Testing the Limits of Ti-in-Quartz Thermometry and Diffusion Modelling to Determine the Thermal History of the Fish Canyon Tuff

To follow the online reunion, follow this zoom link: https://u-paris.zoom.us/j/83085293581?pwd=djlnU2hYSVB3YmQyeEhieW5SQnJpZz09 Meeting ID: 830 8529 3581 Passcode: 745633 Abstract: How are silicic magmas stored in the upper crust? Answering this question is fundamental for our understanding of how these systems form and erupt. While some studies posit storage in an eruptible state at low viscosity (760-740°C) (warm storage), others suggest storage in a rigid state (>50% crystals) at lower, near-solidus temperatures (cold storage). Storage temperature and time spent near the solidus are typically constrained by mineral thermometry and diffusional relaxation modelling, respectively. Since quartz is abundant over a range of temperatures and compositions and can incorporate titanium, a Ti-in-Quartz thermometer has been calibrated and Ti diffusion coefficients (DTi) have been measured. However, simply applying this thermometer or DTi to volcanic quartz is burdened by an ongoing debate regarding their experimental calibration. This debate centers around three recent Ti-in-Quartz thermometers by Huang & Audétat (2012), Zhang et al. (2020), Osborne et al. (2022) and three DTi by Cherniak et al. (2007), Jollands et al. (2020), Audétat et al. (2021), each of which when applied to igneous systems favors either warm or cold storage. To determine their applicability for estimating the pre-eruptive conditions of silicic magmatic systems, we apply the different Ti-in-Quartz thermometers and DTi to quartz from the Fish Canyon Tuff (FCT, USA). This tuff is an optimal location for such a study because it is a prime example of cold storage with multiple previous studies providing constraints on its storage conditions. The Zhang et al. (2020) thermometer results in a temperature of 737 ± 16°C, which is the most consistent with other FCT temperature estimates. Residence times of quartz at this temperature are determined using each of the DTi and compared to timescales from Ba-in-Sanidine diffusion and the total storage time of the mush (derived from zircon U-Pb ages and the local eruption history). Timescales using DTi by Audétat et al. (2021) significantly exceed the total storage time of an FCT mush unless storage temperatures were significantly higher (warm storage). Such a scenario is inconsistent with cold storage of FCT. Timescales derived from DTi by Jollands et al. (2020) and Cherniak et al. (2007) are consistent with cold storage of the Fish Canyon system. While DTi by Jollands et al. (2020) suggest long-term storage near 737°C, DTi by Cherniak et al. (2007) suggests storage below 737°C. More about Kalini: Kalini is currently doing a postdoctoral CNRS funded project on samples of the 2018-2021 submarine Fani Maoré eruption near the island of Mayotte where she applies diffusion chronometry methods to obtain timescales of magmatic processes during this eruption. She received her B.Sc. at the University of Bonn (Germany) with a thesis in experimental petrology. Following this, she completed her M.Sc. in 2018 at the University of Bonn in collaboration with the glass company "Schott AG" in Mainz (Germany) on in-situ high temperature Raman-spectroscopic analysis of glass ceramics. For her Ph.D at the University of Illinois at Urbana-Champaign (USA) she focused on relating silicic volcanic systems to plutonic systems with her research area being the San Juan Volcanic Field (CO, USA).