scholarly journals An Early Ordovician tonalitic–granodioritic belt along the Schistose-Greywacke Domain of the Central Iberian Zone (Iberian Massif, Variscan Belt)

2012 ◽  
Vol 149 (5) ◽  
pp. 927-939 ◽  
Author(s):  
A. RUBIO-ORDÓÑEZ ◽  
P. VALVERDE-VAQUERO ◽  
L. G. CORRETGÉ ◽  
A. CUESTA-FERNÁNDEZ ◽  
G. GALLASTEGUI ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Variscan Belt ◽  
Iberian Massif ◽  
Calc Alkaline ◽  
Central Iberian Zone ◽  
Magmatic Arc ◽  
Early Ordovician ◽  
Icp Ms ◽  
Continental Magmatic Arc

AbstractThe Zarza la Mayor and Zarza de Montánchez tonalites and Arroyo de la Luz granodiorite are part of a tonalitic–granodioritic belt located along the Schistose-Greywacke Domain of the Central Iberian Zone. These intrusions are also part of the Central Extremadura Batholith, a set of plutons ranging from tonalite to leucogranite that have been considered a prime example of Variscan syn-kinematic plutonism. New LA-ICP-MS and CA-ID-TIMS U–Pb dating reveals that the Zarza la Mayor tonalite–granodiorite is an Early Ordovician intrusion. The LA-ICP-MS data show that there is an absence of inherited cores, despite some complex internal zoning with obvious resorption features in some of the zircon crystals. Dating of monazite and zircon by CA-ID-TIMS provides a concordant age of 478.1 ± 0.8 Ma. This age coincides with electron microprobe analysis (EMPA) monazite chemical ages for the Zarza de Montánchez (482 ± 10 Ma) and Arroyo de la Luz (470 ± 15 Ma) intrusions. These new data indicate the presence of an Early Ordovician belt of calc-alkaline tonalite–granodiorite in the Schistose-Greywacke Domain – the Beira Baixa–Central Extremadura tonalite–granodiorite belt – which resembles a continental magmatic arc. This belt is contemporaneous with the Ollo de Sapo magmatic event further north in the Central Iberian Zone.

scholarly journals The Tres Arroyos Granitic Aplite-Pegmatite Field (Central Iberian Zone, Spain): Petrogenetic Constraints from Evolution of Nb-Ta-Sn Oxides, Whole-Rock Geochemistry and U-Pb Geochronology

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1008
Author(s):  
Idoia Garate-Olave ◽  
Encarnación Roda-Robles ◽  
Pedro Pablo Gil-Crespo ◽  
Alfonso Pesquera ◽  
Jon Errandonea-Martin
Keyword(s):  
Mineral Chemistry ◽  
Variscan Orogeny ◽  
P Availability ◽  
Iberian Massif ◽  
Rock Composition ◽  
Central Iberian Zone ◽  
Icp Ms ◽  
Complete Study ◽  
Single Path ◽  
Tres Arroyos

