Quelques aspects pétrographiques et géochimiques du volcanisme archéen du Malartic en Abitibi (Province du Québec, Canada)

1979 ◽  
Vol 16 (5) ◽  
pp. 1041-1059 ◽  
Author(s):  
C. Alsac ◽  
M. Latulippe
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Major Elements ◽  
The Other ◽  
Island Arcs ◽  
Calc Alkaline ◽  
Fine Grained ◽  
Geochemical Study ◽  
Group A ◽  
Copper Zinc

The Archean metavolcanic formations of the Malartic Group in Abitibi, northwestern Quebec (Canada), are several kilometres thick and made up of lavas and pyroclastic rocks, a large part of which are of submarine origin with pillows and hyaloclastites.The mafic phases, with ultramafic material (komatiites), dominate at the base of the unit, the felsitic flows and other derived material, locally associated with copper and zinc sulphides, are located towards the summit of the unit.The regional metamorphism of greenschist and locally amphibolite–almandine facies, has destroyed the magmatic paragenesis; on the other hand, the original textures and structures are generally well preserved.A geochemical study of major elements was carried out on 67 well chosen fine-grained lavas. These were retained for analysis after thin section examination showed them to be nonporphyritic, homogeneous, with a minimum of alteration, and a lack of secondary fillings of amygdales and microfissures. This study led to the following conclusions:(1) The original composition of the volcanic rocks of the Malartic Group is still identifiable in spite of the modification in the content of Na, K, Ca, S, H2O, CO2 and to a lesser degree of Mg and Fe.(2) The variable percentages, generally high in Na and low in K, give to this volcanic group a spilitic characteristic; this may simply be an accentuation of an original tendency for series poor in K.(3) Apart from the ultramafic flows and certain magnesian basalts for which a komatiitic relationship is considered, the Malartic volcanism has magmatic characteristics comparable to those of volcanic island arcs. It begins with dominantly mafic extrusions with a tholeiitic composition poor in K. It continues in the upper Malartic with eruptions in which felsitic phases, locally associated with copper–zinc mineralization, become more abundant; these products seem to belong to two different magmatic series: one tholeiitic, the other calc-alkaline, both poor in K. The phases of these two magmatic series are spatially tightly imbricated.

scholarly journals Mineralogical and Fluid Inclusions Study of Epithermal Type Veins Intruding the Volcanic Rocks of the Kornofolia Area, Evros, NE Greece.

2019 ◽  
Vol 55 (1) ◽  
pp. 202
Author(s):  
Foteini Aravani ◽  
Lambrini Papadopoulou ◽  
Vasileios Melfos ◽  
Triantafillos Soldatos ◽  
Triantafillia Zorba ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fluid Inclusion ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Volcanic Rocks ◽  
The Other ◽  
Calc Alkaline ◽  
Ft Ir ◽  
Host Rocks

The volcanic rocks of Kornofolia area, Evros, host a number of epithermal-type veins. The host rocks are Oligocene calc-alkaline andesites to rhyo-dacites. The andesites form hydrothermal breccias and show hydrothermal alteration. The veins comprise mainly silica polymorphs such as quartz, chalcedony and three types of opal (milky white, transparent and green). Amethyst also forms in veins at the same area. Apart from the silica polymorphs, the veins are accompanied by calcite and zeolites. The main aim of this study is the characterization of the silica polymorphs. Using FT-IR analyses, variations in the crystal structure of the three opals were recognized. The green opal is found to be more amorphous than the other two types. Fluid-inclusion measurements were performed in calcite and were compared with amethyst from previous studies. The Th is between 121-175 °C and the Te between -22.9 and -22.4 °C. The salinities range from 0.9 to 4.5 wt % NaCl equiv.

Tectono-stratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean Orogen

1989 ◽  
Vol 26 (10) ◽  
pp. 2145-2158 ◽  
Author(s):  
P. K. Sims ◽  
W. R. Van Schmus ◽  
K. J. Schulz ◽  
Z. E. Peterman
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Volcanic Rocks ◽  
Alkali Feldspar ◽  
Suture Zone ◽  
Island Arcs ◽  
Calc Alkaline ◽  
The South ◽  
Early Proterozoic ◽  
Felsic Volcanic

