By Joaquin Alberto Cortes

University at Buffalo, SUNY (UB)

Calculates cations per Formula Unit

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Version 1.2.2 - published on 02 Jun 2017

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CFU is a little utility for the calculation of the cation per formula unit from mineral chemistry analyses, usually the raw output of a microprobe. Data The input has to be formated as a text file (separated by tabs or spaces) in which each row represent one analysis. The order of the rows is the following: %SiO2 !TiO2 !Al2O3 !Cr2O3 !Fe2O3 !FeO !BaO !SrO !MnO !MgO !NiO !CaO !Na2O !K2O !P2O5 (NO) if the element has not been measured, simply fill the cell with a zero; NO (number of oxygens) is an optional column (see below). (note that the label row begin with '%'... a comment row can be also added in the file providing that begin with the same character). After the data is prepared (e.g. using Excel or similar), the input of the program can be uploaded in the main window of the tool (currently showing an example), simply doing right-click on such window and "Upload". Your browser will pop out a window for browsing in your system for the data file. Calculation: The program has several options for the calculation that are useful under different contexts; Obviously, the user can decide what is the mineral phase analised; usual mineral phases are already available. Alternatively, the number of cations can also be supplied, when it is an unusual mineral phase. If the mineral phase in question is a pyroxene, the program will estimate the speciation of the iron based on charge balance proposed by Papike, quoted in Lindsey (1983). If the mineral phase is an amphibole, the program will allocate cations and speciation of iron following Schumacher, Appendix 2 in Leake et al., (1997). If the mineral is an oxide; the program will try to calculate the speciation of iron based on charge balance... this is a rather naive processing but as good as the more complex ones ;) The option "input your own (mixed)" is used when the dataset contains several mineral phases that need to be calculated differently. If that is the case, you have to provide an additional column with the number of oxygens of each row after P2O5. Note if you don't want cation allocation/speciation of iron for pyroxenes, amphiboles and oxides you could use this option with the adequate number of oxygen (e.g. 6 for pyroxene). This might be useful for example when estimating the ilmenite content in a titanomagnetite, first processing with 3 and 4 oxygens and then with the charge balance. Equivalently, for standard basaltic phases (olivine, clinopyroxene and plagioclase) the program can be left to "guess" and calculate the best possible mineral for your analysis, this late feature needs to be treated with obvious caution, particularly between opx and olivine. enjoy! Caco (c) 2012

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  • Joaquin Alberto Cortes (2017), "CFU,"

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