Geochemistry and eruptive environment of metavolcanic rocks from the Mona Complex of Anglesey, North Wales, U.K

1993 ◽  
Vol 130 (1) ◽  
pp. 85-91 ◽  
Author(s):  
R. S. Thorpe
Keyword(s):  
Volcanic Rocks ◽  
Fault Zones ◽  
Ultramafic Rocks ◽  
Chemical Analyses ◽  
Late Precambrian ◽  
Suprasubduction Zone ◽  
Metavolcanic Rocks ◽  
North Wales ◽  
Eruptive Environment ◽  
Early Palaeozoic

AbstractThe late Precambrian–early Palaeozoic Monian Supergroup of the Mona Complex is a thick sequence of flysch-type sediments and metavolcanic rocks which were deposited during the late Precambrian–early Palaeozoic and deformed during the late Precambrian and Caledonian (Ordovician/Silurian) orogenies. The Monian Supergroup includes tectonically emplaced, geographically separated outcrops of metabasalt/andesite, gabbro and serpentinized ultramafic rocks all of ophiolite affinity. The major units of the Mona Complex are separated by important faults/fault zones which may represent terrane boundaries. New chemical analyses, together with existing ones, show that the metabasalts and meta-andesites from the older New Harbour Group of north Anglesey have characteristics of suprasubduction zone arc eruptives whereas the metabasalts from the younger Gwna Group of south Anglesey and Lleyn have MORB geochemistry. It is suggested that these volcanic rocks were produced during the late Precambrian–early Palaeozoic development of the lapetus Ocean and emplaced as separate terranes during its closure.

A garnet peridotite and a garnet-amphibole pyroxenite from South Harris, Outer Hebrides, and their bearing on the South Harris eclogite facies status

1967 ◽  
Vol 36 (279) ◽  
pp. 380-388 ◽  
Author(s):  
A. Livingstone
Keyword(s):  
Optical Properties ◽  
Granulite Facies ◽  
Garnet Peridotite ◽  
Ultramafic Rocks ◽  
Chemical Analyses ◽  
The South ◽  
Outer Hebrides ◽  
Eclogite Facies

SummaryA garnet-olivine metaperidotite and a garnet-amphibole pyroxenite are described. Chemical analyses are presented for six rocks and optical properties and chemical analyses are tabulated for clinopyroxene, almandine-pyrope garnet, and hastingsitie amphibole from the garnet-amphibole pyroxenite. A possible origin for the garnet peridotite and chemically similar granulite facies ultramafic rocks is suggested. The eclogite facies in South Harris is reinstated in the light of the data presented.

The Caledonoid faults of northern Lleyn (North Wales)

1970 ◽  
Vol 107 (3) ◽  
pp. 235-247 ◽  
Author(s):  
W. E. Tremlett
Keyword(s):  
Volcanic Rocks ◽  
Strike Slip ◽  
Metamorphic Rocks ◽  
Red Sandstone ◽  
North Wales ◽  
Dextral Strike Slip

SummaryEvidence of substantial dextral strike-slip displacements along the Caledonoid fault-set of northern Lleyn is revealed by the distribution of Pre-Cambrian igneous and metamorphic rocks, Ordovician volcanic rocks and Caledonian ‘early granodioritic’ intrusions. These apparently occurred prior to some smaller sinistral strike-slip movements which left total net dextral displacements of 91/2 km. Both types of movement were completed before the Caledonoid faults were disrupted by NNW sinistral faulting and more intrusions of Lower Old Red Sandstone age were emplaced.

scholarly journals PHYSICAL-MECHANICAL PROPERTIES OF METAVOLCANIC ROCKS OF THE MOUNTAIN CRIMEA

2018 ◽  
Vol 13 (4-5) ◽  
pp. 36-51
Author(s):  
J. V. Frolova ◽  
V. V. Ladygin ◽  
E. M. Spiridonov ◽  
G. N. Ovsyannikov
Keyword(s):  
Mechanical Properties ◽  
Magnetic Susceptibility ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Secondary Mineral ◽  
Grade Metamorphism ◽  
Clastic Rocks ◽  
Metavolcanic Rocks ◽  
Physical Density ◽  
Characteristic Values

