Early Silurian volcanic rocks at Arisaig, Nova Scotia

1979 ◽  
Vol 16 (8) ◽  
pp. 1635-1640 ◽  
Author(s):  
J. Duncan Keppie ◽  
J. Dostal ◽  
M. Zentilli
Keyword(s):  
Nova Scotia ◽  
Lower Devonian ◽  
Basaltic Magma ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Island Arc ◽  
Temporal Association ◽  
Continental Plate

Petrochemical data for the Early Llandovery subaerial volcanic rocks at Arisaig, Antigonish Highlands, Nova Scotia, show that they are a bimodal suite of altered rhyolites and basalts of tholeiitic affinity with some alkaline tendencies extruded in a nonorogenic extensional environment within a continental plate. These data do not support the island arc origin frequently inferred for these rocks but are consistent with recent petrological data from the Silurian – Lower Devonian Coastal Volcanic Belt in southern Maine, which may be a strike continuation of the Arisaig volcanics. The close spatial and temporal association of basalts and rhyolites is attributed to anatexis of the crust upon contact with the rising basaltic magma.

scholarly journals Chau Thoi and Nui Gio volcanic rocks: A remnant of the Loei Phetchabun volcanic belt in Viet Nam

2021 ◽  
Vol 24 (1) ◽  
pp. 1879-1888
Author(s):  
Tuan Anh Nguyen ◽  
Doan Thi Thuy ◽  
Ngo Tran Thien Quy ◽  
Lan Ching Yin
Keyword(s):  
Earth Science ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Major Elements ◽  
Island Arc ◽  
Geochemical Data ◽  
Viet Nam ◽  
Volcanic Island ◽  
Current Time ◽  
Continental Plate

Introduction: Extrusive volcanic rocks, such as dacite, andesite, basalto-andesite, basalt… of Chau Thoi and Nui Gio hills in Bien Hoa and Binh Phuoc provinces, southern Viet Nam, characterize volcanic island arc rocks. These rock suites formed as the convergent tectonic between the Indochina and Sibumasu geological blocks. Methods: Geochemical data of rock samples collected on the field were examined and analyzed by the Academia Sinica I E S (Institute of Earth Science, Taiwan and processed with a GCD kit (Geochemical Data Toolkit) to ascertain their characteristics and geotectonic setting. Result: Geochemical data both in major elements and trace elements of the Chau Thoi – Nui Gioshow a specific characteristic of a volcanic island arc environment. Discussion: Chau Thoi and Nui Gio rocks are suitable to correlate to the Permian Thailand Loei Phetchabun volcanic belt. However, at the current time, Chau Thoi and Nui Gio rocks have been classified as Deo Bao Loc formation - late Jurassic to early Cretaceous in ages - belong Truong Son magmatic belt. This magmatic belt resulted from the Yanshanian orogeny by the subduction of the Paleo-Pacific oceanic plate beneath the Eurasia (Indochina) continental plate. More studies needed to be performed, specially geochronological data to support the study. Conclusion: Chau Thoi and Nui Gio rock suites characterize volcanic island arc rocks, products of a convergence tectonic between Indochina and Sibumasu blocks. They are remnants of the Thailand Loei Phetchabun volcanic belt, the first time reported in Vietnam.

Lithogeochemistry of volcano-plutonic assemblages of the southern Hanson Lake Block and southeastern Glennie Domain, Trans-Hudson Orogen: evidence for a single island arc complex

1999 ◽  
Vol 36 (2) ◽  
pp. 209-225 ◽  
Author(s):  
Ralf O Maxeiner ◽  
Tom II Sibbald ◽  
William L Slimmon ◽  
Larry M Heaman ◽  
Brian R Watters
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Oceanic Island ◽  
Island Arc ◽  
Island Arcs ◽  
Calc Alkaline ◽  
East Central ◽  
South Central ◽  
Volcaniclastic Rocks ◽  
Flin Flon

