportation in veins. By advection-dispersion and advection-diffusion modeling, we estimate a time-averaged fluid flux of 0.0005 to 0.0135 m(3).m(-2).yr(-1) and a carbon flux of 0.04 to 0.71 mol C.m(-2).yr(-1) for fluid flow from the North Esk fault into the Dalradian metasediments. The duration of this fluid flow event is estimated to between 11 and 230 kyr. Our results also indicate that hydrodynamic dispersion was the main reason for broadening of the oxygen isotope front.
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