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 and isotope studies of the metavolcanic rocks of Shimoga greenstone belt, Western Dharwar craton - an effort to deduce the Petrogenesis.

2020 ◽  
Author(s):  
Anshuman Giri ◽  
Rajagopal Anand
Keyword(s):  
Fractional Crystallization ◽  
Greenstone Belt ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Dharwar Craton ◽  
Metavolcanic Rocks ◽  
Depleted Mantle ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

<p>The archaean greenstone belts, dominated by mafic to felsic volcanic rocks followed by younger granitic intrusions occurs associated with volcano-sedimentary sequences. The Dharwar Super group (2600 to 2900 Ma) of rocks in western Dharwar craton, underlie the older TTG gneisses. The Shimoga greenstone belt (SGB) of WDC constitute the basal polymictic conglomerate along with quartzite, pyroclastic rocks, carbonaceous rocks, greywacke-argillite sequences with a thick pile of mafic and felsic metavolcanic rocks (BADR). These rocks are suffered from greenschist to lower amphibolite grade of metamorphism. The Medur metavolcanic volcanic rocks give an age of 2638 ± 66 Ma (1), whereas the Daginakatte felsic volcanic rocks give an age of 2601 ± 6 Ma (2). The present studied age of 2638 ± 66 Ma, tells about the cessation of mafic magmatism in WDC. The metavolcanic rocks of the Medur formation are tholeiitic to calc-alkaline in nature. These rocks show flat to LREE enriched REE pattern with negative europium anomaly. And also show enrichment in LILE and depletion in HFSE elements with significant Nb-Ta anomaly. The geochemical and the isotope data suggest the involvement of partial melting of the depleted mantle by the slab components and assimilation fractional crystallization (AFC) processes for the magma generation. The SGB metavolcanic rocks have 143Nd/144Nd ratios (0.511150 to .513076) and εNd values of -3.1 to -5.5 and the negative εNd values  for the rocks is due to the crustal contamination of the magma in a shallow marine subduction setting. The parental magmas were derived from melting in the mantle wedge fluxed by slab derived fluids and slab components followed by assimilation fractional crystallization (AFC) processes involving continental crust in an active continental margin.</p><ul><li>(1) Giri et al., 2019. Lithos, <strong>330-331</strong>, 177-193</li> <li>(2) Trendall et al., 1997a. J. Geol. Soc. India, <strong>50</strong>, 25-50.</li> </ul>

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.

The geochemistry and fluid history of the Proterozoic Laurel Lake Au–Ag deposit, Flin Flon greenstone belt

1991 ◽  
Vol 28 (2) ◽  
pp. 155-171 ◽  
Author(s):  
Kevin M. Ansdell ◽  
T. Kurtis Kyser
Keyword(s):  
Volcanic Rocks ◽  
Precious Metals ◽  
Gold Deposits ◽  
Fine Grained ◽  
Isotopic Compositions ◽  
Flin Flon ◽  
High Base ◽  
Felsic Volcanic ◽  
Stage 1 ◽  
Felsic Volcanic Rocks