This paper describes the geology, geochemistry, and age of two amphibolite facies volcano-plutonic assemblages in the southern Hanson Lake Block and southeastern Glennie Domain of the Paleoproterozoic Trans-Hudson Orogen of east-central Saskatchewan. The Hanson Lake assemblage comprises a mixed suite of subaqueous to subaerial dacitic to rhyolitic (ca. 1875 Ma) and intercalated minor mafic volcanic rocks, overlain by greywackes. Similarly with modern oceanic island arcs, the Hanson Lake assemblage shows evolution from primitive arc tholeiites to evolved calc-alkaline arc rocks. It is intruded by younger subvolcanic alkaline porphyries (ca. 1861 Ma), synvolcanic granitic plutons (ca. 1873 Ma), and the younger Hanson Lake Pluton (ca. 1844 Ma). Rocks of the Northern Lights assemblage are stratigraphically equivalent to the lower portion of the Hanson Lake assemblage and comprise tholeiitic arc pillowed mafic flows and felsic to intermediate volcaniclastic rocks and greywackes, which can be traced as far west as Wapawekka Lake in the south-central part of the Glennie Domain. The Hanson Lake volcanic belt, comprising the Northern Lights and Hanson Lake assemblages, shows strong lithological, geochemical, and geochronological similarities to lithotectonic assemblages of the Flin Flon Domain (Amisk Collage), suggesting that all of these areas may have been part of a more or less continuous island arc complex, extending from Snow Lake to Flin Flon, across the Sturgeon-Weir shear zone into the Hanson Lake Block and across the Tabbernor fault zone into the Glennie Domain.

A Cambrian island arc in Iapetus: geochronology and geochemistry of the Lake Ambrose volcanic belt, Newfoundland Appalachians

1991 ◽  
Vol 128 (1) ◽  
pp. 1-17 ◽  
Author(s):  
G. R. Dunning ◽  
H. S. Swinden ◽  
B. F. Kean ◽  
D. T. W. Evans ◽  
G. A. Jenner
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Detailed Examination ◽  
Island Arc ◽  
Trace Element Geochemistry ◽  
Geochemical Type ◽  
Element Geochemistry ◽  
South Central ◽  
Iapetus Ocean ◽  
Felsic Volcanic

AbstractThe Lake Ambrose volcanic belt (LAVB) outcrops as a 45 km long northeast-trending belt of mafic and felsic volcanic rocks along the eastern side of the Victoria Lake Group in south-central Newfoundland. It comprises roughly equal proportions of mafic pillow basalt and high silica rhyolite, locally interbedded with epiclastic turbidites. Volcanic rocks have been metamorphosed in the greenschist facies and are extensively carbonatized.U-Pb (zircon) dates from rhyolite at two, widely separated localities give identical ages of 513 ± 2 Ma (Upper Cambrian), and this is interpreted as the eruptive age of the volcanic sequence. Primitive arc and low-K tholeiites can be recognized on the basis of major and trace element geochemistry, ranging from LREE-depleted to LREE-enriched. Geochemical variation between mafic volcanic types is interpreted predominantly to reflect contrasts in source characteristics and degree of partial melting; some variation within each geochemical type attributable to fractional crystallization can be recognized. Detailed examination of some samples indicates that the heavy REE and related elements have locally been mobile, probably as a result of carbonate complexing.The LAVB is the oldest well-dated island arc sequence in Newfoundland, and perhaps in the Appalachian–Caledonian Orogen. Its age requires modification of widely held models for the tectonic history of central Newfoundland. It is older than the oldest known ophiolite, demonstrating that arc volcanism was extant before the generation of the oldest known oceanic crust in this part of Iapetus. It further demonstrates that there was a maximum of approximately 30 Ma between the rift-drift transition which initiated Iapetus, and the initiation of subduction. This suggests that the oceanic sequences preserved in Newfoundland represent a series of arcs and back arc basins marginal to the main Iapetus Ocean, and brings into question whether the Appalachian accreted terranes contain any remnants of normal mid-ocean ridge type Iapetan crust.

Geochemistry of mid- upper eocene intra-continental alkaline volcanic range, south part of central alborz mountains, north of Iran.

2020 ◽  
Vol 33 (02) ◽  
pp. 511-524
Author(s):  
Leila Abbaspour Shirjoposht ◽  
Sayed Jamal al-Din Sheikh Zakariaee ◽  
Mohammad Reza Ansari ◽  
Mohammad Hashem Emami
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Primitive Mantle ◽  
Upper Eocene ◽  
Continental Plate ◽  
Mantle Sources ◽  
Central Alborz ◽  
Volcanic Suite ◽  
North Of Iran ◽  
Significant Enrichment

