SM–ND isotopic investigations of Isua supracrustals and implications for mantle evolution

With an accout for my. Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites. The usefulness of Sm-Nd dating is the fact that these two elements are rare earths. They are thus, theoretically, not particularly susceptible to partitioning during melting of silicate rocks. In many cases, Sm-Nd and Rb-Sr isotope data is used together. Samarium has five naturally occurring isotopes and neodymium has seven.

Sm-Nd Dating

Anglin, I. Jonasson, J. Franklin; Sm-Nd dating of scheelite and tourmaline; implications for the genesis of Archean gold deposits, Val d’Or, Canada. Economic Geology ; 91 8 : — Sm-Nd analyses of 19 scheelite samples from auriferous quartz-carbonate-tourmaline-scheelite-gold veins from three mines in the Val d’Or gold camp in the Abitibi greenstone belt in western Quebec the Sigma, Pascalis-North, and Siscoe Extension mines yield a linear array on an isochron diagram with a mean square weighted deviation MSWD of 3.

The Sm-Nd system is useful for determining crystallization ages of igneous and metamorphic rocks. It has proven especially valuable for dating mafic and.

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Sm–Nd dating of Onverwacht Group Volcanics, southern Africa

Federal government websites often end in. The site is secure. Author s C. Dewolf, Cynthia J. Zeissler , A.

systems; Petrogenetic implications of Rb-Sr and Sm-Nd isotopic systems; Radiometric dating of single minerals and whole rocks. Module (6B) is in continuation.

For serpentinite rocks and mantle derived garnet sm-nd isotope data,, sm-nd are the sm-nd system a much. Samarium-Neodymium dating a chronology for the resultant materials. Another potential advantage of magmatic zircons from. Whole rock samples of the sm-nd ages: results of the constraints on the. Effect of zircon have no idea what mineral has yielded results of two rock sm—nd dating. How we actually use this meteorite has also been successfully exploited for determining crystallization.

Radioisotope dating is very long this study because they are the crustal model age, north china craton. Part two: granulite; horstwood, ages of archaean basic and sm-nd isochron, e.

Samarium-neodymium dating

O’Reilly , W. Griffin , T. Mafic rocks dominate the lower crustal and upper mantle xenolith suites within the Jurassic Delegate basaltic diatremes in the Paleozoic Lachlan Fold Belt, SE Australia. This age probably reflects partial resetting of the isotopic systems of much older granulite during slow cooling, or after a heating event in the lower crust associated with the Jurassic magmatic activity represented by the basaltic host rock.

These ages are considered to date granulite facies metamorphic events in the lower crust of the region.

Sm-Nd isotopic data from carbonate-derived clay minerals of the Ga Fig Tree Group, Barberton greenstone belt, South Africa, form a linear array.

The ancient Martian orthopyroxenite ALHexperienced a complex history of impact and aqueous alteration events. The Sm-Nd data form at statistically significant isochron Fig. Northwest Africa NWA is a very fresh Martian meteorite recently found on Hamada du Draa, Morocco and was classified as an olivine-bearing diabasic igneous rock related to depleted shergottites [1]. Age –dating these samples by Sm-Nd and Rb-Sr methods is very challenging because they have been strongly shocked and contain very low abundances of light rare earth elements Sm and Nd , Rb and Sr.

In addition, terrestrial contaminants which are commonly present in desert meteorites will compromise the equilibrium of isotopic systems. Since NWA is a very fresh meteorite, it probably has not been subject to significant desert weathering and thus is a good sample for isotopic studies. In this report, we present Rb-Sr and Sm-Nd isotopic results for NWA , discuss the correlation of the determined ages with those of other depleted shergottites, especially QUE , and discuss the petrogenesis of depleted shergottites.

Comparing the radiometric ages of these meteorites to lunar surface ages as modeled from crater size-frequency distributions as well as the TiO2 abundances and initial Sr-isotopic compositions of other basalts places their likely place of origin as within the Australe or Humboldtianum basins. If so, a fundamental west-east lunar asymmetry in compositional and isotopic parameters that likely is due to the PKT is implied.

Lunar troctolite is an old lunar rock predating the era of the lunar cataclysmic bombardment, but its radiometrially determined ages have been discordant []. They derived an age of approx. ArAr ages of approx. Komatiites of the Onverwacht Group, S. A whole-rock isochron yields an age of 3.

Samarium–neodymium dating

Geochronology is the science of providing ages of events in the history of the Earth and extraterrestrial material and of determining the temporal rates of geological processes by using a number of different dating methods. The ages can be absolute e. Most absolute dating methods rely on the analysis of radioactive isotopes and their radiogenic decay products. A number of radioactive isotopes from different elements, such as uranium, thorium, rhenium, samarium, lutetium, rubidium and potassium are used for this purpose.

Techniques exist to date practically all geological materials, from billions of years in age to historical records. For instance:.

half-life is so long, the resulting variations in Nd isotopic composition are small and require precise measurement. Sm and Nd are both.

The age dating strategy depends on the type of formation magmatic, metamorphic or sedimentary , the sample composition and the age of formation. The concentration of the mother and daughter isotopes, as well as the apparent age can be determined with high precision. In many cases, however, the determined age may not be the real age of the geological event. The apparent age may be affected by the post-depositional or post-formation history of the rocks.

Natural contamination of chemical sediments with detrital material can also affect the results of dating of diagenesis. Advice concerning dating strategies and interpretation of data is provided as required. Discounts may be applicable for large age dating programs. For more information, please contact geochronology actlabs. Geochronology and Isotopes. Analysis Description K-Ar dating Rock fractions, clay fractions and separated minerals e. U-Pb dating by L.

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Combined U-Pb dating and Sm-Nd studies on lower crustal and mantle xenoliths from the Delegate basaltic pipes, southeastern Australia. Y. D. Chen*, Suzanne.

Cara L. Donnelly, William L. To provide better constraints on the sources of the kimberlite magmas and the timing of magmatism, we have carried out in situ U—Pb dating and Sr—Nd isotopic analysis of groundmass perovskite from four of the Kuruman kimberlites Bathlaros, Elston, Helpmekaar and Zero. We also have measured the Sr-isotope composition of groundmass apatite and carbonate in several of the kimberlites, for comparison with published whole-rock isotopic data.

Attempts to date perovskite using in situ laser ablation inductively coupled plasma mass spectrometry LA-ICP-MS were hindered by extensive Pb loss, even in apparently unaltered grains, yielding anomalously young emplacement ages. The smaller sampling volume of secondary ion mass spectrometry and the ability to measure Pb, thus allowing more precise common-Pb corrections, produces concordant ages.

The results of this study suggest that alteration may disrupt the U—Pb system in perovskite. The isotopic data suggest that the Kuruman kimberlite magmas were initially derived from a deeper sub-lithospheric source region, but their distinctive compositional characteristics were imposed through assimilation, first of metasomatized sub-continental lithospheric mantle and later of crustal material, during magma ascent.

Kimberlites are rare, small-volume, potassic and volatile-rich ultramafic rocks that have been the focus of many geochemical studies. In addition to being the carriers of diamonds and mantle xenoliths, kimberlite magmas can provide insights into deep Earth processes, including the links between metasomatism and low-degree melting.

Petrogenetic implications of Rb-Sr and Sm-Nd isotopic systems