Geology, geochronology, and geochemistry of Archean rocks in the Eqe Bay area, north-central Baffin Island, Canada: constraints on the depositional and tectonic history of the Mary River Group of northeastern Rae Province

2003 ◽  
Vol 40 (8) ◽  
pp. 1137-1167 ◽  
Author(s):  
K M Bethune ◽  
R J Scammell
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Dyke Swarm ◽  
Baffin Island ◽  
Calc Alkaline ◽  
North Central ◽  
Bay Area ◽  
Gneiss Complex ◽  
Southeastern Margin ◽  
Greenstone Belts

Results of stratigraphic, U–Pb geochronological, and geochemical study are reported for rocks in a 2800 km2 area along the southeastern margin of the Archean Rae Province on north-central Baffin Island. Archean rocks include a gneiss complex, two greenstone belts of the Mary River Group, and various younger plutonic rocks. The 3000–2800 Ma gneiss complex contains intrusions of orthogneiss, dated at 2780–2770 Ma. Intermediate-felsic volcanism in overlying greenstone belts occurred at 2740–2725 Ma and was accompanied and outlasted by calc-alkaline plutonism (2730–2715 Ma). Peraluminous plutonism at ca. 2700 Ma, possibly associated with low- to medium-pressure metamorphism, represents the culmination of the Archean tectonic cycle. Dating of metamorphic zircon and titanite in Archean gneissic rocks indicates that overprinting, high-grade metamorphism in the northwest part of the area (footwall of the Isortoq fault zone) is Paleoproterozoic (ca. 1820 Ma). A weaker, somewhat older thermal disturbance (ca. 1850–1840 Ma with large errors) is recorded in the hanging wall of this zone. Additional tectonothermal events at ca. 1500–1400 Ma and ca. 700 Ma may, respectively, correlate with Mesoproterozoic faulting and emplacement of the Franklin dyke swarm. Unlike their age-correlative counterparts in the Mary River area and on the mainland to the southwest, the greenstone belts at Eqe Bay lack abundant orthoquartzite and komatiitic volcanic rocks: calc-alkaline volcanic rocks predominate, suggesting a fundamentally different tectonic environment. Striking similarities, both in lithology and age, to greenstone belts of the Minto block of the Superior Province raises the question of Rae–Superior correlation.

Distinguishing between Archean and Paleoproterozoic tectonism, and evolution of the Isortoq fault zone, Eqe Bay area, north-central Baffin Island, Canada

2003 ◽  
Vol 40 (8) ◽  
pp. 1111-1135 ◽  
Author(s):  
K M Bethune ◽  
R J Scammell
Keyword(s):  
Fault Zone ◽  
Hanging Wall ◽  
Granulite Facies ◽  
Lower Grade ◽  
Baffin Island ◽  
Bay Area ◽  
Southeastern Margin ◽  
Greenstone Belts ◽  
Area North ◽  
Granitoid Intrusions

Structural, metamorphic, and U–Pb geochronological data bear on the distinction between Archean and Paleoproterozoic tectonism along the southeastern margin of the Rae Province on Baffin Island. Archean rocks include ca. 3.0–2.8 Ga gneiss, two greenstone belts of the Mary River Group, and various younger granitoid intrusions. In the greenstone belts, intermediate–felsic volcanism (2.74–2.725 Ga) was accompanied and outlasted by calc-alkaline plutonism (2.73–2.715 Ga). Deformation, low- to medium-pressure metamorphism, and peraluminous plutonism followed at ca. 2.7 Ga. Archean rocks and the locally overlying Piling Group (ca. 2.2–1.9 Ga) were deformed and metamorphosed together during development of the Paleoproterozoic Foxe fold belt. Tectonism is linked to the Isortoq fault zone, a major southeast-dipping structure marking an abrupt northwestward transition to granulite facies. Within a 5-km-wide zone, tight folds of the Archean Mary River Group give way down-section to moderately southeast-dipping, highly transposed, high-grade gneissic rocks. Several northeast- and north-striking ductile–brittle faults, some recording normal-sinistral oblique displacement, truncate early gneissosity and folds. This progression, along with U–Pb metamorphic ages, suggests early northwest-directed thrusting, starting at ca. 1.85 Ga, with peak metamorphism in the footwall at ca. 1.83–1.82 Ga. Later extensional displacement caused juxtaposition of lower grade on higher grade rocks. Archean ages of metamorphism (and deformation) are well preserved only in the hanging wall and the youngest metamorphic ages are restricted to the footwall. The data indicate that mountain building involved thrust-related thickening followed by gravitational collapse, a sequence characteristic of Phanerozoic orogens.

