Petrochemistry of volcanic rocks of the Harbour Main Group, Avalon Peninsula, Newfoundland

1970 ◽  
Vol 7 (6) ◽  
pp. 1485-1498 ◽  
Author(s):  
V. S. Papezik
Keyword(s):  
Volcanic Rocks ◽  
Main Group ◽  
Range Type ◽  
Volcanic Suite ◽  
High Alkali ◽  
Tectonic Belt ◽  
Basic Rocks ◽  
Avalon Peninsula ◽  
Block Faulting ◽  
Different Parts

The predominantly volcanic Harbour Main Group of Proterozoic (Hadrynian) age forms a northerly-trending belt in the central part of the Avalon Peninsula, Newfoundland. The rocks include flows, pyroclastics, and several belts of well-preserved ignimbrites.Twenty-two recent chemical analyses of volcanic rocks, sixteen of them not previously published, show that the Harbour Main volcanic suite is distinctly sodic and weakly alkalic, ranging from basic rocks of the hawaiite–mugearite type to sodic rhyolites with relatively high alkali content; the alkali-lime index of the suite is 52.The Harbour Main rocks are shown to be chemically similar to the Late Precambrian Uriconian volcanic suite in Central Britain, with which it has been previously tentatively correlated on other grounds. It is suggested that the volcanic rocks of the Avalon Peninsula and the British Midlands were formed in different parts of a possibly continuous tectonic belt in a period of post-orogenic block-faulting of the Basin and Range type, prior to the opening of the present Atlantic Ocean.

Basic magmatism in relation to metamorphism and orogeny in Guiana: a speculation

1973 ◽  
Vol 110 (4) ◽  
pp. 365-371 ◽  
Author(s):  
A. Choudhuri
Keyword(s):  
Volcanic Rocks ◽  
High Grade ◽  
Crustal Rocks ◽  
Gneiss Complex ◽  
Mantle Peridotites ◽  
Gravity Measurements ◽  
Basic Magmatism ◽  
High Grade Metamorphism ◽  
Basic Rocks ◽  
Block Faulting

SummaryThe northern part of the Guiana Shield consists of large tracts of basic and intermediate volcanic rocks and sediments which are thought to have formed under geosynclinal conditions. During the 2000 m.y. Trans-Amazonian Orogeny these rocks were subjected to tectonism and metamorphism resulting in a broad belt of green schist facies with local and isolated patches of high grade metamorphic rocks and gneiss complexes. In the early stages of orogeny during which folding and probable block faulting of the sediments and volcanics took place, these rocks were intruded by basic and ultra-basic rocks giving rise to metagabbro-amphibolite-peridotite associations, commonly in the areas of subsequent high-grade metamorphism. In an attempt to account for the frequent supply of basic magma during and after the orogeny it is postulated that mantle peridotites rose diapir-like below the sinking geosyncline, and by partial melting not only provided basic magmas but also thermal energy which spread upwards to metamorphose the already tectonized crustal rocks; recent gravity measurements indicate an upwarped ‘sima’ under the Bartica Assemblage gneiss complex.

Late Precambrian Rocks of Eastern Avalon Peninsula, Newfoundland — A Volcanic Island Complex

1971 ◽  
Vol 8 (8) ◽  
pp. 899-915 ◽  
Author(s):  
C. J. Hughes ◽  
W. D. Brückner
Keyword(s):  
Volcanic Rocks ◽  
Main Group ◽  
Volcanic Island ◽  
Precambrian Rocks ◽  
Crustal Movements ◽  
Late Precambrian ◽  
Isostatic Adjustment ◽  
Avalon Peninsula ◽  
Vertical Crustal Movements

A model of island volcanism is presented in which rocks are referred to (1) a "syn-volcanic" constructional phase represented by rocks of four penecontemporaneous facies—vent, alluvial, marine, and plutonic—whose interrelationships are discussed and (2) a "post-volcanic" destructional phase of erosion and sedimentation accompanied by isostatic adjustment resulting in the spreading of an apron of volcanic sediments around a slowly rising and eroding island core.The late Precambrian rocks of the eastern part of the Avalon Peninsula, southeasternmost Newfoundland, are shown to fit this model rather closely, both petrographically and in their distribution and field relationships. The Harbour Main Group of volcanic rocks, the Conception Group of marine volcanic sediments and tuffs, and the Holyrood Plutonic Series, dated at 574 ± 11 m.y., were all formed during the syn-volcanic constructional phase. Their apparently conflicting age relationships can be reconciled to the view that they are penecontemporaneous facies. The Cabot and Hodgewater Groups of marine and alluvial volcanic sediments were formed during the post-volcanic destructional phase. Apart from vertical crustal movements, only minor diastrophic deformation appears to have occurred during these two phases.This model of volcanic island environment may help in interpreting the geology of several other belts in eastern and central Newfoundland comprising late Precambrian and Paleozoic volcanic rocks and sediments.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