The Laurel Lake Au–Ag deposit is situated 25 km southwest of Flin Flon in the Proterozoic Flin Flon Domain and consists of branching quartz–muscovite–pyrite–tennantite–chalcopyrite–sphalerite–galena–electrum–carbonate veins (stage 1) surrounded by a widespread zone of sericitized and pyritized Amisk Group felsic volcanic rocks. The deposit has been deformed and metamorphosed during the Hudsonian orogeny and is crosscut by nonauriferous quartz–dolomite–tourmaline–pyrite veins (stage 2). The timing of mineralization, the lack of obvious relation to a major shear zone, and high base metal sulphide and Ag/Au ratio (5:1) distinguish this deposit from epigenetic mesothermal gold deposits in the Flin Flon Domain. Fluid inclusion and stable-isotope data indicate that the mineralizing fluids had a high temperature (>300 °C), were saline (>10.3 wt.% NaCl equivalent) and CO2 bearing and had an isotopic composition similar to modified seawater. This fluid leached sulphur, base metals, and precious metals as it interacted with Amisk Group volcanic rocks. The hydrogen isotopic compositions of fine-grained muscovites in the surrounding altered felsic volcanic rocks have been reset during later metamorphism, whereas the coarse stage 1 vein muscovites have partially preserved their primary hydrogen isotopic compositions and fluorine contents. Stage 2 veins were deposited from low-salinity (<6.4 wt.% NaCl equivalent), CO2-bearing fluids, which also have the hydrogen and oxygen isotopic compositions of modified seawater. The Laurel Lake deposit has fluid, vein, and alteration characteristics that distinguish it from both epithermal and mesothermal deposits, and they can be explained by the involvement of modified seawater.

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.

U–Pb zircon ages for the Rice Lake area, southeastern Manitoba

1989 ◽  
Vol 26 (1) ◽  
pp. 23-30 ◽  
Author(s):  
A. Turek ◽  
R. Keller ◽  
W. R. Van Schmus ◽  
W. Weber
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Quartz Diorite ◽  
Granitic Rocks ◽  
Lake Area ◽  
The South ◽  
Metasedimentary Rocks ◽  
The North ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

The Archean Rice Lake greenstone belt in southeastern Manitoba is made up of mafic to felsic volcanic rocks and associated intrusive and metasedimentary rocks. The belt is flanked to the north by the Wanipigow River granitic complex and to the south by the Manigotagan gneissic belt. The Ross River quartz diorite pluton is intrusive into the centre of the greenstone belt. U–Pb zircon ages indicate a major volcanic and plutonic event in the area at 2730 Ma. Ages for two volcanic units of the Rice Lake Group are 2731 ± 3 and 2729 ± 3 Ma. The Ross River pluton yields an age of 2728 ± 8 Ma and the Gunnar porphyry gives an age of 2731 ± 13 Ma; both intrude rocks of the Rice Lake Group. Granitic rocks of the Wanipigow River granitic complex give ages of 2731 ± 10 and 2880 ± 9 Ma, while a post-tectonic granite in the Manigotagan gneissic belt has an age of 2663 ± 7 Ma.

The early Archaean Nulliak (supracrustal) assemblage, northern Labrador

1989 ◽  
Vol 26 (10) ◽  
pp. 2159-2168 ◽  
Author(s):  
A. P. Nutman ◽  
B. J. Fryer ◽  
D. Bridgwater
Keyword(s):  
Water Environment ◽  
Volcanic Rocks ◽  
Granulite Facies ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Shallow Water Environment ◽  
Scale Down ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Chemical Sediments

The Nulliak (supracrustal) assemblage, the remains of ca. 3800 Ma succession of volcanic and sedimentary rocks, was broken up by intrusion of the protoliths of the early Archaean Uivak orthogneisses and then deformed, metamorphosed, and variably metasomatised several times under upper amphibolite to granulite facies conditions in the Archaean. Amphibolites of "komatiitic basalt" and tholeiitic chemical affinity are the most important Nulliak assemblage lithologies. High Al2O3 metagabbroic rocks and anorthosites also occur. Interlayered with the amphibolites are marbles, calc-silicate rocks, and banded iron formation, interpreted as chemical sediments that were probably laid down in a shallow-water environment. Also found are felsic rocks probably derived by reworking of penecontemporaneous felsic volcanic rocks, and garnet- and sillimanite-bearing paragneisses derived from pelites. All these lithologies are randomly interlayered on a scale down to 1 m or less. The occurrence of 3850 – 3900 Ma cores for zircons in the surrounding polyphase Uivak gneisses suggests there may be an ancient sialic component in them, which could possibly represent basement upon which at least part of the Nulliak assemblage formed.

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