The Ziaran volcanic Belt (ZVB), North of Iran contains a number of intra-continental alkaline volcanic range situated on South part of central Alborz Mountains, formed along the localized extensional basins developed in relation with the compressional regime of Eocene. The mid-upper Eocene volcanic suite comprises the extracted melt products of adiabatic decompression melting of the mantle that are represented by small volume intra-continental plate volcanic rocks of alkaline volcanism and their evaluated Rocks with compositions representative of mantle-derived, primary (or near-primary) melts. Trace element patterns with significant enrichment in LILE, HFSE and REEs, relative to Primitive Mantle. Chondrite-normalized of rare earth elements and enrichment in incompatible elements and their element ratios (e. g. LREE/HREE, MREE/HREE, LREE/MREE) shown these element modelling indicates that the magmas were generated by comparably variable degrees of partial melting of garnet lherzolite and a heterogeneous asthenospheric, OIB mantle sources.

scholarly journals Tectonostratigraphy of the Jurassic accretionary prisms in the Sikhote-Alin region of Russian Far East

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Vladimir V. Golozubov ◽  
Ludmila F. Simanenko
Keyword(s):  
Large Scale ◽  
Russian Far East ◽  
Far East ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Accretionary Prism ◽  
Continental Plate ◽  
Flat Slab Subduction ◽  
Accretionary Prisms ◽  
Jurassic Accretionary Prism

AbstractWe propose a scheme to subdivide the Samarka terrane, a Jurassic accretionary prism fragment, into tectonostratigraphic complexes. This subdivision provides a basis to study these formations and map them on a medium- to large-scale. Each complex corresponds to a certain stage in the accretionary prism formation. Thus, the complexes composed of subduction mélange and olistostromes (in our case, Ust-Zhuravlevka and Sebuchar complexes), can be correlated to episodes when the underthrusting of seamounts hampered subduction, as evidenced by seamount fragments contained in the complexes. Episodes of relatively quiet subduction have also been identified, resulting in complexes composed mainly of normally bedded terrigenous and biogenic formations (Tudovaka and Udeka and, partially, Ariadnoe complexes). Particularly considered is the Okrainka-Sergeevka allochthonous complex – a fragment of continental plate overhanging a subduction zone. It was included in the accretionary prism during gravitational sliding on the internal slope of the paleotrench. All volcanic rocks in the accretionary prism are allochthonous fragments of the accreted oceanic crust. The absence of the Jurassic-Berriasian volcanic belt related to this prism, as well as synchronous autochthonous volcanism, indicates that the Samarka terrane accretionary prism formed under conditions of flat-slab subduction, similar to modern examples along the Andean margin.

The Border Ranges ultramafic and mafic complex, south-central Alaska: cumulate fractionates of island-arc volcanics

1985 ◽  
Vol 22 (7) ◽  
pp. 1020-1038 ◽  
Author(s):  
Laurel E. Burns
Keyword(s):  
Fractional Crystallization ◽  
Compositional Data ◽  
Basaltic Magma ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Minor Amount ◽  
The North ◽  
South Central ◽  
Mafic Complex ◽  
Wide Range

A discontinuous, elongate zone of mafic and ultramafic plutonic rock crops out in south-central Alaska for a distance of more than 1000 km. Intermediate- and detailed-scale geologic mapping, petrographic study, and compositional data suggest that the plutonic rocks are compositionally, petrologically, and mineralogically distinct from rocks in mid-ocean ridge and back-arc basin ophiolites. The mafic and ultramafic rocks instead represent part of the plutonic core of an intraoceanic island arc.The mafic–ultramafic zone, referred to as the Border Ranges ultramafic and mafic complex (BRUMC), is composed of ultramafic cumulates, gabbronorite cumulates, and massive gabbronorites. A very minor amount of tectonized ultramafic rock of mantle origin is present in the southern part of the BRUMC. A thick sequence of andesitic volcanic rocks, the Talkeetna Formation of Early Jurassic age, lies to the north of and structurally above the mafic–ultramafic zone. Voluminous calcalkaline plutons composed of quartz diorite, tonalite, and minor granodiorite intrude both the mafic plutonic complexes and the andesitic volcanic rocks.The cumulate ultramafic sections are largely composed of dunite ± chromite, wehrlite, clinopyroxenite, and websterite and are characterized by a wide range of Mg–Fe silicate compositions (Fo90–81; En45–50, Fs1–7, Wo45–49; En88–82, Fs11–17), chrome-rich spinels, and a lack of plagioclase. The gabbroic sections are composed of gabbronorites with up to 10–15% magnetite ± ilmenite. Hornblende, if present, is a very minor phase in most gabbroic rocks. The coexisting mineral compositions seen in the gabbroic rocks of the BRUMC (relatively iron-rich pyroxene—Fs6–13, En45–40; En81–63 —and calcic plagioclase An75–100) and their association with magnetite are common in plutonic xenoliths in island-arc rocks.The mineralogy and composition of the gabbroic rocks in the BRUMC are consistent with the fractional crystallization products predicted to be associated with the formation of andesite from a basaltic magma. Consideration of additional data, including detailed and regional field mapping of the plutonic and volcanic rocks and geochronology of the BRUMC and the nearby Talkeetna arc volcanic rocks, strongly suggests that the BRUMC represents relatively deep fractional crystallization products of magmas that produced the Talkeetna Formation volcanic rocks. Field relationships also indicate that intrusion of quartz diorites, tonalites, and granodiorites of batholithic proportions occurred slightly later than formation of the BRUMC.

