Indirect rock type modeling using geostatistical simulation of independent components in Nohkouhi volcanogenic massive sulfide deposit, Iran

• Two methods are compared including sequential indicator simulation and independent component analysis for geological modeling.
• ICA was also applied as a determination tool for geochemical factors of the rock type.
• The 2D scatterplot is applied to identify intrinsic characteristics for samples in different regions.

Geological modeling is a useful tool for host rock reconstruction in volcanogenic massive sulfide (VMS) deposits. In this paper, we have proposed two rock type models for Nohkouhi copper deposit, which is a siliciclastic felsic volcanogenic massive sulfide in Central Iran zone. In the deposit, copper mineralization is hosted by different copper grade rocks consisting of Black shale and Rhyodacite. Moreover, in the Black shale, the copper grade distribution directly corresponds to the Rhyodacite. Geochemical factors of the rock types distinguished using ICA. Scores of the IC1 via Scores of the IC2 indicated the best discrimination between the Black shale and Rhyodacite. Our manually constructed class boundary provided a bivariate discriminant line that can be used to determine the rock types. Scores of the ICs are simulated using sequential Gaussian simulation (SGS). The discriminant line is used to classify each node of the grid to the rock type for each pair realization. Also, sequential indicator simulation (SIS) is applied to the Black shale and Rhyodacite on account of their wide range of geometries and assumed deterministic geological model.In order to model the deposit, we have compared two methods comprising direct simulation of rock type (using sequential indicator simulation) and indirect simulation of rock type (using independent component analysis). The experimental results indicated that direct simulation, could be employed for both resource evaluation and knowledge of the geological model. Besides, the indirect simulation produces a model which cannot be used for resource evaluation stage; however, it is helpful with respect to the basic understanding of the geology of the deposit. Our two models showed 96% agreement with each other. Also, ICA chemically presented a key relations between Black shale and Rhyodacite.

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