Upper-pressure stability of synthetic margarite plus quartz |
| |
| Authors: | David M Jenkins |
| |
| Institution: | (1) Department of the Geophysical Sciences, University of Chicago, 60637 Chicago, Illinois, USA;(2) Present address: Department of Geological Sciences, State University of New York - Binghamton, 13901 Binghamton, New York, USA |
| |
| Abstract: | Thermodynamic calculations have shown that the dP/dT slope of the reaction 4 margarite+3 quartz 5 kyanite +2 zoisite+3 H2O as determined by Storre and Nitsch (1974) is too steep. This reaction has been reinvestigated using synthetic margarite, zoisite, kyanite, and natural quartz in the starting mixtures and using infrared spectroscopy to examine the run products. The experimentally determined dP/dT slope ranges between –2.2 and –17 bars/ K, which is in excellent agreement with predictions based on thermodynamics. An internally consistent set of univariant curves could be fitted to the experimental reversals for the above reaction and for the reactions margarite+ quartz anorthite+kyanite+H2O and 2 zoisite+kyanite +quartz 4 anorthite+H2O investigated by Nitsch et al. (1981) and Goldsmith (1981), respectively. Addition of up to 40 mol % of the component NaAl2(Si3Al) ·O10(OH)2 (paragonite) to margarite will increase the stability of the margarite solid solution plus quartz by 2–3 kbar without significantly affecting the dP/dT slope, making the paragenesis margarite plus quartz a good geobarometer. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
