An Archaean sill complex and associated supracrustal rocks, Arveprinsen Ejland, north-east Disko Bugt, West Greenland

1999 ◽  
pp. 87-102
Author(s):  
Brian Marshall ◽  
Hans Kristian Schønwandt
Keyword(s):  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Overburden Pressure ◽  
West Greenland ◽  
North East ◽  
Host Materials ◽  
Spider Diagrams ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Felsic Rocks

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Marshall, B., & Schønwandt, H. K. (1999). An Archaean sill complex and associated supracrustal rocks, Arveprinsen Ejland, north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 87-102. https://doi.org/10.34194/ggub.v181.5117 _______________ Archaean supracrustal rocks on Arveprinsen Ejland comprise mafic and felsic volcanic rocks overlain by an epiclastic sedimentary sequence invaded by a mafic to ultramafic sill complex. The latter has a strike-length of 7500 m and a cumulative preserved thickness of 2000–2500 m and amounts to nearly 50% of the exposed thickness of the supracrustal rocks. Chilled and locally peperitic contacts are developed between component sills and the inter-sill metasedimentary septa. The sub-alkalic sill complex and mafi c lavas and tuffs are high-magnesium tholeiites and basaltic komatiites whereas the felsic rocks are calc-alkaline rhyolites and dacites. Chondrite- and MORB-normalised spider diagrams affirm the close similarity of the mafic volcanic rocks and the sill complex; they are also consistent with a tholeiitic or komatiitic affinity. Tectonomagmatic discrimination plots suggest an ensialic arc-related setting for the sill complex and the mafic and felsic volcanic rocks. The sill complex was progressively emplaced, as an upward-younging sequence of component sills, beneath 2 to 2.5 km of seawater and substantially less than 0.5 km of wet sediment. Sills formed when the magmatic pressure exceeded the effective overburden pressure of the sediment plus the vertical tensile strength (To) of the host materials. Intrusion was probably promoted by the drop in To at the interface between contact-lithified and poorly lithified strata. The thickness of the sill complex was accommodated by dilational lifting plus the capacity of an intrusion to create space through expulsion of water from wet sediment.

Permian magmatism in the Carpathian–Panonnian region (Hungary and Romania): New geochronological and geochemical results

2020 ◽  
Author(s):  
Máté Szemerédi ◽  
Réka Lukács ◽  
Andrea Varga ◽  
István Dunkl ◽  
Ioan Seghedi ◽  
...  
Keyword(s):  
Pannonian Basin ◽  
Volcanic Rocks ◽  
Rock Types ◽  
Regional Correlation ◽  
Ne Germany ◽  
Long Time ◽  
Spider Diagrams ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
European Variscides

