Radiometric Ages of Granitic Rocks, Southwestern Nova Scotia

1973 ◽  
Vol 10 (8) ◽  
pp. 1201-1210 ◽  
Author(s):  
R. F. Cormier ◽  
T. E. Smith
Keyword(s):  
Nova Scotia ◽  
Field Work ◽  
Granitic Rocks ◽  
Lower Paleozoic ◽  
Granite Emplacement ◽  
Radiometric Ages ◽  
Eastern Half

Granitic rocks comprising the eastern half of the main batholith of southwestern Nova Scotia have been studied. The granitic rocks intrude Lower Paleozoic metasediments of the Meguma Group. Field work, the chemistry and petrology of the granitic rocks, and Rb–Sr whole-rock isochron dates indicate that there were at least two episodes of granite emplacement, the earlier about 415 m.y. ago and the later about 350 m.y. ago. Samples from a much smaller pluton some 65 mi (104 km) away from the study area were also dated and are correlated with rocks in the main batholith.

Radiometric Ages of Granitic Rocks, Cape Breton Island, Nova Scotia

1972 ◽  
Vol 9 (9) ◽  
pp. 1074-1086 ◽  
Author(s):  
Randall F. Cormier
Keyword(s):  
Nova Scotia ◽  
Mean Value ◽  
Granitic Rocks ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Granitic Intrusion ◽  
Radiometric Ages ◽  
Northern Highlands

Rubidium–strontium whole-rock and mineral ages of granitic rocks from fourteen localities on Cape Breton Island have been measured. The ages cluster about a mean value of about 560 m.y. and indicate that most of the granitic rocks on the island have primary ages that are close to the Cambrian–Precambrian (Hadrynian) boundary. Some of the granitic rocks, particularly in the northern highlands, may have considerably younger, Siluro–Devonian (Acadian?), primary ages. Evidence is presented suggesting that simple biotite ages are not always reliable for the measurement of primary ages of granitic rocks. It. is suggested that, the granitic rocks having primary ages close to the Cambrian-Precambrian boundary be referred to a hitherto generally unrecognized episode of granitic intrusion, the Bretonian.

METAMORPHISM OF THE MEGUMA GROUP OF NOVA SCOTIA

1966 ◽  
Vol 3 (7) ◽  
pp. 959-974 ◽  
Author(s):  
F. C. Taylor ◽  
E. A. Schiller
Keyword(s):  
Nova Scotia ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Contact Metamorphism ◽  
Granitic Rocks ◽  
Structural Elements ◽  
Early Ordovician ◽  
Quartz Veins ◽  
Granite Emplacement

The Meguma group of lithic greywacke, feldspathic quartzite, slate siltstone, and argillite is Early Ordovician or older in age and has undergone both regional and contact metamorphism. Both types of metamorphism have resulted in recrystallization and locally in orientation of newly formed minerals. Metasomatism and retrogressive metamorphism are subordinate and only locally important. Regionally metamorphosed rocks are divided into greenschist and almandine–amphibolite facies, although some assemblages cannot be assigned with certainty. Locally, biotite and garnet isograds are mappable within the greenschist zone.Relationships between regional metamorphism and structural elements (folding) show that deformation preceded regional metamorphism. Intrusion of granitic rocks has produced a zone of contact metamorphism (hornblende–hornfels facies) that is superimposed upon regional greenschist facies rocks, which shows that granite emplacement occurred after the regional grade was reached. Gold–quartz veins are confined to areas lying in the greenschist zone of regional metamorphism, which suggests that the almandine–amphibolite zone is not favorable.

IDENTIFICAÇÃO DAS FEIÇÔES GRANÍTICAS DO MUNICÍPO DE IRAUÇUBA-CEARÁ

2019 ◽  
Vol 21 (2) ◽  
pp. 51-61
Author(s):  
Abner Monteiro Nunes Cordeiro ◽  
Rayane Barroso Araújo ◽  
Frederico De Holanda Bastos ◽  
Augusto César Praciano Sampaio
Keyword(s):  
Field Work ◽  
Granitic Rocks ◽  
Surface Erosion ◽  
Climatic Fluctuations ◽  
Geological Faults ◽  
Dry Climates ◽  
Evolution Understanding ◽  
Geomorphological Features

