Early Silurian paleolatitude for central Newfoundland from paleomagnetism of the Wigwam Formation

1992 ◽  
Vol 29 (8) ◽  
pp. 1652-1661 ◽  
Author(s):  
Kenneth L. Buchan ◽  
Joseph P. Hodych
Keyword(s):  
Volcanic Rocks ◽  
Opposite Polarity ◽  
Secondary Component ◽  
Lake Area ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study

Redbeds and minor volcanic rocks of the Early Silurian Wigwam Formation of the Botwood Group were sampled in the Exploits Subzone of the Dunnage Zone of central Newfoundland. At 18 sedimentary and 3 volcanic sites thermal demagnetization isolated a shallow northward (or southward) magnetization (D = 356.0°, I = −16.8°; k = 12.9; α95 = 9.2°; n = 21 site means) after correction for the tilt of bedding. A positive fold test demonstrates that this remanence predates regional Siluro–Devonian folding. A primary age for the remanence is indicated by positive conglomerate tests on volcanic clasts, and reversals correlated with sedimentary stratigraphy. Antiparallel remanence directions at sites of opposite polarity indicate that the primary remanence is not partially overprinted by a secondary component. The Exploits Subzone of the Dunnage Zone is interpreted to have been at low paleolatitudes (8.5°S ± 5°) during the Early Silurian. We reached a similar conclusion for the Notre Dame Subzone of the Dunnage Zone in a previous paleomagnetic study of Early Silurian redbeds and volcanic rocks of the King George IV Lake area. The low paleolatitudes obtained for the Wigwam and King George IV Lake rocks do not differ significantly and, hence, provide no evidence for a large ocean between the two subzones in the Early Silurian. However, the azimuthal orientation of the subzones at that time is still uncertain, and an ocean with its axis oriented in a north–south direction would not be detected by the paleomagnetic method.

Rare earth element concentrations in Quaternary volcanic rocks of southwestern British Columbia

1984 ◽  
Vol 21 (6) ◽  
pp. 731-736 ◽  
Author(s):  
Nathan L. Green ◽  
Paul Henderson
Keyword(s):  
British Columbia ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Lake Area ◽  
Calc Alkaline ◽  
Lower Light ◽  
The Individual ◽  
High Level ◽  
Ree Patterns

A suite of hy-normative hawaiites, ne-normative mugearite, and calc-alkaline andesitic rocks from the Garibaldi Lake area exhibits fractionated, slightly concave-upward REE patterns (CeN/YbN = 4.5–15), heavy REE contents about 5–10 times the chondritic abundances, and no Eu anomalies. It is unlikely that the REE patterns provide information concerning partial melting conditions beneath southwestern British Columbia because they have probably been modified substantially by upper crustal processes including crustal contamination and (or) crystal fractionation. The REE contents of the Garibaldi Lake lavas are not incompatible with previous interpretations that (1) the hawaiites have undergone considerable fractionation of olivine, plagioclase, and clinopyroxene; and (2) the individual andesitic suites were derived from separate batches of chemically distinct magma that evolved along different high-level crystallization trends. In general, however, the andesites are characterized by lower light REE contents than the basaltic andesites. These differences in LREE abundances may reflect different amounts of LREE-rich accessory phases, such as apatite, sphene, or allanite, assimilated from the underlying quartz diorites.

Étude paléomagnétique des roches protérozoïques de la formation de Sakami, région de la Grande Rivière, Territoire du Nouveau-Québec, Canada

1981 ◽  
Vol 18 (12) ◽  
pp. 1893-1899
Author(s):  
Maurice K. Seguin ◽  
Kamal N. M. Sharma ◽  
Gérard Woussen
Keyword(s):  
Magnetic Memory ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study ◽  
Geological Formation ◽  
The Mean

We describe a paleomagnetic study of Mid-Proterozoic sandstone of the Sakami Formation. The thermal demagnetization is more effective than by alternating field; this indicates that part of the magnetic memory is located in hematite. The mean direction of magnetization after thermal and alternating field treatments is 031, −25 α95 = 7.1°, K = 73 and the corresponding paleopole position is 103°W, 18°S (dm = 11°, dp = 8°). These results are important because a part of this geological formation will be covered with water after completion of the development works of La Grande Rivière. [Journal Translation]

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.

Coeval sedimentation, magmatism, and fold-thrust belt development in the Trans-Hudson Orogen: geochronological evidence from the Wekusko Lake area, Manitoba, Canada

1999 ◽  
Vol 36 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Kevin M Ansdell ◽  
Karen A Connors ◽  
Richard A Stern ◽  
Stephen B Lucas
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Lake Area ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Minimum Age ◽  
Flin Flon ◽  
Felsic Volcanic

