Potassium–Argon Dating of Slates from the Meguma Group, Nova Scotia

1973 ◽  
Vol 10 (7) ◽  
pp. 1059-1067 ◽  
Author(s):  
P. H. Reynolds ◽  
E. E. Kublick ◽  
G. K. Muecke
Keyword(s):  
Nova Scotia ◽  
Regional Metamorphism ◽  
Atlantic Canada ◽  
Plate Tectonic ◽  
Thermal Metamorphism ◽  
Argon Dating ◽  
Granitic Intrusion ◽  
Minimum Age ◽  
Granitic Intrusions ◽  
Orogenic Events

Recent reconstructions of the geologic evolution of Atlantic Canada based on plate-tectonic models have aroused new interest in the timing of orogenic events on both sides of the Atlantic. K–Ar apparent ages ranging from 332–403 m.y. are reported for 15 whole-rock slate and hornfels samples from the Halifax Formation of the Meguma Group. Four biotite concentrates from spatially associated granitic intrusions yield K–Ar ages of 364–369 m.y. A minimum age of about 390 m.y. for the regional metamorphic event is deduced from the whole-rock slate data. Granitic intrusion at approximately 367 m.y. profoundly affected the argon clock in many Halifax slates and resulted in its partial resetting even in slates which do not display mineralogic or textural effects of superimposed thermal metamorphism. The 390 m.y. minimum age for regional metamorphism supports suggestions by other workers that the currently widely-accepted 395 m.y. date for the Devonian–Silurian boundary may need revision.

Temporal Patterns of Acidification of Rivers in Nova Scotia and Newfoundland and their Relationship to Sulphate Emissions

1988 ◽  
Vol 23 (4) ◽  
pp. 532-541
Author(s):  
G. D. Howell ◽  
P.E.J. Green ◽  
C.A. Field ◽  
B. Freedman
Keyword(s):  
Statistical Analysis ◽  
Nova Scotia ◽  
Water Chemistry ◽  
Sulphur Dioxide ◽  
Low Ph ◽  
Hydrogen Ion ◽  
Atlantic Canada ◽  
Atmospheric Loading ◽  
Mineral Acids ◽  
Sulphur Dioxide Emission

Abstract Twenty-eight rivers in Atlantic Canada are sampled monthly, and have periods of record dating back as far as 1965. Statistical analysis of water chemistry for rivers in areas of Nova Scotia and Newfoundland that are believed to be sensitive to acidification has revealed that pH was significantly lower during the late 1960’s and early 1970’s. Annual hydrogen ion export for selected rivers was also greater during this period. This period of relatively low pH and large hydrogen ion export corresponds to a peak of North American sulphur dioxide emission, suggesting that these rivers may be responding to atmospheric loading of anthropogenic mineral acids.

The Granitization Process and its Limitations as Exemplified in Certain Parts of New South Wales

1952 ◽  
Vol 89 (1) ◽  
pp. 25-38 ◽  
Author(s):  
Germaine A. Joplin
Keyword(s):  
Wave Front ◽  
New South ◽  
Regional Metamorphism ◽  
New South Wales ◽  
Compressional Wave ◽  
Thermal Metamorphism ◽  
South Wales ◽  
Strong Compression

AbstractIn an attempt to dissect the granitization process in an area of regional metamorphism, it is suggested that granite is forcibly injected during strong compression, that the compressional wave passes upwards and outwards in advance of the magma, and that several changes take place before its arrival. Six stages in this process are recognized in the Cooma and Albury districts of N.S.W.: (1) Regional Metamorphism, (2) Superimposed Thermal Metamorphism, (3) Permeation without Magmatic Addition, (4) Addition from an Attenuated Magma, (5) Formation of a Potassic Wave-Front, and (6) Injection of the Magma as Concordant Intrusions. The conditions favouring granitization are discussed and the question of basic fronts is considered.

