A series of hydrothermal experiments at 2000 bars have been conducted in order to investigate the systematic relation between biotite composition on the join phlogopite-annite and the composition of pyrrhotite. In an attempt to bracket the sulfide-silicate compositional pairs, three layers within a single capsule were used: 1) pyrite + Fe-rich biotite in the top, 2) sanidine + magnetite in the middle, and 3) troilite + Mg-rich biotite in the bottom. At the conclusion of a bracketing run, the biotite in the top was found to have become more Mg-rich and the biotite in the bottom was found to have become more Fe-rich while a pyrrhotite of apparently homogeneous composition was found throughout the capsule.
Five equilibrium determinations at 700°C have been located:
(N)<sub>Po</sub> = 0.928, (Fe/(Fe + Mg))<sub>Bi</sub> = 0.496
0.936 0.530
0.945 0.541
0.947 0.581
0.950 0.585
The data demonstrate that biotites tend to become more Mg-enriched with increasingly sulfur-rich compositions of pyrrhotite.
This study can be applied to natural systems in which a pyrrhotite-biotite-magnetite-K-spar assemblage is present. Since sulfides have been observed to re-equilibrate at lower temperatures while the composition of the Fe-Mg silicates still mirror the conditions of metamorphism, silicate compositions can potentially be used as a measure of f<sub>S₂</sub> and f<sub>O₂</sub>. From this, one can attempt to calculate the properties of the vapor during the alteration of the silicates and ore genesis. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/54875 |
| Date | January 1977 |
| Creators | Tso, Jonathan Lee |
| Contributors | Geological Sciences |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Thesis, Text |
| Format | iii, 55 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 8041118 |
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