Petrophysical and petrological characteristics of granitoids of the Pavlovsk complex (Voronezh crystalline massif)

Abstract

Introduction: the study of the Pavlovsk migmatite-granite-granosienite complex is of key importance in the formation of the geodynamic model of the Losevo suture zone development. The presence of an overlapping sedimentary cover does not allow for a direct study of the morphology and thickness of the complex under consideration, which makes it necessary to use the results of modern geological and geophysical modeling. The purpose of this work is to create a reliable basis for interpreting the results of geological and geophysical modeling based on a set of interrelated data (petrographic description, petro- and geochemistry, physical properties).

Methodology: analytical studies of the material composition included the manufacture and description of grinders (20 pieces) and X-ray fluorescence analysis (45 samples), which was performed on the S8 TIGER device at the VSU Center for the collective use of scientific equipment. The density of rocks was studied by hydrostatic weighing using scales "HIGHLAND" HCB-1502. The magnetic susceptibility was determined by a KM-7 kappameter. The velocity of the longitudinal waves was measured with an ultrasonic flaw detector UK 10PMS.

Discussion of the results: granitoids of the Pavlovsk complex in the studied sample are represented by granosyenites, moderate-alkaline/alkaline granites, leucogranites and alkaline syenites. Granitoids of the first phase are represented by a long petrochemical series from calcareous to alkaline series, granitoids of the second generation phase are from calcareous to calcareous-alkaline. The density of granitoids varies from 2.61 to 2.70 g/cm³ with an average value of 2.65 g/cm³, and late-phase leucogranites with an average value of 2.63 g/cm³ are distinguished within the subgroup. The distribution of the magnetic susceptibility of granitoids of the early phase is bimodal in nature: an extremum with a positive asymmetry and an average value of 18×10^-3 SI units includes amphibole-biotite granitoids and granosienites; the second maximum with an average value of 45×10^-3 SI units refers to alkaline syenites. Leucogranites of the late generation phase are distinguished by a single peak with an average value of 12×10^-3 SI units. In terms of the velocity of longitudinal waves, the studied sample of rocks has a similar range of parameter variability from 5500 to 6400 m/s. The density is correlated with iron, magnesium, and calcium oxides (R=0.8). The magnetic susceptibility of rocks is closely correlated with the content of high field strength elements (R=0.7). The data obtained is summarized in a table.

Conclusion: the close correlations of the composition with petrophysical properties make it possible to accurately segregate the rocks of the complex and the framing according to the measured physical parameters, which makes it possible to reliably interpret the results of geological and geophysical modeling with subsequent integration of the latter into geodynamic models.