A transmission electron microscope (TEM) study of Paleoproterozoic zircon that has experienced ultra-high temperature (UHT) metamorphism at ca. 570 Ma in the Kerala Khondalite Belt (KKB), southern India, documents the occurrence of metallic Pb nanospheres. These results permit comparison with a previous report from UHT zircon in Enderby Land, Antarctica, and allow further constraints to be plac...

Ion microprobe analysis with a sub-micrometer diameter spot reveals a sharp, 2 μm gradient in oxygen isotope ratio proving that oxygen diffusion in zircon is slow even under prolonged high-grade metamorphism. The data are consistent with an oxygen diffusion coefÞ cient of 10–23.5±1 cm2/s. Furthermore, this gradient is found in a zircon that contains clear textural evidence of recrystallization ...

Introduction: Zircon is a highly refractory and weathering-resistant mineral that has proven useful as an indicator of shock metamorphism in the study of impact structures and formations (e.g., [1-6]). Zircon has advantages compared to quartz or other shockmetamorphosed rock-forming minerals that have been widely used as impact indicators, but are far less refractory than zircon. The purpose of...

To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5-20 μm wide in which [Li]...

Understanding the factors that contribute to U^Pb discordance in zircon is essential for interpreting isotopic data and for assessing the validity of concordia intercept ages. Modification caused by interaction with metamorphic fluids is often cited as a primary means by which significant or even complete isotopic resetting of U^Pb systematics in zircon might be achieved under subsolidus condit...

[1] We report zircon oxygen isotope ratios and reconnaissance Ti-in-zircon concentrations, guided by cathodoluminescence image studies, for detrital zircons up to 4.34 Ga from the Narryer Gneiss Complex of Western Australia. Zircon oxygen isotope results bolster the view that some Hadean (>3.85 Ga) zircon source melts were enriched in heavy oxygen, a sensitive proxy for melt contamination by se...

Zircon mineral (ZrSiO4) is a potential host matrix for the encapsulation of highly radioactive materials, such as dismantled weapons and nuclear waste from power stations (Ewing, 2001). We report a detailed computer modelling study, based on interatomic potentials, to address two fundamental issues concerning radiation processes in the zircon mineral: first, the physics and chemistry of U and P...

Zircon (ZrSiO4) exhibits an extraordinary memory. Its stability, durability, low solubility and low elemental diffusivities combine to preserve in it a record of most of the important events that have affected it, its host rocks, and the crust of which it is a part. The zonation in zircon grains delineate the boundaries of discrete geochemical processes that occurred at different times. Zircon ...

Electrostatic separation is the final separation technique employed in the recovery and upgrade of rutile and zircon feedstocks. This dry separation technique is dependent on the difference in resistivities of the rutile and zircon. Even though both minerals have fairly high resistivities (Kelly and Spottiswood, 1989a), the differences in the resistivities are large enough to ensure separation....

Zircon ages and trace element compositions from recent silicic eruptions in the Lassen Volcanic Center (LVC) allow for an evaluation of the timing and conditions of rejuvenation (reheating and mobilization of crystals) within the LVC magmatic system. The LVC is the southernmost active Cascade volcano and, prior to the 1980 eruption of Mount St. Helens, was the site of the only eruption in the C...