Geochronological evidence for multiple tectono-thermal overprinting events in the East Kemptville muscovite–topaz leucogranite, Yarmouth County, Nova Scotia, Canada

1991 ◽  
Vol 28 (2) ◽  
pp. 209-224 ◽  
Author(s):  
D. J. Kontak ◽  
R. F. Cormier
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Low Temperature ◽  
Thermal Activity ◽  
Geochronological Data ◽  
Step Heating ◽  
Meguma Terrane ◽  
Tin Deposit ◽  
Incremental Step ◽  
Geochronological Evidence

The East Kemptville muscovite–topaz leucogranite, located in Yarmouth County, Nova Scotia, Canada, is host rock to the only producing primary tin deposit in North America (56 Mt, 0.165% Sn). Previous geochronological studies include (i) Rb–Sr whole-rock analyses of the quartz–topaz greisens, which indicated a date of 337 ± 5 Ma, and (ii) 40Ar/39Ar analyses of greisen muscovite, which indicated apparent plateau dates of ca. 300 Ma. However, the pervasive development of deformational fabrics at East Kemptville suggests that both the Rb–Sr whole-rock and 40Ar/39Ar muscovite ages are at best minimum estimates for the inferred time of mineralization. In the present study, Rb–Sr whole-rock and mineral (muscovite, plagioclase, K-feldspar) analyses and 40Ar/39Ar incremental-step heating of a muscovite separate indicate the following: (i) diffusion of Sr on the whole-rock scale terminated at 344 ± 5 Ma (11 point isochron date), coincident with closure of muscovite to intracrystalline diffusion of Ar (apparent plateau date of 338 ± 2 Ma) and (ii) internal reequilibration of Sr among muscovite, feldspar, and whole rock varied considerably such that Rb–Sr whole rock – muscovite pairs give dates of 361–311 Ma (mean = 330 Ma, n = 7), whereas whole rock – plagioclase – K-feldspar give dates of 276–240 Ma (mean = 254 Ma, n = 7). This younger thermal event is reflected in apparent dates of 269–286 Ma for the low-temperature steps of the 40Ar/39Ar muscovite age spectrum.Collectively the data indicate that the East Kemptville area either cooled slowly over a protracted period of time (ca. 100 Ma) or experienced episodic tectono-thermal activity at ca. 344, 330, and 254 Ma. Examination of previously published geochronological data for the southern Meguma Terrane indicates that these aforementioned ages broadly coincide with earlier documented magmatic or tectono-thermal events (e.g., intrusion of Wedgeport Pluton at 315 Ma). Inferences by some workers of mid-Carboniferous magmatism in the Meguma Terrane are, however, not supported by the present study.

40Ar/39Ar dating of micas from the East Kemptville tin deposit, Yarmouth County, Nova Scotia

1985 ◽  
Vol 22 (10) ◽  
pp. 1546-1548 ◽  
Author(s):  
M. Zentilli ◽  
P. H. Reynolds
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Iberian Peninsula ◽  
South Mountain Batholith ◽  
Northwest Africa ◽  
Acadian Orogeny ◽  
Tin Deposit

The East Kemptville tin deposit in Nova Scotia, the largest known tin deposit in North America, lies in a greisen zone within the Davis Lake Pluton, generally considered to be part of the Devonian South Mountain Batholith. Our dating of micas from within the deposit suggests that the greisenization process that accompanied mineralization took place about 295 ± 5 Ma ago, that is, ca. 60 Ma after the emplacement of the batholith.Hydrothermal alteration–mineralization activity in southern Nova Scotia coincided with extensive shearing and tectonism throughout the Hercynian orogen. The East Kemptville deposit appears to be approximately coeval with similar mineralization in southwest England, the Iberian peninsula, and northwest Africa and much younger than the Devonian Acadian orogeny.

