CHARACTERIZATION OF FAULT BRECCIA OF KHETRI COPPER BELT, RAJASTHAN

Abstract

Khetri sub-basin of North Delhi Fold Belt, hosts numerous occurrences of Uranium along shear zones which follow a broad zone of albitization trending NNW-SSE. The irregular occurrences of the Uranium mineralization within the brecciated rocks in the Huraki-Dhani and Maota - Jahaz area of the Khetri Copper Belt (KCB) have called for the need to study the fault breccias in this region. It is found that in parts of the fault zone, some of the breccias are unusually very rounded. There are no surface exposures of these rocks hence data on fault breccias can be collected only from drill core samples. 1-lere an attempt is made to characterize the brecciated rocks by quantification of clasts on the basis of their textural parameters and to have some idea about the mechanism involved in the genesis breccias in this fault. We find that the quantification of textural parameters, such as shape and size parameters, of breccias clasts is not straight forward. Efforts have been made based on existing literature to derive methodologies to quantify shape and size parameters. It has been found in this study that the rock samples of this specific area have high sphericity ranging between 0.6 and 1, high roundness values also ranging between 0.6 and I in most cases and roughness values ranging between 0.8 and I in majority of the cases. Fractal dimension (D) values were also calculated for the samples and it ranged between 1.03 and 2.2. In many cases the plots showed signatures of being multifractals but appropriate values of D could not be generated from the study of the core samples alone. The fractal dimension values were mostly close to 2 and so it can be inferred that they are not examples of simple tectonic breccias which have D value close to 1.6. Values of D for fractals vary between I and 2, and so the values being close to 2 depict the fact that the clasts have anomalously high roundness which might be a result of the development of secondary mineral overgrowth around the clasts.