Le Complexe d'Ascot des Appalaches du sud du Québec: pétrologie et géochimie

1989 ◽  
Vol 26 (12) ◽  
pp. 2407-2420 ◽  
Author(s):  
Alain Tremblay ◽  
Réjean Hébert ◽  
Mario Bergeron
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Continental Crust ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Geochemical Composition ◽  
Basaltic Rocks ◽  
End Members ◽  
Light Rare Earth Elements ◽  
Felsic Rocks

This paper reviews new geochemical data obtained from Ordovician volcanics in the Ascot Complex of the Quebec Appalachians. The Ascot Complex is divided into three distinctive lithotectonic assemblages: the Sherbrooke, Eustis, and Stokes domains. The Sherbrooke Domain includes basalts, pyroclastic breccias, and felsic tuffs. The Eustis Domain is composed of volcanoclastic and pyroclastic rocks. The Stokes Domain is an assemblage of rhyolitic tuffs and basalts. The geochemical composition of the volcanics varies between basaltic and rhyolitic end members. Basaltic rocks are arc tholeiites (La/Yb = 0.5–2). Some basalts found in the Sherbrooke Domain show a composition very close to that of frontal-arc boninites (La/Yb = 1–2) and are depleted of rare-earth elements. Felsic rocks from the Sherbrooke Domain are poorer in light rare-earth elements (La/Yb = 0.5–0.7) than those from the Stokes Domain (La/Yb > 2). All of the felsic rocks are characterized by a negative Eu anomaly (Eu*/Eu = 1.3–3). The Stokes felsites are derived from an enriched magma contaminated by a continental crust component. The Sherbrooke Domain felsites are derived from a source impoverished in incompatible elements and enriched in high-partition-coefficient elements. Volcanic rocks from Sherbrooke and Eustis are thought to represent an incipient intra-oceanic arc. The rocks of the Stokes assemblage represent a more mature section of the same arc, explaining the contamination of generated magmas by continental crust components. The modern architecture of the Ascot Complex is essentially tectonic and may not correspond to the initial internal structure of this Ordovician arc. [Journal Translation]

Paleoproterozoic carbonatitic ultrabasic volcanic rocks (meimechites?) of Cape Smith Belt, Quebec

2001 ◽  
Vol 38 (9) ◽  
pp. 1313-1334 ◽  
Author(s):  
W RA Baragar ◽  
U Mader ◽  
G M LeCheminant
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Hydrothermal Alteration ◽  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Light Rare Earth ◽  
Shallow Marine ◽  
Incompatible Elements ◽  
Thick Lens ◽  
Light Rare Earth Elements

A 500 m-thick lens of carbonatitic ultrabasic lapilli tuffs and lavas interbedded with platformal Povungnituk sediments in the foreland of the Cape Smith Belt is its earliest known magmatism and may relate to its initial rifting. The sequence comprises tuffs capped in part by effusives. Accretionary and cored lapilli in the tuffs and pillows in the lavas suggest emplacement in a shallow marine environment. Its current assemblage of antigorite, chlorite, talc, and (in part primary?) carbonate, magnetite, ilmenite, minor chromite, and phlogopite results from probable concurrent hydrothermal alteration and subsequent greenschist regional metamorphism. Surviving accessory minerals: apatite, monazite, zircon, rutile, and aeschenite(?) are widespread but scarce. Carbonate (mostly dolomite) is a major and integral component of the rock and interpreted as an original, albeit recrystallized, magmatic constituent. Magnetite is conspicuous in the tuffs: as lapilli and lapilli cores, locally as giant crystals, and as stringers. Except in subhedral groundmass crystals, its negligible TiO2 is evidence of its hydrothermal reconstitution. Compositions of chromite cores and rare relicts of phlogopite crystals are consistent with mantle derivation. Rock compositions are low in SiO2 (<35%) and Al2O3 (<3%), high in MgO (>25 wt.%) and alkaline. The immobile incompatible elements (e.g., Zr, average 260 ppm; Nb, average 130 ppm) and the light rare-earth elements are enriched. The rocks are compositionally similar to type Siberian meimechites and closely resemble the "meimechite"–carbonatite eruptives of Castignon Lake, Labrador Trough. Based on experimental evidence, Lac Leclair magmas are interpreted as originating by minor partial melting of carbonated mantle at ~100 km depths and reaching the surface via conduits opened by deep rifting that initiated the Cape Smith segment of the Trans-Hudson Orogen.

