caa a22 4500 465791115 CHVBK 20180323112024.0 cr unu---uuuuu 170327e19900401xx s 000 0 eng 10.1007/BF00306660 doi (NATIONALLICENCE)springer-10.1007/BF00306660 Development of microporosity, diffusion channels and deuteric coarsening in perthitic alkali feldspars [Elektronische Daten] [Richard Worden, F. Walker, Ian Parsons, William Brown] Turbidity is an almost universal feature of alkali feldspars in plutonic rocks and has been investigated by us in alkali feldspars from the Klokken syenite using SEM and TEM. It is caused by the presence of myriads of tubular micro-inclusions, either fluid-filled micropores or sites of previous fluid inclusions, and is associated with coarsening of microperthite and development of sub-grains. Micropores are abundant in coarsened areas, in which porosities may reach 4.5%, but are almost absent from uncoarsened, pristine braind-microperthite areas. The coarsening is patchy, and involves a scale increase of up to 103 without change in the composition of the phases, low albite and low microcline, or in the bulk composition of the crystal. It occurs abruptly along an irregular front within individual crystals, which retain their original shapes. The coherent braid microperthite gives way across the front to an irregular semi-coherent film perthite over a few μm and then to a highly coarsened irregular patch perthite containing numerous small sub-grains on scales of a few hundred nm, in both phases. The coarsening and micropore formation occured at a T≤400°-450° C and it is inferred to have been driven by the release of coherent strain energy, low-angle grain-boundary migration being favoured by a fluid. The patchy nature of the coarsening and the absence of a relationship with initial grain boundaries suggest that the fluid was of local origin, possibly arising in part through exsolution of water from the feldspar. The sub-grain texture and microporosity modify profoundly the permeability of the rock, and greatly enhance the subsequent reactivity of the feldspars. Springer-Verlag, 1990 Worden Richard Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut Walker F. Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut Parsons Ian Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut Brown William CNRS-CRPG, BP 20, F-54501, Vandoeuvre-lès-Nancy cedex, France aut Contributions to Mineralogy and Petrology Springer-Verlag 104/5(1990-04-01), 507-515 0010-7999 104:5<507 1990 104 410 https://doi.org/10.1007/BF00306660 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00306660 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Worden Richard Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut NATIONALLICENCE 700 1- Walker F. Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut NATIONALLICENCE 700 1- Parsons Ian Grant Institute of Geology, University of Edinburgh, West Mains Road, EH9 3JW, Edinburgh, Scotland aut NATIONALLICENCE 700 1- Brown William CNRS-CRPG, BP 20, F-54501, Vandoeuvre-lès-Nancy cedex, France aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 104/5(1990-04-01), 507-515 0010-7999 104:5<507 1990 104 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer