Isotopic measurement of Sr and O exchange between meteoric-hydrothermal fluid and the Coire Uaigneich Granophyre, Isle of Skye, N.W. Scotland

摘要: To determine the scale and magnitude of hydrothermal Sr contamination in an 18 O-depleted granite from Isle Skye, O isotopic electron microprobe mineral analyses were performed on samples Coire Uaigneich Granophyre (CUG), including two cut by mineralised fractures. Unfractured whole-rock have model initial 87 Sr/ 86 ratios between 0.7298 0.7320 δ values within 2% SMOW. Depletions are most severe near intrusive contacts, indicating structural control fluid flux attesting to vigorous subsolidus exchange with circulating fluids. Initial do not correlate values, suggesting that depletion was generally accompanied significant contamination, a probable consequence low concentrations. Fractures CUG fringed bleached zones up about 1 cm wide which contain epidote, chlorite albitised plagioclase. gradients exist these zones, where depressed as much 0.0036. The coincidence marked plagioclase albitisation suggests enhanced, but localised, during reactions at temperatures 400°C. profiles essentially flat 10 final fluids circulate along fractures precipitated effectively plugging plumbing system CUG. Mn zoning epidotes reflects changes trace element chemistries late fluids, increased buffering composition diminished. high exhibited cannot resulted fluid/rock interactions. Provided sampling is conducted care, granites can petrogenetic significance.