A exumação de rochas graníticas do Complexo Tamboril-Santa Quitéria, especificamente, na superfície de aplainamento do município de Irauçuba, Ceará, tem revelado uma grande variedade de feições geomorfológicas que se justificam por fatores litológicos e evidentes flutuações climáticas cenozoicas, comandadas, sobretudo, por morfogênese mecânica, associada a climas secos. São relevos residuais como, maciços, cristas, inselbergs, inselguebergs, lajedos e blocos saprolitizados (boulders) em diferentes graus de desenvolvimento que se sobressaem em meio à superfície erosiva rebaixada, regionalmente conhecida como depressão sertaneja. Nesse trabalho, foram identificadas diferentes formas de relevo granítico condicionadas, sobretudo por intempéries de subsuperfície, controladas por falhas e fraturas, e por remoção do regolito através da erosão superficial, além de eventos de esfoliação. Essas formas graníticas constituem peças fundamentais na compreensão da evolução paleoclimática do município de Irauçuba. Para a realização do presente trabalho foram usadas as seguintes metodologias: revisão bibliográfica, levantamento cartográfico e trabalho de campo.Palavras-chave: Feições graníticas; Superfícies de aplainamento; Erosão diferencial. ABSTRACTThe granitic rocks exhumation of Complexo Tamboril-Santa Quitéria, specifically, on the planing surface of Irauçuba county, Ceará, has revealed a great variety of geomorphological features that are justified by lithologic factors and evident Cenozoic climatic fluctuations, mainly, headed by mechanical morphogenesis, associated with dry climates. Residual reliefs like rocky massives, residual ridges, inselbergs and inselguebergs, slab stones and boulders in different degrees of development stand out in the middle of the lowered erosive surface, regionally known by “depressão sertaneja”. In this study, different forms of granite relief were identified, specially conditioned by subsurface erosion, controlled by geological faults and fractures, but also by regolith removal through surface erosion, plus exfoliation spheroidal events. These granitic features are fundamental in paleoclimatic evolution understanding of Irauçuba municipality. For the accomplishment of the present work the following methodology was used: bibliographical revision, cartographic survey and field work. For the accomplishment of the present work the following methodology was used: bibliographical revision, cartographic survey and field work.Keywords: Granitic features; Planing surface; Differential erosion.RESUMENLa exhumación de rocas graníticas del Complejo tamboril-Santa Quitéria, específicamente en la superficie de aplanado del municipio de Irauçuba, Ceará, ha revelado una gran variedad de rasgos geomorfológicos que se justifican por factores litológicos y evidentes fluctuaciones climáticas cenozoicas, comandadas principalmente por morfogénesis mecánica, asociada a climas secos. Son relieves residuales como, macizos, crestas, Inselbergs, inselguebergs, losas y bloques saprolitizados (Boulders) en diferentes grados de desarrollo que sobresalen en medio de la superficie erosiva rebajada, regionalmente conocida como depresión sertaneja. En este trabajo, se identificaron diferentes formas de relieve granítico condicionadas, principalmente por intemperies de subsuperficie, controladas por fallas y fracturas, y por eliminación del regolito a través de la erosión superficial, además de eventos de exfoliación. Estas formas graníticas constituyen piezas fundamentales en la comprensión de la evolución paleoclimática del municipio de Irauçuba. Para la realización del presente trabajo se utilizaron las siguientes metodologías: revisión bibliográfica, levantamiento cartográfico y trabajo de campo.Palabras clave: Facciones graníticas; Superficies de aplanado; Erosión diferencial.

Layered Granitic Rocks at Chebucto Head, Halifax County, Nova Scotia

1975 ◽  
Vol 12 (3) ◽  
pp. 456-463 ◽  
Author(s):  
T. E. Smith
Keyword(s):  
Grain Size ◽  
Nova Scotia ◽  
Granitic Rocks ◽  
Textural Characteristics ◽  
Rock Types ◽  
Flow Sorting

Structural, mineralogical and textural characteristics of some layered granitic rocks are described. The layers result from the segregation of minerals into bands and lenses of contrasting color and grain size. They were formed near the roof of the pluton prior to final crystallization by flow sorting during episodic shearing generated during intrusion. Comparison of the mineralogy and textures of the layered rocks with those of the main rock types of the pluton shows that the differentiation of the pluton as a whole took place after the formation of the layers by interaction of felsic components concentrated in residual liquids with earlier formed crystals.

A Revision of Cullen (Leguminosae: Papilionoideae)

1997 ◽  
Vol 10 (4) ◽  
pp. 565 ◽  
Author(s):  
James W. Grimes
Keyword(s):  
Phylogenetic Analysis ◽  
Morphometric Analysis ◽  
Field Work ◽  
The Other ◽  
Delayed Development ◽  
Floral Vasculature ◽  
Eastern Half

Cullen Medik. is a member of tribe Psoraleeae, all members of which are characterised by delayed development of floral vasculature, the presence of glands, and uniovulate ovaries. Cullen is distinguished from the other members of the tribe by discontinuous floral vasculature, and glandular, non-beaked fruits. Field work and a morphometric analysis of the Cullen patens-complex including 20 populations collected throughout the eastern half of Australia, indicates that four species, Cullen australasicum, C. discolor, C. pallidum, and C. patens, may be distinguished. A phylogenetic analysis indicates two main clades within Cullen, one including species the stems of which are branched at the base, and one in which the species are unbranched below. Furthermore, this analysis shows Bituminaria to be paraphyletic, Cullen includes 32 known species, 5 of which, C. pogonocarpum, C. leucochaites, C. praeruptorum, C. candidum, and C. corallum are described as new.

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