The Early Proterozoic Penokean Orogen developed along the southern margin of the Archean Superior craton. The orogen consists of a northern deformed continental margin prism overlying an Archean basement and a southern assemblage of oceanic arcs, the Wisconsin magmatic terranes. The south-dipping Niagara fault (suture) zone separates the south-facing continental margin from the accreted arc terranes. The suture zone contains a dismembered ophiolite.The Wisconsin magmatic terranes consist of two terranes that are distinguished on the basis of lithology and structure. The northern Pembine–Wausau terrane contains a major succession of tholeiitic and calc-alkaline volcanic rocks deposited in the interval 1860–1889 Ma and a more restricted succession of calc-alkaline volcanic rocks deposited about 1835 – 1845 Ma. Granitoid rocks ranging in age from about 1870 to 1760 Ma intrude the volcanic rocks. The older succession was generated as island arcs and (or) closed back-arc basins above the south-dipping subduction zone (Niagara fault zone), whereas the younger one developed as island arcs above a north-dipping subduction zone, the Eau Pleine shear zone. The northward subduction followed deformation related to arc–continent collision at the Niagara suture at about 1860 Ma. The southern Marshfield terrane contains remnants of mafic to felsic volcanic rocks about 1860 Ma that were deposited on Archean gneiss basement, foliated tonalite to granite bodies ranging in age from about 1890 to 1870 Ma, and younger undated granite plutons. Following amalgamation of the two arc terranes along the Eau Pleine suture at about 1840 Ma, intraplate magmatism (1835 Ma) produced rhyolite and anorogenic alkali-feldspar granite that straddled the internal suture.

Lithogeochemistry of volcano-plutonic assemblages of the southern Hanson Lake Block and southeastern Glennie Domain, Trans-Hudson Orogen: evidence for a single island arc complex

1999 ◽  
Vol 36 (2) ◽  
pp. 209-225 ◽  
Author(s):  
Ralf O Maxeiner ◽  
Tom II Sibbald ◽  
William L Slimmon ◽  
Larry M Heaman ◽  
Brian R Watters
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Oceanic Island ◽  
Island Arc ◽  
Island Arcs ◽  
Calc Alkaline ◽  
East Central ◽  
South Central ◽  
Volcaniclastic Rocks ◽  
Flin Flon

This paper describes the geology, geochemistry, and age of two amphibolite facies volcano-plutonic assemblages in the southern Hanson Lake Block and southeastern Glennie Domain of the Paleoproterozoic Trans-Hudson Orogen of east-central Saskatchewan. The Hanson Lake assemblage comprises a mixed suite of subaqueous to subaerial dacitic to rhyolitic (ca. 1875 Ma) and intercalated minor mafic volcanic rocks, overlain by greywackes. Similarly with modern oceanic island arcs, the Hanson Lake assemblage shows evolution from primitive arc tholeiites to evolved calc-alkaline arc rocks. It is intruded by younger subvolcanic alkaline porphyries (ca. 1861 Ma), synvolcanic granitic plutons (ca. 1873 Ma), and the younger Hanson Lake Pluton (ca. 1844 Ma). Rocks of the Northern Lights assemblage are stratigraphically equivalent to the lower portion of the Hanson Lake assemblage and comprise tholeiitic arc pillowed mafic flows and felsic to intermediate volcaniclastic rocks and greywackes, which can be traced as far west as Wapawekka Lake in the south-central part of the Glennie Domain. The Hanson Lake volcanic belt, comprising the Northern Lights and Hanson Lake assemblages, shows strong lithological, geochemical, and geochronological similarities to lithotectonic assemblages of the Flin Flon Domain (Amisk Collage), suggesting that all of these areas may have been part of a more or less continuous island arc complex, extending from Snow Lake to Flin Flon, across the Sturgeon-Weir shear zone into the Hanson Lake Block and across the Tabbernor fault zone into the Glennie Domain.

Eocene shoshonitic mafic dykes intruding the Monashee Complex, British Columbia: a petrogenetic relationship with the Kamloops Group volcanic sequence?

