A geodynamic model for some structures within and adjacent to the Okanagan Valley, southern British Columbia

1981 ◽  
Vol 18 (10) ◽  
pp. 1581-1598 ◽  
Author(s):  
John V. Ross
Keyword(s):  
Volcanic Rocks ◽  
High Heat ◽  
Early Jurassic ◽  
Late Triassic ◽  
Second Phase ◽  
The North ◽  
Open Structures ◽  
International Boundary ◽  
Radiometric Ages ◽  
Okanagan Valley

Detailed and reconnaissance mapping of areas along the east and west sides of the Okanagan Valley, from the International Boundary in the south to Kamloops in the north, has revealed a similarity in structural sequence and geometry in rocks ranging in age from Pennsylvanian (Harper Ranch, Anarchist, Kobau, Old Tom, and Shoemaker Groups) through Late Triassic – Early Jurassic (Nicola, Sicamous, and Slocan Groups).Earliest recognizable folds, F1, have northerly trending axes, are isoclinal in form, and are disrupted on all scales by a strongly penetrative second phase of deformation, F2. This second phase is characterized by northerly and southerly verging isoclinal folds having east–west axes that are very nearly parallel with a well-developed stretching lineation, L2. Mylonitic lamination is developed parallel with these F2 axial surfaces. A third phase of folding, F3, comprising more unright open structures having a consistent southerly vergence, deforms the earlier F1 and F3 structures. Later phases of deformation, F4 and F5, almost coeval, have produced the present foliation configuration outlining basins and domes and associated northerly trending normal faults.Progressive metamorphism accompanied F1, F2, and F3 deformations and peaked during F2. F4 and F5 are associated with a thermal event resulting in resetting of most radiometric ages within the region.F1 deformation is probably Permo-Triassic in age and associated with lower greenschist metamorphism, whereas F2 and F3, associated with a much higher metamorphism up to amphibolite facies, affect all the sedimentary rocks within the region and apparently terminated by about 178 Ma (K–Ar on hornblende), Triassic – Early Jurassic. The latest movements, F4 and F5, involve volcanic rocks whose age of crystallization is set radiometrically at about Eocene.A plate model involving easterly obduction during the Permo-Triassic, followed by easterly dipping subduction with associated dextral transform movement during the Late Triassic – Early Jurassic, is proposed to explain the observed geometry. A mantle diapir below the region is rationalized to explain the localized high heat flow during Eocene time.

scholarly journals New insights on the early Mesozoic evolution of multiple tectonic regimes in the northeastern North China Craton from the detrital zircon provenance of sedimentary strata

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1375-1397 ◽  
Author(s):  
Yi Ni Wang ◽  
Wen Liang Xu ◽  
Feng Wang ◽  
Xiao Bo Li
Keyword(s):  
North China Craton ◽  
North China ◽  
Early Jurassic ◽  
Orogenic Belt ◽  
Detrital Zircons ◽  
Late Triassic ◽  
Early Triassic ◽  
The South ◽  
The North ◽  
Early Mesozoic

Abstract. To investigate the timing of deposition and provenance of early Mesozoic strata in the northeastern North China Craton (NCC) and to understand the early Mesozoic paleotectonic evolution of the region, we combine stratigraphy, U–Pb zircon geochronology, and Hf isotopic analyses. Early Mesozoic strata include the Early Triassic Heisonggou, Late Triassic Changbai and Xiaoyingzi, and Early Jurassic Yihe formations. Detrital zircons in the Heisonggou Formation yield  ∼ 58 % Neoarchean to Paleoproterozoic ages and  ∼ 42 % Phanerozoic ages and were sourced from areas to the south and north of the basins within the NCC, respectively. This indicates that Early Triassic deposition was controlled primarily by the southward subduction of the Paleo-Asian oceanic plate beneath the NCC and collision between the NCC and the Yangtze Craton (YC). Approximately 88 % of the sediments within the Late Triassic Xiaoyingzi Formation were sourced from the NCC to the south, with the remaining  ∼ 12 % from the Xing'an–Mongolia Orogenic Belt (XMOB) to the north. This implies that Late Triassic deposition was related to the final closure of the Paleo-Asian Ocean during the Middle Triassic and the rapid exhumation of the Su–Lu Orogenic Belt between the NCC and YC. In contrast,  ∼ 88 % of sediments within the Early Jurassic Yihe Formation were sourced from the XMOB to the north, with the remaining  ∼ 12 % from the NCC to the south. We therefore infer that rapid uplift of the XMOB and the onset of the subduction of the Paleo-Pacific Plate beneath Eurasia occurred in the Early Jurassic.

