Petrology and geochemistry of Cambrian volcanic rocks from the Avalon Zone in New Brunswick

1985 ◽  
Vol 22 (6) ◽  
pp. 881-892 ◽  
Author(s):  
John D. Greenough ◽  
S. R. McCutcheon ◽  
V. S. Papezik
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Middle Cambrian ◽  
Mafic Rocks ◽  
Rock Types ◽  
Petrology And Geochemistry ◽  
Eastern Seaboard ◽  
Highly Evolved

Lower to Middle Cambrian volcanic rocks occur within the Avalon Zone of southern New Brunswick at Beaver Harbour and in the Long Reach area. The Beaver Harbour rocks are intensely altered, but the major- and trace-element geochemistry indicates that they could be highly evolved (basaltic andesites) within-plate basalts. The mafic flows from the Long Reach area form two chemically and petrologically distinct groups: (1) basalts with feldspar phenocrysts that represent evolved continental tholeiites with some oceanic characteristics; and (2) a group of aphyric basalts showing extremely primitive continental tholeiite compositions, also with oceanic affinities and resembling some rift-related Jurassic basalts on the eastern seaboard. Felsic pyroclastic rocks in the Long Reach area make the suite bimodal. This distribution of rock types supports conclusions from the mafic rocks that the area experienced tension throughout the Early to Middle Cambrian.

Episodic Early Proterozoic granitoid plutonism in the Makkovik Province, Labrador: U–Pb geochronological data and geological implications

1992 ◽  
Vol 29 (6) ◽  
pp. 1166-1179 ◽  
Author(s):  
A. Kerr ◽  
T. E. Krogh ◽  
F. Corfu ◽  
U. Schärer ◽  
S. S. Gandhi ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Mobile Belt ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Early Proterozoic ◽  
Rock Types ◽  
Layered Gabbro ◽  
High Level ◽  
Orogenic Belts ◽  
Middle Proterozoic

Episodic granitoid plutonism in the Early Proterozoic Makkovik Province of the easternmost Canadian Shield is revealed by high-precision U–Pb zircon studies of a range of intrusive rock types. The oldest granites yield ages of 1893 ± 2 and 1891 ± 5 Ma and document a previously unrecognized event that may correlate with an early migmatization of reworked Archean basement. These dates also constrain early structural reworking of the basement, the earliest deformational event grouped as part of the Makkovikian orogeny. Four samples have essentially identical zircon ages of 1801 ± 2, 1802 ± 2, [Formula: see text], and 1825–1799 Ma, and a fifth is slightly older, at [Formula: see text]. These ages suggest correlation with local volcanic sequences, dated in part at 1807 ± 4 Ma. The plutonic suites include both syn- and posttectonic granitoid assemblages and define the main magmatic pulse associated with the Makkovikian orogeny and constrain its final deformational episode. Distinctive, fluorine-enriched "A-type" granites yield an age of 1719 ± 3 Ma and represent a previously unrecognized late postorogenic to anorogenic magmatism of regional significance. Two layered, gabbro–diorite–monzonite–syenite suites yield identical zircon ages of 1649 ± 1 and 1649 ± 3 Ma. A regionally extensive granodioritic unit gives an age of 1647 ± 2 Ma, and a high-level alaskitic granite is dated imprecisely at 1640–1650 Ma. These plutonic suites correlate with volcanic rocks previously dated at 1649 ± 1 Ma.These data show that the plutonic evolution of the Makkovik Province is significantly more complex than previously supposed. The clustering of ages suggests episodic, rather than continuous, magmatism. The different age groupings can, to some extent, be correlated with compositional associations defined by major- and trace-element geochemistry. The new data also raise questions about the regional configuration of Early and Middle Proterozoic orogenic belts in Labrador. Previous correlations between the Makkovik Province, the Ketilidian Mobile Belt of Greenland, and the Svecofennian and Trans-Scandinavian belts of Sweden are supported and expanded by these new results.

scholarly journals New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada

2020 ◽  
Author(s):  
T.V. Naber ◽  
S.E. Grasby ◽  
J.P. Cuthbertson ◽  
N. Rayner ◽  
C. Tegner
Keyword(s):  
Volcanic Rocks ◽  
High Arctic ◽  
Ellesmere Island ◽  
Large Igneous Province ◽  
The Arctic ◽  
Trace Element Geochemistry ◽  
Volcanic Complex ◽  
Northern Coast ◽  
Element Geochemistry ◽  
Igneous Province

