Examination of some proposed K-Ar standards: analyses and conventional KAr data

Fuhrmann, Ursula; Lippolt, H. J.; Hess, Jürgen C.

doi:10.1016/0168-9622(87)90027-3

Cited by 116 publications

(80 citation statements)

References 6 publications

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“…About 1.5 to 3 gm of 40-120 mesh from each sample was wrapped in aluminum foil packets and stacked in aluminum canister with LP-6 biotite standard (127.7 ± 1.4 Ma, Odin, 1982) and HDB-1 biotite (24.7 ± 0.4 Ma, Fuhrmann et al, 1987) and irradiated in the Open Pool Reactor at National Tsing-Hua University with neutron flux of 1.566 × 10 13 n/cm 2 sec for 8 hours. After irradiation, samples were loaded in degassed fused silica boats, and placed into a degassed fused quartz tube, baked at 250°C for 24 hours and then incrementally heated following a 30-min.…”

Section: Samples and Analytical Methodsmentioning

confidence: 99%

Geochemical studies of tektites from East Asia

Lee

Chen

et al. 2004

Geochem. J.

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Thirty tektites from East Asia (including Wenchang and Penglei of Hainan Island, Maoming of Guandong, China; Khon-Kaen of Thailand; Bao Loc of Vietnam; Rizal of Luzon, Philippines) have been analyzed for major and trace element contents and Rb-Sr isotopic compositions. All the samples studied are splash form tektites. The trace element ratios Ba/Rb (avg. 3.74), Th/Sm (avg. 2.31), Sm/Sc (avg. 0.43), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents of tektites studied are similar to the average upper continental crust. The chemical data of tektites in this study indicate that they were derived from similar target rocks which may be related to post-Archean upper crustal materials. The tektites from East Asia have high positive ε Sr (0) values-ranging from 164.2 to 198.6, indicating that they were not dominantly derived from recent young sediments, such as soil or loess. The Ar-Ar ages (736.8 ± 55.5~814.6 ± 24.4 ka) of tektites of the present study are consistent with the age of other Australasian tektites, which indicates that all Australasian tektites were derived from a single impact event. Previous studies (Koeberl, 1992;Blum et al., 1992;Schnetzler, 1992) and the present chemical data suggest that these tektites are the result of melting at a single site, which is most probably located in the southern part of the Thailand-Laos border. Mixing calculations based on the model suggested by Ho and Chen (1996) for various amounts and combinations of target rocks indicate that the best fit for East Asia tektites is a mixture of 61% greywacke, 32% sandstone and 7% shale.

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Section: Samples and Analytical Methodsmentioning

confidence: 99%

Geochemical studies of tektites from East Asia

Lee

Chen

et al. 2004

Geochem. J.

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“…The amount of radiogenic 40 Ar was determined by isotope dilution method using a highly enriched 38Ar spike . The spike is calibrated against the biotite standard HD-B1 (Fuhrmann et al 1987). The age calculations are based on the constants recommended by the IUGS quoted in .…”

Section: Discussionmentioning

confidence: 99%

Nd, Pb, and Sr isotope composition of Late Mesozoic to Quaternary intra-plate magmatism in NE-Africa (Sudan, Egypt): high-μ signatures from the mantle lithosphere

Lucassen

Franz

Romer

et al. 2008

Contrib Mineral Petrol

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The isotopic composition of mafic small-volume intra-plate magmatism constrains the compositions of the sub-continental mantle sources. The Nd, Pb, and Sr isotope signatures of widespread late Mesozoic to Quaternary intra-plate magmatism in NE Africa (Sudan, South Egypt) are surprisingly uniform and indicate the presence of a high-µ (µ= 238 U/ 204 Pb) source in the mantle. The rocks are characterized by small ranges in the initial isotopic composition of Nd, Pb, and Sr and most samples fall within ε Nd ca 3 to 6, 206 Sr/ 86 Sr ca. 0.7028 to 0.7034. We interpret this reservoir as lithospheric mantle that formed beneath the Pan-African orogens and magmatic arcs from asthenospheric mantle, which was enriched in trace elements (U, Th, and light REE). Combining our new data set with published data of intra-plate magmatic rocks from the Arabian plate indicates two compositionally different domains of lithospheric mantle in NE-Africa -Arabia. The two domains are spatially related to the subdivision of the Pan-African orogen into a western section dominated by reworked cratonic basement (NEAfrica; high-µ lithospheric mantle) and an eastern section dominated by juvenile Pan-African basement (easternmost NE-Africa and Arabia; moderate µ lithospheric mantle). The compositions of the Pan-African lithospheric mantle and the MORB-type mantle of the Red Sea and Gulf of Aden spreading centers could explain the Nd-Pb-Sr isotopic compositions of the most pristine Afar flood basalts in Yemen and Ethiopia by mixtures of the isotopic composition of regional lithospheric and asthenospheric sources.

