40Ar/39Ar ages of detrital muscovite within early Paleozoic overstep sequences, Avalon composite terrane, southern New Brunswick: implications for extent of late Paleozoic tectonothermal overprint

1990 ◽  
Vol 27 (9) ◽  
pp. 1209-1214 ◽  
Author(s):  
R. D. Dallmeyer ◽  
R. D. Nance
Keyword(s):  
New Brunswick ◽  
Coarse Grained ◽  
Granitic Rocks ◽  
Late Paleozoic ◽  
Low Grade ◽  
Early Paleozoic ◽  
Late Precambrian ◽  
Pelitic Schist ◽  
Gas Fractions ◽  
Thermal Overprint

Concentrates of coarse-grained detrital muscovite from the Ratcliffe Brook Formation (lowermost Cambrian) display internally discordant 40Ar/39Ar age spectra. Gas fractions evolved at intermediate and high experimental temperatures record apparent ages of ca. 610–620 Ma. These are interpreted as dating initial cooling through temperatures appropriate for intracrystalline retention of 40Ar and may indicate derivation from mylonite zones developed within proximal late Precambrian granitic rocks. Gas fractions evolved at lower experimental temperatures record patterns of spectra discordance that suggest the constituent grains experienced partial, intracrystalline diffusive loss of 40Ar during a late Paleozoic, low-grade thermal overprint. A muscovite concentrate from pelitic schist beneath the allochthonous, latest Precambrian Cranberry Head granite records a 40Ar/39Ar plateau age of 318 ± 1 Ma. This is interpreted as closely dating Late Carboniferous thrust emplacement of the allochthon.

40Ar/39Ar whole-rock phyllite ages from late Precambrian rocks of the Avalon composite terrane, New Brunswick: evidence of Silurian–Devonian thermal rejuvenation

1994 ◽  
Vol 31 (5) ◽  
pp. 818-824 ◽  
Author(s):  
R. David Dallmeyer ◽  
R. Damian Nance
Keyword(s):  
New Brunswick ◽  
Low Grade ◽  
Fine Grained ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Minimum Age ◽  
Tectonic Contact ◽  
Age Constraints ◽  
Gas Fractions ◽  
Thermal Overprint

Several variably deformed and metamorphosed, late Precambrian volcanic–sedimentary successions have been recognized within the Avalon composite terrane exposed in the Caledonian Highlands of southern New Brunswick. Whole-rock samples of metasedimentary phyllite and phyllitic metatuff from the oldest (ca. 600–635 Ma) Avalonian succession display similar, internally discordant 40Ar/39Ar age and apparent K/Ca spectra. Intermediate-temperature gas fractions were experimentally evolved solely from very fine grained, cleavage-aligned white micas. These yield apparent ages between ca. 430 and 410 Ma, and are interpreted to closely date a static Late Silurian – Early Devonian thermal rejuvenation.Evidence for a Silurian – Devonian thermal event has not been previously documented in Avalonian rocks of the Caledonian Highlands (Caledonia assemblage). However, a thermal overprint of similar age (ca. 400 Ma) is recorded by metamorphic muscovite in high-grade gneisses and platformal metasedimentary rocks (Brookville assemblage), which are in tectonic contact with the low-grade Caledonia assemblage. These potentially correlative thermal overprints may provide minimum age constraints on the juxtaposition of these contrasting tectono-stratigraphic assemblages, which are likely to have been palinspastically separate tectonic elements during the earliest Paleozoic.

Pre-Silurian stratigraphy and tectonic significance of the St. Croix Belt, southeastern Maine

1987 ◽  
Vol 24 (12) ◽  
pp. 2459-2469 ◽  
Author(s):  
Allan Ludman
Keyword(s):  
New Brunswick ◽  
Continental Slope ◽  
Early Paleozoic ◽  
The West ◽  
Early Devonian ◽  
Late Precambrian ◽  
Iapetus Ocean ◽  
Continental Block ◽  
Tectonic Significance ◽  
Anoxic Basin

The St. Croix Belt of southeastern Maine and southwestern New Brunswick is part of a distinctive terrane situated between the Avalon platform and Miramichi arc—two important physiographic components of the Late Precambrian – early Paleozoic Iapetus Ocean. It bears lithologic and stratigraphic similarities to both of those tracts but is identical to neither. Formerly mapped entirely as the Cookson Formation, it is now divided into four formations of Cambrian through Early Orodovician age assigned to the Cookson Group. These rocks record periodic influxes of terrigenous debris into a deep anoxic basin and may have been part of the west-facing continental slope of the Avalonian continental block. The St. Croix Belt has been strongly affected by both pre-Silurian and Early Devonian (Acadian) folding. Facies changes rather than tectonic sutures are used to explain the relationships between the St. Croix Belt and its neighbouring pre-Silurian tracts.

