(U-Th)/He Dating: Techniques, Calibrations, and Applications

Farley, Kenneth A.

doi:10.2138/rmg.2002.47.18

Cited by 725 publications

(648 citation statements)

References 54 publications

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“…Because the diffusion of He in apatite is sensitive to temperatures found in the uppermost few kilometers of Earth's crust, the production and diffusion of radiogenic 4 He via decay of radioactive nuclides (i.e. along the U and Thseries decay chains) can be used to quantify the timing, rates, and spatial patterns of exhumation over typically >0.1 million year (Ma) timescales (e.g., Farley 2002) . A quantitative description of the diffusion kinetics of 4 He in apatite is required for accurate interpretation of (UTh)/He data.…”

Section: Introductionmentioning

confidence: 99%

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Willett

Fox

Shuster

2017

Earth and Planetary Science Letters

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Widely used to study surface processes and the development of topography through geologic time, (UTh)/He thermochronometry in apatite depends on a quantitative description of the kinetics of 4He diffusion across a range of temperatures, timescales, and geologic scenarios. Empirical observations demonstrate that He diffusivity in apatite is not solely a function of temperature, but also depends on damage to the crystal structure from radioactive decay processes. Commonlyused models accounting for the influence of thermal annealing of radiation damage on He diffusivity assume the net effects evolve in proportion to the rate of fission track annealing, although the majority of radiation damage results from recoil. While existing models adequately quantify the net effects of damage annealing in many geologic scenarios, experimental work suggests different annealing rates for the two damage types. Here, we introduce an alphadamage annealing model (ADAM) that is independent of fission track annealing kinetics, and directly quantifies the influence of thermal annealing on He diffusivity in apatite. We present an empirical fit to diffusion kinetics data and incorporate this fit into a model that tracks the competing effects of radiation damage accumulation and annealing on He diffusivity in apatite through geologic time. Using timetemperature paths to illustrate differences between models, we highlight the influence of damage annealing on data interpretation. In certain, but not all, geologic scenarios, the interpretation of lowtemperature thermochronometric data can be strongly influenced by which model of radiation damage annealing is assumed. In particular, geologic scenarios involving 12 km of sedimentary burial are especially sensitive to the assumed rate of annealing and its influence on He diffusivity. In cases such as basement rocks in Grand Canyon and the Canadian Shield, (UTh)/He ages predicted from the ADAM can differ by hundreds of Ma from those predicted by other models for a given thermal path involving extended residence between ~40 80 ºC.

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Section: Introductionmentioning

confidence: 99%

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Willett

Fox

Shuster

2017

Earth and Planetary Science Letters

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“…Ft: alpha-ejection correction (according to Farley, 2002). Error on average age is 1s, as (SD)/(n) 1/2…”