The High Arctic Large Igneous Province (HALIP) represents extensive Cretaceous magmatism throughout the circum-Arctic borderlands and within the Arctic Ocean (e.g., the Alpha-Mendeleev Ridge). Recent aeromagnetic data shows anomalies that extend from the Alpha Ridge onto the northern coast of Ellesmere Island, Nunavut, Canada. To test this linkage we present new bulk rock major and trace element geochemistry, and mineral compositions for clinopyroxene, plagioclase, and olivine of basaltic dykes and sheets and rhyolitic lavas for the stratotype section at Hansen Point, which coincides geographically with the magnetic anomaly at northern Ellesmere Island. New U-Pb chronology is also presented. The basaltic and basaltic-andesite dykes and sheets at Hansen Point are all evolved with 5.5−2.5 wt% MgO, 48.3−57.0 wt% SiO2, and have light rare-earth element enriched patterns. They classify as tholeiites and in Th/Yb vs. Nb/Yb space they define a trend extending from the mantle array toward upper continental crust. This trend, also including a rhyolite lava, can be modeled successfully by assimilation and fractional crystallization. The U-Pb data for a dacite sample, that is cut by basaltic dykes at Hansen Point, yields a crystallization age of 95.5 ± 1.0 Ma, and also shows crustal inheritance. The chronology and the geochemistry of the Hansen Point samples are correlative with the basaltic lavas, sills, and dykes of the Strand Fiord Formation on Axel Heiberg Island, Nunavut, Canada. In contrast, a new U-Pb age for an alkaline syenite at Audhild Bay is significantly younger at 79.5 ± 0.5 Ma, and correlative to alkaline basalts and rhyolites from other locations of northern Ellesmere Island (Audhild Bay, Philips Inlet, and Yelverton Bay West; 83−73 Ma). We propose these volcanic occurrences be referred to collectively as the Audhild Bay alkaline suite (ABAS). In this revised nomenclature, the rocks of Hansen Point stratotype and other tholeiitic rocks are ascribed to the Hansen Point tholeiitic suite (HPTS) that was emplaced at 97−93 Ma. We suggest this subdivision into suites replace the collective term Hansen Point volcanic complex. The few dredge samples of alkali basalt available from the top of the Alpha Ridge are akin to ABAS in terms of geochemistry. Our revised dates also suggest that the HPTS and Strand Fiord Formation volcanic rocks may be the hypothesized subaerial large igneous province eruption that drove the Cretaceous Ocean Anoxic Event 2.

Petrology of the late Triassic mafic volcanic rocks from the Antalya Complex, southern Turkey: evidence for mantle source characteristics during the Neotethyan rifting

2020 ◽  
Vol 29 (7) ◽  
pp. 1049-1072
Author(s):  
Utku BAĞCI ◽  
Tamer RIZAOĞLU ◽  
Güzide ÖNAL ◽  
Osman PARLAK
Keyword(s):  
Mantle Source ◽  
Volcanic Rocks ◽  
Late Triassic ◽  
Trace Element Geochemistry ◽  
Secondary Phases ◽  
Element Geochemistry ◽  
Source Characteristics ◽  
Enriched Mantle ◽  
Southern Turkey ◽  
Island Basalt

The Antalya Complex in southern Turkey comprises a number of autochthonous and allochthonous units that originated from the Southern Neotethys. Late Triassic volcanic rocks are widespread in the Antalya Complex and are important for the onset of the rifting stage of the southern Neotethys. The studied Late Triassic volcanic rocks within the Antalya Complex are exposed in the southern part of Saklıkent (Antalya) region. They are represented by pillow, massive, and columnar-jointed lava flows with volcaniclastic breccias and pelagic limestone intercalations. Spilitic basalts exhibit intersertal, microlithic porphyritic, and ophitic textures and are represented by plagioclase, pyroxene, and olivine. Secondary phases are characterized by serpentine, calcite, chlorite, epidote, zeolite, and quartz. Based on Zr/Ti vs. Nb/Y ratios, the volcanic rocks are represented by alkaline basalts (Nb/Y = 1.54–2.82). A chondrite normalized REE diagram for the volcanic rocks displays significant LREE enrichment with respect to HREE ([La/Yb]N = 15.14–19.77). Trace element geochemistry of the studied rocks suggests that these rocks are more akin to ocean island basalt (OIB) and were formed by small degrees (~2–4%) of partial melting of an enriched mantle source (spinel + garnet-bearing lherzolite). The volcanic rocks of the Saklıkent region exhibit similarities to the Late Triassic volcanics of the Koçali Complex in SE Anatolia and the Mamonia Complex (Cyprus) in terms of their geochemical features. All evidence suggests that the Late Triassic alkaline volcanics in Antalya, Mamonia (Cyprus), and the Koçali (Adıyaman) Complexes were formed in an extensional environment at the continent-ocean transition zone during the rifting of the southern Neotethyan Ocean.