Abundant Li-Cs-Ta aplite-pegmatite dykes were emplaced in the western Central Iberian Zone of the Iberian Massif during the Variscan Orogeny. Their origin and petrogenetic relationships with the widespread granitoids have led to a currently rekindled discussion about anatectic vs. granitic origin for the pegmatitic melts. To deal with these issues, the aplite-pegmatite dykes from the Tres Arroyos area, which constitute a zoned pegmatitic field related to the Nisa-Alburquerque granitic batholith, have been studied. This work comprises a complete study of Nb-Ta-Sn oxides’ mineralogy, whole-rock geochemistry, and U-Pb geochronology of the aplite-pegmatites that have been grouped as barren, intermediate, and Li-rich. The most abundant Nb-Ta-Sn oxides from Tres Arroyos correspond to columbite-(Fe), columbite-(Mn) and cassiterite. Niobium-Ta oxides show a marked increase in the Mn/(Mn+Fe) ratio from the barren aplite-pegmatites up to the Li-rich bodies, whereas variations in the Ta/(Ta+Nb) ratio are not continuous. The probable factors controlling fractionation of Mn/Fe and Ta/Nb reflected in Nb-Ta oxides may be attributed to the crystallization of tourmaline, phosphates and micas. The lack of a progressive Ta/Nb increase with the fractionation may be also influenced by the high F and P availability in the parental pegmatitic melts. Most of the primary Nb-Ta oxides would have crystallized by punctual chemical variations in the boundary layer, whereas cassiterite formation would be related to an undercooling of the system. Whole-rock composition of the distinguished lithotypes reflects similar tendencies to those observed in mineral chemistry, supporting a single path of fractional crystallization from the parental Nisa-Alburquerque monzogranite up to the most evolved Li-rich aplite-pegmatites. The age of 305 ± 9 Ma, determined by LA-ICP-MS U-Pb dating of columbite-tantalite oxides, reinforces the linkage of the studied aplite-pegmatites and the cited parental monzogranite.

scholarly journals Constraints on the crustal structure of the internal Variscan Belt in SW Europe: A magnetotelluric transect along the eastern part of Central Iberian Zone, Iberian Massif

2011 ◽  
Vol 116 (B2) ◽  
Author(s):  
Jaume Pous ◽  
David Martínez Poyatos ◽  
Wiebke Heise ◽  
Fernando Monteiro Santos ◽  
Jesús Galindo-Zaldívar ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Variscan Belt ◽  
Iberian Massif ◽  
Central Iberian Zone

Geochronology and geochemistry of the Pola de Allande granitoids (northern Spain): their bearing on the Cadomian-Avalonian evolution of northwest Iberia

1998 ◽  
Vol 35 (12) ◽  
pp. 1439-1453 ◽  
Author(s):  
Javier Fernández-Suárez ◽  
Gabriel Gutiérrez-Alonso ◽  
George A Jenner ◽  
Simon E Jackson
Keyword(s):  
Inductively Coupled Plasma ◽  
Trace Element Composition ◽  
Variscan Belt ◽  
Calc Alkaline ◽  
Northern Spain ◽  
Isotopic Signatures ◽  
Magmatic Arc ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Northwest Iberia

The Pola de Allande pre-Variscan tonalite-granodiorite plutons are located in the Narcea Antiform, at the boundary zone between the Cantabrian and west Asturian Leonese zones of the Iberian Variscan belt. These granitoids were intruded into a Neoproterozoic siliciclastic sedimentary sequence with subordinate volcanic intercalations and were subsequently overprinted by Variscan thrust-related shear deformation. U-Pb laser ablation inductively coupled plasma - mass spectrometry (ICP-MS) dating of zircons from two plutons yielded concordant ages of intrusion of 605 ± 10 and 580 ± 15 Ma. To the authors' knowledge, this is the first reported U-Pb Cadomian-Avalonian age for igneous rocks in this section of the Iberian Variscan belt. These intrusions are coeval with the main episode of dominantly calc-alkaline magmatic activity related to Cadomian-Avalonian subduction. Major and trace element composition of the granitoids is characteristic of I-type high-K calc-alkaline granitoids generated in continental arc settings, and are comparable to those of coeval granitoids in other areas of the Cadomian-Avalonian belt. Sr and Nd isotopic signatures indicate that the genesis of the Pola de Allande granitoids involved either mixing of mantle melts of Cadomian extraction with an older enriched crust (Eburnean-Icarthian, i.e., ca. 2 Ga old crust) or melting of a mafic infracrustal protolith with a Grenville age (ca. 1.2 Ga) mantle extraction. The Neoproterozoic sediments, hosting the Pola de Allande granitoids and present in large areas of northwest Iberia, may represent the back-arc basin of the subduction complex in which the Avalon composite terrane constituted the main magmatic arc.