REPEATED TRENDS OF FOLDS AND CROSS-FOLDS IN PALAEOZOIC ROCKS, PARRSBORO, NOVA SCOTIA

1964 ◽  
Vol 1 (3) ◽  
pp. 167-183 ◽  
Author(s):  
W. K. Fyson
Keyword(s):  
Nova Scotia ◽  
Vertical Movements ◽  
Clastic Rocks ◽  
Three Generations ◽  
The North ◽  
North Side ◽  
Two Generations ◽  
Major Fault ◽  
Granitic Intrusions ◽  
Middle Carboniferous

On the north side of a major fault three generations of folds F1, F2, F3 affect pre-Carboniferous phyllites; south of the fault two generations, C1, C2, affect middle Carboniferous clastic rocks. The F1 folds are isoclinal and obscure. The main folds, F2 in the phyllites and C1 in the Carboniferous rocks, trend east-northeast parallel to the fault. F2 are overturned southward and C1 northward, both toward the fault. Cross-folds, F3 in the phyllites and C2 in the Carboniferous rocks, trend northnortheast. Steeply plunging F3 and C2 are asymmetric and Z-shaped in plan profile.The F2 folds in the phyllites, though similar in geometry to folds in the middle Carboniferous rocks, appear, like F1 and F2, to have formed prior to the middle Carboniferous. This is indicated by the occurrence of unfolded Devonian(?) granitic intrusions crossing F3 folds, and a few miles north of the major fault, by middle Carboniferous rocks lying unconformably- above similar intrusions.One possible explanation for the repeated trends, which also accounts for the sense of overturning and asymmetry of the folds, relates the folding to alternating vertical and horizontal movements along the major fault. The vertical movements were followed by gravity sliding toward the fault to produce the main folds, and the horizontal movements, repeatedly dextral in sense, resulted in the Z-shaped cross-folds.

Use of pyrite microfabric as a key to tectono-thermal evolution of massive sulphide deposits – an example from Deri, southern Rajasthan, India

1998 ◽  
Vol 62 (2) ◽  
pp. 197-212 ◽  
Author(s):  
Anju Tiwary ◽  
Mihir Deb ◽  
Nigel J. Cook
Keyword(s):  
Thermal Evolution ◽  
Regional Metamorphism ◽  
Massive Sulphide ◽  
Ductile Deformation ◽  
Sulphide Deposit ◽  
Fine Grained ◽  
Thermal Metamorphism ◽  
Sulphide Ores ◽  
History Of ◽  
South Delhi Fold Belt

AbstractPyrite is an ubiquitous constituent of the Proterozoic massive sulphide deposit at Deri, in the South Delhi Fold Belt of southern Rajasthan. Preserved pyrite microfabrics in the Zn-Pb-Cu sulphide ores of Deri reveal a polyphase growth history of the iron sulphide and enable the tectono-thermal evolution of the deposit to be reconstructed.Primary sedimentary features in Deri pyrites are preserved as compositional banding. Regional metamorphism from mid-greenschist to low amphibolite facies is recorded by various microtextures of pyrite. Trails of fine grained pyrite inclusions within hornblende porphyroblasts define S1-schistosity. Pyrite boudins aligned parallel to S1 mark the brittle–ductile transformation of pyrite during the earliest deformation in the region. Isoclinal to tight folds (F1 and F2) in pyrite layers relate to a ductile deformation stage during progressive regional metamorphism. Peak metamorphic conditions around 550°C, an estimation supported by garnet–biotite thermometry, resulted in annealing of pyrite grains, while porphyroblastic growth of pyrite (up to 900 µm) took place along the retrogressive path. Brittle deformation of pyrite and growth of irregular pyritic mass around such fractured porphyroblasts characterize the waning phase of regional metamorphism. A subsequent phase of stress-free, thermal metamorphism is recorded in the decussate and rosette textures of arsenopyrite prisms replacing irregular pyritic mass. Annealing of such patchy pyrite provides information regarding the temperature conditions during this episode of thermal metamorphism which is consistent with the hornblendehornfels facies metamorphism interpreted from magnetite–ilmenite geothermometry (550°C) and sphalerite geobarometry (3.5 kbar). A mild cataclastic deformation during the penultimate phase produced microfaults in twinned arsenopyrite prisms.

