Single zircon evaporation ages constraining the growth of the Archaean Aravalli Craton, northwestern Indian Shield
TL;DR: In this article, single grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan.
Abstract: Single grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan, northwestern Indian Shield. The protolith ages for two gneisses, collected from east of Udaipur, are ˜3230 Ma and 2887 Ma respectively. The granitoids display an intrusive relationship with the gneisses and yielded ages ranging between 2666 Ma and 2620 Ma. These ages provide the basis for a geochronological model of evolution of the oldest basement of the Aravalli craton.
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TL;DR: In this paper, the authors used ID-NTIMS data to provide a clear Late Archean-Early Paleoproterozoic age for the Malanjkhand deposit and by implication for its calc-alkaline granitoid host.
186 citations
TL;DR: In this article, the authors used the Precambrian mafic dykes intruding granitoids and supracrustals of the Archean Bundelkhand craton (BC) in northern Penin-Sular India to constrain the position of India at 2.0 and 1.1 Ga.
154 citations
Cites methods from "Single zircon evaporation ages cons..."
...The overall stabilization age for the massif has been interpreted to be ∼2.5 Ga based on the 207Pb/206Pb ages of the granitoids (Meert et al., 2010; Crawford, 1975; Mondal et al., 1997, 1998, 2002; Roy and Kröner, 1996)....
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TL;DR: In this article, the authors used laser ablation ICP-MS U-Pb dating of zircon domains to show that granulite-facies metamorphism and charno-enderbite magmatism in the Sandmata Complex were synchronous at ∼1720 Ma.
144 citations
TL;DR: The timing and extent of polymetamorphism in the Mangalwar and Sandmata Complexes from the Aravalli-Delhi Orogenic Belt of Rajasthan (NW India) remains contentious.
129 citations
TL;DR: In this paper, the authors presented new geochronological, petrological, geochemical and isotopic data for granitic and related rocks from the Aravalli Craton, Rajasthan, northwestern India.
117 citations
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TL;DR: In this article, the IUGS definition of trondhjemite as leucotonalite was followed, except that andesine-bearing leucomorphalite be termed calcic trondhmite.
Abstract: Goldschmidt's definition (1916) of the rock name “trondhjemite,” unfortunately, was not quantitative. Furthermore, the trondhjemite intrusives of the type area, south of Trondheim, Norway, have had much of their original mineralogy obliterated by metamorphism to greenschist facies. The author suggests that the IUGS definition of trondhjemite as leucotonalite be followed, except that andesine-bearing leucotonalite be termed calcic trondhjemite, and that albite-bearing leucotonalite, as well as the oligoclase variety, be termed trondhjemite.
857 citations
TL;DR: In this article, the internal precision of Pb isotope analyses using single-zircon evaporation in a double-filament solid source mass spectrometer was improved by combining the single grain with a suitable Pb+ emitter-bedding technique, which is most easily done by stepwise evaporating the investigated grain at temperatures of 1700-1800 K generating on the cold ionization filament a deposit of radiogenic Pb together with further elements and compounds derived directly from the crystal.
Abstract: The internal precision of Pb isotope analyses using single-zircon evaporation in a double-filament solid source mass spectrometer (Kober 1986) can be improved combining the evaporation of Pb directly from the single grain with a suitable Pb+ emitter-bedding technique. This is most easily done by step-wise evaporating the investigated grain at temperatures of 1700–1800 K generating on the ‘cold’ ionization filament a deposit of radiogenic Pb together with further elements and compounds derived directly from the crystal. The heating of the deposit on the ionization filament to 1400–1500 K results in long-lived and stable Pb+ ion beams. The ‘activating reagents’ in the deposit are HfO2 and SiO2. Their release from the zircon grain together with the radiogenic Pb, which presumably is sited in the crystalline zircon domains as Pb4+, is probably due to disintegration reactions of trace-element silicates hosted in the grain.
507 citations
"Single zircon evaporation ages cons..." refers background or methods in this paper
...No correction was made for mass fractionation which is of the order of 1 %o (Kober, 1987), significantly less than the relative standard deviation of the measured 207Pb/206pb r a t i o s ( s e e T a b j e 3) a n d insignificant at the range considered in this study....
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...The analytical technique involves repeated evaporation and deposition of Pb-isotopes from chemically untreated single zircons in a double-filament arrangement (Kober, 1987), and our laboratory procedures as well as comparisons with conventional and ion-microprobe zircon dating are published elsewhere (Kroner & Todt, 1988; Kroner, Compston & Williams, 1989)....
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TL;DR: In this article, a technique has been developed and tested to analyse 207Pb/206Pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains (≤0.3 mm).
Abstract: A technique has been developed and tested to analyse 207Pb/206Pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains (≤0.3 mm). The evaporation analyses are performed in the double-filament arrangement of a thermal ion mass spectrometer (ThIMS). The method is a powerful tool to distinguish between different lead components occurring in the same grain because differing activation energies of the competing lead components cause their sequential evaporation from the zircons. The evaporation of test samples results in 207Pb/206Pb apparent ages in good agreement with U/Pb ages known from literature: single zircons from a granite of the ‘Marble Mountains’/California yield an age of crystallization of 1,410±30 Ma; ‘Ceylon’ zircons from heavy-mineral bearing gravels yield 560± 40 Ma as age of crystallization of the pegmatitic gravel sources; individuals from a heterogeneous zircon population of a diatexite from the Southern Schwarzwald/SW-Germany indicate metamorphic zircon formation around 500 Ma and the existence of Middle-Proterozoic relics (1.95±0.05 Ga).
492 citations
TL;DR: In this paper, age determinations of the Precambrian rocks of Rajasthan by RbSr analyses are summarized and discussed, and a lower limit at 2000 m.y. is indicated.
256 citations
TL;DR: Agarwal et al. as mentioned in this paper showed that granodioritic gneisses from the Aravalli Region, northwestern India, define a Sm-Nd isochron corresponding to an age of 3.31 ± 0.07 Ga and an initial Nd isotopic ratio that is close to chondritic.
216 citations