Geological setting and tectonic significance of Mississippian felsic metavolcanic rocks in the Pelly Mountains, southeastern Yukon Territory

1982 ◽  
Vol 19 (1) ◽  
pp. 8-22 ◽  
Author(s):  
James K. Mortensen
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Yukon Territory ◽  
Early Tertiary ◽  
Metavolcanic Rocks ◽  
Extensional Tectonic ◽  
Tectonic Significance ◽  
Show Evidence ◽  
Thrust Sheets ◽  
Local Geology

The central Pelly Mountains in southeastern Yukon Territory consist of imbricate thrust sheets, which have undergone syn- and post-thrusting deformation and metamorphism. The local geology is further complicated by the intrusion of Late Cretaceous batholiths, and by strike-slip faulting related to the Tintina Fault, a major northwest-trending transcurrent fault of latest Cretaceous or early Tertiary age. This faulting disrupts the northeast edge of the study area.Upper Devonian and Mississippian strata are present in at least two of the structural packages, but the Mississippian metavolcanic rocks occur only in the lowermost package. Rb–Sr geochronology indicates a mid-Mississippian age for the igneous suite. The volcanic rocks consist of volcaniclastic material with minor interbedded flows, and were deposited in a submarine environment. Several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas. Although the volcanic rocks are all highly altered and show evidence of widespread chemical mobility, trace element data indicate that the rocks are metaluminous trachytes, most closely resembling peralkaline volcanics generated in extensional environments. This suggestion of a predominantly extensional tectonic setting in mid-Mississippian time in the Pelly Mountains is consistent with recent tectonic syntheses for the area.

Geochemistry and origin of Mesoproterozoic metavolcanic rocks from Fisher Massif, Prince Charles Mountains, East Antarctica

1996 ◽  
Vol 8 (1) ◽  
pp. 85-104 ◽  
Author(s):  
E. V. Mikhalsky ◽  
J. W. Sheraton ◽  
A. A. Laiba ◽  
B. V. Beliatsky
Keyword(s):  
Tectonic Setting ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Granulite Facies ◽  
Island Arc ◽  
Crustal Component ◽  
Basaltic Rocks ◽  
Metavolcanic Rocks ◽  
High K ◽  
Low K

Fisher Massif consists of Mesoproterozoic (c. 1300 Ma) lower amphibolite-facies metavolcanic rocks and associated metasediments, intruded by a variety of subvolcanic and plutonic bodies (gabbro to granite). It differs in both composition and metamorphic grade from the rest of the northern Prince Charles Mountains, which were metamorphosed to granulite facies about 1000 m.y. ago. The metavolcanic rocks consist mainly of basalt, but basaltic andesite, andesite, and more felsic rocks (dacite, rhyodacite, and rhyolite) are also common. Most of the basaltic rocks have compositions similar to low-K island arc tholeiites, but some are relatively Nb-rich and more akin to P-MORB. Intermediate to felsic medium to high-K volcanic rocks, which appear to postdate the basaltic succession, have calc-alkaline affinities and probably include a significant crustal component. On the present data, an active continental margin with associated island arc was the most likely tectonic setting for generation of the Fisher Massif volcanic rocks.

Tectonic setting and regional correlation of Ordovician–Silurian rocks of the Aspy terrane, Cape Breton Island, Nova Scotia

1991 ◽  
Vol 28 (11) ◽  
pp. 1769-1779 ◽  
Author(s):  
Sandra M. Barr ◽  
Rebecca A. Jamieson
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Volcanic Arc ◽  
Cape Breton Island ◽  
Metasedimentary Rocks ◽  
Tectonic History ◽  
Cape Breton ◽  
Metavolcanic Rocks ◽  
High Grade Metamorphism ◽  
Arc Setting

