Redefinition of the Wild Bight Group, Newfoundland: implications for models of island-arc evolution in the Exploits Subzone

2001 ◽  
Vol 38 (6) ◽  
pp. 889-907 ◽  
Author(s):  
Kate MacLachlan ◽  
Brian H O'Brien ◽  
Greg R Dunning
Keyword(s):  
Spatial Distribution ◽  
Volcanic Rocks ◽  
Field Work ◽  
Stratigraphic Sequence ◽  
Igneous Complex ◽  
Middle Ordovician ◽  
Marine Sedimentation ◽  
Volcanogenic Massive Sulphide ◽  
Stratigraphic Nomenclature ◽  
Back Arc

The Wild Bight Group and correlative plutonic rocks of the South Lake Igneous Complex comprise one of the accreted, Ordovician, peri-Gondwanan, oceanic terranes of the Newfoundland Appalachians. Recent field work and isotopic ages from the eastern Wild Bight Group require that the stratigraphic sequence be redefined. A package of bimodal volcanic rocks, which forms the oldest part of the group and contains all of its volcanogenic massive sulphide deposits, is redefined as the Glovers Harbour Formation. This formation is correlative with intra-oceanic ophiolitic sequences elsewhere in the Exploits Subzone. Previous stratigraphic nomenclature for the upper Wild Bight Group is largely retained, although the lithological variation within and spatial distribution of the Omega Point, Seal Bay Brook, and Pennys Brook formations are revised, and the Side Harbour Formation is included as part of the Seal Bay Brook Formation. The upper Wild Bight Group is interpreted to represent a second and distinct arc sequence that formed on the Gondwanan continental margin. There is a ca. 10 million-year hiatus in volcanic activity between the Glovers Harbour Formation and upper Wild Bight Group, although marine sedimentation was likely continuous during this time. This hiatus corresponds with Penobscot deformation and obduction of Exploits Subzone ophiolites onto the Gander Zone farther to the east and south. The Glovers Harbour Formation is correlated with the Tea Arm and Saunders Cove formations of the Exploits Group, whereas the upper Wild Bight Group can be correlated in some detail with the New Bay and Lawrence Head formations. The upper Wild Bight Group and correlative rocks of the Exploits Group are interpreted to represent the arc and back arc, respectively, of the same Middle Ordovician arc system.

Geochemical and isotopic (Nd, O) data from Ordovician felsic plutonic and volcanic rocks of the Miramichi Highlands: petrogenetic and metallogenic implications for the Bathurst Mining Camp

1998 ◽  
Vol 35 (3) ◽  
pp. 237-252 ◽  
Author(s):  
Joseph B Whalen ◽  
Neil Rogers ◽  
Cees R van Staal ◽  
Frederick J Longstaffe ◽  
George A Jenner ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Middle Ordovician ◽  
Basaltic Rocks ◽  
Volcanogenic Massive Sulphide ◽  
Vms Deposits ◽  
Bathurst Mining Camp ◽  
Felsic Volcanic ◽  
Back Arc ◽  
T Values ◽  
Felsic Volcanic Rocks

Middle Ordovician felsic magmatism contemporaneous with Bathurst Camp Pb-Zn volcanogenic massive sulphide(VMS) deposits consists of strongly altered volcanic to subvolcanic rocks, belonging to the Tetagouche Group, and relativelyunaltered granitoid plutons, which are divided into northern, central, and southern groups within the Miramichi Highlands.Calc-alkalic felsic volcanic rocks and northern plus central plutons have EpsilonNd(T) values ranging from -8.2 to -1.9 and -4.0 to +0.3, respectively. They exhibit within-plate-type volcanic and transitional I- to A-type granite geochemical characteristics.Granitoid rock Delta18O values range from +8.0 to +10.1‰. Published granitoid rock Pb isotopic compositions overlapunpublished galena data from Bathurst VMS deposits. Field, geochemical, and isotopic evidence indicate that these volcanicand granitoids rocks are consanguineous and mainly derived from Proterozoic orolder infracrustal sources. Alkalic felsic volcanic rocks, and associated alkaline basaltic rocks, are more juvenile (EpsilonNd(T) = +3.2 to +4.2) and were possibly derivedfrom slightly enriched mantle sources. Southern plutons exhibit continental arc-type features. The felsic magmatism and VMS deposits likely formed in an Okinawa-type back-arc basin developed from rifting the Early Ordovician Popelogan continentalarc, of which the southern plutons are remnants. Correlations between pluton groups and volcanic formations indicate that felsic magmatism was erupted through and onto the Miramichi Group. As most felsic volcanic formations lack plutonicequivalents, the Tetagouche Group probably does not represent disrupted slices of an originally conformable stratigraphic section. This supports a model in which thrust slices juxtapose remnants of volcanic centres erupted at different locationswithin a back-arc basin.