2005 ◽  
Vol 42 (1) ◽  
pp. 11-24 ◽  
Author(s):  
Matthew G Adams ◽  
David R Lentz ◽  
Cliff SJ Shaw ◽  
Paul F Williams ◽  
Douglas A Archibald ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Field ◽  
Primitive Mantle ◽  
Calc Alkaline ◽  
Mafic Dykes ◽  
Isotopic Signatures ◽  
Fine Grained ◽  
Monashee Complex ◽  
Step Heating ◽  
Element Contents

The newly named Three Valley Suite (TVS) kersantite lamprophyre to shoshonitic mafic dykes of the Monashee Complex are inferred to be hypabyssal feeder dykes to an alkaline to calc-alkaline volcanic suite related to the Kamloops Group. These dykes were emplaced in a subvertical north-trending orientation coincident with inferred Eocene crustal extension (~50.0 Ma), based on the flat 40Ar/39Ar step-heating plateau of contact-metamorphic muscovite on the margin of a TVS dyke. These weakly altered mafic dykes are fine grained with phenocrysts (0.5–2.0 mm) of phlogopite, augite, amphibole, and olivine (pseudomorphed by clays), rare labradorite, and both primary and secondary carbonates set in a fine-grained groundmass of similar mineralogy consistent with their classification as plagioclase-bearing potassic diorite to kersantite lamprophyre. The dykes are weakly silica-undersaturated and alkalic (2.8 wt.% K2O, 7.7 wt.% MgO), with high large ion lithophile element contents (~300 times primitive mantle) and elevated high-field-strength element contents, with a prominent negative Nb (Ta) anomaly, and have radiogenic Nd and Sr isotopic signatures; these geochemical attributes are consistent with a calc-alkaline shoshonitic affinity. Therefore, it is inferred that the subducting oceanic plate influenced subcrustal mantle wedge metasomatism in the region. Decompression partial melting of this metasomatised lithospheric mantle was initiated by coupled rapid unroofing, regional trans pression, slab rollback, and slab window development to the south. The TVS is similar to the mafic volcanic rocks within the nearby Eocene volcanic rocks, suggesting that these dykes represent the feeder system to a volcanic field that is now eroded, i.e., a broad-terrane association.

scholarly journals Mineralogical, Petrological and Geochemical Study of the Agios Ioannis Volcanic Rocks, Kamena Vourla Area, Greece

2019 ◽  
Vol 55 (1) ◽  
pp. 274 ◽  
Author(s):  
Christos Kanellopoulos ◽  
George Vougioukalakis ◽  
Constantinos Mavrogonatos ◽  
Ifigeneia Megremi ◽  
Ioannis Iliopoulos
Keyword(s):  
Volcanic Rocks ◽  
Chemical Study ◽  
Small Islands ◽  
Calc Alkaline ◽  
Plagioclase Composition ◽  
Volcanic Arc ◽  
The North ◽  
Geochemical Study ◽  
High K ◽  
Tectonically Active

The Plio-Pleistocene volcanic center of Lichades is located in the Northern Euboean Gulf, at the western extremity of the North Anatolian Fault and it is one of the most neo-tectonically active areas in Greece. Volcanic rocks are exposed in the form of lava flows and/or domes mostly in the small islands (Lichades) offshore Kamena Vourla, as well as in a small outcrop in mainland, namely the Agios Ioannis area. Based on the results of the present study, the Agios Ioannis volcanic rocks are characterized as trachyandesites with high-K calc-alkaline affinities, similar to several volcanic rocks from the South Aegean Volcanic Arc. The petrological and mineral-chemical study reveal that the studied volcanic rocks are characterized by vitrophyric texture and a matrix dominated by glass, numerous randomly-oriented microlites of plagioclase and minor sanidine, clinopyroxene and amphibole. Phenocrysts comprise of plagioclase, olivine, quartz, clinopyroxene and amphibole. Plagioclase composition ranges from andesine to bytownite (An30-An73). Olivine cores are typically Mg-rich, and the rims display elevated FeO content. Clinopyroxenes display a narrow compositional range between augite and diopside, with the latter being more common. Amphiboles, are calcic and their composition ranges from tschermakite to tschermakitic hornblende. Mineralogical and geochemical similarities with other volcanic rocks in Greece such as Lesvos lamproites, may be helpful in understanding the genesis of the studied Agios Ioannis volcanics.

