Pb-Sr-Nd isotope data from the Valasjaure supracrustal belt, northern Sweden

AbstractThe Mansehra granite in the NW Himalaya is a typical Lesser Himalayan granite. We present here new whole-rock geochemistry, Rb–Sr and Sm–Nd isotope data, together with zircon U–Pb ages and Hf isotope data, for the Mansehra granite. Geochemical data for the granite show typical S-type characteristics. Zircon U–Pb dating yields 206Pb/238U crystallization ages of 483–476 Ma. The zircon grains contain abundant inherited cores and some of these show a clear detrital origin. The 206Pb/238U ages of the inherited cores in the granite cluster in the ranges 889–664, 1862–1595 and 2029 Ma. An age of 664 Ma is considered to be the maximum age of the sedimentary protoliths. Thus the Late Neoproterozoic to Cambrian sedimentary rocks must be the protolith of the Mansehra granitic magma. The initial Sr isotope ratios are high, ranging from 0.7324 to 0.7444, whereas the εNd(t) values range from −9.2 to −8.6, which strongly suggests a large contribution of old crustal material to the protoliths. The two-stage Nd model ages and zircon Hf model ages are Paleoproterozoic, indicating that the protolith sediments were derived from Paleoproterozoic crustal components.

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Nd and Pb isotope mapping of crustal domains within the Makkovik Province, Labrador

Geological Magazine ◽

10.1017/s0016756818000195 ◽

2018 ◽

Vol 156 (5) ◽

pp. 833-848 ◽

Cited By ~ 2

Author(s):

R. M. MOUMBLOW ◽

G. A. ARCURI ◽

A. P. DICKIN ◽

C. F. GOWER

Keyword(s):

Early Stage ◽

Foreland Basin ◽

Mobile Belt ◽

South American ◽

Pb Isotope ◽

Volcanic Arc ◽

Nd Isotope ◽

North American Cordillera ◽

Tectonic Model ◽

Isotope Data

AbstractThe Makkovik Province of eastern Labrador represents part of an accretionary orogen active during an early stage in the development of the Palaeoproterozoic southern Laurentian continental margin. New Nd isotope data for the eastern Makkovik Province suggest that accreted juvenile Makkovik crust was generated in the Cape Harrison domain during a single crust-forming event at c. 2.0 Ga. Pb isotope data support this model, and show a strong similarity to radiogenic crustal signatures in the juvenile Palaeoproterozoic crust of the Ketilidian mobile belt of southern Greenland. As previously proposed, an arc accretion event at c. 1.9 Ga triggered subduction-zone reversal and the development of an ensialic arc on the composite margin. After the subduction flip, a temporary release of compressive stress at c. 1.87 Ga led to the development of a retro-arc foreland basin on the downloaded Archean continental edge, forming the Aillik Group. Unlike previous models, a second arc is not envisaged. Instead, a compressive regime at c. 1.82 Ga is attributed to continued ensialic arc plutonism on the existing margin. The tectonic model for the Makkovikian orogeny proposed here is similar to that for the Ketilidian orogeny. Major- and trace-element analyses suggest that much of the magmatism in the Makkovik orogen results from post-accretionary ensialic arc activity, and that few vestiges remain of the original accreted volcanic arc. This pattern of arc accretion and intense post-accretion reworking is common to many accretionary orogens, such as the South American Andes and North American Cordillera.

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Petrogenesis and Sr-Nd isotope data of the Chadegan metabasites, Sanandaj-Sirjan Zone, Iran

Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen ◽

10.1127/njgpa/2016/0558 ◽

2016 ◽

Vol 279 (3) ◽

pp. 311-322

Author(s):

K. Akbari ◽

S.M. Tabatabaei Manesh ◽

J.F. Santos

Keyword(s):

Nd Isotope ◽

Isotope Data ◽

Sanandaj Sirjan Zone

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Sources of Ore Substance of Carbonatite Complexes of the Ural Fold Belt: Rb–Sr and Sm–Nd Isotope Data

Doklady Earth Sciences ◽

10.1134/s1028334x18060156 ◽

2018 ◽

Vol 480 (2) ◽

pp. 773-777 ◽

Cited By ~ 2

Author(s):

I. L. Nedosekova ◽

V. A. Koroteev ◽

T. B. Bayanova ◽

B. V. Belyatsky

Keyword(s):

Fold Belt ◽

Nd Isotope ◽

Isotope Data

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Sm–Nd isotope evidence of a collisional event in the Precambrian of northern Sweden

Precambrian Research ◽

10.1016/s0301-9268(98)00100-4 ◽

1999 ◽

Vol 93 (1) ◽

pp. 105-117 ◽

Cited By ~ 19

Author(s):

B Öhlander

Keyword(s):

Northern Sweden ◽

Nd Isotope ◽

Isotope Evidence

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Biologically recycled continental iron is a major component in banded iron formations

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1505515112 ◽

2015 ◽

Vol 112 (27) ◽

pp. 8193-8198 ◽

Cited By ~ 66

Author(s):

Weiqiang Li ◽

Brian L. Beard ◽

Clark M. Johnson

Keyword(s):

Continental Margin ◽

Iron Reduction ◽

Banded Iron Formations ◽

Nd Isotope ◽

Isotope Data ◽

Dissimilatory Iron Reduction ◽

Wide Scale ◽

First Time ◽

Iron Formations ◽

Marine Basin

Banded iron formations (BIFs) record a time of extensive Fe deposition in the Precambrian oceans, but the sources and pathways for metals in BIFs remain controversial. Here, we present Fe- and Nd-isotope data that indicate two sources of Fe for the large BIF units deposited 2.5 billion y ago. High-εNd and -δ56Fe signatures in some BIF samples record a hydrothermal component, but correlated decreases in εNd- and δ56Fe values reflect contributions from a continental component. The continental Fe source is best explained by Fe mobilization on the continental margin by microbial dissimilatory iron reduction (DIR) and confirms for the first time, to our knowledge, a microbially driven Fe shuttle for the largest BIFs on Earth. Detailed sampling at various scales shows that the proportions of hydrothermal and continental Fe sources were invariant over periods of 100–103 y, indicating that there was no seasonal control, although Fe sources varied on longer timescales of 105–106 y, suggesting a control by marine basin circulation. These results show that Fe sources and pathways for BIFs reflect the interplay between abiologic (hydrothermal) and biologic processes, where the latter reflects DIR that operated on a basin-wide scale in the Archean.

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