Advances in the U–Pb zircon geochronology of the Michipicoten greenstone belt, Superior Province, Ontario

1992 ◽  
Vol 29 (6) ◽  
pp. 1154-1165 ◽  
Author(s):  
A. Turek ◽  
R. P. Sage ◽  
W. R. Van Schmus
Keyword(s):  
Greenstone Belt ◽  
Superior Province ◽  
Zircon Geochronology ◽  
Volcanic Centre ◽  
Volcanic Tuff ◽  
Metasedimentary Rocks ◽  
Felsic Volcanism ◽  
Felsic Volcanic ◽  
Volcanic Cycle ◽  
Volcanic Cycles

The Michipicoten greenstone belt in the Superior Province in Ontario developed over a period of approximately 240 Ma, between 2900 and 2660 Ma. The belt is made up of supracrustal rocks consisting of mafic to felsic metavolcanic and associated metasedimentary rocks intruded and embayed by granitoids of various ages. Generally, the external granitic terrane, a mosaic of plutons of various ages, is younger than the greenstone belt and equivalent in age to the plutons in the belt. Three major volcanic cycles have been recognized, and the older internal plutonism is coeval with the volcanism.This study reports 10 new U–Pb concordia ages that enhance the existing geochronological framework of the area. The 2889 Ma age determined for the Judith volcanic tuff documents the existence of the oldest volcanic cycle. This age is close to that of the Murray–Algoma porphyry, dated in this study at 2881 Ma, and similar to a previously published age of 2888 Ma for the Regnery granite within the same area. These three ages establish coeval felsic volcanism and plutonism within the oldest volcanic cycle 1.The new ages for the Jubilee volcanic centre are 2746 Ma (volcanic flow) and 2742 Ma (porphyry intrusion). These ages agree with previously published cycle 2 felsic volcanic ages of 2744 and 2749 Ma and hence establish coeval felsic volcanism and plutonism for this volcanic cycle. The Goudreau felsic volcanic terrane yields ages of 2729 Ma at Goudreau and 2741 Ma at Alden, which probably represent different stratigraphic positions within the same cycle.At McCormick Lake the felsic volcanic crystal tuff is 2701 Ma and belongs to cycle 3 volcanism. U–Pb ages have been determined for three plutons: 2677 Ma for the internal Dickenson Lake syenite, 2662 Ma for the internal Lund Lake granodiorite, and 2686 Ma for the external Dubreuilville granodiorite. These ages fit into an established period of granitoid plutonism in the area.

U–Pb zircon ages and the evolution of the Michipicoten plutonic–volcanic terrane of the Superior Province, Ontario

1984 ◽  
Vol 21 (4) ◽  
pp. 457-464 ◽  
Author(s):  
A. Turek ◽  
Patrick E. Smith ◽  
W. R. Van Schmus
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Tectonic Activity ◽  
Superior Province ◽  
Zircon Geochronology ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Before And After ◽  
Volcanic Cycles

The Archean Michipicoten greenstone belt of the Superior Province in Ontario is made up of supracrustal rocks divided into lower, middle, and upper metavolcanic rocks with associated metasedimentary rocks. The belt has been intruded by granitic rocks and is also surrounded by granitic terranes. Based on U–Pb zircon geochronology it appears that volcanism in the area extended from at least 2749 to 2696 Ma, and plutonism and tectonic activity extended from at least 2888 to 2615 Ma. The various granitic (and also one gabbroic) plutons, both internal and external to the greenstone belt, were emplaced concomitantly with the three volcanic cycles as well as before and after the formation of the volcanic rocks. Zircon ages reported here, together with previously published ages, show that the area evolved in six major volcanic and plutonic events: (I) 2888 Ma—plutonism, (II) 2743 Ma—volcanism and plutonism, (III) 2717 Ma—volcanism and plutonism, (IV) 2696 Ma—volcanism and plutonism, (V) 2668 Ma—plutonism, and (VI) 2615 Ma—plutonism. The oldest rock dated at 2888 ± 2 Ma belongs to the external granitic terrane and may be basement to the supracrustal rocks.

