The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

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.

Origin and U–Pb geochronology of amphibolite-facies metamorphic rocks, Miramichi Highlands, New Brunswick

1988 ◽  
Vol 25 (10) ◽  
pp. 1674-1686 ◽  
Author(s):  
Les Fyffe ◽  
Sandra M. Barr ◽  
Mary Lou Bevier
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Amphibolite Facies ◽  
Metamorphic Rocks ◽  
Volcanic Arc ◽  
Rock Types ◽  
Igneous Origin ◽  
Back Arc ◽  
Tectonic Origin

The Miramichi Highlands of New Brunswick are underlain by subgreenschist- to greenschist-facies sedimentary and volcanic rocks of the Cambro-Ordovician Tetagouche Group and by amphibolite-facies paragneisses, amphibolites, and felsic orthogneisses of the Trousers Lake and Sisson Brook suites. New field, geochemical, and geochronologic data for the amphibolites and felsic orthogneisses suggest that they are high-grade metamorphic equivalents of the Tetagouche volcanic rocks and their associated intrusions.Amphibolites in the Miramichi Highlands occur as striped and unstriped varieties that possess chemical characteristics indicative of an igneous origin. However, the two types are compositionally distinct: the striped amphibolites resemble volcanic-arc tholeiites, whereas the unstriped amphibolites are like within-plate tholeiites. The geochemically inferred tectonic origin of these amphibolites is compatible with a recently proposed intracontinental back-arc tectonic setting for the Tetagouche Group.Felsic orthogneisses (Fox Ridge augen granite and Trousers Lake felsic orthogneiss) exhibit concordant contacts with the unstriped amphibolites. U–Pb zircon ages for the Fox Ridge augen granite [Formula: see text] and Trousers Lake felsic orthogneisses [Formula: see text] indicate a Late Ordovician intrusive event. Thus, there is no evidence for Precambrian granite and orthogneiss in the Miramichi Highlands, as had been previously inferred from a correlation with purported Precambrian rocks in the Gander Zone of Newfoundland. The age of the unstriped amphibolites is interpreted as being the same as that of the felsic orthogneisses because these two rock types always exhibit close relationships in the field. The age of the striped amphibolites is less certain, although a correlation with Ordovician basalts of the Tetagouche Group is consistent with their field relationships and tectonic setting.

Geochemical and isotopic characteristics of Early Silurian clastic sequences in Antigonish Highlands, Nova Scotia, Canada: constraints on the accretion of Avalonia in the Appalachian – Caledonlde Orogen

1996 ◽  
Vol 33 (3) ◽  
pp. 379-388 ◽  
Author(s):  
J. Brendan Murphy ◽  
J. Duncan Keppie ◽  
Mary Pat Cude ◽  
Jarda Dostal ◽  
John W. F. Waldron
Keyword(s):  
Nova Scotia ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Structural Data ◽  
Strike Slip ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Oblique Collision ◽  
Isotopic Signatures ◽  
Clastic Sedimentary

Avalonia is a terrane that accreted to Laurentia–Baltica during the development of the Appalachian–Caledonide Orogen. Interpretations of the timing of accretion have been constrained by comparing faunal affinities, overstep sequences, age and kinematics of inferred accretionary deformational events, and controversial paleomagnetic data. We show that the time of accretion of Avalonia may also be constrained by contrasts in the geochemical and isotopic signatures of its igneous rocks (which reflect the characteristics of the underlying continental basement and mantle) and sedimentary rocks (which reflect provenance). Early Silurian clastic sedimentary rocks of the Beechill Cove Formation, Antigonish Highlands, Nova Scotia, were deposited on Avalonian crust. The formation predominantly consists of approximately 80 m of siltstones and shales deposited in a nearshore environment and derived from the northeast. Their age is constrained by paleontological data and by directly underlying Late Ordovician – Early Silurian bimodal volcanic rocks that have typically Avalonian geochemical signatures. In comparison with typical Avalonian rocks, the Beechill Cove sediments are characterized by high SiO2, Ce/Yb, and initial 87Sr/86Sr, low Fe2O3, MgO, and TiO2, and strongly negative εNd(ur). These characteristics cannot be attributed to erosion of underlying Avalonian basement or coeval volcanic rocks and are consistent with derivation via significant transport from radiogenically enriched continental crust. εNd data are typical of Grenvillian basement compositions and suggest that the Beechill Cove sedimentary rocks were derived from an adjacent landmass with Grenvillian crust. The data, in conjunction with paleocontinental reconstructions and recent geochronological and structural data from the northern Appalachians, suggest that the Caledonide orogenic belt is the most likely source. Deposition of the Beechill Cove Formation is inferred to have occurred in an intracontinental basin associated with strike-slip tectonics during the oblique collision of the Avalon with Laurentia–Baltica.