Cambrian volcanism in Nova Scotia, Canada

1985 ◽  
Vol 22 (4) ◽  
pp. 599-606 ◽  
Author(s):  
J. B. Murphy ◽  
K. Cameron ◽  
J. Dostal ◽  
J. Duncan Keppie ◽  
A. J. Hynes
Keyword(s):  
Nova Scotia ◽  
Lower Cambrian ◽  
Basaltic Magma ◽  
Volcanic Rocks ◽  
Felsic Magma ◽  
Middle Cambrian ◽  
Cape Breton Island ◽  
Shallow Marine ◽  
Cape Breton ◽  
Pull Apart Basin

Cambrian volcanic rocks in Nova Scotia occur in small grabens or half grabens in the Avalon Zone (Composite Terrane) as part of a thin sequence of continental to shallow-marine Cambro-Ordovician rocks. In the northern Antigonish Highlands, the volcanic rocks occur mainly in the Lower Cambrian McDonalds Brook Group. In southern Cape Breton Island, they occur predominantly in the Middle Cambrian Bourinot Group. The chemistry of these volcanic rocks indicates that they are bimodal (basalts–rhyolites) and within plate. The basalts are alkalic in the Antigonish Highlands and tholeiitic in Cape Breton Island. The rising basaltic magma is postulated to have produced the felsic magma by anatexis of the crust. It is proposed that the Antigonish Highlands volcanic rocks erupted in a small pull-apart basin. A similar structural setting is probable in southern Cape Breton Island, but there the bounding faults are poorly exposed. These basins probably formed during a period of transpression in the last stages of the late Hadrynian Cadomian deformation.

Geochemistry and Isotope Composition of Paleoproterozoic Granites and Felsic Volcanics of the Elash Graben: Evidence of the Heterogeneity of the Early Precambrian Crust

2021 ◽  
Vol 62 (10) ◽  
pp. 1175-1187
Author(s):  
A.D. Nozhkin ◽  
O.M. Turkina ◽  
K.A. Savko
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Temporal Association ◽  
Metal Deposit ◽  
Wide Range ◽  
Rare Metal Deposit ◽  
Geochronological Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract —The paper presents results of a petrogeochemical and isotope–geochronological study of the granite–leucogranite association of the Pavlov massif and felsic volcanics from the Elash graben (Biryusa block, southwest of the Siberian craton). A characteristic feature of the granite–leucogranites is their spatial and temporal association with vein aplites and pegmatites of the East Sayan rare-metal province. The U–Pb age of zircon from granites of the Pavlov massif (1852 ± 5 Ma) is close to the age of the pegmatites of the Vishnyakovskoe rare-metal deposit (1838 ± 3 Ma). The predominant biotite porphyritic granites and leucogranites of the Pavlov massif show variable alkali ratios (K2O/Na2O = 1.1–2.3) and ferroan (Fe*) index and a peraluminous composition; they are comparable with S-granites. The studied rhyolites of the Tagul River (SiO2 = 71–76%) show a low ferroan index, a high K2O/Na2O ratio (1.6–4.0), low (La/Yb)n values (4.3–10.5), and a clear Eu minimum (Eu/Eu* = 0.3–0.5); they are similar to highly fractionated I-granites. All coeval late Paleoproterozoic (1.88–1.85 Ga) granites and felsic volcanics of the Elash graben have distinct differences in composition, especially in the ferroan index and HREE contents, owing to variations in the source composition and melting conditions during their formation at postcollisions extension. The wide range of the isotope parameters of granites and felsic volcanic rocks (εNd from +2.0 to –3.7) and zircons (εHf from +3.0 to +0.8, granites of the Toporok massif) indicates the heterogeneity of the crustal basement of the Elash graben, which formed both in the Archean and in the Paleoproterozoic.

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