Opaque mineral concentrates from beaches on both sides of foveaux strait

Abstract

Abstract Opaque minerals in one artificial and four natural beach sand concentrates from Southland and Stewart Island were examined by microscope, X-ray, and thermo-magnetic techniques. In all the samples, magnetite, ilmenite, and hematite exhibit a variety of intergrowth textures. Chromite and rutile were found only in Southland concentrates. There are sufficient differences in mineralogy of the assemblages to make it unlikely that any cross-channel transport was involved in formation of the beach sands. Many features of the Southland beach sand concentrates are identical with those characterising opaque minerals in the basic/ultrabasic Bluff complex. A likely reason is that similar basic and ultrabasic rocks are widespread in the Longwood complex, from which these particular concentrates are in part derived. Stewart Island concentrates are mainly derived from the granitic and/or high grade metamorphic rocks forming the island.