scholarly journals Geochemistry of the Serra das Melancias Pluton in the Serra da Aldeia Suite: a classic post-collisional high Ba-Sr granite in The Riacho do Pontal Fold Belt, NE Brazil

2016 ◽  
Vol 46 (2) ◽  
pp. 221-237 ◽  
Author(s):  
Marcela Paschoal Perpétuo ◽  
Wagner da Silva Amaral ◽  
Felipe Grandjean da Costa ◽  
Evilarde Carvalho Uchôa Filho ◽  
Daniel Francisco Martins de Sousa
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Geochemical Data ◽  
Fold Belt ◽  
Heavy Rare Earth ◽  
Pan African ◽  
High K ◽  
Heavy Rare Earth Elements ◽  
Brasiliano Orogeny ◽  
Light Rare Earth Elements

ABSTRACT: The Serra da Aldeia Suite is composed by circular or oval-shaped plutons, intrusive in meta-sedimentary and meta-volcanosedimentary rocks in the Riacho do Pontal Fold Belt, NE Brazil. The Serra das Melancias Pluton, belonging to Serra da Aldeia Suite, is located southeastern of Piaui state, near Paulistana city. These plutons represent a major magmatic expression in this area and contain important information about the late magmatic/collisional geologic evolution of the Brasiliano Orogeny. Based on petrographic and geochemical data, three facies were defined in the Serra das Melancias Pluton: granites, syenites and quartz monzonites. The rocks display high-K and alkaline to shoshonitic affinities, are metaluminous and show ferrous character. They are enriched in Light Rare Earth Elements and Large Ion Lithophile Elements, with negative anomalies in Nb, Ta and Ti. Their high Ba, Sr, K/Rb, low Rb, relatively low U, Th, Nb to very low Heavy Rare Earth Elements and Y resemble those of typical high Ba-Sr granitoids. The geochemical data suggest the emplacement of Serra das Melancias Pluton in a transitional, late to post-orogenic setting in the Riacho do Pontal Fold Belt during the late Brasiliano-Pan African Orogeny.

Geochemistry of two metavolcanic arc suites from the Central Metasedimentary Belt of the Grenville Province, southeastern Ontario, Canada

1991 ◽  
Vol 28 (9) ◽  
pp. 1429-1443 ◽  
Author(s):  
Luc Harnois ◽  
John M. Moore
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Trace Element ◽  
Partial Melting ◽  
Volcanic Rocks ◽  
Parental Magma ◽  
Major Elements ◽  
Grenville Province ◽  
Element Abundances ◽  
Felsic Rocks

Samples of two subalkaline metavolcanic suites, the Tudor formation (ca. 1.28 Ga) and the overlying Kashwakamak formation, have been analysed for major elements and 27 trace elements (including rare-earth elements). The Tudor formation is tholeiitic and contains mainly basaltic flows, whereas the Kashwakamak formation is calc-alkaline and contains mainly andesitic rocks with minor felsic rocks. The succession has been regionally metamorphosed to upper greenschist – lower amphibolite facies. Trace-element abundances and ratios indicate that rocks of the Tudor and Kashwakamak formations are island-arc type. Geochemical modelling using rare-earth elements, Zr, Ti, and Y indicates that the Tudor volcanic rocks are not derived from a single parental magma through simple fractional crystallization. Equilibrium partial melting of a heterogeneous Proterozoic upper mantle can explain the trace-element abundances and ratios of Tudor formation volcanic rocks. The intermediate to felsic rocks of the Kashwakamak formation appear to have been derived from a separate partial melting event. The data are consistent with an origin of the arc either on oceanic crust or on thinned continental crust, and with accretion of the arc to a continental margin between the time of extrusion of Tudor volcanic rocks and that of Kashwakamak volcanic rocks.

