Evidences of talc-white mica assemblage in low-grade metamorphic rocks from the internal zone of the Rif Cordillera (N Morocco)
| Autor: | Mª. Dolores Rodríguez-Ruiz, María Bentabol, Mª. Dolores Ruiz Cruz, Isabel Abad |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Scanning electron microscope Metamorphic rock Mineralogy 020101 civil engineering Geology 02 engineering and technology Vermiculite 021001 nanoscience & nanotechnology Talc 0201 civil engineering Phengite chemistry.chemical_compound chemistry Geochemistry and Petrology Formula unit medicine Mica 0210 nano-technology Chlorite medicine.drug |
| Zdroj: | Applied Clay Science. 195:105723 |
| ISSN: | 0169-1317 |
| DOI: | 10.1016/j.clay.2020.105723 |
| Popis: | Talc-phengite intergrowths were identified in epizone rocks from the Beni Mezala unit (Internal Zone of the Rif). These rocks show the non-common assemblage quartz-K-feldspar-albite-phengite-talc-vermiculite-chlorite/vermiculite mixed-layers. Although X-ray diffraction patterns indicate the presence of talc, talc could not be observed petrographically. In contrast, transmission electron microscopy indicates that white mica consists of nanometer-sized intergrowths of phengite and talc. At the scanning electron microscope scale, these micas show anomalously high contents of Fe + Mg composition (with an average value of 0.51 atoms per formula unit, apfu). The subtraction of the talc component from the mica formula allowed to obtain a mica with a limited phengitic substitution K0.91Na0.03(Al1.74 Fe2+0.23Mg0.03Ti0.03)Σ=2.03(Si3.18Al0.82) which permits an estimation of minimum pressure (P) |
| Databáze: | OpenAIRE |
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