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 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.

Tectonic setting and regional correlation of Ordovician metavolcanic rocks of the Casco Bay Group, Maine: evidence from trace element and isotope geochemistry

2004 ◽  
Vol 141 (2) ◽  
pp. 125-140 ◽  
Author(s):  
DAVID P. WEST ◽  
RAYMOND A. COISH ◽  
PAUL B. TOMASCAK
Keyword(s):  
Trace Element ◽  
Continental Crust ◽  
Isotope Geochemistry ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Mafic Magma ◽  
Ocean Basin ◽  
Middle Ordovician ◽  
South Central ◽  
Back Arc

Ordovician metamorphic rocks of the Casco Bay Group are exposed in an approximately 170 km long NE-trending belt (Liberty-Orrington belt) in southern and south-central Maine. Geochemical analysis of rocks within the Spring Point Formation (469±3 Ma) of the Casco Bay Group indicate that it is an assemblage of metamorphosed bimodal volcanic rocks. The mafic rocks (originally basalts) have trace element and Nd isotopic characteristics consistent with derivation from a mantle source enriched by a crustal and/or subduction component. The felsic rocks (originally rhyolites and dacites) were likely generated through partial melting of continental crust in response to intrusion of the mafic magma. Relatively low initial εNd values for both the mafic (−1.3 to +0.6) and felsic (−4.1 to −3.8) rocks suggest interactions with Gander zone continental crust and support a correlation between the Casco Bay Group and the Bathurst Supergroup in the Miramichi belt of New Brunswick. This correlation suggests that elements of the Early to Middle Ordovician Tetagouche-Exploits back-arc basin can be traced well into southern Maine. A possible tectonic model for the evolution of the Casco Bay Group involves the initiation of arc volcanism in Early Ordovician time along the Gander continental margin on the eastern side of the Iapetus Ocean basin. Slab rollback and trenchward migration of arc magmatism initiated crustal thinning and rifting of the volcanic arc around 470 Ma and resulted in the eruption of the Spring Point volcanic rocks in a back-arc tectonic setting.

Geochemical variations in Middle Ordovician volcanic rocks of the northern Miramichi Highlands and their tectonic significance

1991 ◽  
Vol 28 (7) ◽  
pp. 1031-1049 ◽  
Author(s):  
C. R. Van Staal ◽  
J. A. Winchester ◽  
J. H. Bédard
Keyword(s):  
Volcanic Rocks ◽  
Structural Data ◽  
Middle Ordovician ◽  
Chemical Signatures ◽  
Geochemical Study ◽  
Lower Ordovician ◽  
Geochemical Variations ◽  
Thrust Zone ◽  
Arc Setting ◽  
Back Arc

A detailed geochemical study of Middle Ordovician volcanic rocks, undertaken in the northern Miramichi Highlands of New Brunswick, shows that 10 basaltic suites can be distinguished. These suites are assigned to the Tetagouche and Fournier groups. The contact between these two groups is a major thrust zone, marked for over 70 km by a prominent blueschist zone. All the Tetagouche Group volcanic rocks have chemistries consistent with extrusion in a continental rift, but most Fournier Group basalts in the Miramichi Highlands have chemistries suggestive of an oceanic back-arc setting. The chemical signatures, stratigraphic variations, and structural data indicate that the northern Miramichi Highlands preserve a section across a telescoped Middle Ordovician back-arc basin that initially opened as a result of asthenospheric injection near the rear part of a Lower Ordovician ensialic arc.

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the Yukon–Tanana Terrane in the Finlayson Lake Region, Yukon, Canada

2003 ◽  
Vol 40 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Stephen J Piercey ◽  
James K Mortensen ◽  
Robert A Creaser
Keyword(s):  
Isotope Geochemistry ◽  
Volcanic Rocks ◽  
Lake Region ◽  
Volcanogenic Massive Sulphide ◽  
Depleted Mantle ◽  
Intrusive Rocks ◽  
Felsic Volcanic ◽  
Back Arc ◽  
Finlayson Lake ◽  
Felsic Rocks

