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Ba- and Ti-enriched dark mica from the UHP metasediments of the Seve Nappe Complex, Swedish Caledonides Cover

Ba- and Ti-enriched dark mica from the UHP metasediments of the Seve Nappe Complex, Swedish Caledonides

Open Access
|Feb 2017

Abstract

We report on the occurrence of peculiar Ba- and Ti-enriched dark mica in metasedimentary rocks that underwent high-pressure metamorphism in the diamond stability field followed by decompression to granulite facies conditions. The mica occurs as well-developed preserved laths in a quartzofeldspathic matrix. The mean concentrations of BaO and TiO2 in the mica are 11.54 and 7.80wt%, respectively. The maximum amounts of these components are 13.38wt% BaO and 8.45wt% TiO2. The mean crystallochemical formula can be expressed as (K0.54Ba0.39Na0.02Ca0.01)Σ0.96(Fe1.37Mg0.85Ti0.50Al0.29Mn0.01Cr0.01)Σ3.03(Si2.59Al1.41)Σ4.00O10(OH1.30O0.66F0.02S0.01)Σ1.99, with oxyannite, oxy-ferrokinoshitalite and siderophyllite as dominating end-members. Based on the petrographical observations, it is proposed that the dark mica was formed at a rather late stage in the evolution of the parental rock, i.e. under granulite facies conditions.

DOI: https://doi.org/10.1515/mipo-2017-0001 | Journal eISSN: 1899-8526 | Journal ISSN: 1899-8291
Language: English
Page range: 41 - 50
Submitted on: Jan 25, 2016
Accepted on: Oct 10, 2016
Published on: Feb 18, 2017
Published by: Mineralogical Society of Poland
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year

© 2017 Jarosław Majka, Łukasz Kruszewski, Åke Rosén, Iwona Klonowska, published by Mineralogical Society of Poland
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.