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AN EXPERIMENTAL AND THEORETICAL INVESTIGATION ON THE KINETICS OF WATER EXSOLUTION IN HIGH SILICATE MELTS

Nicholis, Mikes G.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin991137556

Abstract Details

2001, MS, University of Cincinnati, Arts and Sciences : Geology.
The exsolution of volatiles in magma initiates the formation of gas bubbles as a result of the development of a state of supersaturation from either magma ascending in the conduit, decrease in temperature, or the crystallization of anhydrous solid phases. In this analysis rhyolitic glasses were isothermally decompressed in a series of controlled nucleation experiments to investigate the kinetics of bubble nucleation and growth. A two-fold approach was used to synthetically saturate the high silica melt. The first method uses blocks of solid obsidian, while the second technique uses powdered obsidian. The second method evenly saturates the melt by minimizing the volume to surface area ratio, hence the diffusion distance. In all experiments glass charges were saturated with H 2 O at 100 MPa and 850°C, and then isothermally decompressed to final confining pressures of 30, 50, and 70 MPa. Samples were held at the final pressure for periods ranging from 5 to 300 seconds to allow for nucleation to take place. Bubble-bearing glass charges were imaged under SEM and petrographic microscopes, and digitally analyzed. All glass charges produced by the block method contained either no bubbles or only a few bubbles. The only indication of bubble nucleation was limited to a zone on the outer periphery of the glass charges, implying that in the block method, the time given for hydration was insufficient for homogeneous saturation of the melt. We directed our attention to the bubble-bearing glasses generated by the powder experiments. Vesicle Size Distribution was used to determine the kinetic behavior of bubbles at the onset of nucleation and their development in the melt within the known residence time. The more uniform bubble distribution in the melts using the powder method gave rise to nuclei density populations ranging from 10 9 - 10 11 bubbles/cm 4 . The mean vesicle size for all experiments was 0.009 mm in diameter. Growth rates were calculated to be approximately 3.8 x 10 -2 cm/s. Nucleation rates of 10 7 - 10 9 bubbles cm -3 s -1 illustrate how minor fluctuation in pressure can drastically increase the onset of bubble formation in viscous silicate melts. The data generated by VSD was then applied to a conceptual model used to describe explosive volcanic eruptions.
Attila Kiline (Advisor)
Geochemistry; Geology
BUBBLE NUCLEATION; HIGH SILICA MELT; EXSOLUTION; WATER SOLUBILITY; KINATICS OF EXSOLUTION

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Citations

  • Nicholis, M. G. (2001). AN EXPERIMENTAL AND THEORETICAL INVESTIGATION ON THE KINETICS OF WATER EXSOLUTION IN HIGH SILICATE MELTS [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin991137556

    APA Style (7th edition)

  • Nicholis, Mikes. AN EXPERIMENTAL AND THEORETICAL INVESTIGATION ON THE KINETICS OF WATER EXSOLUTION IN HIGH SILICATE MELTS. 2001. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin991137556.

    MLA Style (8th edition)

  • Nicholis, Mikes. "AN EXPERIMENTAL AND THEORETICAL INVESTIGATION ON THE KINETICS OF WATER EXSOLUTION IN HIGH SILICATE MELTS." Master's thesis, University of Cincinnati, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin991137556

    Chicago Manual of Style (17th edition)

ucin991137556
© 2001, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.