Seeing is believing: Visualization of He distribution in zircon and implications for thermal history reconstruction on single crystals
MetadataShow full item record
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. Understanding the effect of these grain-scale phenomena on the distribution of He in analyzed minerals should lead to improvements in data interpretation. We combine laser ablation microsampling and noble gas and trace element mass spectrometry to provide the first two-dimensional, grain-scale zircon He "maps" and quantify intragrain He distribution. These maps illustrate the complexity of intracrystalline He distribution in natural zircon and, combined with a correlated quantification of parent nuclide (U and Th) distribution, provide an opportunity to assess a number of crystal chemistry processes that can generate anomalous zircon (U-Th)/He ages. The technique provides new insights into fluid inclusions as potential traps of radiogenic He and confirms the effect of heterogeneity in parent-daughter isotope abundances and metamictization on (U-Th)/He systematics. Finally, we present a new inversion method where the He, U, and Th mapping data can be used to constrain the high- and low-temperature history of a single zircon crystal.
Showing items related by title, author, creator and subject.
Emplacement age and thermal footprint of the diamondiferous Ellendale E9 lamproite pipe, Western AustraliaEvans, Noreen; McInnes, Brent; McDonald, Bradley; Danisik, M.; Jourdan, Fred; Mayers, C.; Thern, Eric; Corbett, D. (2013)The diamondiferous Ellendale 9 (E9) pipe is a funnel-shaped maar-diatreme volcano consisting of inward-dipping tuff sequences intruded by lamproite plugs and dykes. The host rocks for the E9 pipe are Permian sandstones. ...
Thermal-tectonic history of the Baogutu porphyry Cu deposit, West Junggar as constrained from zircon U-Pb, biotite Ar/Ar and zircon/apatite (U-Th)/He datingLi, G.; Cao, M.; Qin, K.; Evans, Noreen; McInnes, Brent; Liu, Y. (2013)Understanding postmineralization tectonic movements in porphyry deposits, is critical to interpreting the complete thermal-tectonic history. This study reports new zircon U–Pb ages, hydrothermal biotite 39Ar/40Ar age, and ...
Petrogenesis and thermal history of the Yulong porphyry copper deposit, Eastern Tibet: insights from U-Pb and U-Th/He dating, and zircon Hf isotope and trace element analysisLi, J; Qin, K; Li, G; Cao, M; Xiao, B; Chen, L; Zhao, J; Evans, Noreen; McInnes, Brent (2012)The Yulong porphyry copper deposit (6.5 Mt at 0.46 % Cu) in eastern Tibet was formed in a post-collisional setting. New zircon U–Pb and U–Th/He ages, apatite U–Th/He ages and in-situ zircon Hf isotopic and trace element ...