K–Ar and 40Ar/39Ar geochronology of granitoid rocks from southern Nova Scotia: Its bearing on the geological evolution of the Meguma Zone of the Appalachians

1981 ◽  
Vol 18 (2) ◽  
pp. 386-394 ◽  
Author(s):  
P. H. Reynolds ◽  
M. Zentilli ◽  
G. K. Muecke
Keyword(s):  
Nova Scotia ◽  
Age Distribution ◽  
Distribution Patterns ◽  
Data Set ◽  
South Mountain Batholith ◽  
A Value ◽  
Intrusive Rocks ◽  
Geological Evolution ◽  
Granitoid Rocks ◽  
Apparent Age

K–Ar and (or) 40Ar/39Ar apparent ages are reported for 28 samples of biotite and muscovite from Nova Scotia's South Mountain batholith and associated northern satellite stocks. In addition, 14 mica samples from the southern satellite stocks were dated. Previous workers, using primarily K–Ar and Rb/Sr techniques, have reported a spread of apparent ages ranging from ~240–420 Ma for these intrusive rocks. The present data set is internally consistent and has been calibrated against accepted interlaboratory standards. A mean age of 367 Ma was obtained for the South Mountain batholith and the northern stocks, a value consistent with results recently obtained in an Rb/Sr study by Clarke and Halliday. No differences in apparent age among the various phases or clear geographic age distribution patterns were evident. Satellite stocks in the southern part of the province have, in general, younger apparent ages clustered in the range ~300–320 Ma. We suggest that in southern areas mica–argon systems record the effects of a Late Carboniferous intrusive and (or) thermotectonic event. This conclusion may have important metallogenic implications.

Offshore continuation of Meguma Terrane, southwestern Nova Scotia

1989 ◽  
Vol 26 (1) ◽  
pp. 176-191 ◽  
Author(s):  
Georgia Pe-Piper ◽  
Bosko D. Loncarevic
Keyword(s):  
South Carolina ◽  
Nova Scotia ◽  
Gravity Data ◽  
Volcanic Rocks ◽  
Magnetic Anomalies ◽  
Near Surface ◽  
Rock Formation ◽  
South Mountain Batholith ◽  
Granitoid Rocks ◽  
Meguma Terrane

Eight short drill cores have been examined from the continental shelf southwest of Nova Scotia. Four cores recovered granitoid rocks of two types. Ilmenite-bearing granitoid rocks petrographically and geochemically resemble granodiorites of the South Mountain Batholith and granites of the Seal Island Pluton. Magnetite-bearing granitoid rocks are also peraluminous but have no exact analogues onshore in Nova Scotia. Two cores recovered metamorphic rocks in a small area 50 km south of Seal Island. One consits of chlorite–muscovite–quartz schist, geochemically similar to rocks of the Halifax Formation. The second sampled epidote–chlorite–quartz schist similar to metavolcanic rocks of the White Rock Formation. One further core sampled quartzite, and another sampled a metavolcanic rock (possibly erratic).The regional extent of these lithotypes can be inferred from gravity and aeromagnetic data. Regional gravity data suggest the presence of a large granite body off southwestern Nova Scotia. In this area, magnetic anomalies are irregular, apparently reflecting the presence of magnetite-bearing granites. The layer-stripping method of analyzing the magnetic field shows that the area is underlain at depth by high magnetic anomalies. Large near-surface linear magnetic anomalies are used to map the extent of the volcanic rocks of the White Rock Formation. The area is cut by several northwest-trending faults that postdate Acadian folding but predate the earliest Jurassic magmatism of the Shelburne Dyke and North Mountain basalt. The unusual magnetic signature of the area off southwestern Nova Scotia may reflect a different basement; it is possible that Meguma rocks are thrust over the Avalon Terrane. Alternatively, it may be solely the result of magnetite-bearing granites. These granites may be related to a Permian thermal event in southwest Nova Scotia, and they have some petrographic similarity to young granites of the Piedmont Zone of South Carolina.

TRACING GARNET ORIGINS IN GRANITOID ROCKS BY OXYGEN ISOTOPE ANALYSIS: EXAMPLES FROM THE SOUTH MOUNTAIN BATHOLITH, NOVA SCOTIA

2011 ◽  
Vol 49 (2) ◽  
pp. 417-439 ◽  
Author(s):  
J. S. Lackey ◽  
S. Erdmann ◽  
J. S. Hark ◽  
R. M. Nowak ◽  
K. E. Murray ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Oxygen Isotope ◽  
Isotope Analysis ◽  
The South ◽  
South Mountain Batholith ◽  
Granitoid Rocks

Rb–Sr age and geochemical distinctions between the Carboniferous tin-bearing Davis Lake complex and the Devonian South Mountain batholith, Meguma Terrane, Nova Scotia

