High temperature (>350°C) thermochronology and mechanisms of Pb loss in apatite

Article Article scientifique Article High temperature (>350°C) thermochronology and mechanisms of Pb loss in apatite eng 2014 author Cochrane Ryan 702977 author Spikings Richard Alan 550467 author Chew David Michael 135547 author Wotzlaw Joern Frederik 708590 author Chiaradia Massimo 0000-0003-4943-2480 110575 author Tyrrell Shane author Schaltegger Urs 0000-0003-4404-8607 134356 author Van Der Lelij Roelant 564117 39-56 10.1016/j.gca.2013.11.028 0016-7037 http://linkinghub.elsevier.com/retrieve/pii/S0016703713006674 Natural processes driven by heat flow can be understood using quantitative reconstruction of the thermal history of accessory and common minerals that were formed or modified in these processes. Thermochronology assumes that isotopes are lost from minerals by thermally-activated volume diffusion, and forms the basis of many studies of the thermal evolution of the crust. However, some studies challenge this assumption and suggest that the mechanisms controlling isotope transport in minerals over geological time-scales are dominated by aqueous fluid flow within mineral pathways. Here, we test these contrasting hypotheses by inverse modelling apatite uranium–lead (U–Pb) dates to produce theoretical t–T solutions assuming Pb was lost by volume diffusion. These solutions are compared with independent geological constraints and intra-grain apatite U–Pb dates, which demonstrate that volume diffusion governed the displacement of Pb. This confirmation, combined with an inverse-modeling procedure that permits reheating and cooling paths to be distinguished between ∼375 and 570 °C, provides geologists with a unique tool for investigating the high-temperature thermal evolution of accessory minerals using the U–Pb method. Apatite Thermochronology Diffusion U-Pb Dewey 550 42 Département des sciences de la Terre 154 false 663 Isotope Geochemistry, Geochronology and Thermochronology Geochimica et cosmochimica acta 127 d9879e6d-c23e-4031-8797-0733ca83ed2a Article (Published version) Restricted 2014 CochraneGCA.pdf 1683457 application/pdf restrictedAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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Chew, David Michael