Dear Rob,
one of the most convenient methods for performing mass balance
calculations in altered rocks is the so-called isocon method, which has
been described by Grant (1986). The mathematical treatment is based on the
original equations of Gresens. There has been an additional work by
Baumgartner and Olsen (1995), which applies a rigorous statistical
treatment to the isocon method, involving regression analysis and
robust calculation of error propagation. I have extensively used the
isocon method in recent years, with pretty good results. One of the major
advantages is that no a priori immobility of elements is applied and the
methodology is relatively robust with respect to effects of spurious
correlation patterns.
The relevant references are as follows:
Grant JA (1986) The isocon diagram - a simple solution to Gresens equation
of metasomatic alteration. Econ. Geol., 81, 1976-1982.
Baumgartner LP, Olsen SN (1995) A least-squares approach to mass transport
calculations using the isocon method. Econ. Geol., 90, 1261-1270.
I could send you an EXCEL spreadsheet, which calculates the relative mass
change for a standard set of major and trace elements and the respective
Std. Dev. and Std. Err. However, I do not have the FORTRAN code of the
program by Baumgartner & Olsen, so you should contact the authors if you
want to apply the regression analysis to your data.
With kind regards
Thomas
***************
Dr. T. Wagner
Mineralogisches Institut
Universität Würzburg
Am Hubland
D-97074 Würzburg
Germany
***************
-------------------------------------------------------------------------------
Geo-mineralisation is administered by the Mineral Deposits Studies Group (UK)
|