1989 ◽  
Vol 26 (10) ◽  
pp. 2044-2061 ◽  
Author(s):  
Jean M. Richardson ◽  
Keith Bell ◽  
John Blenkinsop ◽  
David H. Watkinson
Keyword(s):  
Nova Scotia ◽  
Trace Element ◽  
Biotite Granite ◽  
Granitic Magma ◽  
Trace Element Geochemistry ◽  
Magmatic Differentiation ◽  
Element Geochemistry ◽  
South Mountain Batholith ◽  
Granitoid Rocks ◽  
Meguma Terrane

The Davis Lake complex (DLC), composed of biotite monzogranite, leucomonzogranite, and cassiterite–topaz greisen, hosts the East Kemptville tin mine in southwestern Nova Scotia. The DLC monzogranite contains glomeroporphyritic biotite with ilmenite and many rare-earth-element (REE) bearing accessory minerals, zircon-bearing quartz phenocrysts, and xenoliths of biotite granite. Primary muscovite is rare. Major- and trace-element geochemical trends indicate well-defined, but limited, magmatic differentiation trends. REE patterns of the least-evolved granites are flat and show a Ce/Yb ratio of 10.The DLC was previously considered cogenetic with the Devonian South Mountain batholith (SMB) on the basis of its location, lithologies, and similarities in major- and trace-element geochemistry. However, new Rb–Sr whole-rock isotopic data indicate an Rb–Sr date of 330 ± 7 Ma (mean square of weighted deviates (MSWD) = 2.8) for the DLC, implying that it is at least 35 Ma younger than the SMB. The initial 87Sr/86Sr ratio of 0.727 ± 0.004 is significantly higher than those for other Meguma Terrane granites and is the highest yet reported from Appalachian granitoid rocks. Rb–Sr data from biotite indicate open-system behaviour between 260 and 240 Ma and provide more evidence for previously documented tectonothermal events after 300 Ma in the Meguma Terrane.The peraluminous nature of the DLC, its high Rb/Sr and high 87Sr/86Sr ratios, high P, F, and Sn contents, low Ca and B contents, and high differentiation indices indicate that the complex was derived from a highly evolved felsic source. Geochemical distinctions indicate that the DLC is neither derived from nor cogenetic with the SMB. A more probable source for the DLC magma is a dehydrated felsic granulite from which a previous H2O-, B-, Cl-, and Zn-rich granitic magma (perhaps the SMB) had been extracted. Such a source is analogous to that postulated for A-type granites and topaz rhyolites.The DLC shows more similarities to the "stitching" Carboniferous Appalachian volatile- and metal-rich granites than to Devonian Meguma granites. Unlike most of these Appalachian plutons, which occur marginal to terrane boundaries and were probably crystallized from locally generated, anatectic magmas, the DLC was emplaced in the centre of the most-outboard Meguma Terrane, adjacent to the Tobiatic shear zone.

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

Geochemistry of the Namurian Lismore Formation, northern mainland Nova Scotia: sedimentation and tectonic activity along the southern flank of the Maritimes Basin

1999 ◽  
Vol 36 (10) ◽  
pp. 1655-1669 ◽  
Author(s):  
Jacquelyn E Stevens ◽  
J Brendan Murphy ◽  
Fred W Chandler
Keyword(s):  
Nova Scotia ◽  
Tectonic Activity ◽  
Isotopic Data ◽  
Rock Fragments ◽  
Metasedimentary Rocks ◽  
Clastic Rocks ◽  
Granitoid Rocks ◽  
Maritimes Basin ◽  
Group B ◽  
Southern Flank

Geochemical and isotopic data from the clastic rocks of the Namurian Lismore Formation in mainland Nova Scotia identify key episodes of tectonic activity during the development of the Maritimes Basin in Atlantic Canada. The Lismore Formation forms part of the Mabou Group and is an upward-coarsening 2500 m thick fluvial sequence deposited in the Merigomish sub-basin along the southern flank of the Maritimes Basin. Based on stratigraphic evidence, the Lismore Formation can be divided into upper and lower members which reflect variations in depositional environment and paleoclimate. The geochemical and isotopic data may also be subdivided into two groupings that primarily reflect varying contributions from accessory phases, clay minerals, or rock fragments. This subdivision occurs 115 m above the base of the upper member. The data from the lower grouping (group A) show an important contribution from underlying Silurian rocks, with a relatively minor contribution from Late Devonian granitoid rocks from the adjacent Cobequid Highlands and possibly metasedimentary rocks from the Meguma Terrane to the south. The data from the upper grouping (group B) reveal a more important contribution from the Cobequid Highlands granitoid rocks. This variation in geochemistry is thought to constrain the age of renewed motion and uplift along the faults along the southern flank of the Maritimes Basin and, more generally, suggests that geochemical and isotopic data of continental clastic rocks may help constrain the age of tectonic events that influence deposition of basin-fill rocks.

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