STABLE O AND H ISOTOPE APPLICATIONS FOR SOURCING COMMERCIAL TALC AND UNDERSTANDING ENVIRONMENTS OF TALC FORMATION

Talc ores are typically formed due to the alteration of carbonate or ultramafic igneous rocks through the influence of fluids. We expected O and H isotope ratios for talc ores within a single mining region to have a limited range with ores from the same region, and observed this result for economic talc deposits in southwest Montana, northern Italy, and North Carolina. Furthermore, ores from these three locations have been incorporated into products which have been the focus of recent asbestos litigation and have proven to be compositionally indistinguishable based on major and trace element concentrations determined by electron microprobe and bulk x-ray fluorescence analyses. Our data suggest that stable O and H isotope ratios may be useful in sourcing commercial talcs for projects related to the aforementioned litigation. However, stable O and H isotope ratios for talc ores from other economically significant deposits did not cluster, leading us to explore mechanisms of talc formation for both homogenous and heterogeneous isotopic compositions within a single mining region.