Interlayered mafic and felsic metavolcanic rocks and metasedimentary rocks of Ordovician to Silurian age are characteristic of the Aspy terrane of northwestern Cape Breton Island. These rocks were affected by medium- to high-grade metamorphism and were intruded by synkinematic granitoid orthogneisses during Late Silurian to Early Devonian times. They were intruded by posttectonic Devonian granitic plutons and experienced rapid Devonian decompression and cooling. The chemical characteristics of the mafic metavolcanic rocks indicate that they are tholeiites formed in a volcanic-arc setting. The volcanic rocks of the Aspy terrane differ from many other Silurian and Silurian–Devonian successions in Atlantic Canada, which have chemical and stratigraphic characteristics of volcanic rocks formed in extensional within-plate settings, and are somewhat younger than the Aspy terrane sequences. Aspy terrane units are most similar to Ordovician–Silurian volcanic and metamorphic units in southwestern Newfoundland, including the La Poile Group and the Port aux Basques gneiss. Together with other occurrences of Late Ordovician to Early Silurian volcanic-arc units, they indicate that subduction-related compressional tectonics continued into the Silurian in parts of the northern Appalachian Orogen. The complex Late Silurian – Devonian tectonic history of the Aspy terrane may reflect collision with the southeastern edge of a Grenvillian crustal promentory.

Geochemistry and age of the Aillik Group and associated plutonic rocks, Makkovik Bay area, Labrador: implications for tectonic development of the Makkovik Province

2002 ◽  
Vol 39 (5) ◽  
pp. 731-748 ◽  
Author(s):  
G S Sinclair ◽  
S M Barr ◽  
N G Culshaw ◽  
J W.F Ketchum
Keyword(s):  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Metamorphic History ◽  
Bay Area ◽  
Metavolcanic Rocks ◽  
Show Evidence ◽  
Tectonic Development ◽  
Plutonic Rocks ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

The Aillik domain of the Makkovik Province is dominated by deformed and metamorphosed sedimentary and bimodal volcanic rocks of the redefined Aillik Group and abundant unfoliated late- to post-orogenic plutonic rocks. Mapping and petrological studies in the Makkovik Bay area of the Aillik domain showed that the upper part of the group, in addition to felsic volcanic rocks, also includes extensive areas of hypabyssal, foliated granitic rocks (Measles Point Granite). Although petrochemically similar to the spatially associated felsic volcanic rocks, a new U–Pb (zircon) age of 1929 Ma suggests that the Measles Point Granite may be about 70 million years older than the volcanic rocks of the Aillik Group, based on published U–Pb dates for the latter unit. The volcanic and granitic rocks show similar structural and metamorphic history, and both have characteristics of crust-derived A-type felsic rocks, although the granite shows less chemical variation than the felsic volcanic rocks. A within-plate setting is postulated, although the associated mafic metavolcanic rocks and amphibolite dykes show evidence of a volcanic-arc influence. Possible solutions of the paradox presented by the U–Pb ages imply that the Measles Point Granite either represents the juvenile basement to the Aillik Group or was derived from a basement with a large juvenile component. The setting for deposition of the Aillik Group that is consistent with current tectonic models for the Makkovik Province is a rifted arc built on a juvenile terrane accreted to Archean crust.

Evolution of 3.1 and 3.0 Ga volcanic belts and a new thermotectonic model for the Hopedale Block, North Atlantic craton (Canada)

2002 ◽  
Vol 39 (5) ◽  
pp. 687-710 ◽  
Author(s):  
D T James ◽  
S Kamo ◽  
T Krogh
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Tholeiitic Basalt ◽  
Amphibolite Facies ◽  
Metasedimentary Rocks ◽  
Rock Types ◽  
Metavolcanic Rocks ◽  
Block Based ◽  
Felsic Volcanic

