Chemical and morphological features of arsenopyrite, concerning its use as a geothermometer

Abstract

Chemical sector zoning is an almost universal feature in arsenopyrite. The present study reveals distinct relations between different crystal area compositions on both the qualitative and quantitative levels. Composition-morphology dependencies are also established. As far as these features reflect environmental conditions during crystal growth, they are considered in the context of the problems of the arsenopyrite geothermometer. The main results of this investigation are: (1) As/S ratio can be used as a unique parameter characterising the composition at a single point; (2) Linear or almost linear relations link the compositions of the different sectors, hence the compositions of all the crystal areas can be derived from the composition of only one sector; (3) Along with kinetic phenomena, zoning may reflect significant environmental changes during growth, hence anatomic investigation should always precede geothermometry; (4) The morphology of arsenopyrite can be used as an approach to its composition, so it can serve as an approximate alternative geothermometric tool in the field.