<p>In the Carpathian–Pannonian region (Pannonian Basin, Hungary and the Apuseni Mts, Romania) several Late Paleozoic magmatic episodes were revealed by zircon U-Pb geochronology. These events were genetically controlled by a post-collisional to extensional tectonic regime and occurred along the European Variscan Orogenic Belt. Detailed geochronological and geochemical information about the products of this magmatism play crucial role in the regional correlation studies which is the main goal of our research.</p><p>In the Tisza Mega-unit, including southern Transdanubia and the eastern Pannonian Basin (Hungary) as well as the Apuseni Mts (Romania), Permian felsic (dominantly rhyodacitic-dacitic) ignimbrites are common. In the western–central part of the Apuseni Mts, they are accompanied by basaltic and subordinate andesitic lavas, corresponding to a bimodal volcanic suite. Cogenetic plutonic (granites, diorites, gabbros) and subvolcanic rocks (felsic–intermediate dykes) occur in the SW part of the Apuseni Mts, Highiş massif. Immobile element features (REE patterns and multi-element spider diagrams) are similar for all of the aforementioned rock types, suggesting fractional crystallization from a common or similar source. Zircon U-Pb ages of this cogenetic rock assemblage overlap each other and fall within a ~10 Myr long time-span (269–259 Ma, Guadalupian). In contrast to the previous assumptions, the Permian felsic volcanites in the Tisza Mega-unit are not in connection with the granitoid rocks known in the basement of the eastern Pannonian Basin (e.g., Battonya granite). Based on our new data, the granitoids represent a Variscan (~356 Ma, Mississippian) plutonic body.</p><p>The dacitic subvolcanic rocks (dykes) and lavas in the ALCAPA Mega-unit, Central Transdanubia (Hungary) represent an older (~281 Ma, Cisuralian) and geochemically distinct volcanic episode than the magmatism in the Tisza Mega-unit. Associated plutonic rocks, however, are not known in the study area.</p><p>Regarding a broader correlation, the zircon U-Pb ages of the studied Permian plutonic and volcanic rocks of the Tisza Mega-unit are significantly younger than the ages of other well-studied parts of the Central European Variscides (e.g., Intra-Sudetic Basin, NE Germany) where much older ages were identified (300–280 Ma). On the other hand, felsic volcanic rocks of the ALCAPA Mega-unit do not differ from the aforementioned parts of the European Variscides in age. Based on whole-rock geochemistry and zircon geochronology, all of the observed Permian magmatic rocks show similarity with the Permian felsic volcanites of the Western Carpathians (Slovakia). Some further assumptions have been raised: (1) felsic volcanic rocks of the Tisza Mega-unit could correlate with similar rocks of the Southern Gemeric (Vozárová et al. 2009) and Silicic Units (Ondrejka et al. 2018) of the ALCAPA Mega-unit, while (2) the studied samples of Central Transdanubia might be in relationship with the felsic volcanites of the Northern Veporic Unit, ALCAPA Mega-unit (Vozárová et al. 2016). This study was financed by NRDIF (K131690).</p><p>Ondrejka, M., Li, X.H., Vojtko, R., Putiš, M., Uher, P., Sobocký, T. (2018). Geol Carpath 69(2):187–198.</p><p>Vozárová, A., Šmelko, M., Paderin, I. (2009). Geol Carpath 60(6):439–448.</p><p>Vozárová, A., Rodionov, N., Vozár, J., Lepekhina, E., Šarinová, K. (2016). Geol Carpath 61:221–237.</p>

U–Pb zircon ages for magmatism in the Red Lake greenstone belt, northwestern Ontario

1986 ◽  
Vol 23 (1) ◽  
pp. 27-42 ◽  
Author(s):  
F. Corfu ◽  
H. Wallace
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Calc Alkaline ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Igneous Activity ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Chemical Sediments

U–Pb dating was carried out on nine volcanic rocks and two felsic intrusions from the Red Lake greenstone belt in order to establish an absolute time framework for the magmatic evolution of the area and yield first indications on the time of deformation and gold mineralization.The data indicate a protracted period of igneous activity spanning at least 270 Ma. Felsic volcanic rocks near the top of the tholeiitic to komatiitic sequence in the eastern part of the belt yield ages of [Formula: see text] and [Formula: see text]. A third unit, dated at [Formula: see text], contains inherited zircons older than 2982 Ma, which casts some uncertainty on the validity of the inferred intercept age. Rocks in the western part of the belt, previously believed to form a relatively young calc-alkalic sequence but now known to be dominantly tholeiitic, are shown to be relatively old, with ages of [Formula: see text] and [Formula: see text]. These two dates also bracket the age of stromatolites occurring in chemical sediments that are under and overlain by the dated units.Another volcanic horizon in the centre of the belt is dated at 2830 ± 15 Ma, and calc-alkaline volcanic sequences on the southern and northern flanks of the belt yield ages of 2739.0 ± 3.0 and [Formula: see text], respectively. An age of [Formula: see text] was determined for tholeiitic pyroclastic rocks near the base of the predominantly calc-alkaline Heyson sequence.The major gold deposits of the Red Lake belt appear to be present dominantly within older supracrustal sequences. On the other hand, they are also associated with late deformation zones that postdate the intrusion of the Dome Stock dated at 2718.2 ± 1.1 Ma ago. The time of an earlier folding event is bracketed by this age and by the age of [Formula: see text] for an isoclinally folded felsic dike.

