Thermochronology of the Talkeetna intraoceanic arc of Alaska: Ar/Ar, U‐Th/He, Sm‐Nd, and Lu‐Hf dating

Abstract

[1] As one of two well-exposed intraoceanic arcs, the Talkeetna arc of Alaska affords an opportunity to understand processes deep within arcs. This study reports new Lu-Hf and Sm-Nd garnet ages, 40 Ar/ 39 Ar hornblende, mica and whole-rock ages, and U-Th/He zircon and apatite ages from the Chugach Mountains, Talkeetna Mountains, and Alaska Peninsula, which, in conjunction with existing geochronology, constrain the thermal history of the arc. The oldest U-Th/He zircon ages are ∼137 to 129 Ma, indicating no Cenozoic regional heating above ∼180°C. Although the signal is likely complicated by Cretaceous and Oligocene postarc magmatism, the aggregate thermochronology record indicates that the thermal history of the Talkeetna arc was spatially variable. Onedimensional finite difference thermal models show that this kind of spatial variability is inherent to intraoceanic arcs with simple construction histories. Citation: Hacker,

Detrital Zircon Record of a Mesozoic Collisional Forearc Basin in South Central Alaska: The Tectonic Transition From an Oceanic to Continental Arc

“…Similarly, the Jurassic‐Cretaceous Chugach terrane is one of the largest exposed accretionary prisms on Earth (Plafker et al, ). Our analysis of the forearc basin strata integrates our findings with recent geochronologic and geochemical studies of both the Jurassic igneous rocks of the Talkeetna arc (Amato et al, ; Behn & Kelemen, ; Clift, Draut, et al, ; DeBari & Greene, ; Draut & Clift, ; Greene et al, ; Hacker et al, , ; Mehl et al, ; Rioux et al, , ) and the Mesozoic accretionary prism rocks of the Chugach terrane (Amato et al, ; Amato & Pavlis, ). The application of U‐Pb detrital zircon geochronology to the Jurassic and Cretaceous forearc basin strata in the context of both the companion arc and accretionary prism rocks provides a powerful approach to chronicling arc erosion and collisional processes along this convergent margin.…”

“…If so, regional uplift/unconformity development in the forearc basin and exhumation/cooling of the Talkeetna arc may also be partly a response to isostatic rebound related to gravitational foundering of the deep roots of Talkeetna arc (in a broad sense of DeCelles et al, ; DeCelles & Graham, ). The thermal history of the Talkeetna arc is spatially variable but in our study area of the eastern Talkeetna Mountains cooling occurred from 149 to 143 Ma based on 40 Ar/ 39 Ar mica ages and from 130 to 119 Ma based on limited (U‐Th)/He ages on zircon and apatite (Hacker et al, ). These cooling ages are consistent with our interpreted syncollisional stage (164–113 Ma in Figure ) and suggest a possible link between delamination of the roots of the Talkeetna arc and surfaces responses in the forearc basin that warrants additional future study.…”

A thermochronometric view into an ancient landscape: Tectonic setting, development, and inversion of the Paleozoic eastern Paganzo basin, Argentina

“…We report the single-grain ages with their analytical error and the mean (U-Th)/He age and the standard deviation as the sample error (Table 2). Due to the old (U-Th)/He ages, the range between single-grain ages appears large (tens of millions of years), but the sample age reproducibility (7%-18% for zircon and 5%-24% for apatite) is common for the (U-Th)/He method (e.g., Flowers et al, 2008;House et al, 2005;Stock et al, 2006;Hacker et al, 2011;Spotila and Berger, 2010). However, since the method is mostly applied to rocks that experienced CretaceousCenozoic cooling, the absolute errors are usually small (<5 m.y.)…”

Thermochronology in Orogenic Systems

“…Exemplary studies have been conducted in the North American Cordillera (Batt et al, 2001;Benowitz et al, 2011;Cecil et al, 2006;Colgan et al, 2008;Farley et al, 2001;Fitzgerald et al, 1995;Hacker et al, 2011;Spotila et al, 2001), the Andes (Barnes et al, 2008;Gunnell et al, 2010;Insel et al, 2010;Schildgen et al, 2007Schildgen et al, , 2009Schildgen et al, , 2010Spikings et al, 2010), the Southern Alps of New Zealand (Batt et al, 2000;Shuster et al, 2011;Kamp, 1993, 1995), and the Himalayan-Tibetan orogenic system (Kirby et al, 2002;Ouimet et al, 2010;Wobus et al, 2008;Zeitler et al, 2001).…”