Mississippian volcanic assemblage conformably overlying Cordilleran miogeoclinal strata, Turnagain River area, northern British Columbia, is not part of an accreted terrane

2005 ◽  
Vol 42 (8) ◽  
pp. 1449-1465 ◽  
Author(s):  
Philippe Erdmer ◽  
Mitchell G Mihalynuk ◽  
Hubert Gabrielse ◽  
Larry M Heaman ◽  
Robert A Creaser
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Lower Paleozoic ◽  
Magmatic Arc ◽  
Structural Relationships ◽  
Geochemical Study ◽  
Tectonic Contact ◽  
Back Arc ◽  
T Values

A Paleozoic volcanic assemblage exposed in northern British Columbia, near the Turnagain River, previously considered to be part of an accreted terrane, was reported to be in depositional contact with a part of the Cordilleran miogeocline. This paper presents an integrated field, U–Pb geochronology, Sm–Nd isotopic, and geochemical study across the basal contact of the volcanic assemblage. Strongly evolved εNd(T) values, between –13 and –21, from samples of lower Paleozoic sedimentary rocks exposed below the volcanic rocks, and correlated with Atan – Kechika – Road River – Earn strata of the miogeocline farther east, support a North American miogeoclinal affinity, consistent with previously established regional stratigraphic and structural relationships. Nd isotopic data from the volcanic assemblage contrast significantly with data from the sedimentary rocks and record a mantle source (εNd(T) values between +4.0 and +7.0), consistent with a magmatic arc or back arc; negative Nb anomalies are similarly compatible with either arc- or back-arc-related magmatism. A concordant 339.7 ± 0.6 Ma U–Pb zircon date was obtained from the volcanic assemblage. The mixed gradational contact between the miogeoclinal and volcanic rocks is marked by interlayering of finely laminated grey and green phyllites on the scale of centimetres, with no evidence of a tectonic contact. Bedding at the contact is folded into tight outcrop-scale folds that are intruded by an Early Jurassic (187.5 ± 2.9 Ma) granodiorite. On the basis of all available evidence, the contact is interpreted as a facies transition. The Mississippian volcanic assemblage may link the miogeocline with the early development of an Angayucham – Slide Mountain basin.

Geochemistry and tectonic environment of the Şarkışla area volcanic rocks in central Anatolia, Turkey

1987 ◽  
Vol 51 (362) ◽  
pp. 553-559 ◽  
Author(s):  
E. Gökten ◽  
P. A. Floyd
Keyword(s):  
Upper Cretaceous ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Central Anatolia ◽  
Magmatic Arc ◽  
Early Tertiary ◽  
Tectonic Environment ◽  
Geochemical Study ◽  
Lithological Composition ◽  
Back Arc

AbstractThe volcanic rocks of the Şarkışla area in northeastern central Anatolia are associated with volcaniclastics, turbiditic limestones and pelagic-hemipelagic shales of Upper Cretaceous-Palaeocene age. A preliminary geochemical study was undertaken to constrain local tectonic models, and due to the variable altered nature of the volcanics, determine the lithological composition and magma type. Chemically the volcanics are an andesite-dominated suite of calc-alkali lavas, probably developed adjacent to an active continental margin in a local (ensialic back-arc?) basinal area. The volcanic activity was probably related to a postulated magmatic arc just south of the area during the early Tertiary.

Provenance of Paleozoic sedimentary rocks in the Canadian Cordilleran miogeocline: a Nd isotopic study

1997 ◽  
Vol 34 (12) ◽  
pp. 1603-1618 ◽  
Author(s):  
Carmala N. Garzione ◽  
P. Jonathan Patchett ◽  
Gerald M. Ross ◽  
JoAnne Nelson
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Middle Devonian ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Isotopic Study ◽  
Middle Ordovician ◽  
Southern Alberta ◽  
T Values