Geochemistry of Sainte-Marguerite volcanic rocks: implications for the evolution of Silurian–Devonian volcanism in the Gaspé Peninsula

2008 ◽  
Vol 45 (1) ◽  
pp. 15-29 ◽  
Author(s):  
Alan D’hulst ◽  
Georges Beaudoin ◽  
Michel Malo ◽  
Marc Constantin ◽  
Pierre Pilote
Keyword(s):  
Lower Devonian ◽  
Volcanic Rocks ◽  
Magma Source ◽  
Volcanic Arc ◽  
Lower Silurian ◽  
Trace Element Signature ◽  
Arc Setting ◽  
Back Arc ◽  
Gaspe Peninsula ◽  
Gaspé Peninsula

The Lower Devonian Sainte-Marguerite volcanic rocks are part of a Silurian–Devonian volcanic sequence deposited between the Taconian and Acadian orogenies in the Gaspé Peninsula, Quebec, Canada. The Sainte-Marguerite unit includes basaltic and dacitic lava flows with calc-alkaline and volcanic-arc affinities. Such affinities are also recorded by the trace-element signature in Lower Silurian and most Lower Devonian volcanic units of the Gaspé Peninsula. However, most of the other Silurian–Devonian volcanic rocks occurring in the Gaspé Peninsula have been previously interpreted to have erupted in an intracontinental setting. A back-arc setting for the Gaspé Peninsula between the Taconian and Acadian orogenies could account for these subduction volcanic-arc signatures, though a metasomatized lithospheric mantle magma source, unrelated to subduction, cannot be excluded. Lower Silurian and Lower Devonian volcanic rocks in the central part of the Gaspé Peninsula show an arc affinity, whereas Upper Silurian and Lower to Middle Devonian volcanic rocks, located in the south and north of the Gaspé Peninsula, respectively, show a within-plate affinity. The Lower Devonian Archibald Settlement and Boutet volcanic rocks of the southern and northern Gaspé Peninsula, respectively, show a trend toward a within-plate affinity. This suggests that within-plate volcanism migrated from south to north through time in an evolving back-arc environment and that the subduction signature of Lower Silurian and Lower Devonian rocks results from a source that melted only under the central part of the Gaspé Peninsula.

The tectonic significance of Ordovician basic igneous rocks in the Southern Uplands, southwest Scotland

1995 ◽  
Vol 132 (5) ◽  
pp. 549-556 ◽  
Author(s):  
E. R. Phillips ◽  
R. P. Barnes ◽  
R. J. Merriman ◽  
J. D. Floyd
Keyword(s):  
Volcanic Rocks ◽  
Accretionary Prism ◽  
Igneous Rocks ◽  
Geochemical Data ◽  
Published Data ◽  
Volcanic Material ◽  
Tectonic Significance ◽  
Arc Setting ◽  
Back Arc ◽  
Midocean Ridge

AbstractIn the northern part of the Southern Uplands, restricted volumes of basic igneous rocks occur at or near the base of the Ordovician sedimentary strata. These rocks have previously been interpreted as ocean-floor tholeiites representative of the subducted Iapetus oceanic plate, preserved as tectonic slivers in a fore-arc accretionary prism. The alternative, back-arc basin model proposed for the Southern Uplands on sedimentological evidence raises questions over the origin of these rocks. New geochemical data and previously published data clearly indicate that the volcanic material does not have a simple single source. The oldest (Arenig) volcanic rocks from the Moffat Shale Group associated with the Leadhills Fault include alkaline within-plate basalts and tholeiitic lavas which possibly display geochemical characteristics of midocean ridge basalts. In the northernmost occurrence, alkaline and tholeiitic basalts contained within the Caradoc Marchburn Formation are both of within-plate ocean island affinity. To the south, in the Gabsnout Burn area, the Moffat Shale Group contains lenticular bodies of dolerite and basalt which have characteristics of island-arc to transitional basalts. This complex association of basaltic volcanic rocks is, at the present time, difficult to reconcile with either a simple fore-arc or back-arc setting for the Southern Uplands. However, the increasing arc-related chemical influence on basic rock geochemistry towards the southeast may tentatively be used in support of a southern arc-terrane, and as a result, a back-arc situation for the Southern Uplands basin. An alternative is that these volcanic rocks may represent the local basement to the basin and include remnants of an arc precursor to the Southern Uplands basin.

