Zircon (U-Th)/He Closure Temperature Lower Than Apatite Thermochronometric Systems: Reconciliation of a Paradox

Minerals

Djordje Grujic¹  Xavier Robert²  Mélanie Balvay²  Benjamin Gérard²  Laurence Audin²  Matthias Bernet²  Cécile Gautheron³ 

[1] Department of Earth and Environmental Sciences, Dalhousie University, Halifax, NS B3H 4R2, Canada;Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France;Université Paris-Saclay, CNRS, GEOPS, 91405 Orsay, France;

关键词: zircon thermochronometry;    α-dose;    (U-Th)/He;    Andes;    Machu Picchu;   

DOI  :  10.3390/min12020145

来源: DOAJ

【 摘 要 】

Here, we present seven new zircon (U-Th)/He (ZHe) ages and three new zircon fission track (ZFT) ages analyzed from an age-elevation profile (Machu Picchu, Peru). ZFT data present ages older than those obtained with other thermochronological data, whereas the ZHe data interestingly present ages similar to those obtained with apatite (U-Th)/He (AHe). It has been proposed that He retention in zircon is linked to the damage dose, with an evolution of the closure temperature from low values associated with a low α-dose (<10¹⁶ α/g), subsequently increasing before decreasing again at a very high α-dose (>10¹⁸ α/g). Studies have focused on He diffusion behavior at high α-dose, but little is known at low doses. We propose that the ZHe closure temperature at α-dose ranging from 6 $\times$ 10¹⁵ to 4 $\times$ 10¹⁶ α/g is in the range of ~60–80 °C. This value is lower than that proposed in the current damage model ZRDAAM and demonstrates that the ZHe and AHe methods could have similar closure temperatures at low α-dose (i.e., similar ages). These new data strengthen our previous geological conclusions and even highlight a cooling rate approximately twice as important as that deduced from AHe and apatite fission track data alone at Machu Picchu.

【 授权许可】

Unknown