Spatial variations in Geometry, Topology and Fractal attributes of a Riedel shear induced Fracture Network system in Granites

Fractures are the manifestation of brittle deformation and act as vital conduits for fluid transport in upper crustal rocks. To measure rock strength and stability, infer deformation mechanisms, and reconstruct the stress condition under which they developed, a systematic examination of their geometrical characteristics is essential which also provide insights on how upper crustal rocks respond to stress. Since fractured rock bodies frequently consist of interconnected networks of different fracture sets, topological characterization aids in quantitative assessment of their connectivity, which directly affects comprehension of their permeability and, consequently, the history of fluid migration through the host rock body. Additionally, characterization of fracture networks has direct implications in recent applications like nuclear waste disposal and carbon sequestration which contribute significantly to environmental sustainability.

The present study examines the origin and characterizes subsequent networking of fractures developed within younger granites (~ 2.61 Ga) of the Chitradurga Schist Belt, an Archean age granite-greenstone belt from the Western Dharwar Craton of peninsular India integrating field-based observations with network topology and fractal analysis. We systematically document the geometrical attributes of fracture patterns developed within the granites across varying outcrop scales to understand their formation and characterize them topologically to assess their connectivity and record if fracturing patterns, intensity, density and connectivity vary across scales and also spatially along the areal extent of the granitic plutons. It is found, that although indicative of being formed by the activation of a Riedel shear system under the same tectonic stress regime, the networking patterns which the fractures have developed through their mutual interaction vary spatially in their geometrical, topological and fractal characters. Our study ventures upon the possible causes of this variation and highlights the role of ambient stress state, rheology, pre-existing mechanical anisotropy, orientation of pluton margin and its proximity to adjacent shear zone and superimposition of fractures behind the development of these spatially varying fracture network patterns across the areal extent of the granitic plutons.