Stochastic Modelling of Lead - Zinc Deposit at Rampura Agucha, Rajasthan

The irregularly spaced assay values of lead and zinc in different boreholes of Rampura-Agucha Pb-Zn deposit (Rajasthan), have been interpolated at equal intervals of one meter using cubic splines to obtain a constant lag, discrete spatial (time) series. The time series has been used subsequently for stochastic modelling of assay values along the drill holes. Univariate stationary models under the integrated autoregressive moving average scheme - ARIMA (p,d,q) - were established for each assay series along four borehole based on statistical analyses of their auto (acl-) and their partial (pacf) correlation functions. These models can be used for univariate forecasting of assay values at different distances. Among the candidate ARlMA (p,d,q) models, ARLMA (1,1,1)and ARIMA (1,1,0) were found to fit spatial distributions of Zn and Pb, respectiveIy, using the principle of parsimony.

Though linear stochastic models were developed for Rampura - Agucha Pb-Zn deposit, a brief review of the scope and use of non-linear stochastic model for modelling of complex ore mineralisation has also been attempted.

Geochemical interpretation has been carried out on the petrochemical data of the amphibolites interlayered with the footwall and the hanging wall rocks using partial correlation coefficients between various oxides. This has led to comprehensive characterisation of the geochemistry and mineralogy of the amphibolites.