The (?) mid Triassic volcanic rocks of Lakonia, Greece

1982 ◽  
Vol 119 (1) ◽  
pp. 77-85 ◽  
Author(s):  
G. Pe-Piper ◽  
A. G. Panagos ◽  
D. J. W. Piper ◽  
C. N. Kotopouli
Keyword(s):  
Major Element ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Potash Feldspar ◽  
Hypabyssal Intrusions ◽  
Major Element Chemistry ◽  
Plate Margin ◽  
Genetic Interpretation ◽  
Basic Rocks ◽  
Primary Minerals

SummaryThick subaerial volcanic sequences of probable mid Triassic age rest unconformably on Permo-Carboniferous limestones in the ‘Phyllite Series’ within the Gavrovo-Tripolitsa zone of the external Hellenide nappes. The volcanic rocks are varied in character. Pyroclastic rocks (often reddened) predominate, but minor basalt or andesite and rhyolitic hypabyssal intrusions and flows are also found. The rocks have experienced low-grade metamorphism and the only relict primary minerals are pyroxene and rare plagioclase in basic rocks and potash feldspar in acid rocks. The most important metamorphic phases are albite, chlorite, potassium mica, epidote, hematite, quartz and pumpellyite. Twenty-seven whole-rock major-element analyses suggest that there has been some exchange of Na2O and K2O for CaO during metamorphism, but that other elements have been relatively stable. A genetic interpretation of the rocks is attempted using published geochemical discriminator diagrams. The basic rocks are tholeiitic in major element chemistry and pyroxene composition. Trace element (Hf, Ta, Th, Ce, Yb) distribution suggests magma generation at a destructive plate margin.

Neoproterozoic arc volcanic rocks of the Nanping-Ninghua tectonic belt, South China: Implications for the collision between the North and South Wuyi blocks

2018 ◽  
Vol 54 (4) ◽  
pp. 2679-2692 ◽  
Author(s):  
Yang Jiang ◽  
Xilin Zhao ◽  
Yanjie Zhang ◽  
Guangfu Xing ◽  
Mincheng Xu ◽  
...  
Keyword(s):  
South China ◽  
Volcanic Rocks ◽  
The North ◽  
Tectonic Belt ◽  
North And South

Copper-Gold Fertility of Arc Volcanic Rocks: A Case Study from the Early Permian Lizzie Creek Volcanic Group, NE Queensland, Australia

2020 ◽  
Author(s):  
Helge Behnsen ◽  
Carl Spandler ◽  
Isaac Corral ◽  
Zhaoshan Chang ◽  
Paul H.G.M. Dirks
Keyword(s):  
Major Element ◽  
Regional Scale ◽  
Volcanic Rocks ◽  
Early Permian ◽  
Magma Evolution ◽  
High Sulfidation ◽  
Volcanic Group ◽  
Volcanic Suite ◽  
Copper Gold

Abstract The Early Permian Lizzie Creek Volcanic Group of the northern Bowen Basin, NE Queensland, Australia, has compositions that range from basalt through andesite to rhyolite with geochemical signatures (e.g., enrichment in Cs, Rb, Ba, U, Th, and Pb, depletion in Nb and Ta) that are typical of arc lavas. In the Mount Carlton district the Lizzie Creek Volcanic Group is host to high-sulfidation epithermal Cu-Au-Ag mineralization, whereas farther to the south near Collinsville (~50 km from Mount Carlton) these volcanic sequences are barren of magmatic-related mineralization. Here, we assess whether geochemical indicators of magma fertility (e.g., Sr/Y, La/Yb, V/Sc) can be applied to volcanic rocks through study of coeval volcanic sequences from these two locations. The two volcanic suites share similar petrographic and major element geochemical characteristics, and both have undergone appreciable hydrothermal alteration during, or after, emplacement. Nevertheless, the two suites have distinct differences in alteration-immobile trace element (V, Sc, Zr, Ti, REE, Y) concentrations. The unmineralized suite has relatively low V/Sc and La/Yb, particularly in the high SiO2 rocks, which is related to magma evolution dominated by fractionation of clinopyroxene, plagioclase, and magnetite. By contrast, the mineralized suite has relatively high V/Sc but includes high SiO2 rocks with depleted HREE and Y contents, and hence high La/Yb. These trends are interpreted to reflect magma evolution under high magmatic H2O conditions leading to enhanced amphibole crystallization and suppressed plagioclase and magnetite crystallization. These rocks have somewhat elevated Sr/Y compared to the unmineralized suite, but as Sr is likely affected by hydrothermal mobility, Sr/Y is not considered to be a reliable indicator of magmatic conditions. Our data show that geochemical proxies such as V/Sc and La/Yb that are used to assess Cu-Au fertility of porphyry intrusions can also be applied to cogenetic volcanic sequences, provided elemental trends with fractionation can be assessed for a volcanic suite. These geochemical tools may aid regional-scale exploration for Cu-Au mineralization in convergent margin terranes, especially in areas that have undergone limited exhumation or where epithermal and porphyry mineralization may be buried beneath cogenetic volcanic successions.

