Why is gold mineralization at Upper Antino considered structurally controlled?

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Gold Mineralization at Upper Antino is Structurally Controlled Due to Shearing and Favorable Host Rock Interactions

Gold mineralization at the Upper Antino target area is considered structurally controlled, meaning that the geological structures present have dictated where the gold is deposited. Specifically, the presence of shear zones is critical. These shears cut through the host rock, creating fractures and open spaces. When these shears intersect a gabbro unit, which is an iron-rich igneous rock, a favorable environment for gold deposition is created.

The competent and brittle nature of the gabbro means it fractures readily when sheared. This fracturing opens up space for quartz veins to form, and these veins are the primary carriers of high-grade gold. Furthermore, the iron-rich composition of the gabbro plays a chemical role in the mineralization process. It promotes the deposition of gold from the mineralizing fluids that flow through the shear-created pathways. As the gabbro unit widens with depth, these structures encounter progressively larger volumes of this conducive host rock, suggesting potential for increased mineralization.
Shears Create Pathways for Mineralizing Fluids

The gold mineralization at Upper Antino is directly linked to the presence and activity of shear zones. These geological structures act as conduits, allowing mineral-rich fluids to migrate through the subsurface. As these shears cut through the gabbro, they create zones of intense fracturing. This fracturing is essential as it provides the physical space, or dilation, necessary for quartz veins to form and for gold to be precipitated within them. The depth and orientation of these shears, as demonstrated by drill hole FR249 intersecting multiple stacked, sub-parallel shears, are key factors in defining the geometry of the gold mineralization.
Gabbro's Properties Enhance Gold Deposition

The gabbro unit at Upper Antino serves as a particularly favorable host for gold mineralization due to its physical and chemical properties. Its competent and brittle texture means that when intersected by shear zones, it fractures predictably, creating open spaces ideal for quartz vein formation. Crucially, the iron-rich nature of the gabbro facilitates the deposition of gold from the hydrothermal fluids circulating through the shears. This chemical interaction, where the gabbro's composition promotes the precipitation of gold, is a significant factor in the development of high-grade gold zones within this host rock. The observed widening of the gabbro unit at depth indicates that the mineralizing structures are intersecting progressively larger volumes of this favorable host rock, enhancing the potential for significant gold accumulation.

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Why is gold mineralization at Upper Antino considered structurally controlled?

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