The article considers the petrogenetic features of the volcanogenic rocks of the Middle Jurassic age of the Mountain Crimea and analyzes their influence on physical (density, porosity, water absorption, and magnetic susceptibility) and physical-mechanical properties (strength, modulus of elasticity, and Poisson's ratio). Among volcanogenic strata there are subvolcanic, effusive and volcanogenic-clastic rocks. All volcanic rocks were altered under the influence of the regional low-grade metamorphism of the zeolite and prehnite-pumpellyite facies, which resulted in a greenstone appearance. Among the secondary mineral the most common are albite, chlorite, quartz, adularia, sericite, calcite, pumpellyite, prenite, zeolites, epidote, sphene, and clay minerals. It is shown that low-grade metamorphism is characterized by heterogenious transformations: there are both slightly modified, practically fresh differences, and fully altered rocks. Tuffs are usually altered to a greater extent than effusive and subvolcanic rocks. In general, effusive and volcanogenic-clastic rocks differ markedly in their physicalmechanical properties, which is due to the peculiarities of their formation: the former are substantially more dense and stronger, less porous and compressible. However, these differences are leveled as a result of intensive changes in mineral composition and porosity in the process of low-grade metamorphism. The most characteristic values of metavolcanite properties were revealed. It is shown that among all studied parameters, the magnetic susceptibility most clearly correlates with the degree of rocks alteration.

Origin of the Tulameen ultramafic-gabbro complex, southern British Columbia

1969 ◽  
Vol 6 (3) ◽  
pp. 399-425 ◽  
Author(s):  
D. C. Findlay
Keyword(s):  
British Columbia ◽  
Internal Structure ◽  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Age Determination ◽  
Upper Triassic ◽  
Ultramafic Rocks ◽  
Metasedimentary Rocks ◽  
Gabbroic Intrusion

The Tulameen Complex is a composite ultramafic-gabbroic intrusion that outcrops over 22 sq. mi. (57 km2) in the Southern Cordillera of British Columbia. The complex intruded Upper Triassic metavolcanic and metasedimentary rocks of the Nicola Group, and on the basis of geologic relations and a K–Ar age determination (186 m.y.) is tentatively dated as Late Triassic.The principal ultramafic units — dunite, olivine clinopyroxenite, and hornblende clinopyroxenite — form an elongate, non-stratiform body whose irregular internal structure is best explained by deformation contemporaneous with crystallization of the rocks. The derivation of the ultramafic rocks is attributed to fractional crystallization of an ultrabasic magma. The gabbroic mass, which consists of syenogabbro and syenodiorite, partly borders and partly overlies the ultramafic body and was apparently intruded by it.The ultramafic and gabbroic parts of the complex probably formed from separate intrusions of different magmas, but the two suites have sufficient mineralogical and chemical features in common to indicate an ultimate petrogenic affinity of the magmas. Comparison of the Tulameen rocks with nearby intrusions of the same general age, in particular the Copper Mountain stock, suggests that they are members of a regional suite of alkalic intrusions. The possibility is also raised that these intrusions may be comagmatic with the Nicola volcanic rocks.

Rb–Sr study of metavolcanic rocks from the La Ronge and Flin Flon domains, northern Saskatchewan

1985 ◽  
Vol 22 (3) ◽  
pp. 452-463 ◽  
Author(s):  
B. R. Watters ◽  
R. L. Armstrong
Keyword(s):  
Source Region ◽  
Volcanic Rocks ◽  
Volcanic Arcs ◽  
Magmatic Arc ◽  
Linear Evolution ◽  
Metavolcanic Rocks ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Flin Flon ◽  
Lynn Lake

Two whole-rock suites of metavolcanic rocks from separate volcanic belts of the Churchill Province in northern Saskatchewan have been dated by Rb–Sr. Samples from the Amisk Group of the Flin Flon – Snow Lake domain provide an isochron date of 1784 ± 44 Ma; suites from the Waddy Lake and Devil Lake areas of the La Ronge (–Lynn Lake) domain yield isochron dates of 1814 ± 26 and 1854 ± 100 Ma, respectively. All are regarded as minima for, but close approximations to, emplacement ages. The maximum crustal age of any suite cannot greatly exceed 1850 Ma.Previous Rb–Sr and U–Pb isotopic dates together with these new determinations confirm the contemporaneous existence of two volcanic arcs, active during the late Aphebian (1875–1784 Ma) in the Churchill Province.Low initial 87Sr/86Sr ratios (0.7017–0.7022) are consistent with a petrochemically inferred subduction-related origin for the volcanic rocks with no closed-system reworking of Archean crust, and a linear evolution of 87Sr/86Sr ratio in the magmatic-arc mantle source region from 4.55 Ga to the present.

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.

