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).

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.

The Westwood Deposit, Southern Abitibi Greenstone Belt, Canada: An Archean Au-Rich Polymetallic Magmatic-Hydrothermal System—Part I. Volcanic Architecture, Deformation, and Metamorphism

2021 ◽  
Author(s):  
D. Yergeau ◽  
P. Mercier-Langevin ◽  
B. Dubé ◽  
M. Malo ◽  
A. Savoie
Keyword(s):  
Fractional Crystallization ◽  
Greenstone Belt ◽  
Massive Sulfide ◽  
Hydrothermal Systems ◽  
Lava Flows ◽  
Intrusive Complex ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
Intrusive Rocks ◽  
Ore Zones

Abstract The Westwood deposit (4.5 Moz Au) is hosted in the 2699–2695 Ma Bousquet Formation volcanic and intrusive rocks, in the eastern part of the Blake River Group, southern Abitibi greenstone belt. The Bousquet Formation is divided in two geochemically distinct members: a mafic to intermediate, tholeiitic to transitional lower member and an intermediate to felsic, transitional to calc-alkaline upper member. The Bousquet Formation is cut by the synvolcanic (2699–2696 Ma) polyphase Mooshla Intrusive Complex, which is cogenetic with the Bousquet Formation. The deposit contains three strongly deformed (D2 flattening and stretching), steeply S-dipping mineralized corridors that are stacked from north to south: Zone 2 Extension, North Corridor, and Westwood Corridor. The North and Westwood corridors are composed of Au-rich polymetallic sulfide veins and stratabound to stratiform disseminated to massive sulfide ore zones that are spatially and genetically associated with the calcalkaline, intermediate to felsic volcanic rocks of the upper Bousquet Formation. The formation of the disseminated to semimassive ore zones is interpreted as strongly controlled by the replacement of porous volcaniclastic rocks at the contact with more impermeable massive cap rocks that helped confine the upflow of mineralizing fluids. The massive sulfide lenses are spatially associated with dacitic to rhyolitic domes and are interpreted as being formed, at least in part, on the paleoseafloor. The epizonal, sulfide-quartz vein-type ore zones of the Zone 2 Extension are associated with the injection of subvolcanic, calc-alkaline felsic sills and dikes within the lower Bousquet Formation. These subvolcanic intrusive rocks, previously interpreted as lava flows, are cogenetic and coeval with the intermediate to felsic lava flows and domes of the upper Bousquet Formation. The change from fractional crystallization to assimilation- and fractional crystallization-dominated processes and transitional to calc-alkaline magmatism is interpreted to be responsible for the development of the auriferous ore-forming system. The Westwood deposit is similar to some Phanerozoic Au ± base metal-rich magmatic-hydrothermal systems, both in terms of local volcano-plutonic architecture and inferred petrogenetic context. The complex volcanic evolution of the host sequence at Westwood, combined with its proximity to a polyphase synvolcanic intrusive complex, led to the development of one of the few known large Archean subaqueous Au-rich magmatic-hydrothermal systems.

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.

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.

scholarly journals Field relations and petrology of the Trafalgar Plutonic Suite and comparisons with other Devonian granitoid plutons in the Meguma terrane, Nova Scotia, Canada

2020 ◽  
Vol 56 ◽  
pp. 001-017
Author(s):  
Raya C. Puchalski ◽  
Sandra M. Barr ◽  
Chris E. White
Keyword(s):  
Nova Scotia ◽  
Quartz Diorite ◽  
Chemical Characteristics ◽  
Volcanic Arc ◽  
Mafic Rocks ◽  
Metasedimentary Rocks ◽  
Mafic Intrusions ◽  
Coarse Texture ◽  
Granitoid Rocks ◽  
Meguma Terrane

The Trafalgar Plutonic Suite intruded metasedimentary rocks of the Goldenville and Halifax groups in the northeastern part of the Meguma terrane of southern Nova Scotia at about 374 Ma, based on previously published U–Pb and 40Ar/39Ar mineral ages. Using field and petrographic observations, the suite is divided into 20 different plutons on the combined basis of variations in grain size (fine, medium, or coarse), texture (equigranular or porphyritic) and modal mineralogy (quartz diorite/tonalite, granodiorite, monzogranite, and syenogranite). The granodiorite, monzogranite, and syenogranite plutons are relatively uniform in composition with little variation in mineralogy or chemistry within each pluton or between plutons of the same lithology. In contrast the quartz diorite/tonalite plutons show mineralogical and chemical variation, both within and between plutons. The granodiorite, monzogranite, and syenogranite plutons closely resemble other peraluminous granitoid plutons characteristic of the Meguma terrane. The quartz diorite/tonalite plutons are varied but chemically resemble minor Devonian mafic intrusions elsewhere in the Meguma terrane. Like other plutons of the Meguma terrane, the Trafalgar Plutonic Suite has chemical characteristics of volcanic-arc to syn-collisional granitoid rocks and likely has experienced extensive contamination by metasedimentary material as documented by previous studies of plutons in the Meguma terrane. The minor quartz diorite/tonalite plutons are additional examples of the mafic rocks that have been proposed in tectonic models of the Meguma terrane to have facilitated melting of the lower crust to generate granodioritic parent magmas, followed by crystal fractionation and extensive contamination by metasedimentary material.

First U–Pb zircon ages of granitoid plutons from the La Grande greenstone belt, James Bay area, New Quebec

1989 ◽  
Vol 26 (5) ◽  
pp. 1068-1073 ◽  
Author(s):  
Karen St. Seymour ◽  
Andrew Turek ◽  
Ronald Doig ◽  
Stephen Kumarapeli ◽  
Robert Fogal
Keyword(s):  
Greenstone Belt ◽  
The Other ◽  
Superior Province ◽  
Present Level ◽  
James Bay ◽  
Zircon Age ◽  
Maximum Deformation ◽  
The Third ◽  
Bay Area ◽  
Greenstone Belts

Zircon ages from three granitoid plutons are the first to be reported from the La Grande greenstone belt. Two of the dated samples are from highly tectonized, early tectonic plutons that at the present level of erosion are just outside the greenstone belt proper. Their zircon ages of ca. 2740 Ma are emplacement ages or alternatively represent the age of maximum deformation of the greenstone belt. The third sample is from a mildly deformed late tectonic pluton within the greenstone belt. Its zircon age of ca. 2670 Ma probably represents the emplacement age. The above dates and the relationships of the dated plutons to the greenstone belt as a whole suggest that the bulk of the volcanism in the La Grande belt is older than 2.7 Ga. This limiting age indicates that the age of the La Grande "supracrustals" is similar to those of the other greenstone belts in the Superior Province.

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.

scholarly journals U-Pb zircon age of quartz diorite from Ben Giang intrusive complex in the Ben Giang area, Quang Nam Province

2015 ◽  
Vol 37 (2) ◽  
Author(s):  
Pham Trung Hieu ◽  
Huynh Trung
Keyword(s):  
Quartz Diorite ◽  
Intrusive Complex ◽  
Zircon Age
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