Tectonic implications of 40Ar/39Ar mineral ages from late Precambrian – Cambrian plutons, Avalon composite terrane, southern New Brunswick, Canada

1992 ◽  
Vol 29 (11) ◽  
pp. 2445-2462 ◽  
Author(s):  
R. David Dallmeyer ◽  
R. Damian Nance
Keyword(s):  
New Brunswick ◽  
Quartz Diorite ◽  
Head Group ◽  
Low Grade ◽  
Marine Strata ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Sedimentary Sequences ◽  
Stratigraphic Record ◽  
Isotope Correlation

Within the Avalon composite terrane exposed in southern New Brunswick, late Precambrian, low-grade volcanic–sedimentary sequences are juxtaposed against late Precambrian gneisses (Brookville Gneiss) and older platformal metasedimentary rocks (Green Head Group) along the Caledonia Fault. Both assemblages host petrographically similar suites of calc-alkalic dioritic and granodioritic plutons. Those intruding volcanic–sedimentary sequences (Caledonia terrane) record ca. 615–625 Ma crystallization ages typical of arc-related magmatism throughout the Avalon composite terrane. However, 40Ar/39Ar age data from stocks intruding gneisses and platformal metasedimentary rocks (Brookville terrane) suggest significantly younger crystallization ages.36Ar/40Ar versus 39Ar/40Ar isotope correlation ages recorded by hornblende are interpreted to closely date postmagmatic cooling within six plutons: Fairville Granite (547 ± 1 Ma); French Village Quartz Diorite (539 ± 2 and 537 ± 1 Ma); Rockwood Park Granodiorite (529 ± 2 and 523 ± 3.5 Ma); Musquash Granite (526 ± 2 Ma); Milkish Head Granite (Red Bridge pluton, 520 ± 1.5 Ma); Lepreau Diorite (Talbot Road pluton, 519 ± 2 Ma and Hansen Stream pluton, 518 ± 1.5 Ma. A hornblende isotope correlation age of 530 ± 2 Ma from penetratively foliated amphibolite within the French Village Quartz Diorite suggests that the magmatic activity was locally accompanied by ductile shear. Muscovite within granitic pegmatite in the Brookville Gneiss records a 40Ar/39Ar plateau age of 510 ± 1 Ma interpreted to date final phases of associated magmatic activity.Arc-related magmatism extending into the Cambrian contrasts with the characteristic tectono-stratigraphic record in the Avalon composite terrane where late Precambrian igneous rocks are overstepped by Cambrian–Ordovician shallow-marine strata with only a local and minor record of rift-related volcanic activity. Although the Brookville terrane shows affinities with the Avalon composite terrane during the late Precambrian, the 40Ar/39Ar age data suggest that it was isolated as a distinct tectono-stratigraphic element by the Early Cambrian.

Geometry and kinematics of a major crustal shear zone segment in the Appalachians of southern New Brunswick

1994 ◽  
Vol 31 (10) ◽  
pp. 1523-1535 ◽  
Author(s):  
Adrian F. Park ◽  
Paul F. Williams ◽  
Steven Ralser ◽  
Albert Léger
Keyword(s):  
New Brunswick ◽  
Shear Zone ◽  
Low Grade ◽  
Northern Boundary ◽  
Crystalline Complex ◽  
Late Precambrian ◽  
The North ◽  
Appalachian Orogen ◽  
Complex Forms ◽  
Geometry And Kinematics

In southern New Brunswick the Kennebecasis Fault follows the northern boundary of a crystalline portion of the late Precambrian – Cambrian Avalon terrane. This low-grade crystalline complex forms the basement to a series of Carboniferous through Triassic basins. This complex also contains a major shear zone relic that is largely flat lying but upturned adjacent to the fault, and that with it defines the Pocologan–Kennebecasis fault zone. The orientation of the main composite foliation (S1) and the included mineral (stretching) lineation (L1) indicate that this geometry is a primary feature of the shear zone, representing a linked pair of horizontal and vertical detachments bounding an allochthonous unit. Kinematic indicators show that this allochthon moved parallel to the strike of the north Appalachian orogen, with top towards the west or west-southwest. The bounding shear zone is not uniform, but consists of a mylonite–phyllonite adjacent to the detachment. The upturned segment of the shear zone has been the site of later, brittle reactivation, one episode of which is represented by the Kennebecasis Fault. The main shear zone relic relates to more fundamental events, such as the accretion of the Avalon terrane.

