Textural evidence for remobilization in metamorphic environments

Abstract

Remobilization of stratabound massive sulphide deposits involves both dislocation flow (mechanical remobilization) and fluid-state processes (chemical remobilization). Textural support for such remobilization is presented at micro-, meso- and macroscales. Microscale evidence establishes the degree (the amount of a deposit affected) of remobilization. Likewise, mesoscale textures establish the degree, and may provide mesoscale models of macroscale remobilization processes, but still do not establish the extent (the distance over which translocation may have occurred) of remobilization. Where macrotexture indicates a departure from an original conformable relationship, gross remobilization is suggested and may be the consequence of mechanical and/or chemical processes. The case for gross mechanical and/or chemical remobilization is often difficult to sustain because alternative hypotheses (e.g., hydrothermal replacement) may be compatible with the observed relationships. Remobilization of a conformable ore layer may involve internal redistribution during which sulphides have been modified by dislocation flow and/or fluid-state processes within the layer constraints, or external where the layer constraints have been substantially transgressed during dislocation flow and/or fluid-phase remobilization. If mesoscale textures indicate remobilization of the external type, then macroscale (gross) remobilization remains a possibility, subject to substantiation.