An exhaustive parameter study involving 133 dynamic crystallization experiments was conducted, to investigate the validity of the planetary embryo bow shock model by testing whether the cooling rates predicted by this model are consistent with the most dominant chondrule texture, porphyritic. Results show that using coarse-grained precursors and heating durations ≤ 5 minutes at peak temperature, porphyritic textures can be reproduced at cooling rates ≤ 600 K/hr, rates consistent with planetary embryo bow shocks. Porphyritic textures were found to be commonly associated with skeletal growth, which compares favorably to features in natural chondrules from Queen Alexandra Range 97008 analyzed, which show similar skeletal features. It is concluded that the experimentally reproduced porphyritic textures are consistent with those of natural chondrules. This work shows heating duration is a major determinant of chondrule texture and the work further constrains this parameter by measuring the rate of chemical dissolution of relict grains. The results provide a robust, independent constraint that porphyritic chondrules were heated at their peak temperatures for ≤ 10 minutes. This is also consistent with heating by bow shocks. The planetary embryo bow shock model therefore remains a viable chondrule mechanism for the formation of the vast majority of chondrules, and the results presented here therefore strongly suggest that large planetary embryos were present and on eccentric orbits during the first few million years of the Solar System’s history.

Explosive mafic (basaltic) volcanism is not easily explained by current eruption models, which predict low energy eruptions from low viscosity magma due to decoupling of volatiles (gases). Sunset Crater volcano provides an example of an alkali basalt magma that produced a highly explosive sub-Plinian eruption. I investigate the possible role of magmatic volatiles in the Sunset Crater eruption through study of natural samples of trapped volatiles (melt inclusions) and experiments on mixed-volatile (H2O-CO2) solubility in alkali-rich mafic magmas.

I conducted volatile-saturated experiments in six mafic magma compositions at pressures between 400 MPa and 600 MPa to investigate the influence of alkali elements (sodium and potassium) on volatile solubility. The experiments show that existing volatile solubility models do not accurately describe CO2 solubility at mid-crustal depths. I calculate thermodynamic fits for solubility in each composition and calibrate a general thermodynamic model for application to other mafic magmas. The model shows that the relative percent abundances of sodium, calcium, and potassium have the greatest influence on CO2 solubility in mafic magmas.

I analyzed olivine-hosted melt inclusions (MIs) from Sunset Crater to investigate pre-eruptive volatiles. I compared the early fissure activity to the sub-Plinian eruptive phases. The MIs are similar in major element and volatile composition suggesting a relatively homogeneous magma. The H2O content is relatively low (~1.2 wt%), whereas the dissolved CO2 content is high (~2300 ppm). I explored rehomogenization and Raman spectroscopy to quantify CO2 abundance in MI vapor bubbles. Calculations of post-entrapment bubble growth suggest that some MI bubbles contain excess CO2. This implies that the magma was volatile-saturated and MIs trapped exsolved vapor during their formation. The total volatile contents of MIs, including bubble contents but excluding excess vapor, indicate pre-eruptive magma storage from 10 km to 18 km depth.

The high CO2 abundance found in Sunset Crater MIs allowed the magma to reach volatile-saturation at mid-crustal depths and generate overpressure, driving rapid ascent to produce the explosive eruption. The similarities in MIs and volatiles between the fissure eruption and the sub-Plinian phases indicate that shallow-level processes also likely influenced the final eruptive behavior.

Volcanic devolatilization is one of the major processes in the global nitrogen cycle. Past studies have often estimated the magnitude of this flux using volcanic emission measurements, which are limited to currently active systems and sensitive to atmospheric contamination. A different methodological approach requires appropriate analytical parameters for nitrogen analysis in silicate glasses by secondary ion mass spectrometry (SIMS), which have not yet been established. To this end, we analyze various ion implanted basaltic and rhyolitic glasses by SIMS. We demonstrate that water content significantly affects the ion yields of 14N+ and 14N16O−, as well as the background intensity of 14N+ and 12C+. Application of implant-derived calibrations to natural samples provide the first reported concentrations of nitrogen in melt inclusions. These measurements are from samples from the Bishop Tuff in California, the Huckleberry Ridge Tuff of the Yellowstone Volcanic Center, and material from the Okaia and Oruanui eruptions in the Taupo Volcanic Center. In all studied material, we find maximum nitrogen contents of less than 45 ppm and that nitrogen concentration varies positively with CO2 concentration, which is interpreted to reflect partial degassing trend. Using the maximum measured nitrogen contents for each eruption, we find that the Bishop released >3.6 x 1013 g of nitrogen, the Huckleberry Ridge released >1.3 x 1014 g, the Okaia released >1.1 x 1011 g of nitrogen, the Oruanui released >4.7 x 1013 g of nitrogen. Simple calculations suggest that with concentrations such as these, rhyolitic eruptions may ephemerally increase the nitrogen flux to the atmosphere, but are insignificant compared to the 4 x 1021 g of nitrogen stored in the atmosphere.