Petrological, structural and stable isotope studies of variably calcareous metapelites, metacarbonates and interbedded metabasite sills from the Argyll and Southern Highland Groups in the Dalradian Supergroup from the SW and Central Scottish Highlands have constrained the mechanisms and timing of metamorphic fluid flow. In the SW Highlands, infiltration of the H<SUB>2</SUB>O-CO<SUB>2</SUB> fluids accompanied greenschist facies metamorphism. The syn-metamorphic fluids were channelled through the Ardrishaig Phyllites, infiltrating metabasite sills and driving carbonation reactions in the sill margins. High fluid pressures resulted in hydrofracture in metabasite sills, and infiltration via microfractures was an important mechanism for fluid transport. Carbonation reactions in the metabasites were kinetically limited by diffusion away from microfractures, but in areas of high fluid flux, metabasite sills were completely carbonated. Calcite-quartz microveins developed as a direct result of fluid infiltration and occur in carbonated metabasite units, in the phyllites and more rarely, in psammitic units. The highest density of microveins occurs in axial regions of the regional Ardrishaig Anticline in the SW Highlands, coinciding with zones of high fluid flux, measured by Skelton et al. (1995). High fluid fluxes and microveining in axial regions also coincide with isotopic homogenisation of calcite and quartz in microveins and their host rocks. Therefore, syn-metamorphic fluid flow was focused in axial regions of the Ardrishaig Anticline Calcite-quartz microveins and all homogenised rock units in axial regions have low negative δ<SUP>13</SUP>C calcite values, indicating that the fluid derived its CO<SUB>2</SUB> from oxidation of graphite-bearing metasediments at depth. In low fluid flux zones, i.e. on the limbs of the Ardrishaig Anticline, incomplete fluid:rock interaction has resulted in heterogeneous δ<SUP>18</SUP>O and δ<SUP>13</SUP>C calcite values. Petrological evidence indicates that metamorphic fluids did not transport heat to the Ardrishaig Phyllites, even in zones of large fluid flux.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:643321 |
| Date | January 1997 |
| Creators | Cole, Coleen Marie |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14621 |
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