Plate Tectonic Reconstruction of Nova Scotia

2010 ◽  
Author(s):  
Matt Luheshi ◽  
Keith Nunn ◽  
David Roberts ◽  
Hamish Wilson
Keyword(s):  
Nova Scotia ◽  
Plate Tectonic ◽  
Tectonic Reconstruction

scholarly journals U–Pb zircon geochronology and phase equilibria modelling of HP-LT rocks in the Ossa-Morena Zone, Portugal

2020 ◽  
Vol 109 (8) ◽  
pp. 2719-2738
Author(s):  
Ismay Vénice Akker ◽  
Lucie Tajčmanová ◽  
Fernando O. Marques ◽  
Jean-Pierre Burg
Keyword(s):  
Phase Equilibria ◽  
Geodynamic Evolution ◽  
Mafic Rocks ◽  
Tholeiitic Magma ◽  
Metamorphic History ◽  
Metamorphic Temperature ◽  
Minimum Age ◽  
Higher Temperature ◽  
Geochemical Analyses ◽  
Orogenic Events

Abstract The Ossa-Morena Zone (OMZ) has a complex geological history including both Cadomian and Variscan orogenic events. Therefore, the OMZ plays an important role in understanding the geodynamic evolution of Iberia. However, the P–T–t evolution of the OMZ is poorly documented. Here, we combine structural and metamorphic analyses with new geochronological data and geochemical analyses of mafic bodies in Ediacaran metasediments (in Iberia known as Série Negra) to constrain the geodynamic evolution of the OMZ. In the studied mafic rocks, two metamorphic stages were obtained by phase equilibria modelling: (1) a high-pressure/low-temperature event of 1.0 ± 0.1 GPa and 470–510 °C, and (2) a medium-pressure/higher-temperature event of 0.6 ± 0.2 GPa and 550–600 °C. The increase in metamorphic temperature is attributed to the intrusion of the Beja Igneous Complex (around 350 Ma) and/or the Évora Massif (around 318 Ma). New U–Pb dating on zircons from the mafic rocks with tholeiitic affinity yields an age between 815 and 790 Ma. If the zircons crystallised from the tholeiitic magma, their age would set a minimum age for the pre-Cadomian basement. The ca. 800 Ma protolith age of HP-LT tholeiitic dykes with a different metamorphic history than the host Série Negra lead us to conclude that: (1) the HP-LT mafic rocks and HP-LT marbles with dykes were included in the Ediacaran metasediments as olistoliths; (2) the blueschist metamorphism is older than 550 Ma (between ca. 790 Ma and ca. 550 Ma, e.g., Cadomian).

scholarly journals The Economics of Bargaining Rights in the Fisheries of Nova Scotia and Atlantic Canada

2005 ◽  
Vol 30 (2) ◽  
pp. 200-216 ◽  
Author(s):  
Charles Steinberg
Keyword(s):  
Nova Scotia ◽  
Special Reference ◽  
Atlantic Canada ◽  
Economic Relations

This paper contends that the legal precedents which have until so recently discouraged positive Canadian legislation, and which could still invalidate fresh legislative efforts, are based on an outdated view of the economic relations of fishermen and fish buyers. The following briefly examines the economic underpinnings of the Canadian fishermen's right to bar gain, with special reference to Nova Scotia and Atlantic Canada.

XX.—The Metamorphism of the Deeside Limestone, Aberdeenshire

1933 ◽  
Vol 57 (2) ◽  
pp. 557-592 ◽  
Author(s):  
Arthur G. Hutchison
Keyword(s):  
Regional Metamorphism ◽  
High Grade ◽  
Thermal Metamorphism

The limestone to be described occurs in two separate areas (fig. 1)—one in Lower Deeside around Banchory, another in Middle Deeside around Aboyne. The whole of the Banchory and a large part of the Aboyne outcrops provide limestone types in a high grade of regional metamorphism (the associated schists contain sillimanite). In the latter outcrop the limestone has undergone thermal metamorphism at the contacts with Newer Granite intrusions. Many of the resulting hornfelses have suffered hydrothermal alterations with development of prehnite and zeolites. Newer Granite pegmatites, intruded at the time of hornfelsing, share in this hornfelsing and later hydrothermal modifications. In addition, they exercise exopneumatolytic and exohydrothermal metamorphism. Quite local metamorphisms take place at hornblende-schist and Older Granite contacts.

