Quantifying fluid pressure events using shallow crustal veins.

Reactivation of pre-existing fractures is attributed to fluid pressure conditions and orientation of fractures with respect to the tectonic stress field. In most cases, multiple fluid pressure events reactivate fracture networks. However, it is difficult to perceive and quantify the number of such fluid pressure events directly from a heterogeneous vein data distribution. In the present study, we undertake a statistical approach, well known and extensively used for fuzzy clustering of planar data to approximate the minimum number of fluid pressure events which formed/reactivated fractures. We have also combined the deterministic method for quantifying the minimum number of such fluid pressure events with the traditional method of scaling 3D Mohr circles to determine the absolute fluid pressure magnitudes. The method has been applied to published data of the Gadag-Chitradurga greenstone belt, a prominent Archean greenstone belt of the western Dharwar Craton, south India, to understand the mechanism behind shallow crustal emplacement of auriferous quartz veins within a transtensional tectonic regime. Further, we provide field evidence of fracture reactivation and estimate their reactivation potential, which play a significant role in the spatial variation of fluid pressure along the greenstone belt. Identifying data clusters using Bingham statistics for Pf determination. [ABSTRACT FROM AUTHOR]