Devonian–Mississippian felsic rocks from the Finlayson Lake region have variable geochemical and Nd isotopic characteristics that provide insights into the tectonic and metallogenic evolution of the Yukon–Tanana terrane (YTT), and the northern Cordillera. Late Devonian (~365–360 Ma) calc-alkaline and tholeiitic arc felsic rocks in the mafic-dominated Fire Lake unit yield εNd350 = –4.8 and +0.1, respectively, and have 1.49–1.94 Ga depleted mantle model ages (TDM). Devonian–Mississippian (~360–356 Ma) felsic volcanic (Kudz Ze Kayah unit, Wolverine succession) and intrusive rocks (Grass Lakes suite) associated with volcanogenic massive sulphide (VMS) deposits have εNd350 = –7.8 to –9.5 with TDM = 1.59–2.25 Ga. A granitoid sample from the Early Mississippian (~350–345 Ma) Simpson Range plutonic suite has εNd350 = –12.9 and TDM = 2.01 Ga, similar to previously reported values for this suite. The VMS-associated Grass Lakes suite of granitoids has higher high field strength element (HFSE) and rare-earth element (REE) contents, and higher Zr/Sc, Zr/TiO2, Nb/La, and Zr/La values relative to the Simpson Range plutonic suite; these geochemical features are similar to coeval VMS-associated felsic volcanic rocks in the Kudz Ze Kayah unit. The identification of similar HFSE–REE-enriched felsic volcanic and subvolcanic intrusive rocks may aid in delineating prospective regions for VMS mineralization in the YTT and other continental-margin arc to back-arc environments. The geochemical and Nd isotopic data for these YTT felsic rocks suggest that they reflect episodic mid-Paleozoic arc (Fire Lake unit; Simpson Range plutonic suite) and back-arc magmatism (Kudz Ze Kudz unit; Wolverine succession) built upon a transitional basement with variable, but significant, influence from evolved (Proterozoic) crustal materials.

scholarly journals Tectonics of Volcanogenic Massive Sulphide (VMS) Deposits at Flores Back Arc Basin: A Review

2020 ◽  
Vol 35 (2) ◽  
Author(s):  
Noor CD Aryanto ◽  
Hananto Kurnio
Keyword(s):  
Gold Mineralization ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Hydrothermal Activity ◽  
Basaltic Lava ◽  
Sulphide Deposit ◽  
Volcanogenic Massive Sulphide ◽  
Submarine Ridge ◽  
Vms Deposits ◽  
Back Arc

The bathymetry, petrology, marine magnetic, and seismic-SBP data have identified the northwest-southeast direction submarine ridge that shows hydrothermal activity. This activity occurred through Mount Baruna Komba, Abang Komba, and Ibu Komba. The volcanic rocks are andesite basaltic lava flows, tuff, and pumice. The andesite basaltic lava shows porphyritic, intergranular, intersertal to glomeroporphyritic textures. The rock composes anhedral minerals of k-feldspar, plagioclase, and pyroxene. These minerals present in small-sized, short prismatic dispersed in very fine groundmass minerals or glasses. Most of the volcanic rocks have experienced various degrees of alteration. The k-feldspar and plagioclase are most dominantly transformed into sericite, clay mineral, carbonate, epidote and oxide mineral, opaque mineral, and secondary plagioclase through the albitization process, while pyroxene replaced by chlorite. Other minerals are biotite and quartz, and base metals are present Cu, Zn, Ag, As, Pb, and gold. Mineralization categorizes as the phyllic zone, sub-prophylithic zone, and phyllic-potassic zone that formed at a temperature range of 250-400oC. The submarine hydrothermal alteration in the Komba Ridge is associated with a volcanogenic sulphide deposit controlled by crust thinning due to the crust rifts in the back-arc tectonic setting.

The geochemical nature of the igneous rocks of the Sharbot Lake domain, Central Metasedimentary Belt, Ontario

2001 ◽  
Vol 38 (7) ◽  
pp. 1037-1057 ◽  
Author(s):  
T E Smith ◽  
M J Harris ◽  
C H Huang ◽  
P E Holm
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Igneous Rocks ◽  
Igneous Complex ◽  
Low Concentrations ◽  
Granitoid Rocks ◽  
High Concentrations ◽  
Back Arc ◽  
Low K

Two bimodal mafic-silicic suites of igneous rocks, the Sharbot Lake volcanic rocks and the Lavant Igneous Complex, are identified geochemically in the Sharbot Lake domain of the Central Metasedimentary Belt in Ontario, and their genesis and thermotectonic environment are evaluated. The Sharbot Lake volcanic rocks comprise a series of basalts characterized by light rare-earth element (LREE) depletion and relatively high concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, together with rhyolites and silicic pyroclastic rocks. They are intruded by rocks of the Lavant Igneous Complex, which comprises tholeiitic gabbros characterized by LREE enrichment and low concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, and granitoid rocks. The trace element signatures of the mafic rocks of the Sharbot Lake volcanic sequences are most like those of back-arc tholeiitic basalts, and those of the Lavant Igneous Complex are comparable to those of low-K tholeiitic basalt suites. The trace element signatures of the silicic rocks associated with both suites are typical of those formed by crustal melting. Volcanic sequences with trace-element signatures very similar to those of the Sharbot Lake suites have been previously described in the Belmont and Grimsthorpe domains of the Central Metasedimentary Belt, suggesting that the three domains all belong to the Bancroft – Elzevir – Mazinaw – Sharbot Lake superterrane. The lithological, structural, and igneous characteristics of this superterrane suggest that it represents part of a complex back-arc basin underlain by areas of rifted and attenuated continental crust and oceanic crust.