Section: He-agementioning

confidence: 99%

Devonian magmatism in the western Sakarya Zone, Karacabey region, NW Turkey

Sunal

2012

Geodinamica Acta

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The Karacabey Pluton is a large magmatic body in the northwestern Turkey overthrust by the probable Triassic metamorphic rocks of the Lower Karakaya Complex. Both the metamorphic rocks and the Karacabey Pluton are unconformably overlain by a Lower Jurassic and younger sedimentary sequence. The Karacabey Pluton was regarded as a Carboniferous intrusion based on the previous K-Ar biotite geochronological data. Here, we provide new geological, geochemical and geochronological data from the Karacabey Pluton. Zircon U-Pb results from two samples yielded ages of 393.8 +/−2.7 to 395.9 +/−4.09 Ma, suggesting that the granitoids intruded in the crust throughout the Early to Middle Devonian. The Karacabey Pluton consists mainly of biotite and locally hornblende bearing granitoid with lesser amounts of S-type leucocratic granodiorite, all of which are cut by pegmatitic bodies. It belongs to the high-K calc-alkaline series with distinct Nb and Ta anomalies in multi-element spider diagram. Sr and Nd isotopes' initial values are 0.709-0.712 and 0.511-0.512, respectively. εNd(i) values range between −7.8 and −9.4. The isotopic characteristics of the rocks indicate lower crustal sources of both metapelitic and metaigneous origin. Geochemical features of the rocks suggest that they developed in an arc-related environment, along with the other Devonian granitoids described from the Biga Peninsula in northwest Turkey. The granitoid shows a low-temperature alteration/metamorphism marked by recrystallization of quartz, sericitization of the feldspar and formation of late chlorite, epidote and muscovite. Possibly because of these, the Ar-Ar biotite ages are scattered with a possible concentration at around Permo-Carboniferous boundary. Zircon (U-Th)/He geochronology suggests that after the granitoid was reburied during Early Jurassic to Early Cretaceous sedimentation, there was renewed uplift and erosion during the Late Cretaceous (Turonian), which is possibly related to the closure of the Intra-Pontide Ocean in the north.Keywords: Karacabey Pluton; Sakarya Zone; geochemistry; zircon U-Pb, biotite Ar-Ar and zircon (U-Th)/He ages IntroductionThe Sakarya Zone of the Pontides is an E-W trending belt bounded by Istanbul Zone in the north and by the Izmir-Ankara Suture in the south (Figures 1 and 2). It consists of a complex basement overlain by Jurassic and younger sedimentary sequence. The basement rocks of the Sakarya Zone can be divided into two separate parts: 1. Paleozoic plutonic and metamorphic rocks possibly related to the Variscan orogeny and 2. Triassic accretionary complexes with blueschists and eclogites, called as the Karakaya Complex (Okay & Göncüoğlu, 2004;Okay & Tüysüz, 1999;Okay, Satır & Siebel, 2006).Most of the plutonic rocks in the basement of the Sakarya Zone are of Carboniferous age (350-320 Ma, Figure 1). These can traced from the Kazdağ Massif in the Biga peninsula (308-329 Ma, Okay et al., 1996, through west of Ankara (~290 Ma, Okay et al., 2006, 319-327 Ma;Robertson, 2012) and Central Pontides (275-295 Ma, Nzeg...

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“…Selected grains were photographed and dimensions were measured for a-ejection correction [Farley, 2002]. Single grain replicates (2 to 6) have been analyzed for all samples.…”

Section: Apatite (U-th)/he Thermochronology (Ahe)mentioning

confidence: 99%

From nappe stacking to out‐of‐sequence postcollisional deformations: Cretaceous to Quaternary exhumation history of the SE Carpathians assessed by low‐temperature thermochronology

Merten¹,

Maţenco

Foeken

et al. 2010

Tectonics

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[1] Apatite fission track (AFT) and (U-Th)/He (AHe) thermochronology have been combined to constrain the exhumation history of the SE Carpathians. Cooling ages generally decrease from Cretaceous for the internal basement nappes (AFT ages), to Miocene-Quaternary (AFT and AHe, respectively) for the external sedimentary wedge. The AFT and AHe data show a Paleogene age cluster, which confirms a suspected but never demonstrated tectonic event. The new data furthermore suggest that the SE Carpathians have been affected by a middle Miocene exhumation phase related to continental collision, which occurred at rates of ∼0.8 mm/yr, similar to the one previously inferred for the East Carpathians. The SE Carpathian tectonic evolution, however, is overprinted by two younger exhumation events in the Pliocene-Pleistocene. The first exhumation phase (latest Miocene-early Pliocene) occurred at high exhumation rates (∼1.7 mm/yr) and is interpreted as a tectonic event and/or associated with a sea level drop in the Paratethys basins during the Messinian low stand. The youngest recorded tectonic phase suggests rapid Pleistocene exhumation (∼1.6 mm/yr) and is interpreted to represent crustal-scale shortening different in mechanics from collisional processes. The data suggest that the SE Carpathians did not develop as a typical double-vergent orogenic wedge; instead, exhumation was related to a foreland-vergent sequence of nappe stacking during collision and was subsequently followed by a large out-of-sequence shortening event truncating the already locked collisional boundary.

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(U-Th)/He Dating: Techniques, Calibrations, and Applications

Cited by 725 publications

References 54 publications

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Devonian magmatism in the western Sakarya Zone, Karacabey region, NW Turkey

From nappe stacking to out‐of‐sequence postcollisional deformations: Cretaceous to Quaternary exhumation history of the SE Carpathians assessed by low‐temperature thermochronology

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