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.

scholarly journals Stratigraphy and depositional setting of the Silurian-Devonian Rockville Notch Group, Meguma terrane, Nova Scotia, Canada

2017 ◽  
Vol 53 ◽  
pp. 337-365 ◽  
Author(s):  
Chris E. White ◽  
Sandra M. Barr
Keyword(s):  
Nova Scotia ◽  
Volcanic Rocks ◽  
Rock Formation ◽  
Metasedimentary Rocks ◽  
South Mountain Batholith ◽  
Metavolcanic Rocks ◽  
Northwestern Margin ◽  
Meguma Terrane ◽  
Two Stages ◽  
Depositional Setting

 The Silurian–Devonian Rockville Notch Group occurs in five separate areas along the northwestern margin of the Meguma terrane of southern Nova Scotia. In each area, the lowermost unit of the group is the White Rock Formation, which unconformably overlies the Lower Ordovician Halifax Group. Early Silurian U–Pb (zircon) dates from metavolcanic rocks in the White Rock Formation indicate that the unconformity represents a depositional gap of about 25 Ma. The U–Pb ages are consistent with early Silurian (Llandovery) trace fossils and sparse shelly faunas in metasedimentary rocks interlayered with the metavolcanic rocks. The metasedimentary rocks locally contain phosphatic ironstone and Mn-rich beds, and are overlain by mainly metasiltstone with abundant quartzite and metaconglomerate lenses. Some of the latter were previously interpreted to be Ordovician tillite. The White Rock Formation is conformably overlain by the slate- and metasiltstone-dominated Kentville Formation, which contains Upper Wenlock to Pridoli graptolites and microfossils. The overlying Torbrook Formation consists of metalimestone, metasandstone and metasiltstone, interbedded with phosphatic ironstone and minor mafic metatuff, and contains Pridoli to early Emsian fossils. It is in part laterally equivalent to the New Canaan Formation in the Wolfville area, which is dominated by slate, pillowed mafic metavolcanic rocks and fossiliferous metalimestone. Volcanic rocks in the Rockville Notch Group are alkalic and formed in a within-plate setting, probably related to extension as the Meguma terrane rifted from Gondwana. This process may have occurred in two stages, Early Silurian and Early Devonian, separated by a hiatus in volcanic activity. Stratigraphic differences suggest that the Meguma terrane was not adjacent to Avalonia before emplacement of the South Mountain Batholith.

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.

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.

Petrology, age, and tectonic setting of the White Rock Formation, Meguma terrane, Nova Scotia: evidence for Silurian continental rifting

2002 ◽  
Vol 39 (2) ◽  
pp. 259-277 ◽  
Author(s):  
Lisa A MacDonald ◽  
Sandra M Barr ◽  
Chris E White ◽  
John WF Ketchum
Keyword(s):  
Nova Scotia ◽  
Shear Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Chemical Characteristics ◽  
Rock Formation ◽  
Meguma Terrane ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

The White Rock Formation in the Yarmouth area of the Meguma terrane of southern Nova Scotia consists mainly of mafic tuffaceous rocks with less abundant mafic flows, epiclastic and clastic sedimentary rocks, and minor intermediate and felsic crystal tuff. It is divided into seven map units that appear to young from west to east, inconsistent with a previously assumed synclinal structure. The White Rock Formation is flanked on both northwest and southeast by mainly the Cambrian to Lower Ordovician Halifax Formation; the western contact is interpreted to be a sheared disconformity, whereas the eastern contact appears to be a major brittle fault and shear zone that juxtaposes different crustal levels. The granitic Brenton Pluton forms a faulted lens within the eastern shear zone. A felsic tuff from the upper part of the White Rock Formation yielded a U–Pb zircon age of 438+3–2 Ma, identical within error to published ages for the Brenton Pluton and felsic volcanic rocks near the base of the White Rock Formation in the Torbrook area of western Nova Scotia. The chemical characteristics of the mafic volcanic rocks and associated mafic intrusions consistently indicate alkalic affinity and a continental within-plate setting. The felsic volcanic rocks and Brenton Pluton have chemical characteristics of within-plate anorogenic granitic rocks, and the pluton is interpreted to be comagmatic with the felsic volcanic rocks. The igneous activity may have occurred in response to extension as the Meguma terrane rifted away from Gondwana in the latest Ordovician to Early Silurian. Epsilon Nd values are similar to those in voluminous Devonian plutonic rocks of the Meguma terrane, and the magmas appear to have been derived from similar sources.

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

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.

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

scholarly journals Field relations and petrology of the Trafalgar Plutonic Suite and comparisons with other Devonian granitoid plutons in the Meguma terrane, Nova Scotia, Canada

2020 ◽  
Vol 56 ◽  
pp. 001-017
Author(s):  
Raya C. Puchalski ◽  
Sandra M. Barr ◽  
Chris E. White
Keyword(s):  
Nova Scotia ◽  
Quartz Diorite ◽  
Chemical Characteristics ◽  
Volcanic Arc ◽  
Mafic Rocks ◽  
Metasedimentary Rocks ◽  
Mafic Intrusions ◽  
Coarse Texture ◽  
Granitoid Rocks ◽  
Meguma Terrane

The Trafalgar Plutonic Suite intruded metasedimentary rocks of the Goldenville and Halifax groups in the northeastern part of the Meguma terrane of southern Nova Scotia at about 374 Ma, based on previously published U–Pb and 40Ar/39Ar mineral ages. Using field and petrographic observations, the suite is divided into 20 different plutons on the combined basis of variations in grain size (fine, medium, or coarse), texture (equigranular or porphyritic) and modal mineralogy (quartz diorite/tonalite, granodiorite, monzogranite, and syenogranite). The granodiorite, monzogranite, and syenogranite plutons are relatively uniform in composition with little variation in mineralogy or chemistry within each pluton or between plutons of the same lithology. In contrast the quartz diorite/tonalite plutons show mineralogical and chemical variation, both within and between plutons. The granodiorite, monzogranite, and syenogranite plutons closely resemble other peraluminous granitoid plutons characteristic of the Meguma terrane. The quartz diorite/tonalite plutons are varied but chemically resemble minor Devonian mafic intrusions elsewhere in the Meguma terrane. Like other plutons of the Meguma terrane, the Trafalgar Plutonic Suite has chemical characteristics of volcanic-arc to syn-collisional granitoid rocks and likely has experienced extensive contamination by metasedimentary material as documented by previous studies of plutons in the Meguma terrane. The minor quartz diorite/tonalite plutons are additional examples of the mafic rocks that have been proposed in tectonic models of the Meguma terrane to have facilitated melting of the lower crust to generate granodioritic parent magmas, followed by crystal fractionation and extensive contamination by metasedimentary material.

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.

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