Correlation of two Helikian peralkaline granite – volcanic centres in central Labrador

1983 ◽  
Vol 20 (5) ◽  
pp. 753-763 ◽  
Author(s):  
J. D. Hill ◽  
A. Thomas
Keyword(s):  
Red Wine ◽  
Lake Superior ◽  
Volcanic Complex ◽  
Continental Rifting ◽  
Alkaline Complex ◽  
Peralkaline Granite ◽  
Space And Time ◽  
Terrestrial Sediments ◽  
Grenvillian Orogeny ◽  
Intrusive Suite

Recent mapping in central Labrador has resulted in the recognition and correlation of two Neohelikian peralkaline silicic igneous centres. The Flowers River igneous suite is circular in shape, covers an area of approximately 1720 km2, and consists of undeformed comenditic granite in contact with extrusive equivalent porphyry, felsite, tuff, and breccia. The Letitia Lake volcanic complex has been deformed by the Grenvillian Orogeny into an elliptical structure that covers approximately 450 km2. The complex consists of comenditic granite and syenite of the Arc Lake intrusive suite and related porphyry, rhyolite, tuff, and volcanogenically derived sediments of the Letitia Lake Group. Undersaturated aenigmatite–nepheline gneisses and syenites of the Red Wine alkaline complex are associated in space and time with the peralkaline silicic rocks of the Letitia Lake complex. The two centres are separated by 175 km and are an integral part of a Neohelikian period of uplift and continental rifting that involved formation of plateau basalts, terrestrial sediments, diabase dikes, and peralkaline magmatic centres in a belt extending from south Greenland to Lake Superior.

The Great Logan Paleomagnetic Loop — The Polar Wandering Path from Canadian Shield Rocks During the Neohelikian Era

1971 ◽  
Vol 8 (11) ◽  
pp. 1355-1372 ◽  
Author(s):  
W. A. Robertson ◽  
W. F. Fahrig
Keyword(s):  
Magnetic Properties ◽  
Depositional Environment ◽  
Lake Superior ◽  
Canadian Shield ◽  
Field Evidence ◽  
Polar Movement ◽  
Key Points ◽  
Grenvillian Orogeny ◽  
Opaque Minerals ◽  
Age Determinations

Normally magnetized dikes and reversely magnetized sills of Neohelikian age near the northwest shore of Lake Superior form two distinct paleomagnetic groups with mean pole positions of 179° W, 35° N, and 140° W, 47° N respectively. Thermal and alternating field demagnetization and the study of magnetic properties and opaque minerals indicate that directions of magnetization of these rocks were acquired at the time of their intrusion. Field evidence suggests that the sills are older than the dikes and radiogenic age determinations indicate that the intrusion of both occurred between 1000 and 1100 m.y. ago.These pole positions, together with those for the Franklin intrusions pole at 167° E, 08° N (675 m.y.), the Abitibi dikes, at 134° W, 27° N (1150 m.y.), and the Mackenzie igneous events, at 171° W, 4° N (1200 m.y.) are used to define the Logan Loop, the path that the pole took in Neohelikian time relative to the Canadian Shield. Other poles well defined magnetically, but less well dated, from rocks of this era, fit the curve quite well.Analysis of available data supports the hypothesis that the relative polar movement that gave rise to the Logan Loop was preceded and followed by polar stability vis à vis North America, whereas polar movement may have been quite rapid during the formation of the loop, which coincided with the time of the Grenvillian orogeny. Comparison of the depositional environment of Neohelikian rocks of the Canadian Shield with their probable paleolatitude as indicated by the 5 key points on Logan Loop should provide a test for the validity of this movement.

