(1) Calculating mineral formula and site occupancies Analysis of silicate minerals for their major element compositions by Electron Microprobe Analysis (EPMA) is a standard technique in geochemistry and petrology. Data is typically presented as oxide abundance (wt %), but it easier to understand if it is recalculated into a form that is directly comparable with the mineral's chemical formula. This information can then be used to work out the end-member mineral type and how mineral compositions reflect changes in conditions of crystallization. a) Using the step-by-step directions given on page 142 of the Gill textbook (Chapter 8) work out the site occupancies, mineral formula and forsterite % content (MgMgtES) for the following olivine probe analysis Taupo mafic inclusion eruption Z olivine Sioz Feo MnO MgO CaO Total 39.96 10.64 0.153 48.27 0.19 99.213 Hint: Produce a very similar looking table to Table 8.3 from the Gill textbook b) This olivine crystal was erupted in a rhyolitic magma, but it did not crystallize from a rhyolitic melt. Instead, it was introduced during magma mixing prior to eruption. What magma composition would this olivine have come from?