Pliocene–Pleistocene genesis for the Murray Brook and Heath Steele Au–Ag gossan ore deposits, New Brunswick, from paleomagnetism

1996 ◽  
Vol 33 (1) ◽  
pp. 1-11 ◽  
Author(s):  
D. T. A. Symons ◽  
M. T. Lewchuk ◽  
D. R. Boyle
Keyword(s):  
New Brunswick ◽  
Ore Deposits ◽  
Age Dating ◽  
Rotational Axis ◽  
Polar Wander ◽  
The Past ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Last Glaciation ◽  
Host Rocks

Several Au–Ag gossans occur over massive sulphide deposits in the Ordovician Tetagouche Group near Bathurst, New Brunswick. The Murray Brook and Heath Steele B zone goethite gossans were about 45 and 15 m thick, respectively, prior to mining. They contain no minerals suitable for radiometric age dating. Geologically they must be younger than the Devonian Acadian orogeny and older than the last glaciation. Paleomagnetic methods were used to analyse specimens from 29 sites, mostly from ore on the pit walls. Host rocks and sulphide mineralization retain characteristic remanent magnetization directions in magnetite and pyrrhotite with a variety of directions that include possible Devonian overprints. Fertile and barren gossan specimens at 21 sites retain antiparallel normal and reversed A characteristic remanence components in goethite and (or) hematite. The A direction is D = 357.7°, I = 61.7 °(α95 = 4.5°, k = 31). Its pole of 134.2°E, 85.2°N (dp = 5.4°, dm = 7.0°) falls on the North American apparent polar wander path and circumscribes the Earth's present rotational axis, indicating that the gossans formed during the Pliocene–Pleistocene. Examination of the site locations in the pits, along with the remanence polarity of their goethite and hematite A components, suggests the gossans formed during Chrons 1 and 2 only, or in the past 2.3 ± 0.3 Ma.

Paleomagnetism of the Lawrenceton Formation volcanic rocks, Silurian Botwood Group, Change Islands, Newfoundland

1989 ◽  
Vol 26 (2) ◽  
pp. 296-304 ◽  
Author(s):  
Julie E. Gales ◽  
Ben A. van der Pluijm ◽  
Rob Van der Voo
Keyword(s):  
North American ◽  
Volcanic Rocks ◽  
Mobile Belt ◽  
Structural Mapping ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Study ◽  
North American Craton

Paleomagnetic sampling of the Lawrenceton Formation of the Silurian Botwood Group in northeastern Newfoundland was combined with detailed structural mapping of the area in order to determine the deformation history and make adequate structural corrections to the paleomagnetic data.Structural analysis indicates that the Lawrenceton Formation experienced at least two folding events: (i) a regional northeast–southwest-trending, Siluro-Devonian folding episode that produced a well-developed axial-plane cleavage; and (ii) an episode of local north-trending folding. Bedding – regional cleavage relationships indicate that the latter event is older than the regional folding.Thermal demagnetization of the Lawrenceton Formation yielded univectorial southerly and shallow directions (in situ). A fold test on an early mesoscale fold indicates that the magnetization of the Botwood postdates this folding event. However, our results, combined with an earlier paleomagnetic study of nearby Lawrenceton Formation rocks, demonstrate that the magnetization predates the regional folding. Therefore, we conclude that the magnetization occurred subsequent to the local folding but prior to the period of regional folding.While a tectonic origin for local folding cannot be entirely excluded, the subaerial nature of these volcanics, the isolated occurrence of these folds, and the absence of similar north-trending folds in other areas of eastern Notre Dame Bay suggest a syndepositional origin. Consequently, the magnetization may be nearly primary. Our study yields a characteristic direction of D = 175°, I = +43°, with a paleopole (16°N, 131 °E) that plots near the mid-Silurian track of the North American apparent polar wander path. This result is consistent with an early origin for the magnetization and supports the notion that the Central Mobile Belt of Newfoundland was adjacent to the North American craton, in its present-day position, since the Silurian.

Paleomagnetism of the komatiitic basalts of the Ottawa Islands, N.W.T.

1985 ◽  
Vol 22 (4) ◽  
pp. 553-566 ◽  
Author(s):  
K. L. Buchan ◽  
W. R. A. Baragar
Keyword(s):  
North American ◽  
Hudson Bay ◽  
The West ◽  
Magnetization Direction ◽  
Polar Wander ◽  
The North ◽  
Dominant Component ◽  
Apparent Polar Wander Path

The komatiitic basalts of the Ottawa Islands in eastern Hudson Bay are on strike with and believed to form a continuation of similar units of the Cape Smith Belt 150 km to the northeast. Units sampled in the Ottawa Islands all dip gently to the west and hence are not suitable for an internal fold test of their age of magnetization. However, before correcting for the tilt of the lavas, the dominant magnetization direction (D = 207.6°, I = 61.9°, k = 168, α95 = 3.7°) does not differ significantly from the uncorrected magnetization direction reported from the steeply dipping, northwest-facing units at Cape Smith (D = 218°, I = 60°, k = 47, α95 = 4°). This negative fold test suggests that the remanence at both locations was acquired after folding. Comparison with the North American Precambrian apparent polar wander path implies that overprinting is related to the Hudsonian Orogeny.A second stable magnetization directed to the west with a shallow inclination is superimposed on the dominant component at a number of sampling sites. Its direction is poorly defined and no fold test is possible. However, magnetic evidence suggests that this component was probably acquired as an overprint after the dominant magnetization, perhaps during a mild reheating associated with the Elsonian Orogeny.

scholarly journals The Apparent Polar Wander Path For the North China Block Since the Jurassic