Petrology and geochemistry of the Kamloops Group volcanics, British Columbia

1981 ◽  
Vol 18 (9) ◽  
pp. 1478-1491 ◽  
Author(s):  
Thomas E. Ewing
Keyword(s):  
British Columbia ◽  
Fractional Crystallization ◽  
Middle Eocene ◽  
Volcanic Rocks ◽  
Primary Source ◽  
Low Pressure ◽  
Rock Types ◽  
South Central ◽  
High K ◽  
Petrology And Geochemistry

The Kamloops Group is an alkali-rich calc-alkaline volcanic suite of Early to Middle Eocene age, widespread in south-central British Columbia. Rock types in the suite range from high-K basalt through andesite to rhyolite. The suite is characterized by relatively high K2O, Sr, and Ba, but low Zr, Ti, and Ni concentrations, only moderate Ce enrichment, and little or no Fe enrichment. Initial ratios 87Sr/86Sr are about 0.7040 in the western half, and about 0.7060 in the eastern half of the study area. No difference in chemistry or mineralogy marks this sharp transition. Chemically similar suites include the Absaroka–Gallatin suite in Wyoming and the lower San Juan (Summer Coon) suite in Colorado. The content of K2O at 60% SiO2 increases regularly eastward across southern British Columbia. The chemical data support the subduction-related continental arc origin of the Kamloops Group volcanics.The volcanic rocks consist in the main of augite–pigeonite andesites ranging from 52 to 62% silica, with subordinate quantities of olivine–augite–pigeonite basalt and biotite rhyodacite and rhyolite. The andesites and basalts were derived by a combination of low-pressure fractional crystallization, higher pressure fractional crystallization, and variable parental magmas, whereas low-pressure fractional crystallization of plagioclase, biotite, and apatite from parental basalt and andesite produced the rhyolites. The parental magmas were basalts and basaltic andesites with high K, Sr, and Ba. The primary source of these magmas is inferred to have been an alkali-enriched hydrous peridotite with neither plagioclase nor garnet present in the residuum.

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.

A petrological and geochemical study of the volcanic rocks of the Crowsnest Formation, southwestern Alberta, and of the Howell Creek suite, British Columbia

2006 ◽  
Vol 43 (11) ◽  
pp. 1621-1637 ◽  
Author(s):  
Melissa Bowerman ◽  
Amy Christianson ◽  
Robert A Creaser ◽  
Robert W Luth
Keyword(s):  
British Columbia ◽  
Trace Element ◽  
Isotope Geochemistry ◽  
Source Region ◽  
Volcanic Rocks ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Geochemical Study ◽  
Geological Sciences ◽  
Ree Patterns

Alkaline igneous rocks of the Crowsnest Formation in southwestern Alberta and in the Howell Creek area in southeastern British Columbia have been suggested previously to be cogenetic. To test this hypothesis, samples of both suites were characterized petrographically and their major and trace element geochemistry was determined. A subset of the samples was analyzed for whole-rock Sr and Nd isotope geochemistry. The samples of the two suites are latites, trachytes, and phonolites based on the International Union of Geological Sciences (IUGS) total alkalis versus silica (TAS) diagram. Samples from both suites show similar patterns on mantle-normalized trace element diagrams, being enriched relative to mantle values but depleted in the high field-strength elements Nb, Ta, and Ti relative to the large-ion lithophile elements. The chondrite-normalized rare-earth element (REE) patterns for both suites are light REE enriched, with no Eu anomaly and flat heavy REE. The isotope geochemistry of both suites is characterized by low initial 87Sr/86Sr (SrT = 0.704 to 0.706) and low εNdT (–7 to –16). The Howell Creek samples have lower εNdT and higher SrT than do the Crowsnest samples. Based on the intra- and intersuite differences in the isotope geochemistry, we conclude that these samples are not cogenetic, but rather represent samples that have experienced similar evolutionary histories from a heterogeneous source region in the subcontinental lithospheric mantle.

Magmatic and Tectonic Setting of Archean Granitoids in the Southeastern Singhbhum Craton, India: Developing constraints with major and trace element geochemistry and geochronology

2020 ◽  
Vol 22 ◽  
Author(s):  
Claudia Banks
Keyword(s):  
Trace Element ◽  
Genetic Relationships ◽  
Tectonic Setting ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Peninsular India ◽  
Singhbhum Craton ◽  
Rock Types ◽  
Granite Emplacement ◽  
Singhbhum Granite

The Singhbhum craton is one of five Archean nuclei comprising Peninsular India. It is a composite Archean block that includes the Older Metamorphic Group, the Older Metamorphic Tonalite Gneisses, the Singhbhum Granite, and the Iron Ore Group as its major units. The ages of these components range from ~3.5 to ~3.1 Ga, although overlapping ages and similar rock types confound their genetic relationships. Plutonic felsic rocks from the southeastern Singhbhum craton (BK1: a foliated tonalite, KP1: a non-foliated granite, and SG14: a non-foliated granite) yield U-Pb (zircon) ages of 3321 ± 2 Ma (BK1), 3301 ± 1 Ma (KP1), and  3261 ± 1 Ma (SG14) that coincide with a pulse of Singhbhum Granite emplacement at 3.27 to 3.33 Ga. REE patterns and tectonic discrimination diagrams based on major and trace element ratios suggest a subduction zone setting for these rocks. We report major and trace element data for and compare them to previous works in order to characterize the Archean felsic plutonic history of the craton.

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