Serpentinites and low-K island arc meta-volcanic rocks in the Lower Köli Nappe of the central Scandinavian Caledonides: Late Cambrian–early Ordovician serpentinite mud volcanoes in a forearc basin?

2012 ◽  
Vol 541-543 ◽  
pp. 19-30 ◽  
Author(s):  
Jens C. Grimmer ◽  
Reinhard O. Greiling
Keyword(s):  
Volcanic Rocks ◽  
Island Arc ◽  
Mud Volcanoes ◽  
Forearc Basin ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Scandinavian Caledonides ◽  
Low K

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.

Geochronology of the Twillingate Granite and Herring Neck Group, Notre Dame Bay, Newfoundland

1976 ◽  
Vol 13 (11) ◽  
pp. 1591-1601 ◽  
Author(s):  
Harold Williams ◽  
R. D. Dallmeyer ◽  
R. K. Wanless
Keyword(s):  
New World ◽  
Linear Array ◽  
Volcanic Rocks ◽  
Ocean Basin ◽  
Late Ordovician ◽  
Island Arc ◽  
Zircon Age ◽  
Mafic Dike ◽  
Plate Convergence ◽  
Late Cambrian

Zircons from the Twillingate Granite form a linear array with a concordia intercept of 510 + 17 – 16 m.y. Mafic dikes that cut deformed granite along the southern contact of the pluton at New World Island record 40Ar/39Ar hornblende ages of 440 ± 10 and 473 ± 9 m.y. These ages indicate that the mafic dikes are Ordovician, and confirm their correlation with mafic volcanic rocks of the nearby Herring Neck Group. The dates also suggest that Herring Neck volcanism and mafic dike intrusion extended from Early to Late Ordovician. Together with the zircon age, they define a narrow chronologic bracket for intrusion, deformation, and metamorphism of the Twillingate Granite (`~510–475 m.y.).Within the central portion of the Twillingate pluton. a metamorphosed mafic dike cutting massive granite and an amphibolite inclusion within Foliated granite yield similar,40Ar/39Ar hornblende ages of 443 ± 11 and 438 ± 9 m.y. These ages are anomalously young compared with the 473 m.y. age of a mafic dike cutting deformed granite at New World Island. They are interpreted to indicate prolonged metamorphism and/or slower post-meta mo rphic cooling for central portions of the pluton compared to its southern margin.The isotopic ages support the view that the Twillingate Granite and nearby mafic volcanic rocks are collectively part of a single island-arc complex. The granite may have been generated during a period of subduction as sociated with plate convergence and closing of the proto-Atlantic ocean. A 510 m.y. (Late Cambrian) age for the granite suggests that convergence began rather early in the evolution of the Northern Appalachians. In addition, where dated Newfoundland ophiolite suites appear to be younger than, or contemporaneous with some granitic plutons (such as Twillingate), it is likely that they formed in a marginal ocean basin environment behind an older island-arc terrane.Les zircons du granite de Twillingate forment un réseau linéaire avec intercept à 510 + 17 – 16 Ma. Les dykes mafiques qui recoupent le granite déformé le long de la bordure sud du pluton à New World Island donnent des âges 40Ar/39Ar pour la hornblende de 440 ± 10 et de 473 ± 9 Ma. Ces âges indiquent que les dykes mafiques sont Ordoviciens et confirment leurs liens avec des roches mafiques volcaniques du groupe de Herring Neck dans le voisinage. Les dates suggèrent aussi que le volcanisme de Herring Neck et l'intrusion de dykes mafiques se sont produits du début à la fin de l'Ordovicien. Avec les âges des zircons, ils définissent un intervalle de temps assez court pour l'intrusion, la déformation et le métamorphisme du granite de Twillingate (~510–475 Ma).A l'intérieur de la portion centrale du pluton de Twillingate, un dyke mafique métamorphisé recoupant un granite massif et une inclusion d'amphibolite dans un granite foliacé donnent des âges 40Ar/39Ar semblables pour les hornblendes de 443 ± 11 et 438 ± 9 Ma. Ces âges sont anormalement faibles si on les compare avec l'âge de 473 Ma du dyke mafique qui recoupe le granite déformé de New World Island. On les interprète comme indiquant un métamorphisme prolongé et/ou un refroidissement post-métamorphique plus lent pour les portions centrales du pluton par comparaison à sa bordure sud.

Early Devonian volcanism in the eastern Klamath Mountains, California: evidence for an immature island arc

1985 ◽  
Vol 22 (2) ◽  
pp. 214-226 ◽  
Author(s):  
H. Lapierre ◽  
F. Albarede ◽  
J. Albers ◽  
B. Cabanis ◽  
C. Coulon
Keyword(s):  
Volcanic Rocks ◽  
Island Arc ◽  
Magmatic Differentiation ◽  
Klamath Mountains ◽  
Early Devonian ◽  
Volcanic Sequence ◽  
Volcanic Succession ◽  
Basic Volcanic ◽  
Almost All ◽  
Low K