Autochthonous and allochthonous rocks in the Pistolet Bay area in northernmost Newfoundland

1968 ◽  
Vol 5 (3) ◽  
pp. 501-513 ◽  
Author(s):  
M. F. Tuke
Keyword(s):  
Lower Cambrian ◽  
Volcanic Rocks ◽  
The Other ◽  
North Central ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Bay Area

Rocks outcropping in the northernmost part of the island of Newfoundland belong to two sequences, which are partly contemporaneous and very different in lithology. One sequence consists of Lower Cambrian sandstones and Lower and Middle Ordovician carbonates and shales. The other sequence consists of graywackes, volcanic rocks, and ultrabasic intrusions, which are, in part, early Ordovician. This latter sequence is interpreted as allochthonous because it is underlain by major low-angle faults and because of its strong facies contrast with the first sequence. The allochthonous rocks occur in three separate klippen.The trend of slickensides, attitude of folds, and deflection of beds at fault surfaces all indicate that movement along the low-angle faults that underlie the klippen was to the northwest. The klippen probably originated from an area 60 km to the southeast, which is on strike with similar rocks in north-central Newfoundland.It is suggested that the klippen moved by gravity sliding in late Middle Ordovician time.

The relationship between adakitic, calc-alkaline volcanic rocks and TTGs: implications for the tectonic setting of the Karelian greenstone belts, Baltic Shield

Lithos ◽  
2005 ◽  
Vol 79 (1-2) ◽  
pp. 83-106 ◽  
Author(s):  
A.V. Samsonov ◽  
M.M. Bogina ◽  
E.V. Bibikova ◽  
A.Yu. Petrova ◽  
A.A. Shchipansky
Keyword(s):  
Baltic Shield ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Greenstone Belts ◽  
The Relationship

Geochemistry and tectonic significance of the mafic volcanic blocks in the Dunnage mélange, north central Newfoundland

1985 ◽  
Vol 22 (9) ◽  
pp. 1248-1256 ◽  
Author(s):  
Janusz J. Wasowski ◽  
Robert D. Jacobi
Keyword(s):  
Chemical Composition ◽  
Alkali Basalt ◽  
Volcanic Rocks ◽  
Pillow Lava ◽  
Calc Alkaline ◽  
North Central ◽  
Head Formation ◽  
Tectonic Significance ◽  
Low Potassium ◽  
Tuff Breccia

Abundant volcanic blocks are present in the Dunnage mélange. These mafic volcanic rocks consist predominantly of pillow lava, tuff breccia, isolated pillow–tuff breccia, and minor amounts of ropy lava.Major- and trace-element compositions of the basalts reveal that these volcanics do not resemble calc-alkaline or low-potassium island-arc suites. Rather, the majority of the samples are enriched-type ocean-floor tholeiites, whereas some show alkali basalt affinities. Discrimination diagrams suggest that these basalts may have been erupted as within-plate basalts. However, the chemical composition of the volcanic blocks is most similar to that of basalts generated at bathymetric highs located astride (or slightly off) mid-ocean ridges.The geochemistry of the Dunnage mélange basalts is very similar to that of the mafic volcanic rocks from the nearby Summerford Group and the Lawrence Head Formation. This correlation is further supported by sedimentary and petrographic evidence and by partial age equivalency.