Geochemistry of volcanic rocks from the Tetagouche Group, Bathurst, New Brunswick, Canada

1978 ◽  
Vol 15 (2) ◽  
pp. 207-219 ◽  
Author(s):  
R. E. S. Whitehead ◽  
W. D. Goodfellow
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Calc Alkaline ◽  
Middle Ordovician ◽  
Intermediate Range ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Tectonic Environments

The volcanic rocks of the Tetagouche Group are predominantly dacitic to rhyolitic pyroclastics and lavas; mafic alkaline and tholeiitic volcanic rocks are less abundant. Lavas representing the intermediate range (such as andesites) are uncommon.As a consequence of intense Na2O and K2O metasomatism, the mafic volcanic rocks have been classified on the basis of relatively immobile elements such as Ti, Y, Zr, Nb, Ni and Cr.By reference to volcanic suites described elsewhere for varying geologic and tectonic environments, the Tetagouche Group appears to represent two geologic environments. It is proposed that the deposition of tholeiitic and alkaline basalts accompanied the rifting associated with the opening of the Proto-Atlantic, which began during Hadrynian times. However the calc-alkaline felsic volcanic rocks were deposited on the top of the basaltic sequence along a mature island arc system that developed with the closing of the Proto-Atlantic during Middle Ordovician time.

scholarly journals Late sodic metasomatism evidences in bimodal volcanic rocks of the Acampamento Velho Alloformation, Neoproterozoic III, southern Brazil

2007 ◽  
Vol 79 (4) ◽  
pp. 725-737 ◽  
Author(s):  
Delia Del Pilar M. de Almeida ◽  
Vitor P. Pereira ◽  
Adriane Machado ◽  
Henrique Zerfass ◽  
Ricardo Freitas
Keyword(s):  
Volcanic Rocks ◽  
Alkali Feldspar ◽  
Southern Brazil ◽  
Santa Barbara ◽  
Crystallization Sequence ◽  
Mafic Rocks ◽  
Mineralogical Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Felsic Rocks

A mineralogical study was carried out in mafic and felsic volcanic rocks of the Acampamento Velho Alloformation at Cerro do Bugio, Perau and Serra de Santa Bárbara areas (Camaquã Basin) in southern Brazil. The Acampamento Velho bimodal event consists of two associations: lower mafic at the base and upper felsic at the top. Plagioclase and alkali-feldspar were studied using an electronic microprobe, and magnetite, ilmenite, rutile, illite and alkali-feldspar were investigated through scanning electron microscopy. The rocks were affected by a process of late sodic autometasomatism. In mafic rocks, Ca-plagioclase was transformed to albite and pyroxenes were altered. In felsic rocks, sanidine was partially pseudomorphosed, generating heterogeneous alkali-feldspar. In this association, unstable Ti-rich magnetite was replaced by rutile and ilmenite. In mafic rocks, the crystallization sequence was: (1) Ti-rich magnetite (?), (2) pyroxene and Ca-plagioclase, (3) albite (alteration to Ca-plagioclase), (4) sericite, chlorite and calcite (alteration to pyroxene), and kaolinite (alteration to plagioclase/albite). In felsic rocks: (1) zircon, (2) Ti-rich magnetite, (3) sanidine, (4) quartz. The introduction of late Na-rich fluids, generated the formation of (5) heterogeneous alkali-feldspar, (6) ilmenite and rutile from the Ti-rich magnetite, (7) albite in the spherulites. Finally, alteration of sanidine, vitroclasts and pumice to (8) illite.

