The implications of crustal architecture and transcrustal upflow zones on the metal endowment of a world-class mineral district

Abstract

Earth’s mineral deposits show a non-uniform spatial distribution from the craton-scale, to the scale of individual mineral districts. Although this pattern of differential metal endowment is underpinned by lithospheric-scale processes the geological features that cause clustering of deposits remains enigmatic. The integration of geological and geophysical (seismic, gravity, and magnetotelluric) features has produced the first whole-of-crust image through an iconic Neoarchean volcanic complex and mineral district in the Abitibi Greenstone Belt, Superior Province, Canada. Observations indicate an asymmetry in surface geology, structure, and crustal architecture that defines deep transcrustal magmatic-hydrothermal upflow zones and the limits of the Noranda District ore system. Here, extreme volcanogenic massive sulfide (VMS) endowment is confined to a smaller area adjacent to an ancestral transcrustal structure interpreted to have localized and optimized magmatic and ore forming processes. Although lithospheric-scale evolutionary processes might act as the fundamental control on metal endowment, the new crustal reconstruction explains the clustering of deposits on both belt and district scales. The results highlight a strong magmatic control on metal and in particular Au endowment in VMS systems. Overprinting by clusters of ca. 30 Ma younger orogenic Au deposits suggest the ore systems accessed an upper lithospheric mantle enriched in Au and metals.

Imaging the subsurface architecture in porphyry copper deposits using local earthquake tomography

“…The spatial distribution of ore deposits is mainly influenced by crustal architecture, which is partly controlled by tectonic and geodynamic processes, due its impacts on the flow of fluids throughout the crust 50 . Thus, crustal features and structural framework inferred from local earthquake tomography can lead to a better understanding of the development of copper metallogenic belts in northern Chile.…”

Constraints on Growth and Stabilization of the Western Superior Craton From Inversion of Magnetotelluric Data

“…While the model and data set presented herein lack sufficient resolution in the upper crust, the occurrence of abundant late hydrous granitoids and sanukatoids with mantle affinity in the study area (e.g., Tóth et al, 2022) suggests that the proposed mechanism could also result in progressive migration of enriched fluids into the upper crust. However, the apparent correlation between significant deposits and crustal conductors within the western Superior is noticeably weaker than that found elsewhere (Jørgensen et al, 2022;Kirkby et al, 2022). Thus, questions remain as to whether the apparent lack of metal endowment within the western Superior Craton is a result of insufficiently fertile melts, a lack of focusing mechanisms (e.g., melts spread across a large area rather than focused into economically viable mineral deposits), or due to relatively limited exploration of the region.…”