Microscopic and Electron Beam Microprobe Study of Sulfide Minerals in Red Sea Mud Samples

Abstract

Base metal distribution in ten Red Sea mud samples recovered by Woods Hole Oceanographic Institution personnel was studied by microscopic and electron beam microprobe techniques.

Most of the base metals in the samples were present as sulfides. The most common sulfide mineral was marcasite, but chalcopyrite and marmatite were also identified in many of the samples. Marcasite occurred as euhedral plate or lath-shaped crystals and were frequently perched along the center line of euhedral anhydrite crystals. Chalcopyrite and marmatite occurred as irregular or subhedral particles. In several cases, marmatite rims completely surrounded chalcopyrite particles or chalcopyrite rims surrounded marmatite particles. Marcasite was observed filling the interiors of microfossils in several instances. Characteristic x-ray display photographs are presented to show the distribution of copper, zinc, sulfur and iron in a number of particles. Static electron beam analysis of the marmatite showed that it contained large amounts of iron. Some of the marmatite also contained substantial amounts of copper and traces of cadmium.

Copper and zinc values also occurred as a sub-micron dispersion in the mud matrix. The mineralogical nature of the dispersed copper and zinc could not be determined, but they were probably present as sulfides since microprobe analysis showed that sulfur had the same distribution pattern as the base metals.