Toss A Pebble In a Pond: Southern Arc Minerals

By Kevin Graham, BA MBA

This report is prompted by recent news, by the reactions of some to that news, and by conversations, this morning with Southern Arc's President, John Proust, and this afternoon with Bob Vidoni, Vice President Project Management.

At some point in your childhood, you may have conducted an experiment with pebbles and a body of water. Toss a pebble into the middle of a pond, and watch the ripples radiate outward in concentric circles. These ripples take a ‘halo’ formation surrounding the ‘core’ of the stone’s path. The bigger the stone, the greater the impact on the pond, both laterally, and vertically.

Here’s another way to consider the image, coming up from the ground, instead of down into water. In geology, involving an igneous intrusive, this phenomenon is called an ‘aura’, or ‘aureole’, or a ‘contact aureole’. See a detailed explanation with a graphic here.

Consider the core ‘finger’ of a mineralized igneous body to be like a hot water pipe, rising vertically through the earth to the surface. The country rock around this body is like an insulating asbestos wrap around that pipe. While that wrap has the effect of containing the heat of the pipe, it will naturally absorb some heat from the igneous rock. In the hydrothermal process by which a porphyry is created, heat and pressure will alter the surrounding rock, cracking and shattering it, creating paths into which liquid mineralized matter can penetrate. Think of this process as one of spillage, or splatter, with much diminished density of mineralization in comparison to the central ore body. This metamorphic process, then, typically results in