Natural age dispersion arising from the analysis of broken crystals: Part II. Practical application to apatite (U–Th)/He thermochronometry

Beucher, Romain; Brown, R. W.; Roper, S. M.; Stuart, Finlay M.; Persano, Cristina

doi:10.1016/j.gca.2013.05.042

Cited by 61 publications

(47 citation statements)

References 49 publications

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“…Many of the apatites are fragments with one or both tips broken. Fragmentation can affect AHe dates for certain thermal histories, but this effect is far less significant than the influence of radiation damage [ Beucher et al ., ; Brown et al ., ]. We evaluated our results to determine whether we could exploit the fragmentation effect to better restrict the thermal history simulations discussed in section 5. Although we suspect that fragmentation may be a secondary source of dispersion in our data, it does not appear to affect the results in a systematic manner (supporting information Figure S2).…”

Section: Resultsmentioning

confidence: 99%

“…[] used AHe dating of kimberlites from a plateau interior location to constrain a regional unroofing pulse at ∼100–90 Ma as well as a more localized Cenozoic erosion phase, and linked these results with information gleaned from mantle xenoliths in the same pipes. In addition, AHe data for a sample from a plateau interior borehole records cooling between 150 and 100 Ma [ Beucher et al ., ], likely due to erosion.…”

Section: Introductionmentioning

confidence: 99%

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Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

Stanley

Flowers

Bell

2015

Geochem Geophys Geosyst

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Flow in the sublithospheric mantle is increasingly invoked as a mechanism to explain both modern and past surface topography, but the importance of this phenomenon and its influence at different localities are debated. Southern Africa is an elevated continental shield proposed to represent dynamically supported topography. However, this region is also characterized by a complex lithospheric architecture variably affected by Cretaceous heating, thinning, and metasomatic alteration. We used apatite (U-Th)/He thermochronometry on 15 Cretaceous kimberlites from an 600 km long transect across the Kaapvaal Craton, combined with information from xenoliths in these pipes, to determine the plateau interior erosion history. The goal was to determine the relationships with lithospheric modification patterns and thereby better isolate the sublithospheric contribution to elevation. The results document a wave of erosion from west to east across the craton from 120 to <60 Ma, initially focused along paleorivers and then retreating as a scarp across the landscape. This spatially variable erosion event was associated with limited modification of the Archean cratonic lithospheric mantle as recorded by mantle xenoliths and xenocrysts, implying that dynamic buoyancy sources may be required to explain the elevations. In contrast, off-craton to the southwest, a more pronounced regional erosion phase at 110-90 Ma was coincident with significant modification of the Proterozoic lithospheric mantle. This relationship suggests that lithospheric processes were more important contributors to erosion and topographic change off-craton than on-craton. Together, these results suggest that lithospheric architecture can have an important control on the surface expression of mantle dynamics.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

Stanley

Flowers

Bell

2015

Geochem Geophys Geosyst

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“…The Kaapvaal craton of southern Africa is a classic example of a craton that initially stabilized in the Archean and was subsequently affected by repeated accretionary and intracratonic magmatic events. A variety of geochronologic and thermochronologic data inform the history of Kaapvaal growth, stabilization, and cooling through temperatures of ∼300°C (e.g., Layer et al, ; Schoene et al, ), as well as the Mesozoic to Cenozoic history of southern African Plateau erosion and cooling through temperatures <120°C (e.g., Beucher et al, ; Brown et al, ; Flowers & Schoene, ; Stanley et al, ). However, thermochronologic constraints on the tT history of the Kaapvaal craton between Precambrian and Mesozoic time are more limited (Cassata et al, ; Flowers & Schoene, ; Jacobs & Thomas, ).…”

Section: Introductionmentioning

confidence: 99%

“…Alpha ejection (Farley et al, ; Gautheron et al, ; Hourigan et al, ; Ketcham et al, ), He injection (e.g., Murray et al, ; Spiegel et al, ), and grain fragmentation (Beucher et al, ; Brown et al, ) are additional considerations in (U‐Th)/He thermochronology. He atoms can travel up to 20 µm during alpha decay, so alpha‐ejection corrections must be made for whole crystals to account for He lost by this effect, which requires an accurate estimate of the grain's surface area to volume ratio (Farley et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Low eU minerals are especially vulnerable to bias from He injection from nearby higher eU phases or grain‐boundary coatings (e.g., Murray et al, ; Spiegel et al, ). Grain fragmentation during mineral separation can also contribute to data scatter if the fragments capture different portions of the mineral's natural He diffusion profile (Beucher et al ; Brown et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Deciphering a 2 Gyr‐Long Thermal History From a Multichronometer (U‐Th)/He Study of the Phalaborwa Carbonatite, Kaapvaal Craton, South Africa

