Project description
Field studies have demonstrated that each barite deposit is closely associated with deposition of chert, but it remains unclear if the link between chert and barite is related to physical processes such as mineral nucleation, or to geochemical parameters such as fluid composition and mineral solubility. In addition, isotopic evidence for microbial sulfate reduction in the barite-forming environments raises the question of to what extent barite formation could have been microbially mediated or inhibited.
This project will investigate intergrowths of barite and chert in Paleoarchean deposits from the Pilbara craton in Western Australia. It specifically aims to assess whether chert precipitation occurred prior to, contemporaneously with, or after barite precipitation. In addition, micro-textural analyses will provide insight into possible post-depositional remobilization of barite by geobiological processes. This work will improve our understanding of the origin of Paleoarchean barite deposits and thereby help with resolving the paradox of sulfate mineral deposition on a low-sulfate planet.
Field-, lab- and analysis work
Thin sections are available from 3.49-3.25 Ga barite deposits from the Pilbara craton in Western Australia. The student will document and study these thin sections using optical microscopy. Findings will be used to select samples for cathodoluminescence (CL) imaging to identify mineral phases and chemical heterogeneities. The most interesting samples will be studied using the newly acquired scanning electron microscope (SEM) to produce backscattered electron (BSE) images and electron backscatter diffraction (EBSD) analyses, which will be used to identify microstructural features such as fine-grained intergrowths, reaction rims and inclusions. For comparison, samples from modern barite chimneys on the Arctic Mid Ocean Ridge will also be included in the study.