Calc-Alkaline Volcanism and Plutonism from the Great Bear Batholith, N.W.T.

1973 ◽  
Vol 10 (8) ◽  
pp. 1319-1328 ◽  
Author(s):  
J. P. N. Badham
Keyword(s):  
Continental Margin ◽  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Calc Alkaline ◽  
Bay Area ◽  
Alkaline Volcanism ◽  
Andean Type ◽  
Felsic Volcanic ◽  
Orogenic Belts ◽  
Felsic Volcanic Rocks

The Camsell River – Conjuror Bay area is a pendant of Aphebian intermediate and felsic volcanic rocks, lying in a granitic complex, and is part of the Great Bear batholith. This batholith complex has been interpreted as being the orogenic belt of the Coronation geosyncline.Twenty-four analyses of volcanic and plutonic rocks are presented; these show that, in spite of alteration, the rocks can be classified as comagmatic and part of an alkali-rich calc-alkaline suite. The suite is chemically similar to younger suites from continental-margin orogenic belts. These similarities support proposals that the Coronation geosyncline was of Andean type and that the magmas may have been generated by subduction.

Geochemistry and geodynamic constraint of volcanic and plutonic magmatism within the Banfora Belt (Burkina-Faso, West-Africa): contribution to mineral exploration

2020 ◽  
pp. SP502-2019-86
Author(s):  
Hermann Ilboudo ◽  
Sâga Sawadogo ◽  
Gounwendmanaghre Hubert Zongo ◽  
Seta Naba ◽  
Urbain Wenmenga ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Mineral Exploration ◽  
Volcanic Rocks ◽  
Mafic Magma ◽  
Calc Alkaline ◽  
High K ◽  
Tectonic Settings ◽  
Arc Setting ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

AbstractPredominant volcano-plutonic (mafic–felsic) activity is expressed in the eastern Banfora Belt. The geochemical signature shows different geodynamic settings: (1) mafic rocks are tholeiitic, subalkaline and show high-Mg tendency, whereas pyroxenolite (MgO c. 15.4 wt%) has komatiite affinity; (2) felsic volcanic rocks are subalkaline; and (3) granitoids surrounding the Banfora Belt are alkaline to calc-alkaline, high K, peraluminous to metaluminous. The geochemistry of mafic volcanic rocks shows an unusual evolution from Mid Oceanic Ridge Basalt to Arc-related. The Western Granite and Eastern Granites were emplaced by fractional crystallization and partial melting, respectively, but sourced from igneous protolith (I-type magma) in a volcanic arc setting. The Sodingue granite was emplaced by fractional crystallization from A-type magma in a ‘within-plate setting’. Two-mica S-type granites located at the central portion of the belt relate to syn-collisional fractional crystallization. The paper highlights the complexity of the magma process through a diversity of sources, geochemical patterns and tectonic settings. An emphasis on the komatiite affinity of mafic magma is a challenge for related commodities, such as copper and gold resources.

scholarly journals The Pennsylvanian Composite Volcanism in the Bogda Mountains, NW China: Evidence for Postcollisional Rift Basins