Where is the Iapetus suture in northern New England? A study of the Ammonoosuc Volcanics, Bronson Hill terrane, New Hampshire1This 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. 189-205 ◽  
Author(s):  
Michael J. Dorais ◽  
Miles Atkinson ◽  
Jon Kim ◽  
David P. West ◽  
Gregory A. Kirby
Keyword(s):  
New England ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
Middle Ordovician ◽  
Isotopic Signatures ◽  
Basement Rocks ◽  
Iapetus Ocean ◽  
Maritime Canada ◽  
Laurentian Margin ◽  
Back Arc

The ∼470 Ma Ammonoosuc Volcanics of the Bronson Hill terrane of New Hampshire have back-arc basin basalt compositions. Major and trace element compositions compare favorably to coeval volcanic rocks in the Miramichi Highlands of New Brunswick and the Munsangan and Casco Bay volcanics of Maine, back-arc basin basalts of known peri-Gondwanan origins. Additionally, the Ammonoosuc Volcanics have Nd and Pb isotopic compositions indicative of peri-Gondwanan provenance. Thus, the Ammonoosuc Volcanics correlate with Middle Ordovician, peri-Gondwanan, Tetagouche–Exploits back-arc rocks of eastern New England and Maritime Canada. This correlation indicates that the Red Indian Line, the principle Iapetus suture, lies along the western margin of the Bronson Hill terrane. However, the younger (∼450 Ma) Oliverian Plutonic Suite rocks that intruded the Ammonoosuc Volcanics, forming domes along the core of the Bronson Hill anticlinorium, have Laurentian isotopic signatures. This suggests that the Ammonoosuc Volcanics were thrust westwardly over the Laurentian margin, and that Laurentian basement rocks are present under the Bronson Hill terrane. A plausible explanation for these relationships is that an easterly dipping subduction zone formed the Ammonoosuc Volcanics in the Tetagoughe–Exploits oceanic tract, just east of the coeval Popelogan arc. With the closure of the Iapetus Ocean, this terrane was thrust over the Laurentian margin. Subsequent to obduction of the Ammonoosuc Volcanics, subduction polarity flipped to the west, with the Oliverian arc resulting from a westerly dipping subduction zone that formed under the Taconic Orogeny-modified Laurentian margin.

Overpressure Identification Using The Eaton Method on The Gumai Formation of Geragai Graben, Jambi Sub Basin

2020 ◽  
Author(s):  
A. O. Marnila
Keyword(s):  
Pressure Data ◽  
Stratigraphic Sequence ◽  
Fine Grained ◽  
Marine Sedimentation ◽  
Plot Analysis ◽  
Significant Reversal ◽  
Porosity And Permeability ◽  
Upper Level ◽  
Type Data ◽  
Fine Grained Sand

Geragai graben is located in the South Sumatera Basin. It was formed by mega sequence tectonic process with various stratigraphic sequence from land and marine sedimentation. One of the overpressure indication zones in the Geragai graben is in the Gumai Formation, where the sedimentation is dominated by fine grained sand and shale with low porosity and permeability. The aim of the study is to localize the overpressure zone and to analyze the overpressure mechanism on the Gumai Formation. The Eaton method was used to determine pore pressure value using wireline log data, pressure data (RFT/FIT), and well report. The significant reversal of sonic and porosity log is indicating an overpressure presence. The cross-plot analysis of velocity vs density and fluid type data from well reports were used to analyze the causes of overpressure in the Gumai Formation. The overpressure in Gumai Formation of Geragai graben is divided into two zones, they are in the upper level and lower level of the Gumai Formation. Low overpressure have occurred in the Upper Gumai Formation and mild overpressure on the Lower Gumai Formation. Based on the analyzed data, it could be predicted, that the overpressure mechanism in the Upper Gumai Formation might have been caused by a hydrocarbon buoyancy, whereas in the Lower Gumai Formation, might have been caused by disequilibrium compaction as a result of massive shale sequence.

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