EASYGRESGRANT - A Microsoft Excel spreadsheet to quantify volume changes and to perform mass-balance modeling in metasomatic systems

Gresens’ initial ideas about the mobility/immobility of elements and the gains and losses of material in hydrothermal systems, together with the subsequent isocon method proposed by Grant, have led to the development of a considerable number of mass-balance computer programs for application to metasomatic systems (e.g., Leitch and Day, 1990; Potdevin, 1993; Sturm, 2003; Coelho, 2006). Nevertheless, some of them (NEWGRES or Gresens 92) do not work properly on today’s computers or only work on the Windows platform (SHEARCAL or Geoiso). To date, all mass-balance programs have other problems: (1) graphical plots, such as Grant’s isocon diagram or Gresens’ composition-volume diagram, are not useful tools in order to find immobile elements when a large data set is being handled, since the large number of lines or symbols represented hinders visualization and the distinction of the elements themselves; (2) the method of arbitrary scaling of compositional data proposed to mitigate this problem in the isocon diagram (Grant, 1986) has recently been reported to be inadequate, since scaling influences the best-fit isocon, yielding errors in the mass-balance calculations (Mukherjee and Gupta, 2008). This short note presents EASYGRESGRANT, a new user-friendly interactive Microsoft Excel spreadsheet program that can be run on the Mac and Windows platforms and that permits correct selection of immobile elements from clusters of slopes, volume factors, and an improved isocon diagram, providing an error-free mass-balance modeling for application in metasomatic systems.