Sr–Nd isotope data of basement rocks from the northernmost argentine Precordillera and its implications for the early Paleozoic evolution of SW Gondwana margin

2014 ◽  
Vol 56 ◽  
pp. 20-29
Author(s):  
Federico Martina ◽  
Ricardo A. Astini ◽  
Marcio M. Pimentel
Keyword(s):  
Early Paleozoic ◽  
Nd Isotope ◽  
Isotope Data ◽  
Basement Rocks ◽  
Gondwana Margin ◽  
Argentine Precordillera ◽  
Sw Gondwana

Reconstructing the pre-Variscan puzzle of Cambro-Ordovician basement rocks in the southwestern European margin of Gondwana

2020 ◽  
pp. SP503-2020-89 ◽  
Author(s):  
J. Javier Álvaro ◽  
Josep Maria Casas ◽  
Cecilio Quesada
Keyword(s):  
Late Ordovician ◽  
Early Paleozoic ◽  
Preliminary Step ◽  
External Zone ◽  
Eastern Pyrenees ◽  
Basement Rocks ◽  
Gondwana Margin ◽  
Montagne Noire ◽  
Sardic Phase ◽  
Early Late

AbstractA Cambro-Ordovician palaeogeographical restoration of the southwestern European margin of Gondwana is proposed based on the relative positions of Variscan tectonostratigraphic units. Four palaeogeographical proximal–distal transects are recognized and comprise: (i) the Cantabrian, West Asturian-Leonese, Central Iberian/Central Armorican and Ossa-Morena/North Armorican zones and domains of the Iberian and Armorican massifs, respectively; (ii) the South Armorican Domain and its lateral prolongation into the Thiviers-Payzac unit and the Occitan Domain, including the transect from the Axial, southern and northern Montagne Noire, and the Albigeois-southern Cévennes unit; (iii) the southern and northern sides of the Canigó Massif in the Eastern Pyrenees; and (iv) the External Zone and the External and Internal nappes of Sardinia. Two geodynamic scenarios are recognized controlled by the presence/absence of: (i) the Furongian–Early Ordovician (Toledanian or ‘lacaune normande’) break-up unconformity across the Ossa-Morena/North Armorican and Central Iberian/Central Armorican belts; (ii) the Early–Late Ordovician (Sardic) Phase across the Occitan and Pyrenean domains and SW Sardinia; and (iii) the migration of peaks in trilobite and cinctan (echinoderm) diversity. Other similar palaeogeographical shifts are recognized in zircon provenance patterns, the occurrence of climatically sensitive subtropical facies and mineral indicators across platform–basinal transects along the Gondwana margin. This multidisciplinary framework is proposed as a preliminary step in the quest to produce more tightly constrained Early Paleozoic reconstructions along southwestern Europe.

scholarly journals Tips on the SW-Gondwana margin: Ordovician conodont-graptolite biostratigraphy of allochthonous blocks in the Rinconada mélange, Argentine Precordillera

2018 ◽  
Vol 45 (3) ◽  
pp. 399 ◽  
Author(s):  
Gustavo G. Voldman ◽  
Juan L. Alonso ◽  
Luis P. Fernández ◽  
Gladys Ortega ◽  
Guillermo L. Albanesi ◽  
...  
Keyword(s):  
Lower Devonian ◽  
Variable Number ◽  
Total Weight ◽  
Standard Laboratory ◽  
Gondwana Margin ◽  
History Of ◽  
Gravity Driven ◽  
Argentine Precordillera ◽  
Sw Gondwana ◽  
Southwestern Margin

The Rinconada Formation is a mélange that crops out in the eastern margin of the Argentine Precordillera, an exotic terrane accreted to Gondwana in Ordovician times. Its gravity-driven deposits have been studied by means of conodont and graptolite biostratigraphy, and complemented with stratigraphic analyses. 46 rock samples (85 kg total weight) were obtained from blocks of limestones and of carbonate-cemented quartz-arenites, and from limestone clasts included in conglomerate blocks and debrites. 16 of these samples were productive after standard laboratory acid procedures, yielding 561 conodont elements. The specimens occur in variable number per sample and are frequently fragmented, but they reveal the occurrence of phantom stratigraphic units in the Darriwilian of the Precordillera. Lithological and fossil evidence from the Rinconada Formation provide new constraints on the biostratigraphy, palaebiogeography and tectonostratigraphic history of the southwestern margin of Gondwana during the Ordovician to Lower Devonian times.

Origin of the Ordovician Mansehra granite in the NW Himalaya, Pakistan: constraints from Sr–Nd isotopic data, zircon U–Pb age and Hf isotopes

2018 ◽  
Vol 481 (1) ◽  
pp. 277-298 ◽  
Author(s):  
Masatsugu Ogasawara ◽  
Mayuko Fukuyama ◽  
Rehanul Haq Siddiqui ◽  
Ye Zhao
Keyword(s):  
Granitic Magma ◽  
Geochemical Data ◽  
Large Contribution ◽  
Crustal Material ◽  
Sr Isotope ◽  
Nw Himalaya ◽  
Nd Isotope ◽  
Isotope Data ◽  
Late Neoproterozoic ◽  
T Values

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.

40Ar/39Ar incremental-release ages of hornblende and biotite from Grenville basement rocks within the Indian Head Range complex, southwest Newfoundland: their bearing on Late Proterozoic – Early Paleozoic thermal history

1978 ◽  
Vol 15 (8) ◽  
pp. 1374-1379 ◽  
Author(s):  
R. D. Dallmeyer
Keyword(s):  
North America ◽  
Continental Margin ◽  
Thermal History ◽  
Structural Unit ◽  
Elevated Temperatures ◽  
Early Paleozoic ◽  
Present Position ◽  
Thermal Peak ◽  
Basement Rocks ◽  
The Times

Hornblende and biotite from autochthonous basement rocks within the Indian Head Range complex of southwest, insular Newfoundland record undisturbed 40Ar/39Ar release spectra with average total-gas ages of 880 Ma (hornblende) and 825 Ma (biotite). These gas-retention ages date the times when this segment of the western Appalachian basement terrane cooled below hornblende and biotite argon retention temperatures (~500 °C and ~300 °C respectively) following culmination of the ~ 1150–1100 Ma Grenville metamorphism. Although these results indicate that elevated temperatures were maintained for a prolonged period following the Grenville thermal peak, once initiated, cooling must have been relatively rapid because hornblende and biotite record generally similar total-gas dates.The undisturbed release spectra of minerals within the Indian Head Range complex indicate that this segment of the western Appalachian basement terrane was not affected by Paleozoic metamorphism. This is consistent with recent tectonic models that indicate that the overlying Humber Arm allochthon was emplaced into its present position as a cold, already assembled structural unit. Lack of Paleozoic metamorphism within the Indian Head basement rocks is also compatible with suggestions that the obduction site of the Bay of Islands ophiolite lay considerably east of the Early Paleozoic continental margin of North America.

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

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

2018 ◽  
Vol 156 (5) ◽  
pp. 833-848 ◽  
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.

scholarly journals Early Paleozoic accretionary orogens along the Western Gondwana margin

2021 ◽  
Vol 12 (1) ◽  
pp. 109-130 ◽  
Author(s):  
Sebastián Oriolo ◽  
Bernhard Schulz ◽  
Silvana Geuna ◽  
Pablo D. González ◽  
Juan E. Otamendi ◽  
...  
Keyword(s):  
Early Paleozoic ◽  
Gondwana Margin

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

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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