The EPR Spectra of X-Ray Irradiated Gypsum

Evaporites: Sulfates and Other Minerals

“…Gl (=B) center (S03"): g = 2.0028 ~ 2.0042 A "Gl center" with an isotropic g-factor was identified as S03" from the hf structure of 33 S ( / = 3/2, abundance 0.76%). This center may correspond to the B center which has been assigned to a trapped electron at a vacancy or lattice defect (Albuquerque and Isotani 1982). S03~ is observed in other sulfates such as anhydrite (CaS04), barite (BaS04) and celestite (SrSQ4) as well as in caicite and aragonite (CaCQ3).…”

“…X-ray irradiated natural gypsum crystal gave four types of ESR signals designated as A, B, C and D centers (Albuquerque and Isotani 1982). Natural gypsum from deserts shows four types of ESR signals termed as 01, G2, G3 and G4, among which two signals Gl and G4 correspond to the B and A centers, respectively (Kasuya et al 1991a).…”

“…This center was previously reported as an A center by Albuquerque and Isotani (1982), who identified it as 02H\ C center (S04~ or S02-? ) : g = 2.002 and 2.006 A "C center" has two magnetically nonequivalent sites.…”

“…Nahcolite and halite have been dated using saline lake sediments at Searles Lake in California (Ikeya and Kai 1988). Meanwhile lattice defects were studied with ESR for gypsum (Albuquerque andIsotani 1982, Kasuya et al 1991a), anhydrite (Bershov et al 1975), barite and celestite (Ryabov et al 1983(Ryabov et al ,1989. Still, only a few investigations on evaporites have been carried out by the early 1990 f s in spite of the importance for studying the paleo-environment in conjunction with the development of deserts.…”

“…: g = 2.002 and 2.006 A "C center" has two magnetically nonequivalent sites. A model of S04-or models of S03~ for g = 2.002 and S02*" for g = 2.006 were suggested (Albuquerque and Isotani 1982). S02~ is a possible candidate from the similarity of g factor in anhydrite (ga = g | = 2.0058, g^ = 2.0022 and g = 2.0092) (Bershov et al 1975).…”