MODAN: an interactive computer program for estimating mineral quantities based on bulk composition

Abstract

MODAN is an interactive computer program written in Microsoft QuickBASIC to estimate mineral quantities (modes) based on bulk and mineralogical compositions of rock, soil and tailings samples. Modes are estimated by applying Gaussian elimination and multiple linear regression techniques to simultaneous mass balance equations where the number of elements available in the bulk composition exceeds or equals the number of contained minerals. Required input data are the bulk chemical analysis, mineral species present and formulas or compositions of those minerals. The program provides estimated mineral modes in weight percent as well as calculated bulk compositions based on the estimated modes. Residual sum of squares and distance between the calculated and observed bulk compositions are used as measures of the goodness of fit. Since whole rock chemical analyses are often available along with mineralogical compositions, this approach to modal analysis may prove to be useful for rapid estimation of modes and screening of large data sets based on approximate or assumed mineral compositions. The approach also allows an assessment of mineral zoning and estimation of mineral compositions. Situations where there are three or more minerals of similar compositions in the mineral assemblage and where the minerals are characterized by one identical variable (such as magnetite and hematite) may produce erroneous results.