A new model for evolution of the Archean Hopedale Block, based on mapping and supporting U–Pb geochronological and geochemical studies, is highlighted by (i) ca. 3.25 Ga emplacement of igneous precursors of Maggo Gneiss; (ii) &gt3.1 Ga, high-grade Hopedalian metamorphism and attendant deformation; (iii) emplacement of the Hopedale mafic dykes; (iv) 3.1 Ga deposition of Hunt River volcanic rocks; (v) ca. 3.0 Ga deposition of Florence Lake volcanic rocks; (vi) 2.88–2.96 Ga, greenschist- to amphibolite-facies Fiordian metamorphism and formation of penetrative, northeast-striking Fiordian structures; and (vii) emplacement of a suite of 2.89–2.83 Ga tonalite to granite intrusions, which partially overlap and locally postdate Fiordian metamorphism and deformation. The Hunt River and Florence Lake volcanic sequences are different in age but similar in most other respects. The former consists mainly of amphibolite-facies mafic metavolcanic rocks and lesser amounts of komatiite flows and metasedimentary and 3105 ± 3 Ma felsic volcanic rocks. The Florence Lake volcanic belt consists mainly of greenschist- to amphibolite-facies mafic metavolcanic rocks, lesser amounts of felsic metavolcanic rocks, dated at 2979 ± 1 and 2990 ± 2 Ma, komatiite flows, and rare metasedimentary rocks. The similarity of rock types, field relationships between different rock types, such as the common association of ultramafic and felsic metavolcanic rocks, and the chemistry of volcanic rocks in both belts suggest a common tectonic setting for each belt. A model involving episodic volcanism, separated by 100 Ma, in ensialic basins is consistent with the dominance of tholeiitic basalt and an abundance of pre-volcanic basement.

Geology of the Chatham Sound region, southeast Alaska and coastal British Columbia

2001 ◽  
Vol 38 (11) ◽  
pp. 1579-1599 ◽  
Author(s):  
George E Gehrels
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Upper Jurassic ◽  
The West ◽  
Southeast Alaska ◽  
Coast Mountains ◽  
Early Tertiary ◽  
Metavolcanic Rocks ◽  
Upper Paleozoic ◽  
Coastal British Columbia

The Coast Mountains orogen is thought to have formed as a result of accretion of the Alexander and Wrangellia terranes against the western margin of the Stikine and Yukon–Tanana terranes, but the nature and age of accretion remain controversial. The Chatham Sound area, which is located along the west flank of the Coast Mountains near the Alaska – British Columbia border, displays a wide variety of relations that bear on the nature and age of the boundary between inboard and outboard terranes. Geologic and U–Pb geochronologic studies in this area reveal a coherent but deformed and metamorphosed sequence of rocks belonging to the Yukon–Tanana terrane, including pre-mid-Paleozoic marble, schist, and quartzite, mid-Paleozoic orthogneiss and metavolcanic rocks, and upper Paleozoic metaconglomerate and metavolcanic rocks. These rocks are overlain by Middle Jurassic volcanic rocks (Moffat volcanics) and Upper Jurassic – Lower Cretaceous strata of the Gravina basin, both of which also overlie Triassic and older rocks of the Alexander terrane. This overlap relationship demonstrates that the Alexander and Wrangellia terranes were initially accreted to the margin of inboard terranes during or prior to mid-Jurassic time. Accretion was apparently followed by Late Jurassic – Early Cretaceous extension–transtension to form the Gravina basin, left-slip along the inboard margin of Alexander–Wrangellia, mid-Cretaceous collapse of the Gravina basin and final structural accretion of the outboard terranes, and early Tertiary dip-slip motion on the Coast shear zone.

scholarly journals Geochemical Characteristics and Tectonic Significance of the Acidic Volcanic Rocks from the Shetang-Boyang Area, Western Qinling Orogenic Belt, China

2016 ◽  
Vol 5 (2) ◽  
pp. 209
Author(s):  
Aiai Ma ◽  
Hao Guan ◽  
Lifei Zou ◽  
Lanlan Sun
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Geochemical Characteristics ◽  
Geochemical Data ◽  
Regional Studies ◽  
Western Qinling ◽  
Continental Extension ◽  
Qinling Orogenic Belt ◽  
Tectonic Significance