Late Jurassic (Kimmeridgian-Tithonian) macrofossil assemblage from Jason Peninsula, Graham Land: evidence for a significant northward extension of the Latady Formation

1997 ◽  
Vol 9 (4) ◽  
pp. 434-442 ◽  
Author(s):  
T.R. Riley ◽  
J.A. Crame ◽  
M.R.A. Thomson ◽  
D.J. Cantrill
Keyword(s):  
Antarctic Peninsula ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Areal Extent ◽  
South Eastern ◽  
Back Arc ◽  
The Antarctic ◽  
Major Sequence

New exposures of fossiliferous sedimentary rocks at Cape Framnes, Jason Peninsula (65°57′S, 60°33′W) are assigned to the Middle–Late Jurassic Latady Formation of the south-eastern Antarctic Peninsula region. A sequence of fine to coarse-grained sandstones of unknown thickness has yielded a molluscan and plant macrofossil assemblage rich in the following elements: perisphinctid ammonites, belemnopseid belemnites, oxytomid, trigoniid and astartid bivalves, and bennettitalean fronds and fructifications. The overwhelming age affinities are with the Kimmeridgian–early Tithonian part of the Latady Formation, as exposed on the Orville and Lassiter coasts. The Cape Framnes sedimentary rocks help to constrain the age of a major sequence of acid volcanic rocks on Jason Peninsula, and show that the Latady Basin was geographically much more extensive than recognized previously. It was the principal depositional centre of Middle–Late Jurassic sedimentation in the Antarctic Peninsula back-arc region and in areal extent may have rivalled the essentially Cretaceous Larsen Basin.

Provenance of Paleozoic sedimentary rocks in the Canadian Cordilleran miogeocline: a Nd isotopic study

1997 ◽  
Vol 34 (12) ◽  
pp. 1603-1618 ◽  
Author(s):  
Carmala N. Garzione ◽  
P. Jonathan Patchett ◽  
Gerald M. Ross ◽  
JoAnne Nelson
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Middle Devonian ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Isotopic Study ◽  
Middle Ordovician ◽  
Southern Alberta ◽  
T Values

Nd isotopes and trace elements in sedimentary rocks of the Yukon, the Northwest Territories, and northern British Columbia are used to examine the source of sediments in the Canadian Cordilleran miogeocline. Previous Nd isotope studies in southern Alberta demonstrated that strata of Neoproterozoic to Late Ordovician age were derived from Archean and Proterozoic Canadian Shield sources, whereas by the Late Devonian, a shift of 6 εNd units to younger crustal sources (εNd (T) = −6 to −9) had occurred. In this study, we found that the shift to younger crustal Nd isotopic signatures in the Yukon and Northwest Territories occurred much earlier than in southern Alberta. Cambrian and older strata have εNd(T) values of −10.0 to −21.1, consistent with derivation from Canadian Shield sources. Lower Ordovician through Permian strata in the Yukon and Northwest Territories, including the Innuitian-derived Imperial Assemblage, have εNd(T) values of −5 to −11.4. In northern British Columbia, the shift to a younger source reflects a wider range of εNd(T) values, from -−8.7 to −14.6 in Middle Ordovician through Middle Devonian strata, suggesting continued input from Canadian Shield sources. By the Middle Devonian, a complete shift to younger crustal signatures (εNd(T) = −5.9 to −10.5) had occurred in northern British Columbia. Several sources for the more juvenile sediments include (1) a mixture of locally erupted volcanic rocks with Canadian Shield sources, (2) a Grenville source, and (3) an Innuitian source. We propose that Ordovician to Lower Devonian strata were derived from a mixture of locally erupted, juvenile volcanics and pre-Cambrian Canadian Shield sources, and post-Middle Devonian strata were sourced from the Innuitian orogen in the Canadian Arctic.

The geology of central Isla Hoste, southern Chile: sedimentation, magmatism and tectonics in part of a Mesozoic back-arc basin

1980 ◽  
Vol 117 (4) ◽  
pp. 339-349 ◽  
Author(s):  
C. P. Andrews-Speed
Keyword(s):  
Sedimentary Rocks ◽  
Igneous Rocks ◽  
Ocean Floor ◽  
Turbidity Currents ◽  
Southern Chile ◽  
Magmatic Arc ◽  
The Pacific ◽  
Pacific Side ◽  
Intrusive Rocks ◽  
Back Arc

SummaryCentral Isla Hoste lies towards the Pacific side of a Mesozoic back-arc basin in southern Chile, behind a magmatic arc represented by the Patagonian batholith. The volcaniclastic sediments on Isla Hoste were derived from the magmatic arc and deposited in the back-arc basin by turbidity currents. These sediments may, in part, overlie mafic volcanic and intrusive rocks. Geochemical and lithologic data are used to suggest an ocean-floor origin for these mafic igneous rocks on central Isla Hoste. The sedimentary and mafic igneous rocks were deformed and uplifted during the middle Cretaceous Andean orogeny. However, the nature of the crust underlying most of the sedimentary rocks in the back-arc basin and the style of deformation in most of this basement are unknown. Therefore the role, if any, of subduction within the back-arc basin during the middle Cretaceous ‘closure’ of this basin is not certain. Post-kinematic intrusions within the back-arc basin are common. These intrusions will confuse attempts to determine by geophysical means the nature of the pre-kinematic basement of the back-arc basin and attempts to outline the present extent of the basin in offshore regions.

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.

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