1991 ◽  
Vol 104 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Zhong Zheng ◽  
Masaru Kono ◽  
Hideo Tsunakawa ◽  
Gaku Kimura ◽  
Qingyun Wei ◽  
...  
Keyword(s):  
North China ◽  
North China Block ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path

Paleomagnetism of the Lac St-Jean anorthosite and related rocks, Grenville Province, Quebec

1983 ◽  
Vol 20 (2) ◽  
pp. 246-258 ◽  
Author(s):  
K. L. Buchan ◽  
W. F. Fahrig ◽  
G. N. Freda ◽  
R. A. Frith
Keyword(s):  
North American ◽  
Regional Metamorphism ◽  
The Other ◽  
Central Portion ◽  
Grenville Province ◽  
Polar Wander ◽  
Thermal Demagnetization ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Normal Polarity

Alternating field and thermal demagnetization study of the Lac St-Jean anorthosite and related rock units in the central portion of the exposed Grenville Province reveals two components of magnetization, one of reversed and the other of normal polarity. Both components are thought to have been acquired during the last regional metamorphism, which was sufficiently intense in this area (mostly amphibolite grade) to reset any earlier magnetization. Corresponding paleopoles at 193°W, 8°S (dm = 7.3°, dp = 4.6°) and 213°W, 19°S (dm = 10.5°, dp = 8.5°) lie along the 950–900 Ma segment of the recently calibrated Grenville track of the North American apparent polar wander path, a track that has thus far been defined largely by results from rock units of the western Grenville.

Paleomagnetism of the Moenkopi and Chinle Formations in central New Mexico: Implications for the North American Apparent Polar Wander Path and Triassic magnetostratigraphy

1991 ◽  
Vol 96 (B9) ◽  
pp. 14239-14262 ◽  
Author(s):  
Roberto S. Molina-Garza ◽  
John W. Geissman ◽  
Rob Van der Voo ◽  
Spencer G. Lucas ◽  
Steve N. Hayden
Keyword(s):  
New Mexico ◽  
North American ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path

Comments and Reply on "Age estimation of the Deccan Traps from the North American apparent polar wander path"

Geology ◽  
1989 ◽  
Vol 17 (1) ◽  
pp. 88 ◽  
Author(s):  
Jean Besse ◽  
Vincent Courtillot ◽  
Didier Vandamme ◽  
A. K. Baksi ◽  
Paul R. Stoddard ◽  
...  
Keyword(s):  
North American ◽  
Age Estimation ◽  
Deccan Traps ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path

The evolution of oceanic oxygen-isotope variability in the North Atlantic over the past three million years

1988 ◽  
Vol 318 (1191) ◽  
pp. 679-688 ◽  
Keyword(s):  
North Atlantic ◽  
Climatic Variability ◽  
Oxygen Isotopic Composition ◽  
Early Pleistocene ◽  
Rotational Axis ◽  
The Past ◽  
The North ◽  
Orbital Geometry ◽  
Precession Cycle ◽  
Oxygen Isotopic

Throughout the past three million years, variability in the oxygen-isotopic composition of the ocean, caused by changing ice-sheet mass on the continents, has been concentrated at the frequencies associated with changes in the earth’s orbital geometry. The amplitude of variability has increased towards the present. An increase in variability associated with changes in the obliquity of the Earth’s rotational axis (period 41 ka) during the early Pleistocene was followed by an increase in power related to the precession cycle (23 ka) and associated ellipticity cycle (ca. 100 ka) during the past million years. Although deep-sea sediments are the best place to observe this evolution in climatic variability, we will not be able to understand it without more data from other geological sources.

Indication for counterclockwise declination deviation in the Cretaceous of the North Paris Basin

2004 ◽  
Vol 175 (3) ◽  
pp. 249-255
Author(s):  
Emó Márton ◽  
László Csontos ◽  
Jean-Louis Mansy ◽  
Françoise Bergerat
Keyword(s):  
Late Cretaceous ◽  
Late Eocene ◽  
Angular Deviation ◽  
Paris Basin ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Result ◽  
Angle Of Deviation ◽  
Paleomagnetic Direction

Abstract Paleomagnetic sampling was carried out in Mesozoic exposures of Northwest France and Southeast Belgium. Cretaceous localities in Hainaut, Boulonnais and Normandie yielded statistically well defined paleomagnetic directions. These localities fall into two groups. Hainaut and Boulonnais are characterized by declinations suggesting 30° counterclockwise (CCW) angular deviation of declination with respect to the present North, while Normandie exhibits moderate (12°) clockwise (CW) angular deviation with respect to the present North. In Normandie, we also observed occasionally very weak signals of a CCW deviated component, which, however, could not be treated statistically. Fold test suggests that both groups of samples were remagnetized during deformation. The overall mean paleomagnetic declination of the first group is westernly, that of the second group practically coincides with post-Eocene European reference directions, From assessing structural inversion and relevant paleostress-directions in Normandie, remagnetization may be connected to tectonic inversion in late Eocene-Oligocene times. While the statistically meaningful paleomagnetic result for the second group fit the synthetic stable European apparent polar wander path (APWP) at about 30 Ma, the overall mean paleomagnetic direction of the first group (based on 5 localities, representing 42 samples) defines a pole which is significantly offset from it, at any time following the deposition of the studied sediments. One explanation of this offset could be intraplate rotation on a small (Brabant Massif) scale. However, the angle of deviation in declination seems to be too large for a tectonic solution. Furthermore the data obtained from the Paleozoic do not show such declination deviation. It seems, therefore, that we need to increase considerably the direct stable European paleomagnetic database for the late Cretaceous-Tertiary, in order to further improve the late Cretaceous-Paleogene segment of the European APWP.

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