Quartz veins in the greenstone belts of Dharwar Craton (India) and their mineralization potential – A hypothesis

Abstract

Structural geological investigations involving statistical analysis of mineralized vs. non-mineralized (barren) veins are important in mineral exploration. In this study, we statistically analyze orientation, thickness, and spacing data of veins intruding metavolcanic rocks of three regions of Eastern Dharwar Craton (EDC, southern India) - Hutti surface (6 transects), Raichur (5 transects), and Gadwal (6 transects). While gold mineralization is known to occur in parts of Archaean greenstone belts of the Dharwar Craton, vein data collected here are from areas with no reported gold deposit. Results from this study are compared with similar published data from gold-bearing and barren domains of the Gadag region in Western Dharwar Craton (WDC). Vein data are used to prepare a “mineralization potential plot” and calculate the mineralization potential parameter (M_d) for each transect. Whilst most transects in EDC have high M_d, implying low mineralization potential, a few transects have a low M_d and fall close to the cluster of points demarcating the mineralized domain of the Gadag region. This brings to light the limitations of the mineralization potential plot developed by earlier workers, which is discussed in this study. We discuss the importance of dispersion of M_d for multiple transects of a particular region in order to evaluate its true mineralization potential. It is noted that all data for EDC (this study), as well as the non-mineralized domain of Gadag (WDC) show high dispersion on the mineralization potential plot, while data from the mineralized domain of the Gadag are clustered (low dispersion) close to the origin. We have developed a “mineralization potential standard deviation (MPSD) plot”, where the mean M_d and its standard deviation (S_d) from multiple transects of the individual regions of EDC and WDC are plotted. This yields a MPSD curve following power law equation, which is unique to the data of quartz veins intruding metavolcanic rocks of the Dharwar Craton. We hypothesize that if data of quartz veins intruding metavolcanic rocks from any part of the Dharwar region are analyzed, a high mineralization potential will be indicated if data fall on this MPSD curve and close to the origin. We envisage that every region will have its unique MPSD curve, which can be prepared from vein data of a particular mineralogical phase intruding a specific lithology. It is concluded that the MPSD curve can be used to identify potential regions of mineralization.