Lithological and structural mapping in the east Wekusko Lake area of the Flin Flon Belt, Trans-Hudson Orogen, suggested an intimate relationship between magmatism, fluvial sedimentation, and initiation of fold and thrust belt deformation. Conventional U-Pb geochronology of volcanic rocks in fault-bounded assemblages provides a minimum age of 1876 ± 2 Ma for McCafferty Liftover back-arc basalts, and ages of between 1833 and 1836 Ma for the Herb Lake volcanic rocks. A rhyolite which unconformably overlies Western Missi Group fluvial sedimentary rocks has complex zircon systematics. This rock may be as old as about 1856 Ma or as young as 1830 Ma. The sedimentary rocks overlying this rhyolite are locally intercalated with 1834 Ma felsic volcanic rocks, and yield sensitive high resolution ion microprobe (SHRIMP) U-Pb and Pb-evaporation detrital zircon ages ranging from 1834 to 2004 Ma. The Eastern Missi Group is cut by an 1826 ± 4 Ma felsic dyke, and contains 1832-1911 Ma detrital zircons. The dominant source for detritus in the Missi Group was the Flin Flon accretionary collage and associated successor arc rocks. The fluvial sedimentary rocks and the Herb Lake volcanic rocks were essentially coeval, and were then incorporated into a southwest-directed fold and thrust belt which was initiated at about 1840 Ma and active until at least peak regional metamorphism.

A Paleomagnetic Study of the Tectonic Deformation in Circum-Marmara Region, NW Anatolia, during the Late Cretaceous and Cenozoic Period

2020 ◽  
Author(s):  
Burak Semih Cabuk ◽  
Mualla Cengiz
Keyword(s):  
Upper Cretaceous ◽  
Rock Magnetism ◽  
Volcanic Rocks ◽  
High Coercivity ◽  
The Black Sea ◽  
Tectonic Deformation ◽  
Marmara Region ◽  
Magnetic Minerals ◽  
Single Plate ◽  
Paleomagnetic Study

<p>The Marmara region is located on the Alpine Himalayan orogenic belt which experienced a active tectonic deformation. The region consists of tectonic units such as the Istanbul Zone, the Strandja Zone and the Sakarya Continent. It is reported in the previous geological studies that the Istanbul Zone began to move southwards appart from the Moesia Platform with the effect of West Blacksea Fault in the west and West Crimea Fault in the east after the the opening of the Black Sea in the Cretaceous. It is known that the Intra Pontide suture is formed after the closure of the Intra-Pontide ocean during the Early Eocene due to the collision between İstanbulzone and the Sakarya continent which moved northwards. As a result of the continental collision, the region has completed its evolution under the influence of basin formation and the emplacement of North Anatolian Fault Zone from Miocene to the present.</p><p> </p><p>In this study, Upper Cretaceous-Oligocene sedimentary and volcanic rocks were sampled at 103 sites to investigate the tectonic deformation of the area. As a result of rock magnetism studies, it was shown that magnetic minerals in sedimentary and volcanic rocks are defined by titanium-rich titanomagnetite showing low coercivity, while in limestone samples, magnetization is defined by hematite showing high coercivity. As a result of anisotropy of magnetic susceptibility (AMS) measurements, it was observed that most of the samples show magnetic foliation and a deformation ellipsoid which is oblate. Paleomagnetic results show counterclockwise rotation of 19.9°±10.9° for the Sakarya continent, 27.4°±11.6°for the Pontides and 15.6°±11.8°for the Strandja Zone from Eocene to present. The results indicate that the region has completed the collision in Eocene and rotated counterclockwise as a large block. Deformation due to basin development or fault bounded block rotations which developed after Miocene could not been detected in this study. Miocene paleomagnetic data from previous studies in the study area are compatible with counterclockwise rotations in Upper Cretaceous-Oligocene which shows that different blocks emplaced in the study area moved together as a single plate during Eocene-Miocene time.</p>

Geochemistry and age of Timiskaming alkali volcanics and the Otto syenite stock, Abitibi, Ontario

1990 ◽  
Vol 27 (10) ◽  
pp. 1304-1311 ◽  
Author(s):  
D. Ben Othman ◽  
N. T. Arndt ◽  
W. M. White ◽  
K. P. Jochum
Keyword(s):  
Volcanic Rocks ◽  
Lake Area ◽  
Incompatible Elements ◽  
Ion Probe ◽  
Mineral Isochron

Tephrites and trachytes of the Timiskaming volcanics from the Kirkland Lake area (Ontario) and syenites and a granite from the nearby Otto Stock are characterized by extreme enrichment of incompatible elements coupled with relative depletion of Nb, Ti, and to a lesser extent Zr and Y.The volcanic rocks have a whole-rock Sm–Nd isochron age of 2740 ± 117 Ma (2σ error), and minerals separated from the Otto Stock, a Sm–Nd age of 2544 ± 50 Ma. Conventional and ion probe U–Pb analyses of zircons from the Otto Stock yielded an upper intercept age of 2700 ± 19 Ma, whereas the more concordant ion probe analyses had a mean 207Pb/206Pb age of 2671 ± 8 Ma (2σ). The latter is interpreted as the age of emplacement of both the volcanics and the pluton, and the Sm–Nd mineral isochron age is thought to reflect a period of later disturbance, probably during regional metamorphism.A high initial εNd of 2.5 ± 1.5 for Kirkland Lake volcanics indicates long-term isotopic depletion of their source. This value is the same as that for volcanic rocks throughout the Abitibi belt and indicates that any chemically enriched material in the source cannot have been much older than the volcanics themselves. An environment remote from older continents is inferred.