Coeval sedimentation, magmatism, and fold-thrust belt development in the Trans-Hudson Orogen: geochronological evidence from the Wekusko Lake area, Manitoba, Canada

1999 ◽  
Vol 36 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Kevin M Ansdell ◽  
Karen A Connors ◽  
Richard A Stern ◽  
Stephen B Lucas
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Lake Area ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Minimum Age ◽  
Flin Flon ◽  
Felsic Volcanic

Lithological and structural mapping in the east Wekusko Lake area of the Flin Flon Belt, Trans-Hudson Orogen, suggested an intimate relationship between magmatism, fluvial sedimentation, and initiation of fold and thrust belt deformation. Conventional U-Pb geochronology of volcanic rocks in fault-bounded assemblages provides a minimum age of 1876 ± 2 Ma for McCafferty Liftover back-arc basalts, and ages of between 1833 and 1836 Ma for the Herb Lake volcanic rocks. A rhyolite which unconformably overlies Western Missi Group fluvial sedimentary rocks has complex zircon systematics. This rock may be as old as about 1856 Ma or as young as 1830 Ma. The sedimentary rocks overlying this rhyolite are locally intercalated with 1834 Ma felsic volcanic rocks, and yield sensitive high resolution ion microprobe (SHRIMP) U-Pb and Pb-evaporation detrital zircon ages ranging from 1834 to 2004 Ma. The Eastern Missi Group is cut by an 1826 ± 4 Ma felsic dyke, and contains 1832-1911 Ma detrital zircons. The dominant source for detritus in the Missi Group was the Flin Flon accretionary collage and associated successor arc rocks. The fluvial sedimentary rocks and the Herb Lake volcanic rocks were essentially coeval, and were then incorporated into a southwest-directed fold and thrust belt which was initiated at about 1840 Ma and active until at least peak regional metamorphism.

The Flinton Group: a late Precambrian metasedimentary succession in the Grenville Province of eastern Ontario

1980 ◽  
Vol 17 (12) ◽  
pp. 1685-1707 ◽  
Author(s):  
John M. Moore Jr. ◽  
Peter H. Thompson
Keyword(s):  
Regional Metamorphism ◽  
Grenville Province ◽  
Arc Volcanism ◽  
Late Precambrian ◽  
Granitic Intrusions ◽  
Group A ◽  
Eastern Ontario ◽  
Orogenic Cycle ◽  
Uplift And Erosion ◽  
Block Faulting

Clastic and carbonate metasediments, preserved in narrow synclines, have been correlated over an area of 2000 km2. These strata, the Flinton Group, lie unconformably on metamorphosed volcanic, clastic, and carbonate rocks, and on large granitic intrusions. The group, which comprises six formations, has undergone at least two major folding episodes and one main regional metamorphism of varying grade. The only post-Flinton intrusions are pegmatites at high grade and one tectonically emplaced ultramafic slice.Depositional environment ranged from fluvial to moderate-depth marine. Rapid facies changes, coupled with persistence of some units along strike and close relationships between facies and underlying lithology, point to local sources and local tectonic control of deposition basins. At the onset of sedimentation, a deeply weathered source terrain yielded mature basal redbeds, which were succeeded by less mature clastics as block faulting caused increase of relief between sources and basins. These facies passed offshore into finer, more reduced sediments. Deposition took place between 1050 and 1080 (±25) Ma ago, after arc volcanism, plutonism, uplift, and erosion, and before major regional metamorphism. All these events can be grouped within the Grenvillian orogenic cycle, spanning at least the interval 1300–1000 Ma and including, in eastern Ontario, the pre-Flinton Elzevirian Orogeny and post-Flinton Ottawan Orogeny.

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