Microfissural mapping of natural cracks in rocks: Implications for fluid transfers quantification in the crust

Fluid migrations in the crust strongly depend on the transport properties of surrounding rocks. Quantification of paleofluid flow is of great importance in developing a better understanding of element transfers in the upper crust (Au, U …) and alteration propagation as a function of time. This paper presents a method which has the ability to quantify paleofluid flows by using structural features such as Fluid Inclusion Planes (F.I.P). The method (AnIma) permits the digitization of geometrical parameters of F.I.P (length and orientation) on sections and quantification of fissural porosities and permeabilities of the rock matrix. An example from a Siberian granite is presented. In this study 3241 cracks were digitized. The F.I.P are present throughout the section and their fissural porosities (5.5%) and fissural permeabilities (5.47 mD or 5.47 10− 15 m2) were quantified. The use of the AnIma method permits a rapid quantification of the different fossil fluid pathways in space and time.