Petrochemistry and tectonic significance of Carboniferous volcanic rocks in New Brunswick

1986 ◽  
Vol 23 (9) ◽  
pp. 1243-1256 ◽  
Author(s):  
L. R. Fyffe ◽  
S. M. Barr
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Age Groups ◽  
Late Paleozoic ◽  
Basement Rocks ◽  
Basaltic Composition ◽  
Tectonic Significance ◽  
Maritimes Basin ◽  
Alkalic Basalts

Carboniferous volcanic rocks from the New Brunswick Platform in the Maritimes Basin are divided into three age groups. Late Tournaisian to early Visean volcanic rocks are tholeiitic basalts and andesites that, in southern New Brunswick, are inter-bedded with abundant calc-alkalic rhyolite. Late Visean to Namurian volcanic rocks consist of an interbedded sequence of alkalic basalts and trachyandesites. Late Westphalian volcanic rocks change in composition up section from trachyte to peralkalic rhyolite. All three age groups display petrochemical features indicative of an intraplate tectonic setting. The volcanic geochemistry is consistent with the development of the Maritimes Basin either as a failed rift formed along the margin of a late Paleozoic ocean or as a rhomb graben formed within a transcurrent zone; the former model is preferred. The change in basaltic composition from tholeiitic to alkalic apparently coincided with a decrease in rate of extension between the Tournaisian and Namurian. Local peralkalic volcanism occurred during regional sagging of the basin as extension ceased and basement rocks cooled in the Late Carboniferous.

Stratigraphy, paleogeography, and tectonic setting of the Coldbrook Group in the Caledonia Highlands of southern New Brunswick

1977 ◽  
Vol 14 (6) ◽  
pp. 1263-1275 ◽  
Author(s):  
P. S. Giles ◽  
A. A. Ruitenberg
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Fine Grained ◽  
Arc Model ◽  
Basement Rocks ◽  
Northwestern Margin ◽  
Intracratonic Basin ◽  
Volcanic Belts

The late Precambrian Coldbrook volcanic sequence and stratigraphic equivalents in southern New Brunswick can be divided into three distinct belts. These have been named the Eastern, Central and Western Volcanic Belts.The Eastern Volcanic Belt, along the Bay of Fundy coast, is characterized by intensely deformed mafic and felsic flows, tuffs, and abundant related volcanogenic sediments. Two thick arkosic sedimentary units in this belt reflect extensive intervals of volcanic quiescence. Fine-grained siliceous siltstone and conglomerate, locally intercalated with these rocks, have probably been derived from erosion of older Precambrian basement rocks to the northwest.The Central Volcanic Belt is composed of generally weakly deformed felsic and lesser mafic flows, and coarse lithic tuffs (including ignimbrites), and very minor intercalated sediments. The almost complete lack of water-lain sediments and presence of ignimbrites suggests subaerial deposition for most of these volcanic rocks. The relationship between rocks of the Central and Eastern Volcanic Belts is one of facies equivalence. The Western Volcanic Belt is also composed of felsic and minor mafic flows and tuffs that resemble those of the Central Volcanic Belt, but they are intensely deformed. Minor volcanogenic sedimentary rocks are intercalated with the volcanic rocks along the northwestern margin of this belt.The nature and distribution of major lithofacies belts in the Coldbrook Group and stratigraphic equivalents appear to be consistent with deposition along the margin of an intracratonic basin. It is possible, however, that further work may prove an ensialic island arc model to be a viable alternative.

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.

Geochemistry and U/Pb geochronology of the Williams Brook area, Tobique-Chaleur zone, New Brunswick: stratigraphic and geotectonic setting of gold mineralization

2021 ◽  
Author(s):  
Dennis Sánchez-Mora ◽  
Christopher R.M. McFarlane ◽  
James A Walker ◽  
David R. Lentz
Keyword(s):  
New Brunswick ◽  
Gold Mineralization ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Volcanic Belt ◽  
Temporal Variations ◽  
Lower Percentage ◽  
Oblique Convergence ◽  
Felsic Volcanic