The Early Devonian volcanic sequence of the eastern Klamath Mountains (northern California) consists of the Copley Greenstone, a basalt–andesite series, overlain by the Balaklala Rhyolite. All the rocks are metamorphosed to the greenschist facies.The Copley Greenstone consists of massive flows and pyroclastic deposits in the lower part that are overlain by pillow lavas. No sediments are interlayered in the volcanic pile except in the easternmost outcrop area, where sandstones with granitic debris and shaly tuffs are interbedded in the uppermost flows. High-Mg andesites occur only near the top of the basic volcanic succession. The Balaklala Rhyolite is formed of massive flows, breccias, and tuffs.The Copley volcanic rocks, poor in titanium, belong to a low-K tholeiitic suite formed in an island-arc geodynamic environment. The occurrence of olivine with chromium spinels in almost all the lava types, the enrichment in magnesium, chromium, and nickel, and the depletion in hygromagmaphile elements suggest that magmatic differentiation was a marginal process. The Balaklala Rhyolite shows very homogeneous petrographic and geochemical features, characteristic of tholeittic products.From its characteristics here described (pillowed flows, lack of sedimentation, presence of high-Mg andesites and low-K rhyolites, bimodality of the volcanism) the Early Devonian volcanic sequence represents an immature island arc related to a back-arc basin, similar to the present-day Mariana island arc.

scholarly journals Formation of the rear slope of the island arc of Chingiz Kaledonid ridge in eastern Kazakhstan

2019 ◽  
pp. 72-80
Author(s):  
S. G. Samygin
Keyword(s):  
Volcanic Activity ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Middle Ordovician ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Landslide Processes ◽  
Mass Frontier ◽  
Eastern Kazakhstan

Process of formation of the island-arc rear slope is considered on the example of the Upper Cambrian–Middle Ordovician arc found in the Chingiz ridge in eastern Kazakhstan. Its occurrence is shown at the end of volcanic activity in the island-arc structure, beginning at the end of the early Arenig (from the end of the Flos century of the Early Ordovician) with tephroturbidites appearance. After the cessation of volcanism, two sedimentation cycles were distinguished in the sedimentary section of the slope in the middle Ordovician: (1) transgressive when the island arc submerged, (2) and regressive when the Chingiz arc began to build up at the beginning of the Llanwyrn (Darrivilian) century. The sedimentation was repeatedly accompanied by landslide processes, which ended in the middle of llanvirna (darrivilia) with the disruption of tectonic-gravity plate composed of Upper Cambrian volcanic rocks with limestone in the sole, resulting in the formation of coarsely fragmented mixtite at the allochthonous mass frontier, the further sedimentation on the rear slope stopped. Keywords: the island-arc; rear slope; sedimentation cycles; landslide processes

Volcanism on the passive margin of Laurentia: an early Paleozoic analogue of Cretaceous volcanism on the northeastern American margin

1988 ◽  
Vol 25 (11) ◽  
pp. 1824-1833 ◽  
Author(s):  
Stephen Kumarapeli ◽  
Karen St. Seymour ◽  
Hillar Pintson ◽  
Elizabeth Hasselgren
Keyword(s):  
Volcanic Rocks ◽  
Passive Margin ◽  
Fracture Zones ◽  
Transform Faults ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Basaltic Rocks ◽  
Sedimentary Sequences ◽  
Late Cambrian ◽  
Cretaceous Volcanism

Allochthonous masses of basaltic lava flows and related tuffs are present in several localities in an approximately 30 km long segment of the western margin of the Granby Nappe, in southeastern Quebec. They occur either as numerous small blocks in the Drummondville wildflysch related to the nappe or as larger masses intercalated with sedimentary sequences of limestone and shale of probable Late Cambrian to Early Ordovician age. These latter occurrences and the associated sedimentary units form "island-like" areas within lithologies of the Granby Nappe consisting of Cambrian sediments that accumulated on the continental rise. Their overall characteristics suggest that they represent slabs derived from the shelf margin of Laurentia and incorporated into the cratonward-moving nappes during the Middle Ordovician Taconian Orogeny.The volcanic rocks are mainly transitional but include some alkali olivine basalts. There are some indications that their affinities are to basaltic rocks of seamount chains localized along leaky transform faults. The segment of the continental margin from which the volcanic rocks were derived originated in the latest Precambian times, by rifting involving a rift–rift–rift (RRR) triple junction. Thus, it was a likely location for deep-seated transverse fracture zones linked to ridge-to-ridge transform faults of Iapetus. Therefore, the best explanation of the volcanism is that it was localized along such fracture zones. This episode of Late Cambrian – Early Ordovician volcanism related to the Iapetus cycle is probably analogous to the recently documented Early Cretaceous volcanism related to the Atlantic cycle on the northeastern American margin.

Early Ordovician alkali-ultramafic Zhilandy complex (Central Kazakhstan): structure and age of formation

2019 ◽  
Vol 484 (1) ◽  
pp. 61-65
Author(s):  
R. M. Antonuk ◽  
A. A. Tretyakov ◽  
K. E. Degtyarev ◽  
A. B. Kotov
Keyword(s):  
Complex Formation ◽  
Central Asian Orogenic Belt ◽  
Early Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Central Asian ◽  
Geochronological Study ◽  
Three Stages ◽  
Late Neoproterozoic ◽  
Quartz Monzodiorites

U–Pb geochronological study of amphibole-bearing quartz monzodiorites of the alkali-ultramafic Zhilandy complex in Central Kazakhstan, whose formation is deduced at the Early Ordovician era (479 ± 3 Ma). The obtained data indicate three stages of intra-plate magmatism in the western part of the Central Asian Orogenic Belt: Late Neoproterozoic stage of alkali syenites of the Karsakpay complex intrusion, Early Cambrian stage of ultramafic-gabbroid plutons of the Ulutau complex formation, and Late Cambrian–Early Ordovician stage of formation of the Zhilandy complex and Krasnomay complex intrusions.

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