Chlorine, titanium and barium-rich biotites: factors controlling biotite composition and the implications for garnet-biotite geothermometry
Article Abstract:
The narrow shear zones in 1800 Ma old noritic granulites in the Flakstadoy Basic Complex, Lofoten, north Norway contain Ba-, Cl-, and Ti- rich biotites with garnet, plagioclase and amphibole. The studies reveal that these have replaced the clinopyroxene, orthopyroxene, biotite and ilmenite during ductile deformation. The multivariate analysis indicates that the compositional differences can be described by two exchange reactions. The biotite chemistry matches it with the last equilibrium fluid with the mineral. The correlation with regression analysis confirm this.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1995
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Activity-composition relationship in Tschermak's substituted Fe biotites at 700 degree centigrade, 2 kbar
Article Abstract:
The activity-composition relation indicates a negative deviation from ideality in case of Tschermak's substituted Fe biotites on the join annite-siderophyllite. The experiments are conducted at 700 degree centigrade and 2 kbar to measure the Ann component and show that the fine-grained assemblage of Fe-Al biotites acts as a sliding scale buffer. Mg-Al and Fe-Al mixing in biotite shows positive deviations and Fe-Mg shows least deviation from ideality. However, this simplistic treatment in the experiments is insufficient to explain the natural biotite data.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Heat capacities of Tschermak substituted Fe-biotite
Article Abstract:
A study was conducted to analyze the heat capacities of Tschermak substituted iron-biotite. The biotite was characterized using microprobe, electron microscopy and X-ray diffraction. It was prepared using nitrates as the source for aluminum and iron, K2Co3 for potassium, and C8H20O4Si for silicon. Results indicated that increases in the Tschermak vector correlated with a rise in the tetrahedral rotation angle from 0 to 13 degree for annite to siderophyllite.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1999
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