Age of volcanic rocks and syndepositional iron formations, Marquette Range Supergroup: implications for the tectonic setting of Paleoproterozoic iron formations of the Lake Superior region

2002 ◽  
Vol 39 (6) ◽  
pp. 999-1012 ◽  
Author(s):  
D A Schneider ◽  
M E Bickford ◽  
W F Cannon ◽  
K J Schulz ◽  
M A Hamilton
Keyword(s):  
Lake Superior ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Age Determination ◽  
Iron Formation ◽  
Continental Rifting ◽  
The South ◽  
Zircon Age ◽  
Iron Formations ◽  
Northern Michigan

A rhyolite in the Hemlock Formation, a mostly bimodal submarine volcanic deposit that is laterally correlative with the Negaunee Iron-formation, yields a sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon age of 1874 ± 9 Ma, but also contains inherited Archean zircons as old as 3.8 Ga. This precise age determination for the classic Paleoproterozoic stratigraphic sequence of northern Michigan, the Marquette Range Supergroup (MRS), necessitates modification of previous depositional and tectonic models. Our new data indicate that the Menominee Group, previously ascribed to continental rifting during early, pre-collision phases of the Penokean orogenic cycle, is coeval with arc-related volcanic rocks now preserved as accreted terranes immediately to the south and is more aptly interpreted as a foredeep deposit. We interpret these to be second-order basins created by oblique subduction of the continental margin rather than basins formed on a rifting margin. Along with a recently reported age for the Gunflint Formation in Ontario of 1878 ± 2 Ma, our data suggest that an extensive foredeep in the western Lake Superior region was the locus of iron-formation deposition during arc accretion from the south. Further, we interpret the lower MRS (Chocolay Group), a glaciogenic and shallow-marine succession that lies atop Archean basement, to be equivalent to the upper part of the Huronian Supergroup of Ontario and to represent the original continental rifting and passive-margin phase of the Penokean cycle. The upper MRS (Baraga Group) represents deeper marine basins, dominated by turbidites and lesser volcanic rocks, resulting from increased subsidence and continued collision. A stitching pluton, which cuts correlatives of the Hemlock Formation in a thrust sheet, yielded a U–Pb zircon age of 1833 ± 6 Ma, consistent with other post-tectonic plutons in Wisconsin and northern Michigan, indicating that Penokean convergence lasted no longer than ~40 million years.

Ferromagnesian silicates in a differentiated alkaline complex: Kûngnât Fjeld, South Greenland

1982 ◽  
Vol 46 (340) ◽  
pp. 283-300 ◽  
Author(s):  
D. Stephenson ◽  
B. G. J. Upton
Keyword(s):  
Late Stage ◽  
Abrupt Change ◽  
Intrusive Complex ◽  
Alkaline Complex ◽  
Layered Series ◽  
Magmatic Source ◽  
Peralkaline Granite ◽  
Cryptic Variation ◽  
Compositional Range

AbstractKûngnât Fjeld is an intrusive complex resulting from three intrusive events involving trachyte, mafic trachyte and hawaiite magmas tapped successively from a single magmatic source. In situ differentiation produced gabbroic, syeno-gabbroic, syenitic, and quartz syenitic cumulates showing strong cryptic variation. Layered sequences of syenitic rocks total c. 3500 m. The compositional range is extended by late-stage minor intrusions of microsyenite and peralkaline granite. The principal cumulus minerals are feldspar (Ab40An60 to Or45Ab51An4); olivine (Fo56 to Fo1) and clinopyroxene (Di70Hd27Ac3 to Di6Hd90Ac4 followed by an abrupt change of trend towards Di3Hd78Ac19 in the layered series and nearly pure aegirine in some peralkaline residues). Intercumulus phases are amphibole (hastingsite to ferro-edenite to ferro-actinolite in the layered series with riebeckite to arfvedsonite in some associated granites) and biotite (annite31 to annite98.5).