Structural and metamorphic relationships between the Mount Ida and Monashee Groups at Mara Lake, British Columbia

1982 ◽  
Vol 19 (2) ◽  
pp. 288-307 ◽  
Author(s):  
Kent C. Nielsen
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Ductile Deformation ◽  
Late Triassic ◽  
Second Phase ◽  
The West ◽  
Late Mesozoic ◽  
The North ◽  
Phase Deformation ◽  
Metamorphic Core

Mara Lake, British Columbia straddles the boundary between the Monashee Group on the east and the Mount Ida Group on the west. Correlation of units across the southern end of Mara Lake indicates lithologic continuity between parts of the groups. Both groups have experienced four phases of deformation. Phases one and two are tight and recumbent, trending to the north and to the west, respectively. Phases three and four are open to closed and upright, trending northwest and northeast, respectively. Second-phase deformation includes large-scale tectonic slides that separate areas of consistent vergence. Slide surfaces are folded by third- and fourth-phase structures and outline domal outcrop patterns. Metamorphic grade increases from north to south along the west side of Mara Lake. Calc-silicate reactions involving the formation of diopside are characteristic. From west to east increasing grade is evident in the reaction of muscovite + quartz producing sillimanite + K-feldspar + water. These prograde reactions are related to relative position in the second-phase structure. The highest grade is located near the lowest slide surface. Greenschist conditions accompanied phase-three deformation. Fourth phase is characterized by hydrothermal alteration, brittle fracturing, and local faulting. First-phase deformation appears to be pre-Late Triassic whereas second and third phases are post-Late Triassic and pre-Cretaceous. The fourth phase is part of a regional Tertiary event. The third folding event is correlated with the development of the Chase antiform and the second-phase folding is related to the pervasive east–west fabric of the Shuswap Complex. The timing of these events indicates that the metamorphic core zone of the eastern Cordillera was relatively rigid during the late Mesozoic foreland thrust development. Ductile deformation significantly preceded thrusting and developed a fabric almost at right angles to the trend of the thrust belt.

Biostratigraphic and biogeographic constraints on the Carboniferous to Jurassic Cache Creek Terrane in central British Columbia

2001 ◽  
Vol 38 (4) ◽  
pp. 551-578 ◽  
Author(s):  
M J Orchard ◽  
F Cordey ◽  
L Rui ◽  
E W Bamber ◽  
B Mamet ◽  
...  
Keyword(s):  
North American ◽  
Early Jurassic ◽  
Late Carboniferous ◽  
Middle Permian ◽  
Late Triassic ◽  
Fine Grained ◽  
North American Continent ◽  
The North ◽  
Carbonate Buildups ◽  
North American Craton

Conodonts, radiolarians, foraminiferids, and corals provide constraints on the geology and tectonics of the Nechako region. They also support the notion that the Cache Creek Terrane is allochthonous with respect to the North American craton. The 177 conodont collections, assigned to 20 faunas, range in age from Bashkirian (Late Carboniferous) to Norian (Late Triassic); 70 radiolarian collections representing 12 zones range from Gzhelian (Late Carboniferous) to Toarcian (Early Jurassic); 335 collections assigned to 11 fusulinacean assemblages (with associated foram-algal associations) range from Bashkirian to Wordian (Middle Permian); and two coral faunas are of Bashkirian and Wordian age. The fossils document a long but sporadic history of sedimentary events within the Cache Creek Complex that included two major carbonate buildups in the Late Carboniferous (Pope limestone) and Middle Permian (Copley limestone), punctuated by intervening Early Permian deepening; basaltic eruptions during the mid Carboniferous and mid Permian; the onset of oceanic chert sedimentation close to the Carboniferous–Permian boundary and its persistence through the Late Triassic (Sowchea succession); latest Permian and Early Triassic mixed clastics and volcanics (Kloch Lake succession); Middle and Late Triassic reworking of carbonates (Whitefish limestone), including cavity fill in older limestones (Necoslie breccia), and fine-grained clastic sedimentation extending into the Early Jurassic (Tezzeron succession). Tethyan, eastern Pacific, and (or) low-latitude biogeographic attributes of the faunas are noted in the Gzhelian (fusulines), Artinskian (conodonts, fusulines), Wordian (fusulines, corals, conodonts), and Ladinian (conodonts, radiolarians). The Cache Creek Terrane lay far to the west of the North American continent during these times.

Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

2002 ◽  
Vol 39 (6) ◽  
pp. 1013-1051 ◽  
Author(s):  
Cynthia Dusel-Bacon ◽  
Marvin A Lanphere ◽  
Warren D Sharp ◽  
Paul W Layer ◽  
Vicki L Hansen
Keyword(s):  
Early Cretaceous ◽  
Final Stage ◽  
Complex Interaction ◽  
Early Jurassic ◽  
Crustal Thickening ◽  
Late Triassic ◽  
East Central ◽  
The North ◽  
Plutonic Rocks ◽  
Lake George

We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon–Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215–212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ~188–186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ~135–115 Ma, and muscovite and biotite ~110–108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

Palaeomagnetism, North China and South China collision, and the Tan-Lu fault

1990 ◽  
Vol 331 (1620) ◽  
pp. 589-598 ◽  
Keyword(s):  
South China ◽  
North China ◽  
Eastern China ◽  
Early Jurassic ◽  
Late Triassic ◽  
Polar Wander ◽  
The North ◽  
Indosinian Orogeny ◽  
North And South ◽  
Transcurrent Faults

Refined Apparent Polar Wander (APW) paths for the North and South China Blocks (ncb and scb) are presented and the collision between the NCB and SCB discussed. We suggest that the amalgamation of the NCB and SCB was completed in the late Triassic-early Jurassic, during the Indosinian Orogeny. This proposed timing is based on an analysis of palaeomagnetic signatures relating to continental collisions, such as the convergence of palaeolatitude, deflections of declination, hairpin-like loops in and superposition of APW paths. Like the Cenozoic India—Eurasia collision, the Mesozoic NCB- SCB collision reactivated ancient faults in eastern China, converting some of them into transcurrent faults, of which the Tan-Lu fault is the most famous.

scholarly journals Geologie et pétrographie des roches sédimentaires et volcaniques kétilidiennes (Protérozoique inférieur) de la baignoire d'Arsuk, Groenland méridional

1974 ◽  
Vol 110 ◽  
pp. 1-157
Author(s):  
J Muller
Keyword(s):  
Volcanic Rocks ◽  
Mobile Belt ◽  
Second Phase ◽  
Early Proterozoic ◽  
The North ◽  
Western Border ◽  
Intense Deformation ◽  
Basic Rocks ◽  
North Western ◽  
Middle Proterozoic

The Arsuk ø area is situated along the north-western border of the Early Proterozoic (> 1750 m.y.) mobile belt of South Greenland. Around Arsuk ø reactivated Archaean (> 2500 m.y.) basement is represented by gneiss, amphibolites and migmatites belonging to several lithological series. In the Arsuk basin Early Proterozoic (Ketilidian) supracrustals consist of a group of sedimentary rocks which is overlain by a group of volcanic rocks. The sedimentary Ikerasârssuk Group, with a thickness between 1000 and 1500 m, consists of semi-pelites and pelites with several zones of pyrite-bearing graphite schists and dolomitic limestones. There are also numerous sills of basic rocks which have the same age as the overlying group of volcanic rocks. In some localities the basal member of the group consists of feldspathic quartzites. The volcanic Arsuk Group, the upper part of which is eroded away, has a measured thickness of 4200 m. It consists of pillow lavas, basic massive lavas, volcanic breccias, lapillis and tuffites. There are also some ultrabasic rocks and thin horizons of pyrite-bearing graphite schists with chert. These supracrustal rocks underwent intense deformation at the close of the Early Proterozoic. Three phases can be recognised. The first phase produced N-S to NNE-SSW recumbent folds and the regional schistosity. Refolding during the second phase resulted in folds with E-W to ESE-trending axial planes and a strain slip cleavage. The last phase produced N-S trending structures. The grade of metamorphism during the first phase of deformation corresponds to greenschist facies. In the supracrustals close to the basement recrystallisation in amphibolite facies took place between the first and third phases of folding. This shows the existence of a gradient towards still higher grade metamorphic conditions in the underlying Archaean basement undergoing thorough reconstitution at the end of the Early Proterozoic. As a result of the deformation the stratigraphical unconformity between the Early Proterozoic (Ketilidian) supracrustals and the Archaean basement has been destroyed. During the Gardar period (Middle Proterozoic: > 950 m.y.) and again during the Mesozoic faulting and dyking occurred.