Rb–Sr whole-rock geochronology of the Gamitagama area, north central Ontario

1981 ◽  
Vol 18 (2) ◽  
pp. 323-329 ◽  
Author(s):  
A. Turek ◽  
T. E. Smith ◽  
C. H. Huang
Keyword(s):  
Greenstone Belt ◽  
Complex Terrain ◽  
Regional Metamorphism ◽  
Superior Province ◽  
The South ◽  
Stratigraphic Sequence ◽  
North Central ◽  
Metasedimentary Rocks ◽  
Area North ◽  
Radiometric Ages

The Gamitagama greenstone belt is situated to the south of the Archean Wawa belt of the Superior Province, and is about 50 km south of Wawa, Ontario. The Rb–Sr ages being reported here show that the metavolcanic and associated metasedimentary rocks are older than 2665 ± 45 Ma, which is a whole-rock isochron age of the pretectonic or syntectonic trondhjemitic plutons. The Gamitagama Lake complex, a calcalkalic differentiated and multiple diorite pluton, postdates the regional metamorphism and gives an age of 2645 ± 100 Ma. Potassic granitoid stocks, which are considered to be coeval with the Gamitagama Lake complex, define an isochron age of 2590 ± 80 Ma. The greenstone belt and associated intrusives are adjacent to the Southern batholith, a complex terrain of gneisses and migmatites, for which an isochron age of 2570 ± 90 Ma has been obtained. The radiometric ages reported here support the established stratigraphic sequence and prove that the rocks are Archean in age.

U–Pb zircon ages of volcanism and plutonism in the Mishibishu greenstone belt near Wawa, Ontario

1990 ◽  
Vol 27 (5) ◽  
pp. 649-656 ◽  
Author(s):  
A. Turek ◽  
R. Keller ◽  
W. R. Van Schmus
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Superior Province ◽  
Calc Alkaline ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Volcanic Pile ◽  
Archean Greenstone Belt

The Mishibishu greenstone belt, located 40 km west of Wawa, is a typical Archean greenstone belt and is probably an extension of the Michipicoten belt. This belt is composed of basic to felsic metavolcanic rocks of tholeiitic to calc-alkaline affinity and of metasedimentary rocks ranging from conglomerate to argillite. Granitoids, diorites, and gabbros intrude and embay supracrustal rocks as internal and external plutons.Six U–Pb zircon ages have been obtained on rocks in this area. The oldest is 2721 ± 4 Ma for the Jostle Lake tonalite. The bulk of the volcanic rocks formed by 2696 ± 17 Ma, which is the age of the Chimney Point porphyry at the top of the volcanic pile. The Pilot Harbour granite has a similar age of 2693 ± 7 Ma. The age of the Tee Lake tonalite is 2673 ± 12 Ma, and the age of the Iron. Lake gabbro is 2671 ± 4 Ma. The youngest age for volcanics in this part of the Superior Province is 2677 ± 7 Ma, obtained from, the David Lakes pyroclastic breccia. these ages agree with those reported for the adjacent Michipicoten and Gamitagama belts.

U–Pb zircon ages for rocks from the Island Lake greenstone belt, Manitoba

1986 ◽  
Vol 23 (1) ◽  
pp. 92-101 ◽  
Author(s):  
A. Turek ◽  
T. M. Carson ◽  
Patrick E. Smith ◽  
W. R. Van Schmus ◽  
W. Weber
Keyword(s):  
Greenstone Belt ◽  
Quartz Diorite ◽  
Superior Province ◽  
Intrusive Complex ◽  
Quartz Porphyry ◽  
Zircon Age ◽  
Metasedimentary Rocks ◽  
Intrusive Rocks ◽  
Granitoid Rocks

The Archean Hayes River Group of the Island Lake greenstone belt (Superior Province, Sachigo Subprovince) comprises mafic to felsic metavolcanics, subvolcanics, and associated metasedimentary rocks. The Hayes River Group is intruded by granitoid rocks belonging to the early intrusive complex. One such pluton, the Bella Lake tonalite, is intrusive into the metabasalt of the Hayes River Group and has a U–Pb zircon age of 2886 ± 15 Ma. Similar intrusives of this complex, either internal or marginal to the greenstone belt, yield zircon ages of 2801 ± 8 Ma (Pipe Point tonalit) and 2768 ± 22 Ma (Linklater Island prophyry). This suggests that the early intrusive complex was emplaced over an ~ 120 Ma long interval by at least three separate intrusive episodes.Subsequent to the emplacement of the early intrusive complex, the isoclinally folded Hayes River Group and the early intrusive complex were uplifted, eroded, and followed by the unconformable deposition of the Island Lake Group, comprising fluvial to marine metasedimentary rocks. The stratigraphically lower part of the Island Lake Group is bracketed by the 2768 ± 22 Ma age of the Linklater Island porphyry and the 2729 ± 3 Ma age obtained for the late tectonic suite—the Pipe Point quartz diorite and feldspar porphyry. A feldspar quartz porphyry belonging to the post-tectonic intrusive rocks intrudes higher stratigraphic levels and has been dated at 2699 ± 4 Ma (Horseshoe Island quartz feldspar porphyry).

