I am currently working on biotites from the Khetri IOCG belt, western India and want to calculate log(fH2O/fHCl) of fluid from biotite halogen chemistry. I find most of the articles have used the following equation (Munoz 1992) for that purpose:
log(fH2O/fHCl)fluid = 1000/T[1.15 + 0.55(Xphl)biotite] + 0.68 - log(XCl/XOH)biotite
However, it is not clear if [1.15 + 0.55(Xphl)biotite] is in numerator or denominator. I see that Marshall and Oliver (2006, Geofluid) have written the equation in such a way (at the end of page 58) that clearly suggest that this part is in denominator. In some papers, the authors have considered this part as numerator. I could not find the original Munoz paper anywhere and am little confused. If anyone have idea on this issue please help. I would love to have a copy of this paper (Munoz 1992), if you have it.
Thanking you,
Abu
Dear Abu Saeed Baidya
It is in the denominator. Also, you can check these two papers:
(1) Zhang, Wei, David R. Lentz, Kathleen G. Thorne, and Christopher McFarlane. "Geochemical characteristics of biotite from felsic intrusive rocks around the Sisson Brook W–Mo–Cu deposit, west-central New Brunswick: An indicator of halogen and oxygen fugacity of magmatic systems." Ore Geology Reviews 77 (2016): 82-96. https://doi.org/10.1016/j.oregeorev.2016.02.004
(2) Yavuz, Fuat. "Evaluating micas in petrologic and metallogenic aspect: I–definitions and structure of the computer program MICA+." Computers & Geosciences 29, no. 10 (2003): 1203-1213. https://doi.org/10.1016/S0098-3004(03)00142-0
The paper of Munoz (1992) is not available online.
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