Gold mineralization at Williams Brook in northern New Brunswick is hosted within the Siluro-Devonian, bimodal, volcano-sedimentary rocks of the Tobique-Chaleur Zone (Wapske Formation). Gold mineralization occurs in two styles: 1) as disseminations (refractory gold) in rhyolite, and 2) in cross-cutting quartz veins (free gold). Dating of the felsic volcanic host rocks by in situ LA-ICP-MS zircon U-Pb geochronology returned ages of 422 ± 3, 409 ± 2, 408 ± 3, 405 ± 2, 401 ± 9 Ma. Zr/Y of subvolcanic felsic intrusion (<8 for syn-mineralization and >8 for post-mineralization) suggests evolution from transitional to more alkalic affinities. Two mineralizing events are recognized; the first is a disseminated mineralization style formed at ~422–416 Ma and the second consists of quartz vein-hosted gold emplaced at 410–408 Ma. Felsic rocks from Williams Brook and elsewhere in the Tobique Group (i.e. Wapske, Costigan Mountain, and Benjamin formations), and the Coastal Volcanic Belt have similar Th/Nb ratios of ~0.1 to 1, reflecting similar levels of crustal contamination, and similar Nb and Y content, suggesting A-type affinities. These data indicate a similar environment of formation. Regionally, mafic rocks show similar within-plate continental signatures and an E-MORB mantle source that formed from partial melts of 10–30%. Mafic volcanic rocks from Williams Brook have a more alkaline affinity (based on Ti/V), and derivation from lower percentage partial melting (~5%). The chemical and temporal variations in the Williams Brook rocks suggest that they were erupted in an evolving transpressional tectonic setting during the oblique convergence of Gondwana and Laurentia.

U–Pb ages, geochemistry, and tectonomagmatic history of the Cambro-Ordovician Annidale Group: a remnant of the Penobscot arc system in southern New Brunswick?1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 166-188 ◽  
Author(s):  
Susan C. Johnson ◽  
Leslie R. Fyffe ◽  
Malcolm J. McLeod ◽  
Gregory R. Dunning
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Conclusive Evidence ◽  
The Past ◽  
Late Cambrian ◽  
Suprasubduction Zone ◽  
History Of ◽  
Group A ◽  
Back Arc

The Penobscot arc system of the northeastern Appalachians is an Early Cambrian to early Tremadocian (ca. 514–485 Ma) ensialic to ensimatic arc–back-arc complex that developed along the margin of the peri-Gondwanan microcontinent Ganderia. Remnants of this Paleozoic arc system are best preserved in the Exploits Subzone of central Newfoundland. Correlative rocks in southern New Brunswick are thought to occur in the ca. 514 Ma Mosquito Lake Road Formation of the Ellsworth Group and ca. 497–493 Ma Annidale Group; however in the past, the work that has been conducted on the latter has been of a preliminary nature. New data bearing on the age and tectonic setting of the Annidale Group provides more conclusive evidence for this correlation. The Annidale Group contains subalkaline, tholeiitic to transitional, basalts to basaltic andesites, picritic tuffs and calc-alkaline to tholeiitic felsic dome complexes that have geochemical signatures consistent with suprasubduction zone magmatism that was likely generated in a back-arc basin. New U–Pb ages establish that the Late Cambrian to Early Tremadocian Annidale Group and adjacent ca. 541 Ma volcanic rocks of the Belleisle Bay Group in the New River belt were affected by a period of younger magmatism ranging in age from ca. 479–467 Ma. This provides important constraints on the timing of tectonism in the area. A ca. 479 Ma age for the Stewarton Gabbro that stitches the faulted contact between the Annidale and Belleisle Bay groups, demonstrates that structural interleaving and juxtaposition occurred during early Tremadocian time, which closely coincides with the timing of obduction of Penobscottian back-arc ophiolites onto the Ganderian margin in Newfoundland.

Geological setting and tectonic significance of Mississippian felsic metavolcanic rocks in the Pelly Mountains, southeastern Yukon Territory

1982 ◽  
Vol 19 (1) ◽  
pp. 8-22 ◽  
Author(s):  
James K. Mortensen
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Yukon Territory ◽  
Early Tertiary ◽  
Metavolcanic Rocks ◽  
Extensional Tectonic ◽  
Tectonic Significance ◽  
Show Evidence ◽  
Thrust Sheets ◽  
Local Geology

The central Pelly Mountains in southeastern Yukon Territory consist of imbricate thrust sheets, which have undergone syn- and post-thrusting deformation and metamorphism. The local geology is further complicated by the intrusion of Late Cretaceous batholiths, and by strike-slip faulting related to the Tintina Fault, a major northwest-trending transcurrent fault of latest Cretaceous or early Tertiary age. This faulting disrupts the northeast edge of the study area.Upper Devonian and Mississippian strata are present in at least two of the structural packages, but the Mississippian metavolcanic rocks occur only in the lowermost package. Rb–Sr geochronology indicates a mid-Mississippian age for the igneous suite. The volcanic rocks consist of volcaniclastic material with minor interbedded flows, and were deposited in a submarine environment. Several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas. Although the volcanic rocks are all highly altered and show evidence of widespread chemical mobility, trace element data indicate that the rocks are metaluminous trachytes, most closely resembling peralkaline volcanics generated in extensional environments. This suggestion of a predominantly extensional tectonic setting in mid-Mississippian time in the Pelly Mountains is consistent with recent tectonic syntheses for the area.