Physical volcanology of the footwall rocks near the Mattabi massive sulphide deposit, Sturgeon Lake, Ontario

1988 ◽  
Vol 25 (2) ◽  
pp. 280-291 ◽  
Author(s):  
D. A. Groves ◽  
R. L. Morton ◽  
J. M. Franklin
Keyword(s):  
Repetitive Sequences ◽  
Volcanic Rocks ◽  
Massive Sulphide ◽  
Lava Flows ◽  
Pyroclastic Flows ◽  
Lake Area ◽  
Massive Sulphide Deposit ◽  
Sulphide Deposit ◽  
Water Influx ◽  
Felsic Lava

Subaerial and shallow subaqueous mafic hyalotuffs, lava flows, and flow breccias, felsic lava flows, and pyroclastic flows and falls form a 2 km thick succession beneath the Mattabi massive sulphide deposit. The lowermost 800 m of section comprises massive to amygdaloidal mafic flows and flow breccias interlayered with repetitive sequences of thinly bedded felsic tuff: pillow lavas and hyaloclastites are absent. Amygdaloidal felsic lavas overlie the mafic flows and are locally capped by coarse explosion breccia. This breccia is believed to represent the start of mafic hydrovolcanism, which produced ash falls, surges, and flows. These pyroclastic deposits formed thin- to thick-bedded hyalotuffs that contain highly vesicular and quenched juvenile and accessory lithic fragments. Periods of water influx probably led to the construction of a tuff cone, which represents a submergent hydrovolcanic cycle.In the Mattabi area, pyroclastic flow deposits form the immediate mine footwall strata and include (i) massive basal beds and overlying bedded ash tuffs and (ii) massive pumiceous units. These deposits overlie and, to the west in the Darkwater Lake area, are intercalated with the mafic hyalotuff sequence. The morphology of the footwall volcanic rocks indicates that the Mattabi and the F-zone massive sulphide deposits formed in a shallow subaqueous environment.

Paleomagnetic Study and Chemistry of Newer Dolerites from Singhbhum, Bihar, India

1974 ◽  
Vol 11 (8) ◽  
pp. 1043-1054 ◽  
Author(s):  
R. K. Verma ◽  
S. N. Prasad
Keyword(s):  
Free Space ◽  
Regional Metamorphism ◽  
Magnetic Mineral ◽  
Polished Section ◽  
Thermal Demagnetization ◽  
Paleomagnetic Study ◽  
Younger Age ◽  
Igneous Activity

Results of paleomagnetic studies on seventeen dikes sampled from the Newer Dolerites of Singhbhum, between latitude 22°0′N to 22°45′N and longitude 85°48′E to 86°25′E are reported. The dikes are of Precambrian age, probably older than 1000 my. Stable directions of magnetization were obtained for eleven sites by thermal demagnetization in a field free space in temperatures ranging from 250° to 400 °C. These studies showed that the dikes had been reheated by igneous activity of neighboring dikes of a younger age or by regional metamorphism of a younger period. Polished section studies carried out on these dikes showed that the magnetic mineral had been significantly altered as a result of these processes. Reliable virtual geomagnetic poles were obtained for ten different sites. These pole positions can be collected into three different groups which may represent three episodes of igneous activity of the Newer Dolerites. A very tentative polar wandering curve for the Precambrian in India is given.

A paleomagnetic study of volcanic rocks from Mistastin Lake, Labrador, Canada

1969 ◽  
Vol 6 (4) ◽  
pp. 309-315 ◽  
Author(s):  
K.L. Currie ◽  
A. Larochelle
Keyword(s):  
Volcanic Rocks ◽  
Paleomagnetic Study

Regional implications of Upper Triassic metavolcanic and metasedimentary rocks on the Chilkat Peninsula, southeastern Alaska

1980 ◽  
Vol 17 (6) ◽  
pp. 681-689 ◽  
Author(s):  
George Plafker ◽  
Travis Hudson
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Upper Triassic ◽  
Late Triassic ◽  
Low Grade ◽  
Lake Area ◽  
Metasedimentary Rocks

A low-grade metamorphic sequence consisting of thick mafic volcanic rocks overlain by calcareous flysch with very minor limestone underlies much of the Chilkat Peninsula. Fossils collected from both units are of Triassic age, probably late Karnian. This sequence appears to be part of the Taku terrane, a linear tectono-stratigraphic belt that now can be traced for almost 700 km through southeastern Alaska to the Kelsall Lake area of British Columbia. The age and gross lithology of the Chilkat Peninsula sequence are comparable to Upper Triassic rocks that characterize the allochthonous tectono-stratigraphic terrane named Wrangellia. This suggests either that the two terranes are related in their history or that they are allochthonous with respect to one another and coincidentally evolved somewhat similar sequences in Late Triassic time.

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