Le magmatisme basique de la boutonniere d'Igherm (Anti-Atlas occidental, Maroc); un jalon des distensions neoproterozoiques sur la bordure nord du craton ouest-africain

2001 ◽  
Vol 172 (3) ◽  
pp. 309-317 ◽  
Author(s):  
El Hassan El Aouli ◽  
Dominique Gasquet ◽  
Moha Ikenne
Keyword(s):  
Field Studies ◽  
The Other ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Mafic Magmatism ◽  
Fine Grained ◽  
Eu Anomaly ◽  
Northern Border ◽  
Ree Patterns ◽  
Group 1

Abstract In the Igherm inlier (western Anti-Atlas, Morocco) doleritic dyke swarms with various directions and gabbroic intrusive bodies were emplaced during Neoproterozoic times, cutting across either Eburnean micaschists and granites or Panafrican limestones and quartzites. All these rocks were deformed by the main Panafrican schistosity and covered by molassic and volcanic Upper Neoproterozoic series. The primary mineralogical assemblages (plagioclase, augite, olivine...) of the mafic rocks are nearly completely replaced by secondary assemblages (albite, actinolite, chlorite, epidote, calcite, quartz, leucoxene, magnetite, hematite...). However, three main groups have been recognized by the means of relative chronology and petrography. The group 1 is earlier, as shown by the intrusive character of the dykes of the other two groups into its gabbroic bodies. Using incompatible trace elements and rare earth elements it appears that this magmatism is truly heterogeneous and that the three groups have different magmatic affinities. The group 1 corresponds to tholeiitic dolerites and gabbros characterized by intersertal and ophitic textures and by high contents in Fe 2 O 3 (12.16 to 16.64%), TiO 2 (1.46 to 2.5%), Zr (90 to 174 ppm), Nb (7 to 13 ppm), Y (21.68 to 38.74 ppm) and V (264 to 419 ppm). The REE contents are low (Sigma REE = 49 to 137 ppm) and the REE patterns are flat [1.99<(La/Yb) N <4.56] showing a relative slight enrichment in LREE and no anomaly in Eu (0.89>Eu/Eu (super *) <1.11). These features as the TiO 2 vs FeO (super *) /MgO and V vs Ti/1000 diagrams are characteristic of anorogenic intraplate magmas. The group 2 corresponds to calc-alkaline dolerites and gabbros showing fine-grained intersertal textures and high contents of Al 2 O 3 (14.10 to 20.64%) and low contents of Fe 2 O 3 (8.35 to 12.91%), TiO 2 (0.68 to 1.41%), Zr (66 to 106 ppm), Nb (5 to 7 ppm), Y (16.41 to 20.75 ppm) and V (144 to 264 ppm). The REE contents vary from 67 to 155 ppm and the REE patterns are fractionated (2.78<(La/Yb) N <6.62) with a strong enrichment in LREE. The slight positive Eu anomaly (0.91<Eu/Eu (super *) <1.37) is related to the wealth of plagioclases frequently observed in these rocks. The TiO 2 contents of these rocks and their low FeO (super *) /MgO ratios give them a calc-alkaline affinity similar to that of calc-alkaline orogenic basalts related to an oceanic subduction. The group 3 corresponds to alkaline dolerites characterized by fine-grained intersertal textures with high contents of TiO 2 (3.85 to 3.97%), P 2 O 5 (0.66 to 0.77%), Nb (33 to 39 ppm), Zr (262 to 287 ppm), Y (39.6 to 47.7 ppm) and REE (Sigma REE = 205 to 218 ppm). The REE patterns are fractionated (7.77<La/Yb) N <6.65) without no Eu anomaly (0.99<Eu/Eu (super *) <1.02). The Ti/V and Y/Nb ratios (65.26 to 74.95 and 1.19 to 1.22, respectively) are those of alkaline rocks found in intraplate environments. The detailed petrographical, geochemical and field studies of the Igherm inlier show that the mafic magmatism is more complex than previously described. The mafic tholeiitic and alkaline magmatism occurring in the Igherm inlier is also present in the other inliers of the Moroccan Anti-Atlas during Neoproterozoic times. On the other hand the calc-alkaline Neoproterozoic mafic magmatism is very rare elsewhere in the Anti-Atlas except in the Siroua Massif and locally in the Bas Draa and Tagragra d'Akka inliers (western Anti-Atlas). The geodynamical environment of this mafic magmatism is linked to a strong extensional tectonic regime occurring at the northern border of the West African craton during Neoproterozoic times. This regime is related to the oceanic opening described in Central Anti-Atlas and to the emplacement of the ophiolites of Bou Azzer and Siroua or occurs immediately after the oceanic opening. The chemical heterogeneities observed in the three defined groups can be related to heterogeneities of mantellic sources and/or various partial melting ratios of the sub-continental mantle. We can assume that this major fissural magmatic event, not precisely dated, is equivalent to that observed in the other Neoproterozoic provinces in Hoggar, Cameroon, north America and Brazil.

