Correlation Between Dynamic Response and Mineralogical Micro-Structures in Mineralized and Metamorphic Geological Formations: A Vibration-Based Approach

Abstract

This study examines the complex interplay between dynamic response and mineralogical microstructures across various geological formations, particularly differentiating between mineralized and metamorphic rocks. Utilizing a comprehensive vibration-based approach, in conjunction with petrographic analysis and ultrasonic wave propagation, the study clarifies the significant impact of microstructural features, such as disseminated sulfides and foliated planes, on the complex’s global dynamic behavior. This study investigates six representative rock samples from mineralized and metamorphic geological zones using integrated petrographic analysis, ultrasonic wave velocity testing, density and physical property measurements, and free-vibration dynamic analysis. The results show that the composition and mechanical properties differ significantly. Mineralized rocks contain a high proportion of sulfide minerals, reaching approximately 75% in some samples, and exhibit significantly higher densities, with the APZ sample reaching 3950 kg/m3. In contrast, metamorphic rocks have an average density of 2700 kg/m3. This difference in composition leads to different dynamic responses. Mineralized zones have dynamic elastic moduli that are much higher than those of metamorphic rocks, with Young’s Modulus reaching up to 134.17 GPa and shear moduli ranging from 49.78 GPa to 56.14 GPa, which is about 50% higher than metamorphic rocks (28.9 GPa to 30.5 GPa). However, macro-mechanical deflection tests show that highly foliated metamorphic rocks (like PFT) exhibit the largest deflection of 0.52 mm, while demineralized rocks (like CP) exhibit the smallest deflection of 0.26 mm. Dynamic vibration analysis shows that microstructural “flaws” significantly affect energy dissipation. For example, the Transitional Phase Zone (TPZ) in mineralized rocks has the highest damping ratio (1.67%) and the lowest natural frequency (270 Hz) in its suite. This is different from the more rigid Advanced Pyritization Zone (APZ), which has a damping ratio of 1.1% and a frequency of 395 Hz. These new correlations provide a more accurate basis for the non-destructive assessment of structural stability in mineralized settings, highlighting that local micro-stiffness does not necessarily indicate macroscopic dynamic rigidity.