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-22
Author(s):  
Jialin Wang ◽  
Chaodong Wu ◽  
Zhuang Li ◽  
Tianqi Zhou ◽  
Yanxi Zhou ◽  
...  
Keyword(s):  
Mantle Source ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Rift Basins ◽  
Basaltic Rocks ◽  
High K ◽  
Depleted Mantle ◽  
Subaqueous Volcanism ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract In this paper, we present new petrological, zircon U–Pb–Hf isotopic, bulk-rock geochemical, and Sr–Nd isotopic data for the rocks from the Pennsylvanian Liushugou and Qijiagou Formations, Bogda Mountains (BMs), northwest China. The new data help in understanding the petrogenesis and geodynamic background of the two formations, further constraining the evolution of BMs during the Pennsylvanian. The eastern Liushugou Formation is composed mainly of bimodal volcanic rocks, while the western Liushugou Formation is dominated by pillow basalts with interstitial limestones, peperites, and pyroclastic rocks. The Qijiagou Formation consists principally of bioclastic limestones, peperites, and volcanic and volcaniclastic rocks with turbidites. Depositional environment analyses of the Liushugou and Qijiagou Formations reveal subaqueous volcanism and a progressively deepening shallow marine environment with times. Zircon LA-ICP-MS U–Pb dating of felsic volcanic rocks from the Liushugou Formation indicates that the subaqueous volcanism occurred at ca. 310–302 Ma, viz., the Pennsylvanian era. The basaltic rocks from the Liushugou and Qijiagou Formations are high-K calc-alkaline, enriched in light rare earth elements and large-ion lithophile elements, and depleted in high-field-strength elements (Nb, Ta, and Ti). The above characteristics, together with their depleted isotopic signature (εNdt=3.0-8.1, εHft=8.0-15.6, and ISr=0.703-0.707), suggest the derivation from a depleted mantle source metasomatized by slab-derived fluids and sediment-derived melts. Most felsic volcanic rocks of the high-K calc-alkaline to shoshonite series from the Liushugou and Qijiagou Formations show features of the A2-type granites and have similar trace and isotopic composition to the basaltic rocks, which were probably generated from the partial melting of juvenile continental crust. Combining the newly acquired data with the regional geology, we propose that the Pennsylvanian volcanic and sedimentary rocks in the BMs were formed in a series of postcollisional rift basins which were related to local strike-slip faulting. Moreover, the volcanic rocks in the east were derived from a relatively deeper mantle source (thick lithosphere) due to their smaller rifting.

Geochemistry and Isotope Composition of Paleoproterozoic Granites and Felsic Volcanics of the Elash Graben: Evidence of the Heterogeneity of the Early Precambrian Crust

2021 ◽  
Vol 62 (10) ◽  
pp. 1175-1187
Author(s):  
A.D. Nozhkin ◽  
O.M. Turkina ◽  
K.A. Savko
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Temporal Association ◽  
Metal Deposit ◽  
Wide Range ◽  
Rare Metal Deposit ◽  
Geochronological Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract —The paper presents results of a petrogeochemical and isotope–geochronological study of the granite–leucogranite association of the Pavlov massif and felsic volcanics from the Elash graben (Biryusa block, southwest of the Siberian craton). A characteristic feature of the granite–leucogranites is their spatial and temporal association with vein aplites and pegmatites of the East Sayan rare-metal province. The U–Pb age of zircon from granites of the Pavlov massif (1852 ± 5 Ma) is close to the age of the pegmatites of the Vishnyakovskoe rare-metal deposit (1838 ± 3 Ma). The predominant biotite porphyritic granites and leucogranites of the Pavlov massif show variable alkali ratios (K2O/Na2O = 1.1–2.3) and ferroan (Fe*) index and a peraluminous composition; they are comparable with S-granites. The studied rhyolites of the Tagul River (SiO2 = 71–76%) show a low ferroan index, a high K2O/Na2O ratio (1.6–4.0), low (La/Yb)n values (4.3–10.5), and a clear Eu minimum (Eu/Eu* = 0.3–0.5); they are similar to highly fractionated I-granites. All coeval late Paleoproterozoic (1.88–1.85 Ga) granites and felsic volcanics of the Elash graben have distinct differences in composition, especially in the ferroan index and HREE contents, owing to variations in the source composition and melting conditions during their formation at postcollisions extension. The wide range of the isotope parameters of granites and felsic volcanic rocks (εNd from +2.0 to –3.7) and zircons (εHf from +3.0 to +0.8, granites of the Toporok massif) indicates the heterogeneity of the crustal basement of the Elash graben, which formed both in the Archean and in the Paleoproterozoic.

Sign in / Sign up

Export Citation Format

Share Document