40Ar–39Ar ages for detrital white mica in Meguma terrane, Nova Scotia, Canada: implications for provenance of the Goldenville and Halifax groups

2012 ◽  
Vol 49 (7) ◽  
pp. 781-795 ◽  
Author(s):  
P.H. Reynolds ◽  
C.E. White ◽  
S.M. Barr ◽  
C.M. Muir
Keyword(s):  
Nova Scotia ◽  
Source Region ◽  
White Mica ◽  
Source Rocks ◽  
Low Grade ◽  
Rock Formation ◽  
Step Heating ◽  
Single Grain ◽  
Meguma Terrane ◽  
Late Neoproterozoic

Single-grain 40Ar/39Ar ages are reported for detrital white mica, along with conventional step-heating data for whole rocks, from low-grade metasandstone samples from the Goldenville, Halifax, and Rockville Notch groups in the Meguma terrane of southern Nova Scotia. The majority (166) of single grains from 11 samples yielded ages between ca. 615 and 350 Ma, and the remaining 12 grains yielded ages between ca. 1900 and 870 Ma. The late Neoproterozoic–Paleozoic age distributions are consistent with derivation of sediments from the rapidly uplifted flanks of an active rift, where partial to complete resetting of white mica ages occurred at ca. 520–500 Ma, preceding sediment deposition. The ca. 615 Ma ages may be relics of the original detrital white mica that existed in the source rocks prior to the rifting event. Ages from the Upper Silurian White Rock Formation appear to reflect this same ca. 520–500 Ma event, suggesting that sediments in the White Rock Formation were recycled from the Goldenville and Halifax groups. The older Precambrian ages are inferred to represent white mica in the source region, likely Amazonia. The whole-rock age spectra are discordant, with pronounced age gradients and no well-defined age plateaus. Initial gas released from five of the samples at low laboratory extraction temperatures (ca. 450–500 °C) yielded ages of ca. 260–300 Ma, not seen in the single-grain data, whereas gas released at the highest extraction temperatures yielded ages in the range ca. 510–530 Ma, possibly reflecting the principal result obtained from the single-grain data.

U–Pb and Rb–Sr geochronology of the Wedgeport granitoid pluton, southwestern Nova Scotia

1988 ◽  
Vol 25 (2) ◽  
pp. 255-261 ◽  
Author(s):  
R. F. Cormier ◽  
J. D. Keppie ◽  
A. L. Odom
Keyword(s):  
Nova Scotia ◽  
Shear Zone ◽  
Large Scale ◽  
Shear Zones ◽  
Potassium Feldspar ◽  
Slow Cooling ◽  
Northwestern Margin ◽  
Meguma Terrane ◽  
Tin Deposit ◽  
Straight Lines

Zircons from biotite monzogranite of the Wedgeport Pluton, intrusive into deformed metasediments of the Cambrian(?) Goldenville Formation in the southwestern Meguma Terrane of Nova Scotia, yield concordant U–Pb ages of 316 ± 5 Ma. This is interpreted as the time of intrusion and crystallization. Within the error limits, the 323 ± 12 Ma Rb–Sr whole-rock isochron age is identical and gives an initial 87Sr/86Sr ratio of 0.7137 ± 0.0056. Rb–Sr analyses of mineral separates of biotite, potassium feldspar, and quartz–plagioclase from several samples yield subparallel, internal isochrons with an average age of 257 ± 8 Ma. Initial ratios of the internal isochrons range from 0.716 to 0.759. A slow-cooling model for these latter data is discarded because the mineral data fall on straight lines. Instead, a reheating event related to plutonism ca. 257 Ma ago, which was sufficient to cause local grain-to-grain migration and reequilibration of strontium and rubidium but not large-scale redistribution, is invoked. This reheating is also inferred to be responsible for the hydrothermal alteration and Sn–U mineralization concentrated along the northwestern margin of the pluton. A dextral northeast–southeast shear zone cutting the pluton is also inferred to be ca. 257 Ma old. It may be related to the last stages of westward obduction of the Meguma Terrane.These results provide a clear example of Permo-Carboniferous plutonism in the southwestern Meguma Terrane and suggest a similar interpretation may apply to other anomalously young ages recorded in this area. In light of these results, the Permo-Carboniferous age of the large East Kemptville tin deposit and its location in a dextral shear zone suggest that the association of younger plutonism and shear zones may be a significant factor for economic mineralization.

