Authors
Rachelle B Turnier, Yaron Katzir, Kouki Kitajima, Ian J Orland, Michael J Spicuzza, John W Valley
Publication date
2020/1
Journal
Journal of Metamorphic Geology
Volume
38
Issue
1
Pages
53-70
Description
Corundum (Crn), including sapphire, occurs in emery pods surrounded by marble on the island of Naxos, Greece. The emery formed from bauxite deposited in karst that was metamorphosed to 400–700°C at 20–15 Ma. Many of these rocks initially appeared well suited for refractory accessory mineral (RAM) thermometry, which uses oxygen isotope fractionation between a RAM – corundum – and a modally dominant phase with faster diffusion of oxygen – calcite (Cc) – to determine peak metamorphic temperatures. However, previous attempts at oxygen isotope thermometry were confounded by highly variable fractionations (Δ18O) measured at mm‐scale and the uncertain calibration of Δ18O(Cc‐Crn) versus temperature. Secondary ion mass spectrometry (SIMS) permits in situ analysis of δ18O in corundum and calcite at the 10‐μm scale in adjacent grains where textures suggest peak metamorphic equilibrium …
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RB Turnier, Y Katzir, K Kitajima, IJ Orland, MJ Spicuzza… - Journal of Metamorphic Geology, 2020