Petrological and geodynamic evolution of the Late Cretaceous subduction-related volcanism in the eastern Sakarya Zone, NE Turkey

2020 ◽  
Author(s):  
Simge Oğuz Saka ◽  
Faruk Aydin ◽  
Cüneyt Şen ◽  
Abdurrahman Dokuz ◽  
Thomas Aiglsperger ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Spinel Lherzolite ◽  
Volcanic Event ◽  
Geochemical Composition ◽  
Basaltic Rocks ◽  
Rock Types ◽  
Sakarya Zone ◽  
Felsic Volcanic

&lt;p&gt;Based on the volcanostratigraphic studies, zircon U-Pb dating and geochemical data, the Late Cretaceous volcanic rocks (LCVs) from the Artvin region in the eastern Sakarya zone (NE Turkey) consist of mafic/basaltic (S1-&amp;#199;atak and S2-&amp;#199;a&amp;#287;layan) and felsic/acidic (S1-K&amp;#305;z&amp;#305;lkaya and S2-Tirebolu) rock types that occurred in two successive stages: (i) first stage (S1: Turonian to Early Santonian) and (ii) second stage (S2: Late Santonian to Campanian). In both stages, the basaltic rocks contain generally calcic plagioclase and lesser augite crystals, whereas the acidic samples commonly contain quartz, sodic plagioclase and K-sanidine phenocrysts. Data from clinopyroexene thermobarometry point to the S2-&amp;#199;a&amp;#287;layan basaltic rocks having crystallised at higher temperatures and under deeper crustal conditions (T = 1128 &amp;#177; 15 &lt;sup&gt;o&lt;/sup&gt;C, P = 6.5 &amp;#177; 0.7 kbar and D = 19.5 &amp;#177; 2.1 km) than those of the S1-&amp;#199;atak rocks (T = 1073 &amp;#177; 11 &lt;sup&gt;o&lt;/sup&gt;C, P = 2.2 &amp;#177; 1.0 kbar, D = 6.6 &amp;#177; 3.0 km).&lt;/p&gt;&lt;p&gt;The LCVs show a wide compositional spectrum, ranging from tholeiite to calc-alkaline/shoshonite and are typically represented by a geochemical composition resembling subduction-related arc rocks although the &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr&lt;sub&gt;(i)&lt;/sub&gt; (0.7044&amp;#8211;0.7071) and &amp;#603;Nd&lt;sub&gt;(i)&lt;/sub&gt; values (-0.63 to +3.47) as well as &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb&lt;sub&gt;(i)&lt;/sub&gt; (18.07 to 18.56), &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb&lt;sub&gt;(i)&lt;/sub&gt; (15.57 to 15.62) and &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb&lt;sub&gt;(i)&lt;/sub&gt; (37.12 to 38.55) ratios show very limited variation. The average &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O isotope values of the S1-K&amp;#305;z&amp;#305;lkaya (5.3 &amp;#177; 0.5&amp;#8240;) and S2-Tirebolu (4.9 &amp;#177; 0.8&amp;#8240;) zircons are quite consistent with average mantle values (5.3 &amp;#177; 0.3&amp;#8240;). The similar isotopic compositions of the studied mafic and felsic volcanic rocks, and the relatively high Mg# values (up to 0.4&amp;#8211;0.51) of the felsic samples indicate a cogenetic origin. The parent magmas of the S1-&amp;#199;atak and S2-&amp;#199;a&amp;#287;layan mafic volcanic rocks were derived from underplated basaltic melts that originated by partial melting of metasomatised spinel lherzolite and spinel-garnet lherzolite, respectively. It is proposed that the compositions of the S1-K&amp;#305;z&amp;#305;lkaya (mainly dacitic) and S2-Tirebolu (rhyolitic to trachytic) felsic rocks were particularly controlled by metasomatised mantle&amp;#8211;crust interaction and MASH zone plus shallow crustal fractionation processes.&lt;/p&gt;&lt;p&gt;Our data, together with data from previous studies, suggest that the S1- and S2-mafic and felsic rock types of the LCVs (~95&amp;#8211;75 Ma) are the products of two-stage volcanic event that took place during the northward subduction of the northern Neotethys Ocean.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Acknowledgement&lt;/p&gt;&lt;p&gt;This study was financially supported by Scientific and Technological Research Council of Turkey (TUBITAK) with grant# 112Y365.&lt;/p&gt;

scholarly journals Vulcânicas potássicas intemperizadas como protólitos dos filitos hematíticos da Serra do Espinhaço Meridional (Minas Gerais)

