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Journal Article

Precise Pb–Pb Baddeleyite Ages of 1765 Ma for a Singhbhum 'Newer Dolerite' Dyke Swarm

10 May 2014-Current Science-Vol. 106, Iss: 9, pp 1306-1310
TL;DR: In this paper, two dykes from the WNW-ESE trending dyke swarm in the south central region of the Singhbhum craton were dated using Pb-Pb baddeleyite thermal extraction-thermal ionization mass spectrometer method.
Abstract: The Singhbhum craton in eastern India hosts a number of mafic dyke swarms popularly called 'newer dolerites'. Previous attempts to obtain emplacement ages of these rocks were limited to a few poor-precision K-Ar whole-rock and Rb-Sr isochron ages. Here, two prominent dykes from the WNW-ESE trending swarm in the south central region of the craton were dated using Pb-Pb baddeleyite thermal extraction-thermal ionization mass spectrometer method. These dykes yielded identical baddeleyite Pb-Pb ages of 1766.2 ± 1.1 Ma (SKJ-10) and 1764.5 ± 0.9 Ma (SKJ-15) respectively, which are interpreted as the time of emplacement of the WNW-ESE trending 'newer dolerite' dyke swarm. The predominantly parallel dyke trend in this swarm for over 100 km along strike indicates these dyke fractures were formed due to horizontal compressive stresses in a region that may have been associated with a palaeo compressional system. Coeval ∼1770 Ma magmatism in the Singhbhum craton and in China, Australia, Brazil and Uruguay confirms this event was globally widely dispersed. The timing of this event also coincides with orogenic activity in majority of continents that may have formed during the assembly of supercontinent Columbia.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors reported eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India.

89 citations

Journal ArticleDOI
TL;DR: In this article, the authors report new zircon U-Pb and Hf isotopic data from key stratigraphic intervals in the Archean nucleus and the North Singhbhum Mobile Belt.

87 citations

Journal ArticleDOI
TL;DR: Based on trend, cross-cutting relationships and U-Pb dating, Precambrian mafic dykes in the Singhbhum craton, earlier collectively identified as ‘Newer Dolerite Swarm’, have been separated into seven distinct swarms, which are thought to be the plumbing systems for Large Igneous Provinces (LIPs).

62 citations

References
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TL;DR: New determinations of the half-lives of half-life values of $ −235 and −238 have been made improved techniques have allowed the halflife values to be measured with greater accuracy than has been heretofore achieved as discussed by the authors.
Abstract: New determinations of the half-lives of $^{235}\mathrm{U}$ and $^{238}\mathrm{U}$ have been made Improved techniques have allowed the half-life values to be measured with greater accuracy than has been heretofore achieved Samples were prepared by molecular plating and counted in a intermediate-geometry $\ensuremath{\alpha}$-proportional counter with an extremely flat pulse-height plateau The small amount of residual nonplated uranium was counted in a $2\ensuremath{\pi}$ counter Energy analysis with a silicon-junction detector was used to measure the presence of "foreign" activities For $^{235}\mathrm{U}$, the measured specific activity was (47981\ifmmode\pm\else\textpm\fi{}33) (dis/min)/(mg $^{235}\mathrm{U}$), corresponding to a half-life of (70381\ifmmode\pm\else\textpm\fi{}00048) \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ yr For $^{238}\mathrm{U}$, the specific activity was measured as (74619\ifmmode\pm\else\textpm\fi{}041) (dis/min)/(mg $^{238}\mathrm{U}$), corresponding to a half-life of (44683\ifmmode\pm\else\textpm\fi{}00024) \ifmmode\times\else\texttimes\fi{} ${10}^{9}$ yr Errors quoted are statistical (standard error of the mean), based upon the observed scatter of the data This scatter exceeds that expected from counting statistics alone We believe that systematic errors, if present, will no more than double the quoted errors

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Journal ArticleDOI
TL;DR: The pre-Rodinia supercontinent was assembled along global-scale 2.1-1.8 Ga collisional orogens and contained almost all of Earth's continental blocks as mentioned in this paper.

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01 Jan 1993
TL;DR: Baddeleyite (ZrO 2 ) occurs in many terrestrial and lunar samples and some achondrite meteorites as a trace constituent that most often crystallizes in the late-stage, most chemically fractionated portions of mafic magmas together with apatite, ilmenite, ± zircon, ± Zirconolite as discussed by the authors.
Abstract: The mineral baddeleyite (ZrO 2 ) occurs in many terrestrial and lunar samples and some achondrite meteorites as a trace constituent that most often crystallizes in the late-stage, most chemically fractionated portions of mafic magmas together with apatite, ilmenite, ± zircon, ± zirconolite. In terrestrial mafic rocks these interstitial regions commonly contain K-feldspar, Cl-rich mica, amphibole and a small amount of quartz. In addition, baddeleyite occurs in tektites as a dissociation product of zircon during meteorite impact and as rims on mantle zircon megacrysts recovered from kimberlites. Baddeleyite is a major carrier of Hf, Ti, Fe and U and strongly fractionates Hf from Zr as it can have very high Zr/Hf (> 50)

390 citations