U-Pb Monazite Geochronology of Granitic Rocks from Maine: Implications for Late Paleozoic Tectonics in the Northern Appalachians

1996 ◽  
Vol 104 (2) ◽  
pp. 185-195 ◽  
Author(s):  
Paul B. Tomascak ◽  
Eirik J. Krogstad ◽  
Richard J. Walker
Keyword(s):  
Granitic Rocks ◽  
Late Paleozoic

scholarly journals Forensic igneous petrology: locating the source quarry for the “black granite" Titanic headstones in Halifax, Nova Scotia, Canada

2017 ◽  
Vol 53 ◽  
pp. 087-114
Author(s):  
D. Barrie Clarke ◽  
Christopher R.M. McFarlane ◽  
David Hamilton ◽  
David Stevens
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Coarse Grained ◽  
Chemical Compositions ◽  
Dimension Stone ◽  
Forensic Evidence ◽  
Igneous Petrology ◽  
Temporal Properties ◽  
Textural Parameters ◽  
The Right

In Halifax, Nova Scotia, 149 victims of the 1912 sinking of the Titanic lie beneath petrologically identical "black granite" headstones. Those headstones, supplied by the White Star Line, arrived in Halifax in late 1912, but no known historical document reveals their source. They consist of medium- to coarse-grained olivine-bearing gabbro, with cumulus phases consisting of randomly oriented euhedral plagioclase laths, corroded olivine, and titaniferous magnetite, and intercumulus material consisting of augite with reaction rims of hornblende, both of which are variably altered to actinolite and biotite. Three types of forensic evidence [quantitative – radiometric age of 422.1 ± 1.3 Ma (n = 17), mean olivine FeO/(FeO + MgO) values ranging from 0.43 to 0.46, augite rim trace- element compositions (35 elements), and whole-rock chemical compositions (48 elements), including statistical analysis of all these data showing no significant differences between the headstones and their putative source quarry; qualitative – mineral assemblages, modal proportions, textural parameters, style and degree of alteration; and circumstantial – regional reputation, quarrying history, local logistics, regional transportation, McGrattan marker] connect the Titanic headstones to the Saint George Batholith in southwestern New Brunswick. Precise matching of any dimension stone to its source quarry is problematic, because that material connects only to a void in the quarry. Ideally, all physical-chemical-temporal properties of the dimension stone and source quarry should match, both quantitatively and qualitatively, but in reality only the ages must almost certainly match. Thus it is remotely possible for the right quarry to mismatch most of the properties of the dimension stone, and for a wrong quarry to match most of the properties of the dimension stone. However, in the case of the Titanic headstones, the cumulative weight of all the quantitative, qualitative, and circumstantial evidence, combined with a process of elimination and application of Ockham’s razor, indicate that the Charles Hanson quarry near Bocabec, southwestern New Brunswick, is the likely source for the gabbroic Titanic headstones in Halifax, Nova Scotia.

Chapter 6 Conclusions, differences between the Jabal Akhdar and Saih Hatat domes and unanswered questions

10.1144/m54.6 ◽  
2021 ◽  
Vol 54 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Andreas Scharf ◽  
Frank Mattern ◽  
Mohammed Al-Wardi ◽  
Gianluca Frijia ◽  
Daniel Moraetis ◽  
...  
Keyword(s):  
Large Scale ◽  
Late Paleozoic ◽  
Future Research ◽  
Early Paleozoic ◽  
Chronological Order ◽  
Oman Mountains ◽  
Tectonic Events ◽  
Major Fault ◽  
Tethys Ocean ◽  
Semail Ophiolite

AbstractThis chapter provides the conclusions/outlines of the tectonics, affecting the Southeastern Oman Mountains, including the Jabal Akhdar and Saih Hatat domes. The main tectonic events include amongst others (1) Neoproterozoic rifting, (2) two distinct early Paleozoic compressive events, (3) large-scale open ‘Hercynian’ folding and formation of a pronounced unconformity during the late Paleozoic, (4) rifting preceding the opening of the Neo-Tethys Ocean during the late Paleozoic, (5) late Cretaceous obduction of the Semail Ophiolite and the response of the Arabian lithosphere as well as (6) post-obductional tectonics. Also of major geological significance are the three major glaciations (Sturtian, Marinoan and Late Paleozoic Gondwana glaciation) which have been recorded in the rocks of northern Oman. Moreover, major lithological, structural and metamorphic differences exist between the Jabal Akhdar and Saih Hatat domes. It appears likely that a major fault, striking parallel to the eastern margin of the Jabal Akhdar Dome, probably originating during Neoproterozoic terrain accretion, acted as a divide between both domes until present. This fault was multiple times reactivated and could explain the differences between the two domes. A catalogue of unanswered questions is included in chronological order to express that many geological aspects need further investigation and future research projects.

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