Marathon dikes: Rb–Sr and K–Ar geochronology of ultrabasic lamprophyres from the vicinity of McKellar Harbour, northwestern Ontario, Canada

1983 ◽  
Vol 20 (6) ◽  
pp. 961-967 ◽  
Author(s):  
R. Garth Platt ◽  
Roger H. Mitchell ◽  
Paul M. Holm
Keyword(s):  
Upper Mantle ◽  
Lake Superior ◽  
Alkaline Rock ◽  
Alkaline Complex ◽  
Northwestern Ontario ◽  
Isotopic Studies ◽  
Mantle Sources ◽  
Ar Geochronology ◽  
Magmatic Event

The ultrabasic lamprophyre dikes from the vicinity of McKellar Harbour, northwestern Ontario, are composed essentially of a mixture of phlogopite, olivine, primary carbonate, spinel, and apatite with associated perovskite and (?) melilite. Petrologically and chemically they have strong affinities with alnöites and magmas derived from upper mantle sources in stable continental regimes.Rb–Sr isotopic studies give an isochron age of 1.65 ± 0.12 Ga (2σ) with an initial 87Sr/86Sr ratio of 0.70167 ± 0.00036 (2σ). This age is considerably older than the Neohelikian Keweenawan magmatic event associated with the development of the Lake Superior Basin (e. g., 950–1170 Ma). K–Ar data indicate a mean whole-rock age for the dikes of 1144 Ma and a pseudoisochron age of 1120 ± 34 Ma (2σ). These ages are thought to reflect partial degassing of phlogopite and incomplete updating of the rocks under thermal influences induced by the intrusion of the Coldwell alkaline complex at 1044 Ma.Ages of carbonatitic and alkaline rock intrusions in the general vicinity of the McKellar Harbour – Marathon region closely approximate those associated with the intrusion of similar magmas in the Kapuskasing structural zone, i.e., 1650–1700 and 1020–1050 Ma. By analogy with the Kapuskasing zone, it is suggested that periodic activation of a deep-seated, long-lived structural zone in the Marathon region has lead to the tapping of upper mantle magmas. The McKellar Harbour ultrabasic lamprophyres are the product of one such event.

scholarly journals Geology and petrology of the red wine alkaline complex, central Labrador

1981 ◽  
Author(s):  
L W Curtis ◽  
K L Currie
Keyword(s):  
Red Wine ◽  
Alkaline Complex

Mineral deposits of the Mesoproterozoic Midcontinent Rift system in the Lake Superior region – A space and time classification

2020 ◽  
Vol 126 ◽  
pp. 103716 ◽  
Author(s):  
Laurel G. Woodruff ◽  
Klaus J. Schulz ◽  
Suzanne W. Nicholson ◽  
Connie L. Dicken
Keyword(s):  
Lake Superior ◽  
Mineral Deposits ◽  
Rift System ◽  
Midcontinent Rift ◽  
Space And Time ◽  
Midcontinent Rift System

scholarly journals Late Miocene volcanic activity in the České středohoří Mountains (Ohře/Eger Graben, northern Bohemia)

2009 ◽  
Vol 60 (6) ◽  
pp. 519-533 ◽  
Author(s):  
Vladimír Cajz ◽  
Vladislav Rapprich ◽  
Vojtěch Erban ◽  
Zoltan Pécskay ◽  
Miroslav Radoň
Keyword(s):  
Volcanic Activity ◽  
Late Miocene ◽  
Volcanic Complex ◽  
Basaltic Rocks ◽  
Eruptive Style ◽  
Volcanic Formation ◽  
Chemical Character ◽  
Intrusive Suite ◽  
Lava Cone ◽  
Scoria Cones

Late Miocene volcanic activity in the České středohoří Mountains (Ohře/Eger Graben, northern Bohemia)First occurrences of superficial bodies of Late Miocene volcanic activity were found in the western part of the České středohoří Volcanic Complex (CSVC) and extended our knowledge of its volcanostratigraphy. Their K-Ar ages (9.59, 9.61 and 11.36 Ma) correspond to the age of alkaline basaltic rocks of the youngest known Intrusive Suite of this area. Unlike the previously known subvolcanic bodies of this system, the newly observed bodies are represented by superficial products: two scoria cones with remnants of lava flows and one exclusive lava flow produced from a lava cone. The magmas forming all three occurrences are basanitic. Their primitive chemical composition Sr (0.70347-0.70361) and Nd (0.51279-0.51284) isotope ratios are similar to the products of the first and third volcanic formation of the CSVC. The proved existence of superficial products of the youngest volcanic formation, together with clear superposition relations to sedimentary formations and the chemical character of the youngest magmas in the central part of the Ohře (Eger) Graben support the stratigraphic scheme of volcanic activity in the České středohoří Mts. The eruptive style of the youngest formation volcanoes was purely magmatic (Strombolian) with no phreatic influence.