scholarly journals The final stage of the Acid Island Arc magmatism in the Northern Urals

2019 ◽  
Vol 489 (2) ◽  
pp. 166-169
Author(s):  
G. A. Petrov ◽  
N. I. Tristan ◽  
G. N. Borozdina ◽  
A. V. Maslov
Keyword(s):  
Volcanic Rocks ◽  
Southern Urals ◽  
Island Arc ◽  
Continental Margins ◽  
Island Arcs ◽  
Calc Alkaline ◽  
The Southern Urals ◽  
Northern Urals ◽  
Active Continental Margins ◽  
First Time

For the first time, the time of completion of the formation of calc-alkaline volcanic complexes of the Devonian Island Arc (Franian) in the Northern Urals was determined. It is shown that the late Devonian volcanic rocks of the Limka series have geochemical characteristics that bring them closer to the rocks of developed island arcs and active continental margins. The detected delay of the final episode of calc-alkaline volcanism in the Northern Urals in comparison with the similar event in the southern Urals may be due to the oblique nature of the subduction.

scholarly journals PETROLOGY - GEOCHEMISTRY AND METALLOGENESIS OF VOLCANIC ROCKS IN THE PETROTA GRABEN/MARONIA, W.THRACE

2004 ◽  
Vol 36 (1) ◽  
pp. 482 ◽  
Author(s):  
Κ. Αρίκας ◽  
Π. Βουδούρης ◽  
M. R. Kloos ◽  
Ch. Tesch
Keyword(s):  
Fractional Crystallization ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Mixing Processes ◽  
Geochemical Study ◽  
High K

The penological, mineralogical and geochemical study of tertiary volcanic rocks from Petrota Graben/Maronia, resulted in the distinction of the following pétrographie groups: a) a high-K calcalkaline group (andesites-dacites), b) a shoshonitic group (shoshonitic andésites, trachytic lavas, c) rhyodacitic ignimbrites and ignimbritic tuffs with high-K calc-alkaline to shoshonitic affinity, and d) rhyolites. The shoshonitic volcanic rocks and the rhyolites are probably originated from the neighbouring Maronia plutonio complex. In addition the calc-alkaline group is related to similar volcanics outcroping in the Mesti-Kassiteres area (the northeastern extension of the Graben). The petrogenesis of the volcanic rocks of the Petrota gragen is attibuted to fractional crystallization and/or magma mixing processes. Epithermal style mineralizations in Mavrokoryfi, Perama Hill and Odontoto are believed to be genetically related to the rhyolitic magmatism in the area.

Geochemistry of amphibolites from the southern part of the Kohistan arc, N. Pakistan

1988 ◽  
Vol 52 (365) ◽  
pp. 147-159 ◽  
Author(s):  
M. Qasim Jan
Keyword(s):  
Shear Deformation ◽  
Bulk Composition ◽  
Volcanic Rocks ◽  
Metamorphic Grade ◽  
Island Arc ◽  
Intrusive Rock ◽  
Chemical Characteristics ◽  
Island Arcs ◽  
Calc Alkaline ◽  
The North

AbstractThe southern part of the Cretaceous Kohistan island arc is occupied by an extensive belt dominantly comprised of amphibolites. These include banded amphibolites of partly meta-volcanic parentage, and non-banded amphibolites derived from intrusive rock. In addition to being relict, banding has also been produced by shear deformation, metamorphic/metasomatic segregation and, possibly, by lit-par-lit injection of plagiogranitic material. Non-banded amphibolites also occur as retrograde products of noritic granulites forming the lopolithic Chilas complex. The chemistry of 37 rocks has been compared with those of known tectonic environments. The amphibolites have chemical characteristics similar to volcanic rocks found in island arcs and most of the analyses apparently support affinity with the calc-alkaline series. The amphibolites consist essentially of hornblende, plagioclase and/or epidote. Garnet and clinopyroxene have developed locally in rocks of appropriate bulk composition. Metamorphism may have taken place during the mid-Cretaceous under conditions of 550 to 680°C and 4.5 to 6.5 kbar PH2O. The metamorphic grade appears to increase from the centre of the southern belt toward the Chilas complex to the north and Indus-Zangbo suture (IZS) to the south. In the vicinity of the IZS, garnet-clinopyroxene ± amphibole assemblage developed locally in response to high P-T.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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