Health & Environmental Research Online (HERO)


Print Feedback Export to File
514171 
Journal Article 
(U-Th)/(HE-Pb) double dating of detrital zircons 
Reiners, PW; Campbell, IH; Nicolescu, S; Allen, CM; Hourigan, JK; Garver, JI; Mattinson, JM; Cowan, DS 
2005 
Yes 
American Journal of Science
ISSN: 0002-9599 
305 
4 
259-311 
English 
Geochronology and thermochronology on detrital material provides unique constraints on sedimentary provenance, depositional ages, and orogenic evolution of source terrains. In this paper we describe a method and case-studies of measurement of both U/Pb and (U-Th)/He ages on single crystals of zircon that improves the robustness of constraints in each of these areas by establishing both fort-nation and cooling ages of single detrital grains. Typically these ages correspond to crystallization and exhumation or eruption ages, and their combination can be used to more confidently resolve candidate source terrains, establish maximum depositional ages, and constrain the thermal histories of orogenic source regions. U/Pb dating is accomplished by laser-ablation ICP-MS in a small pit on the exterior of the crystal, and He dates are then determined on the bulk grain by conventional laser-heating and dissolution techniques. We present examples from Mesozoic aeolian sandstones, both modern and Paleogene fluvial sediments, and active margin turbidite assemblages from the Cascadia and Kamchatka margins. Important results include the fact that detritus from ancient orogens may dominate sediments thousands of kilometers away, crustal melting and exhumation appear to be spatially temporally decoupled in at least two orogens, and first-cycle volcanic zircons older than depositional age are surprisingly rare in most settings except in the continental interior. In the case of the Kamchatkan, and possibly Olympic, turbidites, zircon He ages are partially reset. We present a method for estimating the extent of resetting of each grain and the thermal history of the sample, based on coupled (U-Th)/(He-Pb) age patterns among all the grains. 
fish canyon tuff; fission-track ages; metamorphic core complex; western; united-states; precise k-ar; u-pb ages; bighorn mountains; rb-sr; (u-th)/he thermochronometry; reference-standard