On Li-bearing micas: estimating Li from electron microprobe analyses and an improved diagram for graphical representation
| Autor: | G. Tischendorf, Baerbel Gottesmann, Hans-Juergen Foerster, Robert B. Trumbull |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Bearing (mechanical)
010504 meteorology & atmospheric sciences Chemistry Diagram Thermodynamics chemistry.chemical_element Mineralogy Electron microprobe engineering.material 010502 geochemistry & geophysics Zinnwaldite 01 natural sciences law.invention Octahedron Geochemistry and Petrology law engineering Lithium Mica Representation (mathematics) 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 61:809-834 |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/minmag.1997.061.409.05 |
| Popis: | Lithium may constitute an essential element in micas, yet it cannot be detected by the electron microprobe. Since Li is critical for correctly classifying micas and properly calculating their formulae, several methods have been proposed to overcome this analytical deficiency. We offer empirical relationships between Li2O and SiO2, MgO, F, and Rb in trioctahedral micas, and between Li2O and F as well as Rb in dioctahedral micas. The resultant regression equations enable lithium contents to be sufficiently well estimated from EPM analyses within the range of validity discussed.Secondly, we introduce an easy to handle, new diagram with the axis variables [Mg-Li] and [Fetot + Mn + Ti-AlVI] for graphical representation and discuss its scientific rationale. Being based on absolute abundances of cations in the octahedral layer, the diagram provides a simple means to classify micas in terms of composition and octahedral site occupancy, and it also allows compositional relationships between Li-bearing and Li-free mica varieties as well as between trioctahedral and dioctahedral micas to be displayed on a single, two-dimensional diagram. |
| Databáze: | OpenAIRE |
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