Acidic volcanic rocks of Shetang-Boyang area are located in the western Qinling orogenic belt, consist of rhyolite and granite porphyry. They are comparable in the chemical composition, enriched in Si, alkali, Al and a little bit of Mg, Ca and Ti. The contents of HFSE (Zr, Hf) and LILE (Rb, Th, U) are high, however, the content of Ba, Sr, Ti, P have obviously depleted and there are obvious negative Eu anomalies (Eu/Eu*=0.06-0.13). These geochemical characteristics are revealed that these volcanic rocks have an A1 type affinity. Geochemical data combined with regional studies, show that these volcanic rocks were formed in a continental extension setting and the western Qinling orogenic belt in 211Ma has been in the tectonic setting of post-collisional extension.

A unifying lithostratigraphy of late Cretaceous–early Tertiary fore-arc volcanic sequences on Alexander Island, Antarctica

1997 ◽  
Vol 9 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Joe J. McCarron
Keyword(s):  
Antarctic Peninsula ◽  
Late Cretaceous ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Magmatic Arc ◽  
Ridge Subduction ◽  
Volcanic Group ◽  
Early Tertiary ◽  
Plutonic Rocks ◽  
The Antarctic

Late Cretaceous–early Tertiary subduction-related fore-arc volcanic rocks are exposed in a north–south linear belt along the length of Alexander Island. The age and tectonic setting of these rocks is well understood; they are not considered to represent “normal” arc magmas but were generated in the fore-arc as a result of ridge subduction. Due to their distinct composition and mode of formation, they are no longer considered to be genetically related to the Antarctic Peninsula magmatic arc. They are therefore removed from the Antarctic Peninsula Volcanic Group and placed in a newly defined Alexander Island Volcanic Group. The group is made up of the Monteverdi, Staccato, Walton, Colbert, Elgar and Finlandia formations, which vary widely in lithology, facies and age. The Colbert and Elgar formations are subdivided into nine and three members respectively. Type localities, representative lithologies and age of each of the formations are discussed. The Staccato and Colbert Magmatic complexes are defined to include volcanic and plutonic rocks that are considered to be coeval. The Rouen Intrusive complex combines the plutonic rocks from the Rouen Mountains and Rothschild Island on the basis of age and chemistry.

Petrochemistry and tectonic significance of Carboniferous volcanic rocks in New Brunswick

1986 ◽  
Vol 23 (9) ◽  
pp. 1243-1256 ◽  
Author(s):  
L. R. Fyffe ◽  
S. M. Barr
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Age Groups ◽  
Late Paleozoic ◽  
Basement Rocks ◽  
Basaltic Composition ◽  
Tectonic Significance ◽  
Maritimes Basin ◽  
Alkalic Basalts

Carboniferous volcanic rocks from the New Brunswick Platform in the Maritimes Basin are divided into three age groups. Late Tournaisian to early Visean volcanic rocks are tholeiitic basalts and andesites that, in southern New Brunswick, are inter-bedded with abundant calc-alkalic rhyolite. Late Visean to Namurian volcanic rocks consist of an interbedded sequence of alkalic basalts and trachyandesites. Late Westphalian volcanic rocks change in composition up section from trachyte to peralkalic rhyolite. All three age groups display petrochemical features indicative of an intraplate tectonic setting. The volcanic geochemistry is consistent with the development of the Maritimes Basin either as a failed rift formed along the margin of a late Paleozoic ocean or as a rhomb graben formed within a transcurrent zone; the former model is preferred. The change in basaltic composition from tholeiitic to alkalic apparently coincided with a decrease in rate of extension between the Tournaisian and Namurian. Local peralkalic volcanism occurred during regional sagging of the basin as extension ceased and basement rocks cooled in the Late Carboniferous.