Massive sulfide deposits of the Noranda area, Quebec. IV. The Mobrun mine

1992 ◽  
Vol 29 (7) ◽  
pp. 1349-1374 ◽  
Author(s):  
T. J. Barrett ◽  
S. Cattalani ◽  
L. Hoy ◽  
J. Riopel ◽  
P.-J. Lafleur
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Calc Alkaline ◽  
Sulfide Deposits ◽  
Calculated Mass ◽  
Higher Temperature ◽  
Felsic Volcanic ◽  
Clear Change

The Mobrun polymetallic deposit near Rouyn–Noranda comprises two complexes of massive sulfide lenses within mainly felsic volcanic rocks of the Archean Blake River Group. The Main lens contained 3.37 Mt of massive sulfides, with 1989 reserves of 0.95 Mt at 0.81% Cu, 2.44% Zn, 30.3 g/t Ag, and 2.2 g/t Au. The 1100 complex, located ~250 m to the southeast of the Main complex, contains estimated 1989 reserves of 10.4 Mt at 0.76% Cu, 5.43% Zn, 37.4 g/t Ag, and 1.35 g/t Au.Host volcanic rocks of the Main complex are mostly massive, brecciated, and tuffaceous rhyolites. The rhyolites are commonly strongly sheared parallel to lithological contacts, which are locally displaced by high-angle faults. Immobile-element plots such as Y–Zr and Nb–Zr show a separation of rhyolite data into two distinct alteration trends that generally correspond to massive and in situ brecciated rhyolite of the footwall, and tuffaceous rhyolite of the hanging wall. The hanging wall has tholeiitic Zr/Y ratios (3–5), whereas the footwall has mildly calc-alkaline Zr/Y ratios (7–9). Several immobile-element trends indicate that there was a subtle but clear change in rhyolite composition near the time of ore deposition. Identification of chemically distinct footwall and hanging wall rhyolites allows these units to be recognized and traced along strike, even where alteration is strong. Sericitization and silicification extend at least 100 m from the orebody, with local chloritic zones in the upper footwall. Calculated mass changes indicate that the footwall generally has lost silica mass relative to the hanging wall. Alteration zones associated with mineralization have mass gains in FeO + MgO and K2O gains, but mass loss in silica.The 1100 complex, located stratigraphically below the Main complex, is hosted by rhyolite, with one main andesite interval in the footwall. The footwall contains three chemically distinct rhyolite types, all tholeiitic. Hanging-wall rhyolites are, however, mildly calc-alkaline, and thus are chemically comparable to, and correlated with, the footwall of the Main complex. Rhyolites within ~100 m stratigraphically of the Main and 1100 complexes commonly have positively shifted δ18O whole-rock values of 11–13‰. These high values are interpreted as the result of an initial, widespread phase of low-temperature hydrothermal alteration that increased δ18O values by 3–5‰ relative to unaltered rhyolites. Some footwall rhyolites, however, are relatively depleted in 18O, strongly depleted in Ca–Na and depleted in Eu2+. Rhyolites with these chemical features have been overprinted by higher temperature alteration, presumably in localized feeder zones. All four rhyolite types near the 1100 complex are chemically recognizable despite contrasting alteration.The orebodies are interpreted as synvolcanic, based on their occurrence along distinctive volcanic contacts, and the presence of primary sulfide textures where deformation is minor. The chemostratigraphic framework defined for the host rhyolite sequence can be used to trace critical volcanic contacts through lithologically monotonous, strongly altered, and faulted stratigraphy.

scholarly journals Gold mobilization during metamorphic devolatilization of Archean and Paleoproterozoic metavolcanic rocks