2020 ◽  
Vol 34 (2) ◽  
pp. 183-194
Author(s):  
Alexandre Chaves ◽  
Luiz Knauer
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Volcanic Rocks ◽  
Alkaline Rock ◽  
Major Elements ◽  
Volcanic Origin ◽  
Espinhaço Range ◽  
Weathering Processes ◽  
Igneous Layering ◽  
Hematitic Phyllite

The hematitic phyllite is a rock that occurs in the São João da Chapada and Sopa-Brumadinho formations of the southern Espinhaço range. Its origin is widely discussed in papers on Espinhaço, but there is no consensus on its protolith due to certain characteristics of the lithotype, such as its chemical composition and textural features. The pattern of rare earth elements strongly enriched [(La/Yb)N 6.80-17.68], with light rare earth elements [(La/Sm)N 2.54-4.83] richer than heavy ones [(Gd/Yb)N 1.28-3,32], suggests that the protolith was an alkaline volcanic rock formed during the rift that generated the Espinhaço basin. The major elements indicate that the alkaline rock met weathering processes, becoming a regolith. During the Brasiliano metamorphism, it finally became hematitic phyllite. Other characteristics of the lithotype, such as the presence of sericite-bearing rounded parts (possibly formed by alteration and deformation of leucite crystals) and the preservation of igneous layering, suggest a potassic volcanic origin for hematitic phyllite. In diagram that allows identifying altered and metamorphic volcanic rocks, the investigated samples have composition similar to a feldspathoid-rich alkali-basalt, probably a leucite tephrite, a leucitite or even a lamproite, rocks from mantle source.

scholarly journals Geochemical features and formation conditions of Early-Devonian cherty-argillaceous shales and the underlying basalts in the Ishkildino section (eastern slope of the Southern Urals)

LITOSFERA ◽  
2019 ◽  
pp. 30-47
Author(s):  
A. M. Fazliakhmetov
Keyword(s):  
Volcanic Rocks ◽  
Southern Urals ◽  
Geochemical Data ◽  
Upper Ordovician ◽  
The Southern Urals ◽  
Geochemical Composition ◽  
Early Devonian ◽  
Ocean Ridges ◽  
Clay Shales ◽  
Conodont Zone

Research subject.The West Magnitogorsk zone of the Southern Urals in the vicinity of the Ishkildino village features a subaerially exposed basaltic sequence superposed by cherts and siliceous-clay shales. The basalts and the overlying shales are assumed to have formed during the Ordovician and Silurian (?)–Early Devonian (up to the conodont zone excavates inclusive) periods, respectively. The aim of this research was to reconstruct, using geochemical data, the conditions under which the rocks present in this geological location were formed.Materials and methods. Five samples of the basalts (XRD and ICP-MS methods), 27 samples of the siliceous-clay shales and 10 samples of the cherts (XRD and ICP-AES methods) were analyzed.Results.According to the ratio of SiO2, Na2O and K2O, the volcanic rocks from the lower part of the section are represented by basalts and trachybasalts. Their geochemical composition corresponds to the N-MORB and is established to be similar to that of the basalts in the Polyakovskaya formation (the Middle–Upper Ordovician). In terms of main elements, the shales under study consist of quartz and illite with a slight admixture of organic matter, goethite, quartzfeldspar fragments, etc. The degree of the sedimentary material weathering according to the CIA, CIW and ICV index values is shown to be moderate. The values of Strakhov’s and Boström’s moduli correspond to sediments without the admixture of underwater hydrothermal vent products. The values of Cr/Al, V/Al and Zr/Al correspond to those characteristic of deposits in deep-water zones remote from the coasts of passive and active continental margins, basalt islands and areas adjacent to mid-ocean ridges. For most samples, the values of Ni/Co, V/Cr, Mo/Mn are typical of deposits formed under oxidative conditions. However, several samples from the upper part of the section, which is comparable to the kitabicus and excavatus conodont zones, demonstrate the Ni/Co, V/Cr, and Mo/Mn values corresponding to deposits formed under reducing atmospheres. An assumption is made that the existence of these deposits can be associated with the Bazal Zlichov event.Conclusion.The investigated pre-Emsian shales have shown no signs of volcanic activity in the adjacent areas. The studied deposits are established to correspond to the central part of the Ural Paleoocean.

