9:45 AM - 10:00 AM
[MIS23-04] What geomaterials science needs to contribute to the future deciphering of the Earth's history
Keywords:geological survey, metasomatism, accessory mineral
Geology is a science that draws boundaries within the interior of planets, delving into geological bodies to decipher the history of planetary activities. The patterns of sedimentary layers and surface geological structures such as faults and volcanic dykes are visually clear. However, boundaries of igneous bodies, metamorphic/metasomatic rock bodies formed at depths of >ca. 5 km are often ambiguous, characterized by gradual transitions or irregular boundaries. Near these boundaries, rock deformation and fractures occur, alongside the formation of numerous mineral veins due to fluid flow through rock fractures, further complicating exploration and research. Traditional methods for studying such bodies can be classified into two types; one is relied on field observations of visually identifiable deformation structures, analyzed through structural geology based on continuum mechanics, and the other is the examination of rock formation conditions through analytical petrology based on chemical thermodynamic equilibrium. Additionally, various high-precision geochemical analyses, including radiometric dating of microdomains within geological samples, have been conducted. While these methods have significantly contributed to the advancement of Earth sciences since the latter half of the 20th century, limitations in deciphering geological phenomena using these conventional methods are becoming apparent, necessitating innovation in research techniques. In recent years, researchers, including the authors, have discovered regions ranging from several tens of centimeters to tens of meters in size, locally rich in millimeter to micrometer-scale rare element mineral particles within metasomatized ultramafic rock bodies and their boundary regions. These suggest that the presence of larger heterogeneities in metasomatized rock bodies than previously imagined. Standardized geological survey methods for mapping constituent minerals including accessory minerals and their structures in outcrops of this scale are currently lacking, and these discoveries often rely on chance or the geologists’ guts. Through the combination of 3D imaging of outcrops using LiDAR, systematic oriented sample collection, and rapid and large-area elemental imaging using micro-XRF, it will be possible to capture the heterogeneity within geological bodies more systematically and quantitatively, contributing to the decoding of further having overlooked geological records.