Oxygen isotope ratios and rare earth element (REE) concentrations provide independent tests of competing models of injection v. anatexis for the origin of migmatites from amphibolite and granulite facies metasedimentary rocks of the Adirondack Mountains, New York. Values of dO and REE profiles were measured by ion microprobe in garnet–zircon pairs from 10 sample localities. Prior U–Pb SIMS dati...

A recurring challenge to ion microprobe U^Pb zircon geochronology has been to discriminate between preservation of original igneous zircon populations and inherited grains. This has proved particularly problematic in studying the polyphase metamorphic rocks that dominate Early Archean gneissic terranes. For example, differing interpretations exist for the origin of complex zircon populations in...

Single grain zircon U-Pb geochronology has demonstrated great potentials in extracting tectonic and atmospheric circulation signal carried by aeolian, fluvial, and fluviolacustrine sediments. A routine in this sort of studies is analyzing 100-150 grains and then compares zircon U-Pb age spectra between the measured sample and the potential sources. Here we compared the zircon U-Pb age results o...

12 Abstract 13 14 The full U-Pb isotopic systematics in a complex lunar zircon ‘Pomegranate’ 15 from lunar impact breccia 73235 have been investigated by the development of a 16 novel Secondary Ion Mass Spectrometry (SIMS) scanning ion imaging (SII) 17 technique. This technique offers at least a four-fold increase in analytical spatial 18 resolution over traditional SIMS analyses in zircon. Res...

Here we report the occurrence, chemistry, and U-Th-Pb isotopic systematics of three meteoritic zircon assemblages, two from the Vaca Muerta mesosiderite and one from the Simmern H5 chondrite. One of the Vaca Muerta zircons occurs in the mesosiderite proper, the other in a eucritic clast associated with chromite, ilmenite, and tridymite, whereas the Simmern zircon occurs in a chondrule composed ...

Integrated petrographic and chemical analysis of zircon, garnet and rutile from ultrahigh-temperature (UHT) granulites in the Anápolis–Itauçu Complex, Brazil, is used to constrain the significance of zircon ID-TIMS U–Pb geochronological data. Chondrite-normalized rare earth element (REE) profiles of zircon cores have positive-sloping heavy-REE patterns, commonly inferred to be magmatic, whereas...

Detrital zircon studies are providing new insights on the evolution of sedimentary basins but the role of sedimentary recycling remains largely undefined. In a broad region of northwestern North America, this contribution traces the pathway of detrital zircon sand grains from Proterozoic sandstones through Phanerozoic strata and argues for multi-stage sedimentary recycling over more than a bill...

A long-standing goal in high-precision and high-accuracy U–Pb zircon geochronology is the total elimination of discordance caused by Pb loss. In theory, this is fairly straightforward, but in reality it has proven extremely difficult to attain (or even demonstrate attainment of) this goal. However, a new method, bCA (Chemical Abrasion)-TIMSQ, is capable of completely removing zircon domains tha...

We have investigated U-Pb discordance and oxygen isotopic composition of zircon using high– spatial resolution !O measurement by ion microprobe. !O in both concordant and discordant zircon grains provides an indication of the relationship between fluid interaction and discordance. Our results suggest that three characteristics of zircon are interrelated: (1) U-Pb systematics and concomitant age...

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...