Tectonic setting and geochemistry of Miocene alkalic basalts from the Jones Mountains, West Antarctica

1994 ◽  
Vol 6 (1) ◽  
pp. 85-92 ◽  
Author(s):  
M. J. Hole ◽  
B. C. Storey ◽  
W. E. LeMasurier
Keyword(s):  
Antarctic Peninsula ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
West Antarctica ◽  
Geochemical Composition ◽  
Crustal Block ◽  
Volcaniclastic Rocks ◽  
Geochemical Analyses ◽  
The Antarctic ◽  
Alkalic Basalts

Within the Jones Mountains, which form part of the Thurston Island crustal block, up to 700 m of Miocene (c. 10 Ma) pillow basalt and palagonitized volcaniclastic rocks unconformably overlie Jurassic granitic basement and Cretaceous volcanic rocks and dykes. New geochemical analyses demonstrate the alkalic nature of the basalts, which range in composition from alkali basalt to basanite. Unradiogenic Sr-isotope ratios (0.7031–0.7034), coupled with low LILE/HFSE ratios (e.g. Th/Ta c. 1.4, Rb/Nb 0.3–0.9) indicate a predominantly asthenospheric source for the basalts. The Jones Mountains basalts are geochemically similar to the alkalic basalts of Marie Byrd Land, but have consistently lower K/Ba and higher Ba/Nb ratios than Late Cenozoic alkalic basalts along the Antarctic Peninsula. These regional variations in geochemical composition apparently reflect differences in tectonic setting and are not the result of lithospheric interaction or partial melting/crystallization effects. The generation of alkalic magmas along the Antarctic Peninsula was causally related to the formation of slab windows following ridge crest-trench collision and the cessation of subduction, whereas the Jones Mountains alkalic basalts may represent the expression of the northward propagation of the head of the Marie Byrd Land plume.

Petrology and the Western Rift of Central Africa

1932 ◽  
Vol 69 (11) ◽  
pp. 497-510 ◽  
Author(s):  
A. W. Groves
Keyword(s):  
Rift Valley ◽  
Volcanic Rocks ◽  
Central Africa ◽  
Volcanic Field ◽  
Thin Sections ◽  
Basement Rocks ◽  
Geochemical Study ◽  
Northern Half ◽  
Tectonic Significance ◽  
Near Future

IN the course of several journeys between Masindi and Butiaba, and one from Butiaba to Hoima (via Waki Camp), specimens of the various gneisses were collected from roadside exposures. Thin sections of these were subsequently studied by the writer in England with the result that they were found to yield evidence of tectonic significance. In addition, the writer has, during the last three years, examined petrographically a large number of other rocks from those parts of Uganda bordering the Lake Albert Depression. In particular he has made a special study of the Charnockite Series, which are widely spread over the northern half of the Protectorate, with the result that it has been possible to observe the effects of the rift valley movements on these rocks in the regions adjacent to Lake Albert. It is hoped to publish a petrological and geochemical study of the Charnockite Series of Uganda in the near future. In the following pages it is proposed in Part I to present petrological evidence from the basement rocks of various districts in the hinterland of the Lake Albert scarps and then in Part II to point out the tectonic significance of this evidence in the light of the various theories of rift valley formation. In Part III the relation between the petrological characters of the volcanic rocks and the rift valley tectonics will be briefly reviewed. In the case of the basement rocks the remarks will be confined to the Lake Albert Depression, but in the case of the volcanic rocks the discussion will extend also to Lakes George and Edward and the Birunga volcanic field.

scholarly journals Geochemical Characteristics and Tectonic Significance of the Acidic Volcanic Rocks from the Shetang-Boyang Area, Western Qinling Orogenic Belt, China

2016 ◽  
Vol 5 (2) ◽  
pp. 209
Author(s):  
Aiai Ma ◽  
Hao Guan ◽  
Lifei Zou ◽  
Lanlan Sun
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Geochemical Characteristics ◽  
Geochemical Data ◽  
Regional Studies ◽  
Western Qinling ◽  
Continental Extension ◽  
Qinling Orogenic Belt ◽  
Tectonic Significance

Acidic volcanic rocks of Shetang-Boyang area are located in the western Qinling orogenic belt, consist of rhyolite and granite porphyry. They are comparable in the chemical composition, enriched in Si, alkali, Al and a little bit of Mg, Ca and Ti. The contents of HFSE (Zr, Hf) and LILE (Rb, Th, U) are high, however, the content of Ba, Sr, Ti, P have obviously depleted and there are obvious negative Eu anomalies (Eu/Eu*=0.06-0.13). These geochemical characteristics are revealed that these volcanic rocks have an A1 type affinity. Geochemical data combined with regional studies, show that these volcanic rocks were formed in a continental extension setting and the western Qinling orogenic belt in 211Ma has been in the tectonic setting of post-collisional extension.

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