Permian volcanism in the Mongolian orogenic zone, northeast China: geochemistry, magma sources and petrogenesis

2001 ◽  
Vol 138 (2) ◽  
pp. 101-115 ◽  
Author(s):  
YONGFENG ZHU ◽  
SHIHUA SUN ◽  
LIBING GU ◽  
YOSHIHIDE OGASAWARA ◽  
NENG JIANG ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Major Elements ◽  
Mantle Metasomatism ◽  
Primary Magma ◽  
Lower Permian ◽  
Depleted Mantle ◽  
Incompatible Trace Elements ◽  
Basic Rocks ◽  
Orogenic Zone

Lower Permian volcanism was the first magmatic activity to occur after the collision events in the Mongolian orogenic zone, east China. The Permian volcanic rocks are therefore a key to understanding the dynamics of the unified continental lithosphere. The volcanic rocks consist of basic and intermediate rocks. The intermediate rocks with high initial 87Sr/86Sr ratios (0.7051 to 0.7052) and low εNd values (−0.73 to −3.57) generally overlie the basic rocks in the field. The basic rocks have relatively low initial 87Sr/86Sr ratios (0.7034 to 0.7051) and high εNd values (2.72 to −0.10). Two parallel Rb–Sr isochrons give almost the same age, about 270 Ma. One consists of the basic rocks giving an initial isochron 87Sr/86Sr ratio of 0.7035. The other consists of the intermediate rocks and one sample of basalt, which give an initial isochron 87Sr/86Sr value of 0.7051. The strong correlations between SiO2 and other major elements suggest that fractional crystallization played an important role in the magmatic processes. However, fractional crystallization cannot explain the geochemistry of most incompatible trace elements and Sr–Nd isotope characteristics. The positive correlation between Th/Nb and (La/Sm)N ratios demonstrates the direct relation between the enrichment of the light rare earth elements and the contamination of continental sediments. The high contents of large ion lithosphere elements (LILE) in the Permian volcanic rocks may suggest an additional ‘crust + fluid’ component, especially in the intermediate rocks, which are highly enriched in Ba (> 400 ppm) relative to the basic rocks (> 200 ppm). We propose that the subduction slab dropped into depleted mantle and released fluid, which induced the mantle metasomatism and LILE enrichment. The metasomatized mantle partially melted and formed the ‘primary’ magma. This primary magma assimilated with the Proterozoic biotite–quartz schist during its rise, and finally formed the Permian volcanic rocks. Magma assimilated with the Proterozoic biotite–quartz schist in small amounts could have produced the basic rocks, while assimilation of larger amounts of magma (because of longer assimilation time) would generate intermediate rocks.

scholarly journals Petrographic Characteristics and Geochemistry of Volcanic Rocks in the Kyaukmyet Prospect, Monywa District, Central Myanmar

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Toe Naing Oo ◽  
Agung Harijoko ◽  
Lucas Donny Setijadji
Keyword(s):  
Middle Miocene ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Volcanic Field ◽  
Research Area ◽  
Eu Anomaly ◽  
Volcanic Suite ◽  
Copper Gold ◽  
Arc Setting ◽  
Insight Into

The Kyaukmyet prospect lies approximately 5 km ENE of the highsulfidation Kyisintaung copper-gold deposit, Monywa district, central Myanmar. Geologically, the research area is remarked by magmatic extrusion that occurred during the Late Oligocene to Middle Miocene of Magyigon Formation which led to the outcrops of volcanic rocks. Study detailed on petrographical and geochemical of the Kyaukmyet volcanic rocks has not been performed before the present work. The principal aim of this paper is to document the petrographical and geochemical characteristics of volcanic suite rocks exposed in the Kyaukmyet prospect. The results of this data have provided insight into the origin of the rocks and petrogenetic processes during evolution. Petrographically, all the studied volcanic rocks in the research area show that trachytic and porphyritic textures with phenocrysts of quartz, plagioclase, and K-feldspar which are embedded in a fine to medium grained groundmass. The accessory minerals of this rock consist of biotite, chlorite and opaque mineral.Geochemically, these volcanic rocks having calc-alkaline nature and classified as volcanic field (rhyolite) as well as volcanic arc setting. Based on the chondrite normalized spider diagram, LREE has enriched to HREE in this area which indicated negative Eu anomaly and subduction tectonic setting.

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.

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