Applications of Natural Radiation-Induced Paramagnetic Defects in Quartz to Exploration in Sedimentary Basins
- Received Date: 2017-03-02
- Accepted Date: 2017-03-02
- Available Online: 2017-03-02
Abstract: Quartz grains in contact with uranium-bearingminerals or fluids are characterized bynatural radiation-induced paramagnetic defects(e. g. , oxygen vacancy centers, silicon vacancy centers, and peroxy radicals), which are amenable to studyby electron paramagnetic resonance(EPR) spectroscopy.These natural radiation-induced paramagnetic defects, except for the oxygen vacancy centers, in quartz are concentrated in narrow bandspenetrated byαparticles:(1) in halosaround U-and Th-bearingmin-eral inclusions and(2) in outer rims or along fractures. The second type of occurrence provides information about uranium mineralization or remobilization (i. e. , sources of uranium, timing of mineralization or remobilization, pathways of uranium-bearing fluids). It can also be used toevaluate sedimentary basins for potential of uranium mineralization. In particular, the peroxy radicals are stable up to 800 ℃ and, therefore, are useful for evaluating metasedimentaryrocks(e. g. , Paleoproterozoic metasedimentary sequences in the central zone of the North China craton). EPRstudy of the Changcheng Series can focus on quartz fromthe sediment-basement unconformity and faults todetermine the presence and types of natural radiation-induced paramagnetic defects, with which to identify and prioritize uranium anomalies. Other potential applications of natural radiation-induced paramagnetic defects in quartz include uranium-bearing hydrocarbon deposits in sedimentary basins. For example, the Junggar, Ordos, and Tarim basins in northwestern China all contain important oil and natural gas fields and are well known for elevated uranium concentrations, including economic sandstone-hosted uraniumdeposits. Therefore,systematic studies on the distribution of natural radiation-induced paramagnetic defects in quartz from host sedimentary sequencesare expected toprovide information about the migration of oil and natural gas in those basins.