METALLOGENIC PROVINCES, EPOCHS AND ENVIRONMENTS IN AN EVOLVING PLATE TECTONIC FRAMEWORK

Hydrothermal ore deposits form in four major settings:

1. In subduction zones at converging plates: within a main magmatic arc, a magmatic back arc, a collision zone, or in the lower crust.

2. In spreading rifts at diverging oceanic or cratonic plates.

3. In a plate: within basins, uplifts or regional faults.

4. In association with mantle plumes and/or hot spots.

Over time, subducting plates steepen and flatten, causing the magmatic arcs to shift laterally. This can cause a given arc to produce at different times submarine, subaerial and/or intracrustal deposits, or to cease magmatic activity (either temporarily or along stretches of an arc). The surface of a subduction related orogen may change from being above to being below sea level, producing subaerial and intracrustal deposits in one stretch but submarine deposits in another. Thus, ores formed in submarine subduction settings may look similar to ores formed along mid-ocean ridges. Spreading ridges may pass from an ocean to a cratonic plate or split orogens. Basins, uplifts and regional fractures or faults in cratons may be active over limited time periods, and be temporarily subaerial or submarine. In addition, ubiquitous mantle plumes and hot spots may generate hydrothermal ores. Thus, metallogenic provinces, epochs and environments are the result of a variety of geological processes operating in an evolving plate tectonic framework.