scholarly journals Ortoneises en la Franja Silos-Babega, Macizo de Santander, Colombia: evidencias de la orogenia famatiniana en los Andes del norte

2017 ◽  
Vol 44 (3) ◽  
pp. 307 ◽  
Author(s):  
Carlos Alberto García-Ramírez ◽  
Vanessa Rey León ◽  
Víctor Alejandro Valencia
Keyword(s):  
Amphibolite Facies ◽  
Crustal Melting ◽  
Magmatic Arc ◽  
Metamorphic Peak ◽  
The North ◽  
Colombian Andes ◽  
Icp Ms ◽  
Continental Magmatic Arc

The Orthogneiss unit in the Santander Massif, Northern Colombian Andes, mainly consists of quartzfeldspathic, pelitic and minor mafic orthogneisses and amphibolites. Petrographic, geochemical and geochronological studies carried out on orthogneisses from the Silos-Babega belt, indicate that they are granodioritic and granitic in composition with protolith formed by crustal melting in an active continental magmatic arc. They were syntectonically emplaced in the Silgara Schists unit. Metamorphic peak of the Orthogneiss unit reach amphibolite facies conditions in the range of 4.3-10 kbar in pressure and 540-690 °C in temperature. Zircon U-Pb LA-ICP-MS ages of 471±11 and 479±10 Ma were obtained and these ages are similar to those known for the Orthogneiss unit in the central and the eastern Santander Massif and confirm the continuity to the north of the Andean protomargin as a result of the Famatinian orogeny.

Topaz as an important host for Ge in granites and greisens

2013 ◽  
Vol 77 (4) ◽  
pp. 403-417 ◽  
Author(s):  
K. Breiter ◽  
N. Gardenová ◽  
T. Vaculovič ◽  
V. Kanický
Keyword(s):  
Mass Spectrometry ◽  
Trace Elements ◽  
Inductively Coupled Plasma ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
Important Host ◽  
Ga Content

AbstractThe composition of topaz from different granites and greisen in the Krušné Hory/Erzgebirge area was investigated using electron microprobe analysis (EMPA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). All topaz grains are rich in F (17.9 19.8 wt.%, 1.73 1.90 a.p.f.u.) and the most important minor/trace elements are P, Ge and Ga. Contents of P up to 1 wt.% P2O5 (0.025 a.p.f.u.) were found in topaz from the strongly peraluminous P-rich magmatic systems at Podlesí. Regardless of genetic type, topaz from granites typically contains 50 100 ppm Ge. The greatest amounts (up to 204 ppm Ge) were found in topaz from quartz-topaz-apatite greisen in Krásno. In fractionated granites and greisens, topaz is calculated to contain 23 87% of the bulk Ge content in the rock. In contrast, topaz does not concentrate Ga. The Ga content of topaz (typically 5 35 ppm in S-type granites, <10 ppm Ga in A-type granites) is usually smaller than the bulk Ga content of the rock. In addition, up to 16 ppm Sc, 23 ppm Sn and >400 ppm Fe may be present.

Melt-enhanced deformation during emplacement of gabbro and granodiorite in the Sunnhordland Batholith, west Norway

1991 ◽  
Vol 128 (3) ◽  
pp. 207-226 ◽  
Author(s):  
Torgeir B. Andersen ◽  
Peter Nielsen ◽  
Erling Rykkelid ◽  
Hanne Sølna
Keyword(s):  
Internal Structure ◽  
Shear Zones ◽  
Island Arc ◽  
Upper Crust ◽  
Calc Alkaline ◽  
Magmatic Arc ◽  
Plate Convergence ◽  
Relative Age ◽  
Early Ordovician ◽  
Partial Melts