Chapter 14: The Brucejack Au-Ag Deposit, Northwest British Columbia, Canada: Multistage Porphyry to Epithermal Alteration, Mineralization, and Deposit Formation in an Island-Arc Setting

2020 ◽  
pp. 289-311
Author(s):  
Warwick S. Board ◽  
Duncan F. McLeish ◽  
Charles J. Greig ◽  
Octavia E. Bath ◽  
Joel E. Ashburner ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Island Arc ◽  
Late Triassic ◽  
Low Grade ◽  
Coarse Aggregates ◽  
History Of ◽  
Arc Setting ◽  
Mineral District

Abstract The Brucejack intermediate-sulfidation epithermal Au-Ag deposit, located 65 km north of Stewart, BC, forms part of a well-mineralized, structurally controlled, north-south gossanous trend associated with Early Jurassic intrusions straddling the Late Triassic-Early Jurassic Stuhini-Hazelton Group unconformity in the Sulphurets mineral district. Mining of the deposit commenced in mid-2017 after a long history of exploration dating back to the 1880s. Mineralization is hosted in deformed Lower Jurassic island-arc volcanic rocks of the Hazelton Group exposed on the eastern limb of the Cretaceous McTagg anticlinorium. High-grade Au-Ag mineralization was formed from ~184 to 183 Ma in association with a telescoped, multipulsed magmatic-hydrothermal system beneath an active local volcanic center. Precious metal mineralization occurs as coarse aggregates of electrum and silver sulfosalts in steeply dipping, E- to SE-trending quartz-carbonate vein stockwork zones cutting low-grade intrusion-related phyllic alteration. Epithermal vein development is interpreted to have occurred during the waning stages of Early Jurassic sinistral transpression in a compressive arc environment, followed by a limited Cretaceous deformation overprint.

scholarly journals Geochronology and thermochronology of Cretaceous plutons and metamorphic country rocks, Anyui-Chukotka fold belt, North East Arctic Russia

2009 ◽  
Vol 4 ◽  
pp. 157-175 ◽  
Author(s):  
E. L. Miller ◽  
S. M. Katkov ◽  
A. Strickland ◽  
J. Toro ◽  
V. V. Akinin ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
High Heat ◽  
White Mica ◽  
The Arctic ◽  
Second Phase ◽  
Quartz Veins ◽  
North East ◽  
Chukotka Volcanic Belt ◽  
Uplift And Erosion

