Is apatite U–Th zonation information necessary for accurate interpretation of apatite (U–Th)/He thermochronometry data?

Ault, Alexis K.; Flowers, Rebecca M.

doi:10.1016/j.gca.2011.11.037

Cited by 87 publications

(59 citation statements)

References 33 publications

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“…Several reasons for the seemingly anomalous and wide dispersion of AHe ages have been proposed, including actinide-enriched micro-inclusions, crystal size variation, U-Th zoning, α-radiation damage, He implantation from external sources and breakage of crystals (e.g. Fitzgerald et al 2006;Shuster et al 2006;Spiegel et al 2009;Brown et al 2011;Ault & Flowers 2012). These are not discussed in any detail here, but may in part also account for some of the slight intra-sample AHe age variation observed.…”

Section: Apatite Fission-track Datingmentioning

confidence: 92%

Neogene rock uplift and erosion in northern Borneo: evidence from the Kinabalu granite, Mount Kinabalu

Cottam

Hall

Sperber

et al. 2013

JGS

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Thermochronological data from the Kinabalu granite, emplaced between c. 7.2 and 7.8 Ma, provide a unique record of northern Borneo's exhumation during the Neogene. Biotite 40 Ar/ 39 Ar ages (c. 7.32-7.63 Ma) record rapid cooling of the granite in the Late Miocene as it equilibrated with ambient crustal temperatures. Zircon fission-track ages (c. 6.6-5.8 Ma) and apatite (U-Th-Sm)/He ages (central age c. 5.5 Ma) indicate rapid cooling during the Late Miocene-Early Pliocene. This cooling reflects exhumation of the granite, uplift and erosion bringing it closer to the Earth's surface. Thermochronological age versus elevation relationships suggest exhumation rates of more than 7 mm a −1 during the latest Miocene and Early Pliocene. Neither the emplacement of the Kinabalu granite nor its exhumation is related to the Sabah orogeny, which terminated in the Early Miocene. Instead, granite magmatism was caused by extension related to subduction rollback of the Sulu Arc, and Mio-Pliocene exhumation of the Kinabalu granite was driven either by lithospheric delamination or break-off of a subducted slab beneath Sabah. Plio-Pleistocene tectonism offshore and onshore northern Borneo reflects continuing large-scale gravity-driven tectonics in the region.

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Section: Apatite Fission-track Datingmentioning

confidence: 92%

Neogene rock uplift and erosion in northern Borneo: evidence from the Kinabalu granite, Mount Kinabalu

Cottam

Hall

Sperber

et al. 2013

JGS

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“…Second, U-Th zonation would produce uneven 4 He distributions, resulting in differential fractional He losses for individual apatite grains. However, this effect can cause an age bias of only a few percent even for significantly zoned (up to 40% eU corerim contrast) apatite grains (Ault and Flowers 2012). Previous fission-track analysis indicates that the U zonation is insignificant for the Kythera and Peloponnese apatites, so that uneven U-Th distribution may have contributed only a small portion of the age scatter.…”

Section: Discussionmentioning

confidence: 95%

“…Intrasample scatter of (U-Th)/ He apparent ages, some of which are older than coexisting AFT apparent ages (i.e., the inverted AHe-AFT age relationship) is not uncommon in AHe thermochronology and has been attributed to several different processes, including (1) differential He diffusion properties mainly controlled by radiation damage in individual apatite crystals (Green et al 2006;Shuster et al 2006;Flowers et al 2009;Flowers and Kelley 2012); (2) uneven distribution of U-Th within single-apatite grains, leading to incorrect alpha-recoil corrections and resulting in complex 4 He profiles and radiation damage distributions (Hourigan et al 2005;Farley et al 2011;Ault and Flowers 2012); (3) fragmentation of originally larger grains, resulting in AHe age that represents only a portion of He distribution in the original grain (Beucher et al 2012;Brown et al 2013); (4) injection of alpha particles from U-Th-rich inclusions such as zircon, monazite, or allanite (House et al 1997;Ehlers and Farley 2003;Vermeesch et al 2007); and (5) implantation of 4 He from adjacent U-Th-rich phases (Farley 2003;Spiegel et al 2009;Murray et al 2011).…”

Section: Discussionmentioning

confidence: 99%

Rapid Exhumation of High-Pressure Metamorphic Rocks in Kythera-Peloponnese (Greece) Revealed by Apatite (U-Th)/He Thermochronology

Marsellos

Min

Foster

2014

The Journal of Geology

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A B S T R A C TApatite (U-Th)/He and apatite fission-track cooling ages from high-pressure (HP) metamorphic rocks in the South Aegean forearc along the Kythera Strait (Kythera and southeastern Peloponnese) suggest rapid exhumation during Middle to Late Miocene times. HP rocks from the Kythera Strait exhibit two perpendicular extensional structures. Samples with arc-normal or arc-parallel extensional fabrics yielded apatite (U-Th)/He cooling ages of ∼8-10 Ma. The more precise (U-Th)/He ages are consistent with previously reported apatite and zircon fission-track ages obtained from the same rock units. The less precise, but still accurate, fission-track data provided a reference for (U-Th)/He dating on relatively young uranium-poor apatites. The combined data, therefore, precisely and accurately constrain the exhumation history of HP rocks and indicate that localized arc-parallel extension in the Kythera Strait was active for an ∼5 m.yr. interval during the regional arc expansion.

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“…Parent nuclide zonation is another commonly cited source of apatite He age irreproducibility. However, intragranular parent zonation in apatite grains in the vast majority of cases is unlikely to cause He age inaccuracies larger than~10-15% (Farley et al, 2011;Ault and Flowers, 2012;Gautheron et al, 2012;Johnstone et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Effects of U–Th-rich grain boundary phases on apatite helium ages

Murray¹,

Orme²,

Reiners³

2014

Chemical Geology

100

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Is apatite U–Th zonation information necessary for accurate interpretation of apatite (U–Th)/He thermochronometry data?

Cited by 87 publications

References 33 publications

Neogene rock uplift and erosion in northern Borneo: evidence from the Kinabalu granite, Mount Kinabalu

Neogene rock uplift and erosion in northern Borneo: evidence from the Kinabalu granite, Mount Kinabalu

Rapid Exhumation of High-Pressure Metamorphic Rocks in Kythera-Peloponnese (Greece) Revealed by Apatite (U-Th)/He Thermochronology

Effects of U–Th-rich grain boundary phases on apatite helium ages

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