U–Pb geochronology and trace element composition of zircon from the Horseshoe Lake greenstone belt, Superior Province, Canada: implications for the tectonic and metamorphic history

2018 ◽  
Vol 55 (2) ◽  
pp. 172-187 ◽  
Author(s):  
C.J. Kelly ◽  
D.A. Schneider ◽  
M.-È. Lajoie ◽  
S.E. Jackson ◽  
C.R. McFarlane
Keyword(s):  
Mass Spectrometry ◽  
Depth Profile ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Secondary Ion Mass Spectrometry ◽  
Depth Profiling ◽  
Trace Element Composition ◽  
Superior Province ◽  
Metasedimentary Rocks ◽  
Horseshoe Lake

Depth profile techniques for U–Pb geochronology and rare earth element (REE) geochemistry were conducted on unpolished, Archean zircon with metasomatic rims from metasedimentary rocks within the Horseshoe Lake greenstone belt, western Superior Province, Canada. These zircon crystals are shown to have isotopically distinct rims (typically <5 μm thick) compared with the interiors of the crystal. Secondary ion mass spectrometry (SIMS) U–Pb depth profile analyses of the rims define two different 207Pb/206Pb age populations at ca. 2920 and 2869 Ma, which are >100 million years younger than the cores. The 207Pb/206Pb rim ages can be temporally correlated with regional magmatism and with a later, potentially Au-bearing, hydrothermal event synchronous with greenschist-facies metamorphism and regional deformation. Notably, the zircons do not record evidence of local ca. 2741–2715 Ma magmatism manifested by the emplacement of a quartz–feldspar porphyry dike swarm. Laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) REE depth profile analyses on the same unpolished zircon show that the rims are commonly characterized by low Th/U ratios, elevated Hf, and variable REE concentrations in comparison with the interior of the grains. The variations in rim and core chemistry suggest that these elements, along with common Pb, were mobilized by fluids and interacted with zircon in the metasediments, resulting in the production of the metasomatic rims. In summary, this paper shows that depth profiling techniques applied to unpolished zircon can be useful to elucidate the tectonic, and potentially metallogenic, history of a complex Archean terrane.

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.

Age and timing of igneous activity in the Temagami greenstone belt, Ontario: a preliminary report

1991 ◽  
Vol 28 (11) ◽  
pp. 1873-1876 ◽  
Author(s):  
R. J. Bowins ◽  
L. M. Heaman
Keyword(s):  
Greenstone Belt ◽  
Preliminary Report ◽  
Superior Province ◽  
Early Proterozoic ◽  
The North ◽  
Intrusive Rocks ◽  
Abitibi Subprovince ◽  
Igneous Activity ◽  
The Town ◽  
Volcanic Cycle

The southernmost remnants of Archean supracrustal and intrusive rocks in eastern Ontario are exposed through a window in the Early Proterozoic Huronian Supergroup near the town of Temagami. U–Pb zircon ages from this area indicate the presence of some of the oldest felsic magmatism so far discovered in this portion of the Superior Province. The Iceland Lake pluton (2736 ± 2 Ma) and a nearby rhyolite flow ([Formula: see text]) are contemporaneous, which establishes that at least some of the intrusive rocks in the region are synvolcanic and coeval with the oldest volcanic cycle. The youngest plutonic activity is the emplacement of a late rhyolite porphyry dike at 2687 ± 2 Ma, an age that is bracketed by the 2675–2700 Ma emplacement ages of late internal plutons found throughout the Abitibi Subprovince. The 2736 Ma dates, however, are older than the nearest portion of the exposed Abitibi, some 120 km to the north near Kirkland Lake.

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