Geology ◽  
2020 ◽  
Vol 48 (11) ◽  
pp. 1110-1114 ◽  
Author(s):  
C.G.C. Patten ◽  
I.K. Pitcairn ◽  
F. Molnár ◽  
J. Kolb ◽  
G. Beaudoin ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Source Rocks ◽  
Magmatic Evolution ◽  
Mass Variation ◽  
Calc Alkaline ◽  
Potential Source ◽  
Metavolcanic Rocks ◽  
Good Potential ◽  
Greenstone Belts ◽  
Central Lapland Greenstone Belt

Abstract Volcanic rocks in Archean and Paleoproterozoic greenstone belts are abundant and have been suggested as a potential Au source for orogenic Au deposits. The behavior of Au during metamorphism of these rocks is, however, poorly known. We present ultra-low-detection-limit Au analyses from a suite of variably metamorphosed rocks from the Archean La Grande subprovince, Canada, and the Paleoproterozoic Central Lapland greenstone belt, Finland. Both areas are well endowed in Au and have great potential for discovery of new orogenic Au deposits. The metavolcanic rocks in these belts are grouped into tholeiite and calc-alkaline magmatic series, for which the protolith Au contents are calculated using Au versus Zr/Y power-law regressions from greenschist facies samples. In the tholeiitic rocks, Au is compatible during magmatic processes and decreases with differentiation, whereas in the calc-alkaline rocks, Au is incompatible and increases with differentiation. Mass-variation calculations show that as much as 77% and 59% of the initial Au content is lost during progressive metamorphism to upper amphibolite facies conditions (>550 °C) in La Grande and Central Lapland respectively. This study highlights, first, that metavolcanic rocks release Au during metamorphism in Archean and Paleoproterozoic greenstone belts and are thus a good potential source rocks for orogenic Au deposits; second, that the Au fertility of the metavolcanic rocks is controlled by their mantle source and magmatic evolution; and third, that the metamorphic devolatilization model can be applied to Archean and Paleoproterozoic orogenic Au deposits.

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.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany)

2019 ◽  
Vol 108 (6) ◽  
pp. 1879-1895 ◽  
Author(s):  
Rainer Altherr ◽  
Michael Hanel ◽  
Winfried H. Schwarz ◽  
Wolfhard Wimmenauer
Keyword(s):  
Zircon Age ◽  
Gneiss Complex ◽  
Southeastern Margin

Rubidium–strontium ages from the Oxford Lake – Knee Lake greenstone belt, northern Manitoba

1980 ◽  
Vol 17 (5) ◽  
pp. 560-568 ◽  
Author(s):  
G. S. Clark ◽  
S.-P. Cheung
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Superior Province ◽  
Granitic Intrusion ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

Rb–Sr whole-rock ages have been determined for rocks from the Oxford Lake – Knee Lake – Gods Lake greenstone belt, in the Superior Province of northeastern Manitoba.The age of the Magill Lake Pluton is 2455 ± 35 Ma (λ87Rb = 1.42 × 10−11 yr−1), with an initial 87Sr/86Sr ratio of 0.7078 ± 0.0043. This granitic stock intrudes the Oxford Lake Group, so it is post-tectonic and probably related to the second, weaker stage of metamorphism.The age of the Bayly Lake Pluton is 2424 ± 74 Ma, with an initial 87Sr/86Sr ratio of 0.7029 ± 0.0001. This granodioritic batholith complex does not intrude the Oxford Lake Group. It is syn-tectonic and metamorphosed.The age of volcanic rocks of the Hayes River Group, from Goose Lake (30 km south of Gods Lake Narrows), is 2680 ± 125 Ma, with an initial 87Sr/86Sr ratio of 0.7014 ± 0.0009.The age for the Magill Lake and Bayly Lake Plutons can be interpreted as the minimum ages of granitic intrusion in the area.The age for the Hayes River Group volcanic rocks is consistent with Rb–Sr ages of volcanic rocks from other Archean greenstone belts within the northwestern Superior Province.

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