The tectonic significance of basalts and dacites in the Wagwater Belt, Jamaica

1979 ◽  
Vol 116 (5) ◽  
pp. 365-374 ◽  
Author(s):  
T. A. Jackson ◽  
T. E. Smith
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Arc ◽  
Blue Mountain ◽  
Tectonic Events ◽  
East Pacific ◽  
Early Tertiary ◽  
Tectonic Significance ◽  
Cenozoic Era ◽  
The Caribbean ◽  
Geochemical Analyses

SummaryThe Wagwater Belt is a fault-bounded structural unit in which more than 3000 m of early Tertiary sedimentary and volcanic rocks are exposed. Geochemical analyses of the volcanic rocks show that they comprise a bimodal suite of plateau-type tholeiitic basalts and calcalkaline dacites. The extrusion of these volcanics is associated with the development of an interarc basin, the Wagwater Basin, at the beginning of the Cenozoic Era. The Wagwater Basin formed as a result of the splitting of a mature late Cretaceous volcanic arc into a frontal and third arc represented by the Blue Mountain Massif and the Clarendon Block respectively. This model for Jamaica can be correlated with tectonic events occurring in the NW Caribbean during the early Tertiary. The creation of the Wagwater Basin and the eruption of the basalts is related to the initial opening of the Cayman Trough. The cessation of dacite volcanic activity in Jamaica signified the separation of the Caribbean Plate from the East Pacific Farallon Plate.

Geology and U–Pb geochronology of the Klondike District, west-central Yukon Territory

1990 ◽  
Vol 27 (7) ◽  
pp. 903-914 ◽  
Author(s):  
J. K. Mortensen
Keyword(s):  
Large Body ◽  
Yukon Territory ◽  
Geological Mapping ◽  
Late Triassic ◽  
Second Phase ◽  
Small Bodies ◽  
Thrust Faulting ◽  
New Information ◽  
Metavolcanic Rocks ◽  
Thrust Sheets

Geological mapping and U–Pb geochronology of the Klondike District provide new information on the nature and evolution of the Yukon–Tanana terrane (YTT) in western Yukon. The area is underlain by a sequence of thrust panels of regional extent. A continuously mappable sequence of interlayered metasedimentary and metavolcanic rocks is intruded by a variety of deformed metaplutonic rocks within two of these thrust sheets. Layering in the metasediments and metavolcanics is considered to be at least in part transposed stratigraphy. Small bodies of greenstone and altered ultramafic rocks thought to be part of the Slide Mountain terrane occur discontinuously along the thrust faults.U–Pb age determinations indicate that the uppermost thrust panel (assemblage I), which underlies much of the Klondike District, consists largely of metamorphosed, mid-Permian felsic plutonic, subvolcanic, and tuffaceous rocks. Beneath assemblage I is a second thrust panel (assemblage II), also of large areal extent, of mid-Paleozoic or older metasedimentary and mafic and felsic metavolcanic rocks, intruded by a large body of latest Devonian – Early Mississippian granitic augen orthogneiss. U–Pb analyses of zircon from the orthogneiss reflect both lead loss and a significant inherited zircon component. A third structural unit (assemblage III), which consists mainly of carbonaceous schist and phyllite, crops out in the northern part and along the southwestern edge of the study area, where it underlies both assemblages I and II.The earliest stage of deformation and metamorphism that affected the area (F1) produced the pervasive recrystallization fabric characteristic of all of the metamorphic rocks in assemblages I, II, and III, and occurred between mid-Permian and Late Triassic time. Thrust faulting, presumed to be northerly or northeasterly directed, postdates Late Triassic but predates mid-Cretaceous. The second phase of deformation (F2) was either synchronous with or later than thrust faulting. Monazite ages for the augen orthogneiss indicate that at least local metamorphism and (or) deformation lasted until Early Cretaceous time.Close similarities between composition, U–Pb ages, as well as timing and style of deformation, documented in the Klondike District and observed elsewhere in the YTT in southeastern Yukon and east-central Alaska suggest that much of the YTT either evolved as a single entity or else shared a very similar history.

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