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“…The amount of radiogenic 40 Ar was determined by isotope dilution method using a highly enriched 38 Ar spike (Schumacher, 1975), which was calibrated against the biotite standard HD-B1 (Fuhrmann et al, 1987;Hess and Lippolt, 1994). The released gases were subjected to a two-stage purification procedure via Tigetters and SORB-ACs getters.…”

Section: K-ar Fault Gouge: Data Acquisitionmentioning

confidence: 99%

Exhumation history and landscape evolution of the Sierra de San Luis (Sierras Pampeanas, Argentina) - new insights from low - temperature thermochronological data

Bense

Costa

Oriolo

et al. 2017

andgeo

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ABSTRACT. This paper presents low-temperature thermochronological data and K-Ar fault gouge ages from the Sierra de San Luis in the Eastern Sierras Pampeanas in order to constrain its low-temperature thermal evolution and exhumation history. Thermal modelling based on (U-Th)/He dating of apatite and zircon and apatite fission track dating point to the Middle Permian and the Triassic/Early Jurassic as main cooling/exhumation phases, equivalent to ca. 40-50% of the total exhumation recorded by the applied methods. Cooling rates are generally low to moderate, varying between 2-10 °C/Ma during the Permian and Triassic periods and 0.5-1.5 °C/Ma in post-Triassic times. Slow cooling and, thus, persistent residence of samples in partial retention/partial annealing temperature conditions strongly influenced obtained ages. Thermochronological data indicate no significant exhumation after Cretaceous times, suggesting that sampled rocks were already at or near surface by the Cretaceous or even before. As consequence, Cenozoic cooling rates are low, generally between 0.2-0.5 °C/Ma which is, depending on geothermal gradient used for calculation, equivalent to a total Cenozoic exhumation of 0.6-1.8 km. K-Ar fault gouge data reveal long-term brittle fault activity. Fault gouge ages constrain the end of ductile and onset of brittle deformation in the Sierra de San Luis to the Late Carboniferous/Early Permian. Youngest K-Ar illite ages of 222-172 Ma are interpreted to represent the last illite formation event, although fault activity is recorded up to the Holocene. RESUMEN. Historia de la exhumación y evolución del paisaje de la sierra de San Luis (Sierras Pampeanas, Argentina)-nuevas perspectivas a partir de datos termocronológicos de baja temperatura. Esta contribución presenta datos de termocronología de baja temperatura y edades de illitas generadas en zonas de fallas de la sierra de San Luis, en las Sierras Pampeanas Orientales de Argentina, con el propósito de aportar al conocimiento de la historia de su exhumación y evolución termal de baja temperatura. El modelado termal basado en dataciones de (U-Th)/He, apatita, circón y trazas de fisión sugiere que las principales fases de exhumación y enfriamiento ocurrieron durante el Pérmico medio y Triásico/Jurásico inferior, contribuyendo con aproximadamente 40-50% de la exhumación total registrada por los métodos utilizados. Las tasas de enfriamiento son, en general, bajas a moderadas, variando entre 2-10 °C/Ma durante el Pérmico y Triásico y 0,5-1,5 °C/Ma después del este último período. El lento enfriamiento y la persistente residencia de las muestras analizadas en condiciones térmicas de retención parcial (partial annealing) ha influenciado notoriamente las edades obtenidas. Los datos termocronológicos indican que no ha habido una exhumación 276 Exhumation history and LandscapE EvoLution of thE siErra dE san Luis (siErras pampEanas, argEntina)... significativa después del Cretácico o incluso antes. Consecuentemente, las tasas de enfriamiento durante el Cenozoico, son bajas, ge...

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Examination of some proposed K-Ar standards: analyses and conventional KAr data

Cited by 116 publications

References 6 publications

Geochemical studies of tektites from East Asia

Geochemical studies of tektites from East Asia

Nd, Pb, and Sr isotope composition of Late Mesozoic to Quaternary intra-plate magmatism in NE-Africa (Sudan, Egypt): high-μ signatures from the mantle lithosphere

Exhumation history and landscape evolution of the Sierra de San Luis (Sierras Pampeanas, Argentina) - new insights from low - temperature thermochronological data

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