Water and fluorine contents in Mt. Hood magmas recorded by plagioclase phenocrysts

Volatiles have a significant effect on the properties of minerals and melts, even when present in trace amounts. They impact the phase equilibria (Wyllie 1979; Gaetani and Grove 1998), rheological properties (Dingwell et al. 1985; Hirth and Kohlstedt 1996), and volcanic eruption dynamics (Roggensack et al. 1997; Cashman 2004). H2O is the most well-studied volatile component of magmas, but other volatiles species (e.g. F) are the subject of increasing interest (Dasgupta and Dixon 2009). Magmatic volatiles are often measured in melt inclusions (MIs) (e.g. Straub and Layne 2003; Plank et al. 2013), but may be uncommon in some rocks or subject to post-entrapment modification (PEC) (Wallace 2005). Alternatively, measurements of volatiles in minerals can be used to calculate melt volatile contents with a known partition coefficient (e.g. Wade et al. 2008). In this study, concentration profiles of H2O and F in plagioclase from Mt. Hood, OR are paired with previously studied MI volatile contents from the same pyroclasts (Koleszar et al. 2012) to assess the fidelity of H2O and F records retained in volcanic plagioclase. The spatial resolution of secondary ion mass spectrometry (SIMS) analyses allows us to detect volatile loss, and possibly constrain syn- and post-eruptive processes.

Author dc:creator

• Caseres, Jennifer

• andesitic arc volcano
• hydrogen partitioning
• magma recharge
• nominally anhydrous minerals

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/11299/206708

OAI identifier oai:identifier

oai:conservancy.umn.edu:11299/206708