Nd isotopes and trace elements in sedimentary rocks of the Yukon, the Northwest Territories, and northern British Columbia are used to examine the source of sediments in the Canadian Cordilleran miogeocline. Previous Nd isotope studies in southern Alberta demonstrated that strata of Neoproterozoic to Late Ordovician age were derived from Archean and Proterozoic Canadian Shield sources, whereas by the Late Devonian, a shift of 6 εNd units to younger crustal sources (εNd (T) = −6 to −9) had occurred. In this study, we found that the shift to younger crustal Nd isotopic signatures in the Yukon and Northwest Territories occurred much earlier than in southern Alberta. Cambrian and older strata have εNd(T) values of −10.0 to −21.1, consistent with derivation from Canadian Shield sources. Lower Ordovician through Permian strata in the Yukon and Northwest Territories, including the Innuitian-derived Imperial Assemblage, have εNd(T) values of −5 to −11.4. In northern British Columbia, the shift to a younger source reflects a wider range of εNd(T) values, from -−8.7 to −14.6 in Middle Ordovician through Middle Devonian strata, suggesting continued input from Canadian Shield sources. By the Middle Devonian, a complete shift to younger crustal signatures (εNd(T) = −5.9 to −10.5) had occurred in northern British Columbia. Several sources for the more juvenile sediments include (1) a mixture of locally erupted volcanic rocks with Canadian Shield sources, (2) a Grenville source, and (3) an Innuitian source. We propose that Ordovician to Lower Devonian strata were derived from a mixture of locally erupted, juvenile volcanics and pre-Cambrian Canadian Shield sources, and post-Middle Devonian strata were sourced from the Innuitian orogen in the Canadian Arctic.

Crustal velocity structure of the southern Nechako basin, British Columbia, from wide-angle seismic traveltime inversion1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 1050-1063 ◽  
Author(s):  
A.L. Stephenson ◽  
G.D. Spence ◽  
K. Wang ◽  
J.A. Hole ◽  
K.C. Miller ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Velocity Structure ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Velocity Model ◽  
Seismic Profile ◽  
Wide Angle ◽  
Seismic Velocities ◽  
Coast Mountains

In the BATHOLITHSonland seismic project, a refraction – wide-angle reflection survey was shot in 2009 across the Coast Mountains and Interior Plateau of central British Columbia. Part of the seismic profile crossed the Nechako Basin, a Jurassic–Cretaceous basin with potential for hydrocarbons within sedimentary strata that underlies widespread volcanic rocks. Along this 205 km-long line segment, eight large explosive shots were fired into 980 seismometers. Forward and inverse modelling of the traveltime data were conducted with two independent methods: ray-tracing based modelling of first and secondary arrivals, and a higher resolution wavefront-based first-arrival seismic tomography. Material with velocities less than 5.0 km/s is interpreted as sedimentary rocks of the Nechako Basin, while velocities from 5.0–6.0 km/s may correspond to interlayered sedimentary and volcanic rocks. The greatest thickness of sedimentary rocks in the basin is found in the central 110 km of the profile. Two sub-basins were identified in this region, with widths of 20–50 km and maximum sedimentary depths of 2.5 and 3.3 km. Such features are well-defined in the velocity model, since resolution tests indicate that features with widths greater than ∼13 km are reliable. Beneath the sedimentary rocks, seismic velocities increase more slowly with depth — from 6.0 km/s just below the basin to 6.3 km/s at ∼17 km in depth, and then to 6.8–7.0 km/s at the base of the crust. The Moho is found at a depth of 33.5–35 km beneath the profile, and mantle velocities are high at 8.05–8.10 km/s.

Late Jurassic (Kimmeridgian-Tithonian) macrofossil assemblage from Jason Peninsula, Graham Land: evidence for a significant northward extension of the Latady Formation

1997 ◽  
Vol 9 (4) ◽  
pp. 434-442 ◽  
Author(s):  
T.R. Riley ◽  
J.A. Crame ◽  
M.R.A. Thomson ◽  
D.J. Cantrill
Keyword(s):  
Antarctic Peninsula ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Areal Extent ◽  
South Eastern ◽  
Back Arc ◽  
The Antarctic ◽  
Major Sequence

New exposures of fossiliferous sedimentary rocks at Cape Framnes, Jason Peninsula (65°57′S, 60°33′W) are assigned to the Middle–Late Jurassic Latady Formation of the south-eastern Antarctic Peninsula region. A sequence of fine to coarse-grained sandstones of unknown thickness has yielded a molluscan and plant macrofossil assemblage rich in the following elements: perisphinctid ammonites, belemnopseid belemnites, oxytomid, trigoniid and astartid bivalves, and bennettitalean fronds and fructifications. The overwhelming age affinities are with the Kimmeridgian–early Tithonian part of the Latady Formation, as exposed on the Orville and Lassiter coasts. The Cape Framnes sedimentary rocks help to constrain the age of a major sequence of acid volcanic rocks on Jason Peninsula, and show that the Latady Basin was geographically much more extensive than recognized previously. It was the principal depositional centre of Middle–Late Jurassic sedimentation in the Antarctic Peninsula back-arc region and in areal extent may have rivalled the essentially Cretaceous Larsen Basin.

