Common naturally occurring orthosilicates can be grouped into those in which the major non-tetrahedral cations are (1) FeII and/or Mg, plus or minus Al (olivine, pyralspite garnets, staurolite); (2) Al (Al2SiO5 polymorphs), or (3) Zr. Feand Mg-bearing orthosilicates have the weakest bonds between non-tetrahedral cations and structural oxygen (M-O bonds), and zircon the strongest, with Al-O bond...

The Chenaillet Ophiolite is one of the best-preserved remnants of the Piemont-Liguria oceanic basin, a branch of the Central Atlantic that opened during the separation of Adria/Africa from Europe. Despite numerous studies of structure, petrology, geochemistry and isotope geochronology, the timing and genesis of various magmatic rocks within the Chenaillet Ophiolite are still controversial. We p...

Volume, edited by S. L. Baldwin and G. S. Lister, pp. 13 –14, Geol. Soc. of Am., Boulder, Colo. Black, L. P., S. L. Kamo, C. M. Allen, J. N. Aleinikoff, D. W. Davis, R. J. Korsch, and C. Foudoulis (2003), TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology, Chem. Geol.,

The rate of ejection of alpha-recoil thorium-234 into solution from the surface of zircon sand gives an alpha-recoil range of 550 angstroms. The alpha-recoil thorium-234 atoms ejected into the groundwater may supply excess uranium-234. In pelagic sediments, ejected alpha-recoil thorium-234 may contribute to the supply of mobile uranium-234 in the sedimentary column.

A voluminous ([600 km) and long-lived (*520–75 ka) phase of rhyolitic eruptions followed collapse of the Yellowstone caldera 640 ka. Whether these eruptions represent a dying cycle, or the growth of a new magma chamber, remains an important question. We use new U–Th zircon ages and dO values determined by ion microprobe, and sanidine Pb isotope ratios determined by laser ablation, to investigat...

Many materials that are usually found in the earth's crust contain small but measurable amount of naturally occurring radioactivity (NORM). Some particular ores contain natural radionuclide at levels much higher those usually present in earth's crust; and are also subject to radioisotope enrichment, during technological process, known as technologically enhanced natural radioactivity (TENORM). ...

Irradiation effects were investigated in zircon crystals by methods of optical absorption and luminescence. Special attention was given to the effects of vacuum ultraviolet (VUV) radiation. The same main thermoluminescence (TL) peaks with the same thermal activation energies appeared after VUV as after X- or beta irradiation, indicating that the same traps were induced by the different irradiat...