Petrophysics is the study of physical and chemical rock properties in order to determine their composition, structure and thermodynamic condition.
The difference of rock properties produce geophysical anomalies, which can be used in geological studies. These anomalies are caused by such physical properties of rocks as: density, magnetic susceptibility, remanent magnetization, electric resistivity, chargeability etc.
Therefore, the geological interpretation of geophysical data is usually complicated when either there are no data about rock physical properties or these data are fragmentary and non-systematic. The analysis of geophysical data often allows us only to assume the nature of geophysical anomalies.
The interpretation quality significantly increases when the geophysical surveys are complemented by systematic studies of rock’s physical properties.
From the one hand, these data are used as a-priory information for the inversion of geophysical data (start model). The appropriate start conditions of inverse problem provide its better and more precise solution.
From the other hand, well-investigated physical properties of geological formations in general as well as rocks and ores in particular make possible to transform the abstract geophysical constructions into specific geological information.
Measurements of rocks magnetic susceptibility of is usually done using portable kappa-meters. These studies occurs with geological surveys along traverses through the detected Earth magnetic field anomalies. These studies allows one to make measurements in-situ at outcrops and bedrock exposures. The survey density and statistical confidence can be as high as it is necessary.
Such physical properties as density, remanent magnetizationand its direction, electrical resistivity, chargeability etc. are determined in laboratory conditions. Rock samples are also collected during the geological mapping when they are supplied by all necessary documentation according to the sampling technique. It is also possible to take rock specimens both in core of prospecting wells and directly in excavations. At least 15-20 samples of particular rock should be taken in order to provide reliable and statistically valid analysis of its physical properties. Simultaneously with physical properties, the petrographic description of thin sections is often take place. Sometimes, these studies are accompanied by X-ray micro-tomography of samples in order to estimate the volume content and distribution of particular minerals (for example, sulfides etc.).
The goals of these studies are either petrophysical or geological models, which could allow one to detect and formalize geophysical characteristics of deposits, mineralized zones or ore fields.