Abstract. U-Pb isotopic dating of seven granitoid plutons and associated intrusions from the Bilibino region (Arctic Chukotka, Russia) was carried out using the SHRIMP-RG. The crystallization ages of these granitoids, which range from approximately 116.9±2.5 to 108.5±2.7 Ma, bracket two regionally significant deformational events. The plutons cut folds, steep foliations and thrust-related structures related to sub-horizontal shortening at lower greenschist facies conditions (D1), believed to be the result of the collision of the Arctic Alaska-Chukotka microplate with Eurasia along the South Anyui Zone (SAZ). Deformation began in the Late Jurassic, based on fossil ages of syn-orogenic clastic strata, and involves strata as young as early Cretaceous (Valanginian) north of Bilibino and as young as Hauterivian-Barremian, in the SAZ. The second phase of deformation (D2) is developed across a broad region around and to the east of the Lupveem batholith of the Alarmaut massif and is interpreted to be coeval with magmatism. D2 formed gently-dipping, high-strain foliations (S2). Growth of biotite, muscovite and actinolite define S2 adjacent to the batholith, while chlorite and white mica define S2 away from the batholith. Sillimanite (± andalusite) at the southeastern edge the Lupveem batholith represent the highest grade metamorphic minerals associated with D2. D2 is interpreted to have developed during regional extension and crustal thinning. Extension directions as measured by stretching lineations, quartz veins, boudinaged quartz veins is NE-SW to NW-SE. Mapped dikes associated with the plutons trend mostly NW-SE and indicate NE-SW directed extension. 40Ar/39Ar ages from S2 micas range from 109.3±1.2 to 103.0±1.8 Ma and are interpreted as post-crystallization cooling ages following a protracted period of magmatism and high heat flow. Regional uplift and erosion of many kilometers of cover produced a subdued erosional surface prior to the eruption of volcanic rocks of the Okhotsk-Chukotka volcanic belt (OCVB) whose basal units (~87 Ma) overlie this profound regional unconformity. A single fission track age on apatite from granite in the Alarmaut massif yielded an age of 90±11 Ma, in good agreement with this inference.

Geochemical discriminators and the palaeotectonic environment of the North Mountain basalts, Nova Scotia

1980 ◽  
Vol 17 (12) ◽  
pp. 1740-1745 ◽  
Author(s):  
J. M. Wark ◽  
D. B. Clarke
Keyword(s):  
Nova Scotia ◽  
Continental Crust ◽  
Early Jurassic ◽  
Late Triassic ◽  
Chemical Characteristics ◽  
Sea Floor ◽  
The North ◽  
Sea Floor Spreading

The late Triassic – early Jurassic North Mountain basalts of Nova Scotia have been analyzed for various elements believed to be useful in determining the palaeotectonic environment of eruption. The discriminant diagrams show these basalts to have within-plate affinities, with a possible indication of oceanic chemical characteristics. An oceanic environment, however, is at variance with the field relations, which show the within-plate environment to be continental; thus the oceanic chemical characteristics may suggest eruption through a continental crust that was thinning prior to the onset of active sea-floor spreading later in the Jurassic.

K–Ar isochron age and paleomagnetism of diabase along the trans-Avalon aeromagnetic lineament—evidence of Late Triassic rifting in Newfoundland

1980 ◽  
Vol 17 (4) ◽  
pp. 491-499 ◽  
Author(s):  
J. P. Hodych ◽  
A. Hayatsu
Keyword(s):  
Nova Scotia ◽  
Early Jurassic ◽  
Late Triassic ◽  
The North ◽  
Two Samples ◽  
Avalon Peninsula

A prominent aeromagnetic lineament crosses the Avalon Peninsula of Newfoundland from 46°50.4′N, 53°45.9′W to 47°22.1′N, 52°30.0′W. It is shown to be at least partly caused by diabase dikes of Late Triassic and possibly Early Jurassic age which are probably related to the Shelburne diabase dike and the North Mountain basalt, both of Nova Scotia. All are thought to have resulted from rifting which preceded opening of the Atlantic.Unmetamorphosed diabase was found at three sites along the trans-Avalon aeromagnetic lineament: as narrow sills at site 1 (46°58.0′N, 53°25.4′W), as a narrow dike at site 2 (47°4.7′N, 53°7.6′W), and as large angular boulders at site 3 (47°11.0′N, 52°52.2′W).For sites 1 and 2, analyses of seven diabase samples fall on a single K–Ar isochron whose intercept on the 40Ar/36Ar axis is at 215 ± 45 and whose slope gives a Late Triassic age of 201.1 ± 2.6 Ma. Analyses of two diabase samples from the Shelburne dike fall close to this isochron suggesting a similar age. Paleomagnetism adds support; the virtual paleopole measured for sites 1 and 2, using 12 oriented diabase samples demagnetized in 300 Oe (23 880 A/m) alternating field (AF), falls at 87.8°E, 72.9°N (dp = 3.0°, dm = 4.3°), close to the virtual paleopole reported for the Shelburne dike.For site 3, analyses of two samples fall on the K–Ar isochron reported for the North Mountain basalt, tentatively suggesting that the intrusion at site 3 occurred about 10 Ma later than at sites 1and 2.

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