U-Pb thermochronology: creating a temporal record of lithosphere thermal evolution

Blackburn, Terrence; Bowring, Samuel A.; Schoene, Blair; Mahan, K. H.; Dudás, Francis Ő.

doi:10.1007/s00410-011-0607-6

Cited by 74 publications

(64 citation statements)

References 42 publications

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“…We interpret these features to imply a short transit time through the partial retention zone (i.e. Condition B), yet different Pb closure temperatures between grains, likely a consequence of grain size (Blackburn et al, 2011).…”

Section: Thermally Activated Pb Diffusionmentioning

confidence: 96%

“…10 presents probability density plots of 207 Pb corrected apparent age versus grain size for both apatite samples. Radiogenic-Pb loss has been shown in some apatite systems to be solely, or at least dominantly, a function of thermally activated diffusion (Blackburn et al, 2011), a key requirement to use the mineral in thermochronometry modelling. In a situation of thermally activated volume diffusion it would be expected to observe distinct grain size populations that correspond to grain age populations; for example, a larger grain size population would correspond to an older age component, whereas a smaller grain size component may relate to a younger age component given Pb-in-apatite diffusion and spherical geometry characteristics (Cherniak, 2005;Cherniak et al, 1991).…”

Section: Apatite Grain Size and Apparent Agementioning

confidence: 99%

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Apatite: a U-Pb thermochronometer or geochronometer?

Kirkland

Yakymchuk

Szilas

et al. 2018

Lithos

122

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Apatite is an accessory mineral that is frequently found in both igneous and clastic sedimentary rocks. It is conventionally considered to be characterized by a closure temperature range between 375 and 600°C and hence has been employed to address mid-temperature thermochronology questions relevant to the reconstruction of thermal events in the middle to lower crust. However, questions remain as to whether apatite faithfully records thermally-activated volume diffusion profiles, or rather is influenced by recrystallization and new growth processes. We present a case study of two apatite samples from the Akia Terrane in Greenland that help chart some of the post magmatic history of this region. Apatite in a tonalitic gneiss has distinct U-enriched rims and its U-Pb apparent ages correlate with Mn chemistry, with a high Mn group yielding an age of c. 2813 Ma. The U-Pb and trace element chemistry and morphology support an interpretation in which these apatite crystals are originally igneous and record cooling after metamorphism, with subsequent generation of discrete new rims. Epidote observed in the sample implies a b600°C fluid infiltration event associated with apatite rims. The second sample, from a granitic leucosome, contains apparently homogeneous apatite, however U-Pb analyses define two distinct discordia arrays with different common Pb components. An older, c. 2490 Ma, component is associated with elevated Sr, whereas a younger, c. 1800 Ma, component has lower Sr concentration. A depth profile reveals an older core with progressively younger ages towards a compositionally discrete late Paleoproterozoic rim. The chemical and age profiles do not directly correspond, implying different diffusion rates between trace elements and U and Pb. The variation in core ages is interpreted to reflect radiogenic-Pb loss from a metamorphic population during new rim growth. The younger, c. 1800 Ma U-Pb age is interpreted to date new apatite growth from a compositionally distinct reservoir driven by tectonothermal and fluid activity, consistent with regional mica Ar-Ar ages. Results from these two samples show that recrystallization, dissolution and regrowth processes likely formed the younger rim overgrowths, and at temperatures below those often considered to be closure temperatures for Pb diffusion in apatite. The results from these samples imply many apatite grains may not record simple thermally activated Pb diffusion profiles and cautions against inversion of apatite U-Pb data to thermal histories without detailed knowledge of the grain growth/alteration processes.

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Section: Thermally Activated Pb Diffusionmentioning

confidence: 96%

Section: Apatite Grain Size and Apparent Agementioning

confidence: 99%

Apatite: a U-Pb thermochronometer or geochronometer?

Kirkland

Yakymchuk

Szilas

et al. 2018

Lithos

122

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“…However, a higher closure temperature for Pb in rutile has not been universally accepted, with some workers arguing for a lower T C (Pb-Rt) based on the fact that U-Pb ages of rutile are generally similar to or slightly younger than U-Pb titanite and Ar-Ar hornblende ages for the same area (e.g. Blackburn et al 2011;Li et al 2003;Schmitz and Bowring 2003). It is noted that these studies presented TIMS (whole-grain) U-Pb ages of rutiles, which do not allow assessment of the development of diffusion-related age profiles within grains.…”

Section: Closure Temperature Of Pb In Rutilementioning

confidence: 97%

Constraints on the thermal evolution of the Adriatic margin during Jurassic continental break-up: U–Pb dating of rutile from the Ivrea–Verbano Zone, Italy

Ewing

Rubatto

Beltrando

et al. 2015

Contrib Mineral Petrol

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documented along the western margin of the Adriatic plate. The ~160 Ma age population postdates the activity of all known rift-related structures within the Adriatic margin, but coincides with extensive gabbroic magmatism and exhumation of sub-continental mantle to the floor of the Alpine Tethys, west of the Ivrea Zone. We propose that this ~160 Ma early post-rift age population records regional cooling following episodic heating of the distal Adriatic margin, likely related to extreme lithospheric thinning and associated advection of the asthenosphere to shallow levels. The partial preservation of the ~175 Ma age cluster suggests that the post-rift (~160 Ma) heating pulse was of short duration. The regional consistency of the data presented here, which is in contrast to many other thermochronometers in the IVZ, demonstrates the value of the rutile U-Pb technique for probing the thermal evolution of high-grade metamorphic terrains. In the IVZ, a significant decoupling between Zr-in-rutile temperatures and U-Pb ages of rutile is observed, with the two systems recording events ~120 Ma apart.

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“…6). Slow secular cooling is recorded by isotopic systems (Mezger et al, 1990;Schmitz and Bowring, 2003;Blackburn et al, 2011) but falls outside the scope of this paper. Over the time interval of interest here (a few tens of million years after accretion), the thermal evolution of the lower crust is dominated by local heating and is affected by heat loss to the lithospheric mantle only weakly.…”

Section: Heating Due To Crustal Heat Productionmentioning

confidence: 99%