Step-wise growth of biotite porphyroblasts in pelitic schists of the western Lys-Caillaouas massif (Pyrenees) |
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| Affiliation: | 1. Institute of Geological Sciences, Polish Academy of Sciences (ING PAN), Research Centre in Kraków, Senacka 1, PL–31002 Kraków, Poland;2. The Czech Academy of Sciences, Institute of Geology, Rozvojová 269, Prague 6, 16500, Czech Republic;1. Institute of Earth Sciences Jaume Almera ICTJA, CSIC, Barcelona, Spain;2. Géosciences Environnement Toulouse, UMR 5563, Observatoire Midi Pyrénées, Université Paul Sabatier, 31400 Toulouse, France;3. Institut d''Astrophysique et de Planétologie (IRAP), CNRS/UPS, Toulouse, France;4. Departamento de Geología, Universidad de Oviedo, Spain;1. Italian Institute for Genomic Medicine, c/o IRCSS Candiolo, Torino, Italy;2. Candiolo Cancer Institute, FPO - IRCCS, Candiolo, Italy;3. Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA;4. Sandra and Edward Meyer Cancer Center, New York, NY, USA;5. Caryl and Israel Englander Institute for Precision Medicine, New York, NY, USA |
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| Abstract: | Detailed optical and electron microscope (SEM and TEM) examination of biotite blasts from pelitic schists of the western Lys-Caillaouas massif in the Pyrenees reveals a variety of microstructures suggesting growth of the blasts before and after a thermal peak during the D2 deformation. In the early stages of growth the biotites had (001) at high angles to S1, and they appear to have existed as thin (001) parallel plates. In many cases blastesis is suggested to have involved growth of the biotites into their own continuously dilating pressure shadows. Inclusions with dentate grain boundaries, banded structures, and ‘radiator-fin’ intergrowths suggest a mechanism analogous to the Ramsay crack seal model for vein formation, but here involving step-wise dilation of a pressure-shadow cavity into which the adjacent blast itself was growing. |
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