A petrological and geochemical study of the volcanic rocks of the Crowsnest Formation, southwestern Alberta, and of the Howell Creek suite, British Columbia

2006 ◽  
Vol 43 (11) ◽  
pp. 1621-1637 ◽  
Author(s):  
Melissa Bowerman ◽  
Amy Christianson ◽  
Robert A Creaser ◽  
Robert W Luth
Keyword(s):  
British Columbia ◽  
Trace Element ◽  
Isotope Geochemistry ◽  
Source Region ◽  
Volcanic Rocks ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Geochemical Study ◽  
Geological Sciences ◽  
Ree Patterns

Alkaline igneous rocks of the Crowsnest Formation in southwestern Alberta and in the Howell Creek area in southeastern British Columbia have been suggested previously to be cogenetic. To test this hypothesis, samples of both suites were characterized petrographically and their major and trace element geochemistry was determined. A subset of the samples was analyzed for whole-rock Sr and Nd isotope geochemistry. The samples of the two suites are latites, trachytes, and phonolites based on the International Union of Geological Sciences (IUGS) total alkalis versus silica (TAS) diagram. Samples from both suites show similar patterns on mantle-normalized trace element diagrams, being enriched relative to mantle values but depleted in the high field-strength elements Nb, Ta, and Ti relative to the large-ion lithophile elements. The chondrite-normalized rare-earth element (REE) patterns for both suites are light REE enriched, with no Eu anomaly and flat heavy REE. The isotope geochemistry of both suites is characterized by low initial 87Sr/86Sr (SrT = 0.704 to 0.706) and low εNdT (–7 to –16). The Howell Creek samples have lower εNdT and higher SrT than do the Crowsnest samples. Based on the intra- and intersuite differences in the isotope geochemistry, we conclude that these samples are not cogenetic, but rather represent samples that have experienced similar evolutionary histories from a heterogeneous source region in the subcontinental lithospheric mantle.

The geology of central Isla Hoste, southern Chile: sedimentation, magmatism and tectonics in part of a Mesozoic back-arc basin

1980 ◽  
Vol 117 (4) ◽  
pp. 339-349 ◽  
Author(s):  
C. P. Andrews-Speed
Keyword(s):  
Sedimentary Rocks ◽  
Igneous Rocks ◽  
Ocean Floor ◽  
Turbidity Currents ◽  
Southern Chile ◽  
Magmatic Arc ◽  
The Pacific ◽  
Pacific Side ◽  
Intrusive Rocks ◽  
Back Arc

SummaryCentral Isla Hoste lies towards the Pacific side of a Mesozoic back-arc basin in southern Chile, behind a magmatic arc represented by the Patagonian batholith. The volcaniclastic sediments on Isla Hoste were derived from the magmatic arc and deposited in the back-arc basin by turbidity currents. These sediments may, in part, overlie mafic volcanic and intrusive rocks. Geochemical and lithologic data are used to suggest an ocean-floor origin for these mafic igneous rocks on central Isla Hoste. The sedimentary and mafic igneous rocks were deformed and uplifted during the middle Cretaceous Andean orogeny. However, the nature of the crust underlying most of the sedimentary rocks in the back-arc basin and the style of deformation in most of this basement are unknown. Therefore the role, if any, of subduction within the back-arc basin during the middle Cretaceous ‘closure’ of this basin is not certain. Post-kinematic intrusions within the back-arc basin are common. These intrusions will confuse attempts to determine by geophysical means the nature of the pre-kinematic basement of the back-arc basin and attempts to outline the present extent of the basin in offshore regions.

The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

The Hozameen fault system and related Coquihalla serpentine belt of southwestern British Columbia

1986 ◽  
Vol 23 (7) ◽  
pp. 1022-1041 ◽  
Author(s):  
G. E. Ray
Keyword(s):  
British Columbia ◽  
Sedimentary Rocks ◽  
Oceanic Island ◽  
Fault System ◽  
Ultramafic Rocks ◽  
Spreading Ridge ◽  
Early Triassic ◽  
Directed Movement ◽  
Serpentine Belt ◽  
Back Arc