Meguma terrane orocline: U-Pb age and paleomagnetism of the Silurian Mavillette gabbro, Nova Scotia, Canada

2020 ◽  
Author(s):  
Halima Sadia Warsame ◽  
Phil J.A. McCausland ◽  
Chris E White ◽  
Sandra M. Barr ◽  
Greg R. Dunning ◽  
...  
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Tectonic Evolution ◽  
Volcanic Rocks ◽  
Late Carboniferous ◽  
Early Devonian ◽  
Rock Formation ◽  
Metasedimentary Rocks ◽  
Meguma Terrane ◽  
New Evidence

Paleomagnetic results and a U-Pb baddeleyite age from the Silurian Mavillette gabbroic sill in southwest Nova Scotia provide new evidence about the Paleozoic tectonic evolution of the Meguma terrane. The Mavillette gabbro sill intruded ca. 440-430 Ma bimodal rift-related metavolcanic and metasedimentary rocks of the White Rock Formation in the Silurian-Devonian Rockville Notch Group. The 426.4±2.0 Ma Mavillette gabbro age is notably younger than the ca. 440 Ma magmatism, but is part of a geochemically-defined suite of within-plate sills and volcanic rocks of the Rockville Notch Group with ages as young as Early Devonian. Paleomagnetic investigation of thirteen sites distributed along the Neoacadian (ca. 390 Ma) synclinal limbs of the Mavillette sill reveal magnetization directions that fail a fold test and therefore postdate Silurian emplacement of the gabbro. The post-folding remanence has a mean direction of D=153.4, I=17.1°; α95=6.5° (n=12 sites), with corresponding paleopole 31.9°S, 325.2 E; dp=3.5°, dm=6.7° that resembles a pervasive Late Carboniferous Kiaman overprint magnetization in North America, but is rotated significantly 22.2°±8.1° counter-clockwise (CCW). Mavillette remanence acquisition likely occurred in concert with fluid mobilization related to Alleghanian deformation, recorded locally by ca. 320 Ma muscovite 40Ar-39Ar ages. Previously published paleomagnetic results from the Meguma terrane also have Carbonifereous remanence directions with similar ~24° CCW discordance. The regional CCW rotation of the southwest Meguma terrane post-dates this ca. 320 Ma tectonothermal remanence acquisition event, likely recording the development of an oroclinal bend of the Meguma terrane during Alleghanian orogeny.

Syn-Acadian emplacement model for the South Mountain batholith, Meguma Terrane, Nova Scotia: Magnetic fabric and structural analyses

1997 ◽  
Vol 109 (10) ◽  
pp. 1279-1293 ◽  
Author(s):  
Keith Benn ◽  
Richard J. Horne ◽  
Daniel J. Kontak ◽  
Geoffrey S. Pignotta ◽  
Neil G. Evans
Keyword(s):  
Nova Scotia ◽  
Magnetic Fabric ◽  
The South ◽  
South Mountain Batholith ◽  
Meguma Terrane

CHAETOCNEMA CONCINNA (MARSHAM, 1802), A EUROPEAN FLEA BEETLE INTRODUCED IN NORTH AMERICA (COLEOPTERA: CHRYSOMELIDAE: ALTICINAE)

1990 ◽  
Vol 122 (4) ◽  
pp. 647-650
Author(s):  
Laurent Lesage
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Prince Edward Island ◽  
Host Plants ◽  
Flea Beetle ◽  
Collection Data ◽  
First Time

AbstractChaetocnema concinna (Marsham, 1802), a European flea beetle, is reported for the first time from Canada. Preliminary collection data indicate that it may feed on the same host plants as in Europe. It has been collected to date in Prince Edward Island, Nova Scotia, and Maine.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

Chrysomyxa arctostaphyli. [Distribution map].

1999 ◽  
Author(s):  
Keyword(s):  
New York ◽  
British Columbia ◽  
New Mexico ◽  
Nova Scotia ◽  
North America ◽  
New Brunswick ◽  
South Dakota ◽  
Geographical Distribution ◽  
Distribution Map ◽  
New Distribution

Abstract A new distribution map is provided for Chrysomyxa arctostaphyli Dietel Fungi: Basidiomycota: Uredinales Hosts: Picea spp. and Arctostaphylos uva-ursi. Information is given on the geographical distribution in NORTH AMERICA, Canada, Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland, Northwest, Territories, Nova Scotia, Ontario, Quebec, Saskatchewan, Yukon, USA, Alaska, Arizona, Colorado, Idaho, Maine, Michigan, Montana, New Mexico, New York, Oregon, South Dakota, Utah, Washington, Wisconsin, Wyoming.

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