Consideration is given to the premise that certain electron paramagnetic resonance signals in natural quartz are the result of age-indicative accumulations of alpha recoil-induced lattice damage. The point defects potentially responsible for the observed EPR signals are reviewed, as a basis for consideration of point defect production by ionizing radiation of and alpha recoil fragment transport in quartz. The production of oxygen vacancies in the quartz lattice by individual alpha recoil fragments in both the $\sp{238}$U and $\sp{232}$Th decay chains is calculated using two different methods. The Monte Carlo transport method provides a detailed collision history for each of the recoil fragments. The EPR experiments focus on the size of the E' and oxygen hole-related center (OHRC) signals in five different types of quartz: pegmatitic, unmetamorphosed plutonic, metamorphosed plutonic, hydrothermal vein and volcanic. The effects of gamma and neutron irradiation on the EPR spectra are also considered. The concentrations of $\sp{238}$U, $\sp{232}$Th and $\sp{147}$Sm are determined using neutron activation analysis in many of the quartzes that were extracted from rocks (or were intimately associated with minerals) of known age. Significant correlations between the age of the quartz and the size of both the E' and OHRC signals are initially established, and improved correlation is observed after the signal sizes are normalized to the respective total alpha activity of each sample (based on its $\sp{238}$U, $\sp{232}$Th and $\sp{147}$Sm concentration). These correlations establish the basis for a potential quartz geochronometer. / Theoretical considerations involve factors related to (1) recoil damage efficiency, (2) paramagnetic fractions of precursor defect populations, (3) overlap of alpha recoil track volumes and (4) fluid inclusion-hosted alpha activity. It is hypothesized that spherical, alpha recoil-induced lattice damage halos may develop around alpha-active fluid inclusions. A method is proposed for quartz age determinations, and suggestions are made toward overcoming the present limitations. It is concluded that approximate age determinations ($\pm$15-20%) may eventually be possible, and that maximum age determinations might also eventually be possible. / Source: Dissertation Abstracts International, Volume: 51-07, Section: B, page: 3289. / Major Professors: Arthur Leroy Odom; George W. Devore. / Thesis (Ph.D.)--The Florida State University, 1990.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77765 |
| Contributors | Rink, William Jack., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 368 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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