Baughman

Flowers

2018

Geochem Geophys Geosyst

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(U‐Th)/He data were obtained for four minerals (baddeleyite‐BHe, titanite‐THe, zircon‐ZHe, apatite‐AHe) from the 2.06 Ga Phalaborwa carbonatite complex and nearby Archean basement of the Kaapvaal craton, South Africa. Our goals are to evaluate the relative He temperature sensitivities of these phases, better understand how radiation damage and other factors affect them, and inform aspects of the craton's thermal history. BHe dates overlap with Phalaborwa emplacement and record the highest temperatures of the dated phases. THe dates are 700–1,100 Ma and display a limited negative date‐eU correlation. ZHe dates are negatively correlated with eU, are younger (561–32 Ma) and have higher eU than the THe data, with the highest‐eU grains younger than the AHe dates. AHe dates are reproducible with a mean of 107 ± 7 Ma. The THe and ZHe data show radiation damage reduction of their He retentivities manifested as the negative date‐eU correlations. Alpha dose estimates for zircon are several orders of magnitude higher than for titanite, consistent with the ZHe dates recording lower temperatures and a younger portion of the history than the THe dates. Thermal history modeling yields time‐temperature paths that (1) explain the AHe, ZHe, and THe data while honoring existing geologic constraints, thus demonstrating the internal consistency of the data set, (2) imply possible reheating during Namaqua‐Natal orogenesis, and (3) limit maximum probable temperatures to ∼180°C during 300–183 Ma Karoo basin burial. The results show that exploiting multiple (U‐Th)/He thermochronometers and radiation damage effects can provide new insights into long‐term craton evolution.

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Identifying spatial variations in glacial catchment erosion with detrital thermochronology

Ehlers

Szameitat

Enkelmann

et al. 2015

J. Geophys. Res. Earth Surf.

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Understanding the spatial distribution of glacial catchment erosion during glaciation has previously proven difficult due to limited access to the glacier bed. Recent advances in detrital thermochronology provide a new technique to quantify the source elevation of sediment. This approach utilizes the tendency of thermochronometer cooling ages to increase with elevation and provides a sediment tracer for the elevation of erosion. We apply this technique to the Tiedeman Glacier in the heavily glaciated Mount Waddington region, British Columbia. A total of 106 detrital apatite (U-Th)/He (AHe) and 100 apatite fission track (AFT) single-grain ages was presented from the modern outwash of the Tiedemann Glacier with catchment elevations between 530 and 3960 m. These data are combined with nine AHe and nine AFT bedrock ages collected from ã 2400 m vertical transect to test the hypotheses that erosion is uniformly or nonuniformly distributed in the catchment. A Monte Carlo sampling model and Kuiper statistical test are used to quantify the elevation range where outwash sediment is sourced. Model results from the AHe data suggest nearly uniform erosion in the catchment, with a preference for sediment being sourced from~2900 to 2700 m elevation. Ages indicated that the largest source of sediment is near the present-day ELA. These results demonstrate the utility of AHe detrital thermochronology (and to a lesser degree AFT data) to quantify the distribution of erosion by individual geomorphic processes, as well as some of the limitations of the technique.

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Natural age dispersion arising from the analysis of broken crystals: Part II. Practical application to apatite (U–Th)/He thermochronometry

Cited by 61 publications

References 49 publications

Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

Erosion patterns and mantle sources of topographic change across the southern African Plateau derived from the shallow and deep records of kimberlites

Deciphering a 2 Gyr‐Long Thermal History From a Multichronometer (U‐Th)/He Study of the Phalaborwa Carbonatite, Kaapvaal Craton, South Africa

Identifying spatial variations in glacial catchment erosion with detrital thermochronology

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