The Shoals/Sandbanks
These areas would actually be analogous to the Disseminated Mineralization.

The Faster Flowing Outside Bends in the Magma River would be where the more Heavily Mineralized Massive Mineralization is located. And likely in large part due to these Faster Flowing areas being the actual Conduit (having eaten a clear path through the surrounding rock) and the Disseminated areas being the partially eaten away Shoal Rock in the Flowing River of Sulfide laden Magma.

Brecciated areas would be where the Host Rock simply broke up under pressure but essentially remained in place - analogous to Swampy Marches along the River Valley. Rivers tend to Slow in terms of Flow in relatively Flat parts of the River Valley and Meander from one side of the Valley to the other (just fluid dynamics at work there, for the most part) and with the Magma the Meandering would be controlled to large extent by the Degree of Fracturing in the Host Rock and somewhat also by the type/nature of the Host Rock.
Old Joe