DIGITAL MAPPING AND ANALYSIS OF ACCOMMODATION STRUCTURES AND DEFORMATION ASSOCIATED WITH THE EMPLACEMENT OF MAGMATIC INTRUSIONS, HENRY MOUNTAINS, UTAH

Digital field mapping and 3D modelling techniques have been utilised in our study of accommodation structures associated with emplacement of magmatic intrusions in the Henry Mountains, Utah. These classic outcrops, in particular those of the satellite intrusions to the Mt Hillers intrusive complex, provide excellent 3D exposures across both the intrusions and their surrounding host rocks, hence making it the perfect study area. Traditional field mapping, outcrop studies and detailed data collection of deformation and accommodation structures have been combined with state-of-the-art digital mapping methodologies (inc terrestrial laser scanning - TLS) to capture the 3D architecture of the outcrops, enabling us to build more detailed models of the intrusive bodies and their emplacement-related host rock deformation.

Two satellite intrusions have been the focus of our studies: Trachyte Mesa (low to moderate complexity, comprised of stacked sheets); and Maiden Creek (complex geometry, comprised of an elliptical shaped body with several finger-like lobes). The full extent of our study areas have been captured using TLS to collect both regional (360⁰) panorama and high resolution outcrop scans: helping to capture the regional framework and more detailed intrusion host-rock contact, fracture and bedding geometries from inaccessible outcrops. Models presented shall include detailed outcrop studies across two adjacent intrusive lobes in Maiden Creek, where a sub-horizontal shear zone has been identified, running along the top contact of each lobe. This shear zone acts as a detachment zone, separating low-/moderately-deformed sandstones above from highly deformed sandstones below and between the two lobes. In the field, the challenging topography of the lobe-bounded gully, with steep-sided slopes and cliff-faces, make several important outcrops inaccessible. Due to the structural complexity within the shear zone study area it is difficult to capture the 3D geometry and spatial distribution of the structural framework and deformation using conventional methods. This further leads to difficulty in conveying the science to an audience. We believe that combining TLS models with detailed outcrop studies has helped us to fully visualise the complex 3D structural setting, as well as providing a sharing platform.