The geochemistry of quartz-hosted melt (MI) and fluid inclusions (FI) in quartz syenite from Terceira, Azores was investigated to provide insight into late-stage evolution of peralkaline melts and the behaviour of high field strength (HFSE) and rare-earth elements (REE) at the magmatic-hydrothermal transition. Crystalline and hydrous MI analyzed by laser ablation-inductively-coupled plasma mass-spectrometry (LA-ICP-MS) show extreme magmatic enrichment of HFSE and REE. Sanidine crystallization resulted in enrichment of the melt in HFSE, REE and volatiles. Halite-saturated FI analyzed by LA-ICP-MS show lower total REE abundances than melts, and a general enrichment in HREE. Comparison of REE distribution patterns of MI and miarolitic zircon and monazite suggest late-stage melt evolution by monazite, then zircon and pyrochlore fractionation. Microthermometry of FI suggests maximum trapping conditions of 675°C, 120 MPa. The residual evolved to very volatile-rich compositions and initially exsolved a hydrosaline melt that was diluted to lower salinities by aqueous-fluid exsolution on cooling.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/65540 |
| Date | 24 June 2014 |
| Creators | Beland, Caitlin |
| Contributors | Mungall, James |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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