Dissertation
The Magmatic-Hydrothermal Behaviour of Trace and Ore Elements Within Intermediate-Evolved Igneous Systems
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/111746
Abstract
The integration of data derived from systematic experimental petrology investigations with data obtained through the analysis of natural igneous rocks and their phenocryst assemblages is a vital tool for understanding the magmatic-hydrothermal evolution of arc volcanoes. The overall aim of this research is to assimilate complimentary information from experiments and natural samples to better constrain the fluid-crystal-melt partitioning behaviour and fluid transport of trace and ore elements in intermediate-evolved magmatic systems, and their associated hydrothermal ore deposits.
Chapters one and two document and discuss the results of twenty four crystallisation-partitioning experiments. Chapter one outlines the behaviour of major elements and halogens in amphibole, plagioclase, and clinopyroxene phenocrysts grown in hydrous rhyodacitic melts at shallow crustal conditions. Chapter two details how the partitioning of economically important metals such as Li, Cu, Mo, Sn, and W between crystal phases is a complex function of several variables. Further new data in this chapter on volcanic rocks from Augustine volcano, AK, suggest that volatile fluxing of shallowly stored magmas immediately prior to eruption may be recorded by the trace-element concentration profiles of plagioclase phenocrysts in particular, and that the experimentally determined mineral-melt partition coefficients closely replicate those seen in natural systems.
The final chapter presents data from the natural granitic Spirit Lake Pluton, WA, USA, detailing how a series of complex fluid exsolution stages during late-stage cooling and degassing are responsible for tourmaline, biotite, and amphibole crystallisation, with each mineral population developing a distinct geochemical signature. These chemical and isotopic signatures allow for reconstruction of fluid composition and tracing metal movement in the shallow plutonic environment. Furthermore, the results of this study have wider applicability to tracing proximal barren and mineralised processes, and for distinguishing between formation mechanisms for primary and secondary halogen-bearing minerals.
Overall, this research further contributes to better understanding of fluid-mediated processes, such as melt evolution and fractionation, and the concentration of economically important metals. Additionally, the data are directly applicable to deciphering the elemental record stored within phenocryst phases, and are a robust tool to aid in constraining the metal variations in minerals and melts seen in volcanic systems.
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Details
- Title
- The Magmatic-Hydrothermal Behaviour of Trace and Ore Elements Within Intermediate-Evolved Igneous Systems
- Creators
- Alexander Andrew Iveson
- Contributors
- John A Wolff (Advisor)James D Webster (Committee Member)Michael C Rowe (Committee Member)Peter B Larson (Committee Member)Owen K Neill (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 233
- Identifiers
- 99900581829301842
- Language
- English
- Resource Type
- Dissertation