U–Pb age constraints on arenaceous and volcanic rocks of the Wakeham Group, eastern Grenville Province

2005 ◽  
Vol 42 (10) ◽  
pp. 1677-1697 ◽  
Author(s):  
O van Breemen ◽  
L Corriveau
Keyword(s):  
Volcanic Rocks ◽  
Detrital Zircons ◽  
Morphological Evidence ◽  
Ionization Mass ◽  
Grenville Province ◽  
Metavolcanic Rocks ◽  
Southeastern Margin ◽  
Depositional Age ◽  
Age Constraints ◽  
Group Yield

Combined sensitive high-resolution ion microprobe (SHRIMP) and thermal ionization mass spectrometry (TIMS) U–Pb zircon data from a tightly constrained stratigraphic context of the Wakeham Group provide a precise depositional age for sedimentation within this extensive basin of the Grenville Province. Metavolcanic rocks at the eastern exposure of the Wakeham Group yield ages of 1511 ± 13, 1506 ± 11, 1502 ± 9, and 1491 ± 7 Ma. A crosscutting 1493 ± 10 Ma porphyry vein marks the end of volcanism. The older two volcanic rocks rest stratigraphically above metasediments, with a 1517 ± 20 Ma maximum age of sedimentation derived from the youngest detrital zircons of an arenite. Five 1.61–1.55 Ga inherited zircons in the volcanics, reinforced by coeval inheritance in nearby plutons, indicate a Labradorian basement source to the supracrustals. The predominant arenite detrital zircons dates are in the 1.95–1.75 Ga range, however, and feature both trace element and morphological evidence for metamorphism in the source terrane. Together with zircons as old as 2.95 Ga, the detrital age spectrum is consistent with a circum-Superior provenance. The ages obtained imply that Wakeham Group volcanism and sedimentation were, at least in part, coeval with the onset of 1.52–1.46 Ga Pinwarian plutonism along the southeastern margin of Laurentia. U–Pb zircon analyses record a late Grenvillian metamorphic event around 1019 Ma. U–Pb monazite analyses from one sample yield 1010–1000 Ma ages, and the end of Grenvillian metamorphism is marked by 990 Ma U–Pb titanite ages.

Zircon ages of the metavolcanic rocks and metagranites of the Ollo de Sapo Domain in central Spain: implications for the Neoproterozoic to Early Palaeozoic evolution of Iberia

2007 ◽  
Vol 144 (6) ◽  
pp. 963-976 ◽  
Author(s):  
P. Montero ◽  
F. Bea ◽  
F. González-Lodeiro ◽  
C. Talavera ◽  
M. J. Whitehouse
Keyword(s):  
Passive Margin ◽  
Variscan Orogeny ◽  
Compositional Variation ◽  
The West ◽  
Middle Ordovician ◽  
Pan African ◽  
Metavolcanic Rocks ◽  
High Fraction ◽  
Early Palaeozoic ◽  
High Level

AbstractDating the pre-Middle Ordovician metavolcanic rocks and metagranites of the Ollo de Sapo Domain has, historically, been difficult because of the small compositional variation, the effects of the Variscan orogeny and, as revealed in this paper, the unusually high fraction of inherited zircon components. The first reliable zircon data (U–Pb ion microprobe and Pb–Pb stepwise evaporation) indicate that the Ollo de Sapo volcanism spanned 495±5 Ma to 483±3 Ma, and was followed by the intrusion of high-level granites from 483±3 Ma to 474±4 Ma. In both metavolcanic rocks and metagranites, no less than 70–80% of zircon grains are either totally Precambrian or contain a Precambrian core overgrown by a Cambro-Ordovician rim. About 80–90% of inherited zircons are Early Ediacaran (602–614 Ma) and derived from calc-alkaline intermediate to felsic igneous rocks generated at the end of the Pan-African arc–continent collision. In the Villadepera region, located to the west, both the metagranites and metavolcanic rocks also contain Meso-Archaean zircons (3.0–3.2 Ga) which ultimately originated from the West African Craton. In the Hiendelaencina region, located to the east, both the metagranites and metavolcanic rocks lack Meso-Archaean zircons, but they have two different inherited zircon populations, one Cryogenian (650–700 Ma) and the other Tonian (850–900 Ma), which suggest older-than-Ediacaran additional island-arc components. The different proportion of source components and the marked variation of the 87Sr/86Srinit. suggest, at least tentatively, that the across-arc polarity of the remnants of the Pan-African arc of Iberia trended east–west (with respect to the current coordinates) during Cambro-Ordovician times, and that the passive margin was situated to the west.

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.

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