Zircon (ZrSiO4) is the most commonly used geochronometer, preserving age and geochemical information through a wide range of geological processes. However, zircon U-Pb geochronology can be affected by redistribution of radiogenic Pb, which is incompatible in the crystal structure. This phenomenon is particularly common in zircon that has experienced ultra-high temperature metamorphism, where io...

U–Pb zircon geochronology is hampered by problems acquiring meaningful geologic ages on zoned grains that retain isotope signatures from multiple growth or thermal events. We present a new method using laser ablation-multicollector-inductively coupled plasma-mass spectrometry to overcome complications asso­ ciated with intricately zoned zircon crystals through in situ sampling of zircon volumes...

Watson and Harrison (Reports, 6 May 2005, p. 841) interpreted low temperatures (approximately 700 degrees C) for Hadean zircons as evidence of the existence of wet, minimum-melting conditions within 200 million years of solar system formation. However, high-temperature melts (approximately 900 degrees C) are zircon-undersaturated and crystallize zircon only after substantial temperature drop du...

A new computer code (MARVIN) has been developed for the simulation of surfaces and interfaces. The models and methodologies employed within the program are briefly discussed. One application of the code, calculating crystal morphologies, is explored using zircon, quartz and et-Al203 as examples. The new code enables the use of covalent type force fields and the effect of surface relaxation on t...

Introduction: The Lu-Hf decay system can be used to resolve planetary differentiation timescales, but this application requires knowledge of Hf isotopic evolution for bulk planets. Because Lu and Hf are refractory and lithophile, the isotopic evolution of bulk planets and their silicate portions can be reconstructed by back-calculation from the present-day Hf/Hf and Lu/Hf in chondrites [1–3]. H...

Zircon (U-Th)/He thermochronometry is an established radiometric dating technique used to place temporal constraints on a range of thermally sensitive geological events, such as crustal exhumation, volcanism, meteorite impact, and ore genesis. Isotopic, crystallographic, and/or mineralogical heterogeneities within analyzed grains can result in dispersed or anomalous (U-Th)/He ages. Understandin...

Located in the southeastern parts of the Baoulé Mossi domain of the West African Craton, the Birimian terrane in Ghana is known to consist of predominantly juvenile crust emplaced during the Eburnean orogeny. Here we present novel coupled zircon U-Pb and Lu-Hf isotope data from nine Birimian granitoids intruding different domains from northwestern, western and southeastern Ghana. Sub-chondritic...

We report, for the first time, a direct, atomic-scale characterization of Pb in zircon (4.4–3.1 Ga) from the early Archean Yilgarn craton in Australia using high-resolution HAADF-STEM. Two forms of Pb have been identified: Pb concentrated at 3 atom% as a nanoscale patch in zircon structure, and Pb concentrated within the amorphous domain created by fission fragment damage. The first result sugg...

Zircon and monazite from granitic sheets and dikes in the Monashee complex, Canadian Cordillera, were investigated to determine whether igneous crystallization occurred at 1.9 Ga or 50 Ma with 1.9 Ga inherited zircon and monazite. Four of the five samples are weakly deformed to undeformed, despite occurring in a gneiss dome at the structurally deepest exposed level of the orogen that elsewhere ...

The red sand which is known as Teri sand in Tamil Nadu consists of 5.5% Total Heavy Minerals (THM) out of which 3.7% is ilmenite. The other minerals, zircon, sillimanite and garnet are in the order of abundance identified. On processing this feed to recover ilmenite by using spirals followed by dry high intensity magnetic separator and high tension separator, the ilmenite concentrate obtained c...