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Journal ArticleDOI

Structural relationships and SrNd isotope systematics of polymetamorphic granitic gneisses and granitic rocks from central Rajasthan, India: implications for the evolution of the Aravalli craton

TL;DR: A review of the state of the art of structural and geochronological knowledge of cratonic rocks in part of central Rajasthan, India, and contributions new observations and isotopic data on the structural features and age of granitic rocks in the area are presented in this paper.
About: This article is published in Precambrian Research.The article was published on 1994-01-01. It has received 98 citations till now. The article focuses on the topics: Isochron & Volcanic rock.
Citations
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Journal ArticleDOI
TL;DR: The end-Paleozoic Pangea appears to have contained three continents that had grown in the Precambrian and remained intact until Mesozoic rifting: Ur, formed at 3 Ga and accreted to most of East Antarctica in the middle Proterozoic to form East Gondwana; Arctica, an approximately 2.5-2 Ga continent that contained Archean terranes of the Canadian and Siberian shields and Greenland; and Atlantica formed at 2 Ga of cratons of ~2 Ga age that now occur in West Africa and
Abstract: The end-Paleozoic Pangea appears to have contained three continents that had grown in the Precambrian and remained intact until Mesozoic rifting: Ur, formed at ~3 Ga and accreted to most of East Antarctica in the middle Proterozoic to form East Gondwana; Arctica, an approximately 2.5-2 Ga continent that contained Archean terranes of the Canadian and Siberian shields and Greenland; and Atlantica, formed at ~2 Ga of cratons of ~2 Ga age that now occur in West Africa and eastern South America. Arctica grew at ~1.5 Ga by accretion of most of East Antarctica plus Baltica to form the continent of Nena. Collision of Nena, Ur, and Atlantica, plus minor plates, formed the supercontinent of Rodina at ~1 Ga. Rifting of Rodinia between 1 and 0.5 Ga formed three continents: East Gondwana; Atlantica (which became the nucleus for West Gondwana); and Laurasia (which contained North America, Greenland, Baltica, and Siberia). Gondwana formed at ~0.5 Ga by amalgamation of its eastern and western parts. Various plates accret...

530 citations

Journal ArticleDOI
TL;DR: In this article, an ion microprobe was used to measure the ages of zircons from six samples collected from the southern Aravalli Mountains, and the results indicated that the southern segment of the Aravali Craton had broadly stabilized by ∼ 2.5 Ga.

191 citations

Journal ArticleDOI
TL;DR: The Seychelles islands consist of undeformed and unmetamorphosed basaltic magmas derived from metaluminous monzogranites and granodiorites of Neoproterozoic depleted mantle, variably contaminated by Archaean age (> 750 Ma.
Abstract: compositions ( Nd 750 = +5·46 to −0·87; ISr 750 = 0·7021– The Seychelles islands consist of undeformed and unmetamorphosed, 0·7061) that can be modelled as basaltic magmas derived from metaluminous monzogranites and granodiorites of Neoproterozoic depleted mantle, variably contaminated (0–15%) by Archaean age (>750 Ma). Subsolvus, and lesser hypersolvus granitoids are silicic crust. All petrologic, petrographic, geochemical, isotopic and crosscut by coeval dolerite dykes, dominantly of olivine tholeiite chronologic data for Neoproterozoic magmatic rocks of the Seychelles, composition. Field relations suggest that mixing between granitoid coupled with palaeomagnetic data indicating its position at the and doleritic magmas generated a variety of minor intermediate margin of the Rodinia supercontinent at >750 Ma, are at least rocks that occur as irregular masses and enclaves; their compositions consistent with, if not suggestive of, a continental or Andean-type plot as linear arrays between those of dolerites and granitoids. Two arc setting. We argue, therefore, that the conventionally accepted groups of granitoids can be distinguished based on colour, chemistry notion of an extensional (i.e. rift or plume) setting for Seychelles and isotopic signature. Mahe Group granitoids are grey, with magmatism is vulnerable. relatively low incompatible element concentrations and primitive isotopic signatures that cluster at Nd 750 = +2·85 ± 0·17 and ISr 750 = 0·7031 ± 0·0008 (some samples with impossibly low ISr 180 ppm,

182 citations

Journal ArticleDOI
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.

181 citations

Journal ArticleDOI
TL;DR: In this paper, single zircon dating of the Rampur metabasalts of the Larji-Kullu-Rampur window in the Lesser Himalayas yielded an evaporation age of 1800±13 Ma.

159 citations


Additional excerpts

  • ...Available geochronological data suggest that several periods of acid magmatism have affected the Aravalli domain between c. 3.3 and 0.8 Ga (e.g. Tobisch et al., 1994; Wiedenbeck et al., 1996)....

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References
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Journal ArticleDOI
TL;DR: The IUGS Subcommission on Geochronology (FOOTNOTE 4) as discussed by the authors recommended the adoption of a standard set of decay constants and isotopic abundances in isotope geology.

9,474 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that none of the analyzed meteorite samples deviated more than 0.5 e-units from a 4.6-AE reference isochron and defined an initial 4.5-AE value for CHUR using the Juvinas data of Lugmair.

1,800 citations

Journal ArticleDOI
TL;DR: In this paper, the average ratio of Sm/Nd is about 0.19 in the upper continental crust, and has remained so since the early Archean, thereby precluding the likelihood of major mafic-to-felsic or felsicto-mafic trends in the overall composition of the sedimentary mass through earth history.

1,594 citations

Journal ArticleDOI
TL;DR: In this article, the deformation of two granitic massifs along a dextral wrench fault zone (the South Armorican Shear Zone) is examined at the sample and grain scales.

1,200 citations

Journal ArticleDOI
TL;DR: In this paper, a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent, diapiric emplacement and expansion, or regional deformation post-dating emplacements.

764 citations