The Hozameen Fault of southwestern British Columbia is associated with the Coquihalla serpentine belt and separates two distinct crustal units. Northeast of the fault are greenstones of the Early Triassic (?) Spider Peak Formation, which are unconformably overlain by Jurassic to Cretaceous turbidite and successor basin deposits of the Pasayten Trough. The oldest sedimentary rocks in the trough, the Ladner Group, contain a locally developed basal unit that hosts the Carolin mine gold orebody. Southwest of the fault, the Permian to Jurassic Hozameen Group represents a dismembered ophiolite succession comprising ultramafic rocks of the Petch Creek serpentine belt, overlain in turn by greenstone and chert units. The greenstones in the Hozameen Group and the Spider Peak Formation are geochemically distinguishable; the latter represent sodic, ocean-floor, subalkaline basalts formed in a spreading ridge environment, while the former include both arc tholeiites and oceanic island–seamount subalkaline basalts.Farther west, the major Petch Creek Fault separates the Hozameen Group from the Custer–Skagit Gneiss. This fault is locally associated with the Petch Creek serpentine belt and is considered to be a northern extension of the Ross Lake Fault of Washington State.The rocks in the Hozameen Group, Spider Peak Formation, and Pasayten Trough were probably deposited within a single basin that initiated as an extensive, multirifted, marginal back-arc basin and eventually evolved into the steadily narrowing Pasayten Trough.Following Early to Middle Cretaceous closure of the Pasayten Trough, oblique, easterly-directed movement along westerly-dipping thrusts caused the Custer–Skagit Gneiss to override the Hozameen Group, which in turn overrode rocks of the Pasayten Trough farther east; these boundary thrusts formed precursor structures for the Hozameen and Petch Creek faults. Ultramafic basement material underlying the Spider Peak Formation and the Hozameen Group was thrust up the bounding fractures, producing the Coquihalla and Petch Creek serpentine belts, respectively.Large-scale dextral transcurrent displacement, possibly related to movement along the Fraser Fault system, occurred subsequently along the Petch Creek and Hozameen faults. This wrench movement was preceded by the Mid-Eocene (?) intrusion of the Needle Peak pluton and was followed by emplacement of the 16–35 Ma Chilliwack batholith.

Cretaceous slab segmentation in southwestern Gondwana

2009 ◽  
Vol 147 (2) ◽  
pp. 193-205 ◽  
Author(s):  
MANUEL SUÁREZ ◽  
RITA DE LA CRUZ ◽  
MICHAEL BELL ◽  
ALAIN DEMANT
Keyword(s):  
Marine Sediments ◽  
Late Cretaceous ◽  
Volcanic Rocks ◽  
Transform Fault ◽  
Calc Alkaline ◽  
The West ◽  
Magmatic Arc ◽  
Volcanic Chain ◽  
Magallanes Basin ◽  
Back Arc

AbstractThe Mesozoic Austral Basin of Patagonia, in southwestern Gondwana, experienced a major tectonic segmentation during Aptian times. Sometime between 121 and 118 Ma (Aptian), the northern part of the Austral Basin, known as the Aisén Basin or Río Mayo Embayment, was inverted, with the sediments overlain by calc-alkaline subaerial volcanic rocks of Aptian to Maastrichtian age. In the southern segment of the Austral Basin, known as the Magallanes Basin, predominantly marine sediments accumulated until Cenozoic times in a back-arc position, relative to a magmatic arc located to the west. The subduction-related N–S-trending volcanic chains of both segments were geographically displaced during Aptian to Late Cretaceous times. In the Aisén segment north of ~49–50° S, the volcanic chain was located further east than the coeval arc in the Magallanes segment. A transform fault connected the trenches of both segments, with the Aisén segment dipping at a shallower angle than the Magallanes segment.

Radiometric Age of the Keppoch Formation, Browns Mountain Group, Northern Mainland of Nova Scotia

1974 ◽  
Vol 11 (9) ◽  
pp. 1325-1329 ◽  
Author(s):  
R. F. Cormier
Keyword(s):  
Nova Scotia ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Initial Ratio ◽  
Lower Paleozoic ◽  
Middle Cambrian ◽  
Lower Silurian

The lower Paleozoic Browns Mountain Group of volcanic and sedimentary rocks underlies much of the Antigonish Highlands on the northern mainland of Nova Scotia. The rocks are apparently unfossiliferous and pre-Lower Silurian in age. Volcanic rocks belonging to the Keppoch Formation give a Rb–Sr whole-rock isochron age of 528 ± 40 m.y.; the indicated value for the initial ratio 87Sr/86Sr is 0.7032 ± 0.0020. The apparent stratigraphic age of the lower part of the Browns Mountain Group then is Cambrian with a middle Cambrian age favored.

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