AbstractThe Caledonian Sunnhordland Batholith comprises calc-alkaline plutons that have been assigned to three units according to their relative age and composition: a gabbro-diorite unit, a granodiorite unit and a later granodiorite-granite unit. The batholith was emplaced into an envelope including ophiolite and island-arc complexes, sediments and volcanites of early Ordovician age that were developed in a zone of plate convergence. Continued convergence resulted in the formation of a mature magmatic arc and a thickened crust; the late granitoids (unit 3), which commenced their crystallization at pressures around 6 to 7 kb, rose as permitted diapiric intrusions. The ingress and ascent of the magmas in this setting is considered to have been facilitated by the presence of major shear zones developed in relation to plate convergence. In this model, plastic instabilities were formed in an otherwise elastic middle and upper crust. Non-coaxial deformation was accelerated by the emplacement of magmas and the formation of abundant partial melts in water-rich sediments of the envelope. The deformation, which was accelerated by magma and melt lubrication in aureoles, controlled both the shape and internal structure in the gabbro and granodiorite plutons.

U–Pb geochronology of a Paleoproterozoic continental magmatic arc on the western margin of the Archean Nain craton, northern Labrador, Canada

1995 ◽  
Vol 32 (11) ◽  
pp. 1870-1882 ◽  
Author(s):  
David J. Scott
Keyword(s):  
Shear Zone ◽  
Calc Alkaline ◽  
Western Margin ◽  
Magmatic Arc ◽  
Eastern Margin ◽  
Two Samples ◽  
Plutonic Rocks ◽  
Continental Magmatic Arc

The Paleoproterozoic Torngat Orogen, in northernmost Labrador and northeastern Quebec, records the collision between the western margin of the Nain Province and the eastern margin of the Rae Province. Six samples from a suite of calc-alkaline plutonic rocks that intrude the Nain craton have been dated using the U–Pb method at 1895 ± 2, 1888 ± 2, [Formula: see text], 1885 ± 2 (two samples), and >1859 Ma, and support the interpretation that east-dipping subduction occurred below the Nain craton during this interval. A granitic dyke that truncates the sinistral shear fabric in the Abloviak shear zone is 1824 ± 2 Ma, placing a younger limit on the timing of this deformation in the area. A second granitic dyke, emplaced synchronously with dextral deformation in the bend in the Abloviak shear zone, is 1798 ± 3 Ma. A model is proposed in which subduction occurred beneath the Nain craton along its entire exposed length from 1.91 to 1.86 Ga, and collision occurred between 1.86 and 1.84 Ga, followed by oblique uplift of the southern part of the Rae craton from 1.80 to 1.71 Ga.

Scanning Electron Microscopy and Electron Microprobe Analysis of Malignant Cell Cultures

1968 ◽  
Vol 26 ◽  
pp. 164-165
Author(s):  
R. I. Johnsson-Hegyeli ◽  
A. F. Hegyeli ◽  
D. K. Landstrom ◽  
W. C. Lane
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Cultures ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Three Dimensional ◽  
Malignant Cell ◽  
Interference Microscopy ◽  
Scanning Electron

Last year we reported on the use of reflected light interference microscopy (RLIM) for the direct color photography of the surfaces of living normal and malignant cell cultures without the use of replicas, fixatives, or stains. The surface topography of living cells was found to follow underlying cellular structures such as nuceloli, nuclear membranes, and cytoplasmic organelles, making possible the study of their three-dimensional relationships in time. The technique makes possible the direct examination of cells grown on opaque as well as transparent surfaces. The successful in situ electron microprobe analysis of the elemental composition and distribution within single tissue culture cells was also reported.This paper deals with the parallel and combined use of scanning electron microscopy (SEM) and the two previous techniques in a study of living and fixed cancer cells. All three studies can be carried out consecutively on the same experimental specimens without disturbing the cells or their structural relationships to each other and the surface on which they are grown. KB carcinoma cells were grown on glass coverslips in closed Leighto tubes as previously described. The cultures were photographed alive by means of RLIM, then fixed with a fixative modified from Sabatini, et al (1963).

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