40Ar/39Ar phlogopite and U – Pb perovskite dating of lamprophyre dykes from the eastern Lake Superior region: evidence for a 1.14 Ga magmatic precursor to Midcontinent Rift volcanism

1996 ◽  
Vol 33 (6) ◽  
pp. 958-965 ◽  
Author(s):  
M. Queen ◽  
J. A. Hanes ◽  
D. A. Archibald ◽  
E. Farrar ◽  
L. M. Heaman
Keyword(s):  
Temporal Relationship ◽  
Lake Superior ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Rift System ◽  
Alkaline Complex ◽  
Complex Activity ◽  
Midcontinent Rift ◽  
Midcontinent Rift System ◽  
The Relationship

Thin lamprophyre dykes are abundant in the vicinity of the ca. 1.1 Ga Midcontinent Rift System and the late Archean – Early Proterozoic Kapuskasing Uplift in the Canadian Shield northeast of Lake Superior. However, the relationship between these dykes and spatially associated alkalic-carbonatite complexes has been unclear. To ascertain the temporal relationship between the two, we have determined, by 40Ar/39Ar and U–Pb dating, precise emplacement ages for six lamprophyre dykes from the region. The [Formula: see text] Ma U–Pb date for perovskite from the western Marathon and Wawa areas is indistinguishable from the 1144 ± 7 Ma 40Ar/39Ar date for phlogopite from the eastern Kapuskasing Uplift, and it is concluded that these dykes are part of a regional 1.14 Ga swarm that extends over 300 km. These dykes were therefore emplaced some 35 Ma prior to the 1109 Ma commencement of Midcontinent Rift volcanism and coeval alkaline-complex activity, but essentially simultaneously with emplacement of the 1141 ± 2 Ma Abitibi diabase dyke swarm. It is suggested that these widespread 1144 Ma lamprophyre dykes and the Abitibi diabase dykes represent the first magmatic response of initiation of the Midcontinent rifting event, and were precursors to the main rift magmatism at 1109 Ma.

Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

1983 ◽  
Vol 41 ◽  
pp. 462-463
Author(s):  
Richard L. Leino ◽  
Jon G. Anderson ◽  
J. Howard McCormick
Keyword(s):  
Confidence Interval ◽  
Chronic Exposure ◽  
Lake Superior ◽  
Pimephales Promelas ◽  
Chloride Cells ◽  
Fathead Minnows ◽  
Secondary Lamellae ◽  
Untreated Water ◽  
Water Ph ◽  
Flow Through

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

Enumeration and Identification of Asbestos Fibres in Water

1974 ◽  
Vol 32 ◽  
pp. 526-527 ◽  
Author(s):  
O. Mudroch ◽  
J. R. Kramer
Keyword(s):  
Water Supply ◽  
Water Samples ◽  
Drainage Basin ◽  
Lake Superior ◽  
Research Work ◽  
List Type ◽  
The West ◽  
Asbestos Fibre ◽  
Amphibole Asbestos

Approximately 60,000 tons per day of waste from taconite mining, tailing, are added to the west arm of Lake Superior at Silver Bay. Tailings contain nearly the same amount of quartz and amphibole asbestos, cummingtonite and actinolite in fibrous form. Cummingtonite fibres from 0.01μm in length have been found in the water supply for Minnesota municipalities.The purpose of the research work was to develop a method for asbestos fibre counts and identification in water and apply it for the enumeration of fibres in water samples collected(a) at various stations in Lake Superior at two depth: lm and at the bottom.(b) from various rivers in Lake Superior Drainage Basin.

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