Depletion of light rare-earth elements in felsic magmas

Geology ◽  
1982 ◽  
Vol 10 (3) ◽  
pp. 129 ◽  
Author(s):  
Calvin F. Miller ◽  
David W. Mittlefehldt
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Light Rare Earth ◽  
Light Rare Earth Elements

Petrogenesis of the Upper Cretaceous volcanism in the Kefken region, Western Pontides, NW Turkey

2021 ◽  
Author(s):  
Turgut Duzman ◽  
Ezgi Sağlam ◽  
Aral I. Okay
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Early Eocene ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Elements ◽  
Cretaceous Volcanism ◽  
Oceanic Slab

&lt;p&gt;The Upper Cretaceous volcanic and volcaniclastic rocks crop out along the Black Sea coastline in Turkey. They are part of a magmatic arc that formed as a result of northward subduction of the Tethys ocean beneath the southern margin of Laurasia. The lower part of the Upper Cretaceous volcanism in the Kefken region, 100 km northeast of Istanbul, is represented by basaltic andesites, andesites, agglomerates and tuffs, which have yielded Late Cretaceous (Campanian, ca. 83 Ma) U-Pb zircon ages. The volcanic and volcanoclastic rocks are stratigraphically overlain by shallow to deep marine limestones, which range in age from Late Campanian to Early Eocene.&amp;#160; Geochemically, basaltic andesites and andesites display negative anomalies in Nb, Ta and Ti, enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). Light rare earth elements (LREE) show slightly enrichment relative to heavy rare earth elements (La&lt;sub&gt;cn&lt;/sub&gt;/Yb&lt;sub&gt;cn&lt;/sub&gt; =2.51-3.63) and there are slight negative Eu anomalies (Eu/Eu* = 0.71-0.95) in basaltic andesite and andesite samples. The geochemical data indicate that Campanian volcanic rocks were derived from the partial melting of the mantle wedge induced by hydrous fluids released by dehydration of the subducted oceanic slab.&lt;/p&gt;&lt;p&gt;There is also a horizon of volcanic rocks, about 230 m thick, within the Late Campanian-Early Eocene limestone sequence.&amp;#160; This volcanic horizon, which consists of pillow basalts, porphyritic basalts,&amp;#160; andesites and dacites, is of Maastrichtian age based on paleontological data from the intra-pillow sediments and U-Pb zircon ages from the andesites and dacites (72-68 Ma).&amp;#160; The Maastrichtian andesites and dacites are geochemically distinct from the Campanian volcanic rocks. They show distinct adakite-like geochemical signatures with high ratios of Sr/Y (&gt;85.5), high La&lt;sub&gt;cn&lt;/sub&gt;/Yb&lt;sub&gt;cn &lt;/sub&gt;(16.4-23.7) ratios, low content of Y (7.4-8.6 ppm) and low content of heavy rare-earth elements (HREE). The adakitic rocks most probably formed as a result of partial melting of the subducting oceanic slab under garnet and amphibole stable conditions.&lt;/p&gt;&lt;p&gt;The Upper Cretaceous arc sequence in the Kefken region shows a change from typical subduction-related magmas to adakitic ones, accompanied by decrease in the volcanism.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Recycling and substitution of light rare earth elements, cerium, lanthanum, neodymium, and praseodymium from end-of-life applications - A review

2019 ◽  
Vol 236 ◽  
pp. 117573 ◽  
Author(s):  
Linda Omodara ◽  
Satu Pitkäaho ◽  
Esa-Matti Turpeinen ◽  
Paula Saavalainen ◽  
Kati Oravisjärvi ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
End Of Life ◽  
Light Rare Earth ◽  
Light Rare Earth Elements
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