The Topsails igneous suite, western Newfoundland: an Early Silurian subduction-related magmatic suite?

1989 ◽  
Vol 26 (12) ◽  
pp. 2421-2434 ◽  
Author(s):  
Joseph B. Whalen
Keyword(s):  
Late Ordovician ◽  
Magmatic Activity ◽  
Calc Alkaline ◽  
Middle Ordovician ◽  
Continental Arc ◽  
Type Granite ◽  
Granite Complex ◽  
Opening And Closing ◽  
Magmatic Suite ◽  
Best Fit

The Topsails igneous suite contains several Late Ordovician to Early Silurian volcanic and intrusive sequences, which overlie and intrude Early to Middle Ordovician oceanic and arc rocks. The oldest components of this suite may represent calc-alkaline, continental-arc magmatism. The younger components are bimodal, with felsic compositions vastly predominating, and include a major (> 2200 km2) alkaline (A-type) granite complex. These felsic components have similarities to peralkaline suites formed in unusual subduction-related settings. Younger mafic components resemble within-plate basalts emplaced in a continental setting.Silurian magmatic activity in the Canadian Appalachians is widespread, includes diverse magmatic types, and has contrasting metamorphic and tectonic overprinting, even in contiguous areas. These features and the probability of major post-Silurian displacements in the orogen render correlation and interpretation difficult. Tectonic models that consider basin closure and major plate movements to be complete by Middle Ordovician time fail to adequately explain the Silurian activity. Available data best fit a model that relates Late Ordovician to Silurian magmatic activity to the opening and closing of small, discontinuous basins, portions of which may have been floored by oceanic crust.

The causes of continental arc flare ups and drivers of episodic magmatic activity in Cordilleran orogenic systems

Lithos ◽  
2021 ◽  
pp. 106307
Author(s):  
James B. Chapman ◽  
Jessie E. Shields ◽  
Mihai N. Ducea ◽  
Scott R. Paterson ◽  
Snir Attia ◽  
...  
Keyword(s):  
Magmatic Activity ◽  
Continental Arc

Nucularcidae: a new family of palaeotaxodont Ordovician pelecypods (Mollusca) from North America and Australia

2007 ◽  
Vol 44 (10) ◽  
pp. 1479-1501 ◽  
Author(s):  
John Pojeta Jr. ◽  
Christopher A Stott
Keyword(s):  
New Species ◽  
Type Species ◽  
New Genus ◽  
Late Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
New Family ◽  
Central Australia ◽  
Northeastern Usa ◽  
Subjective Synonym

The new Ordovician palaeotaxodont family Nucularcidae and the new genus Nucularca are described. Included in Nucularca are four previously described species that have taxodont dentition: N. cingulata (Ulrich) (the type species), N. pectunculoides (Hall), N. lorrainensis (Foerste), and N. gorensis (Foerste). All four species are of Late Ordovician (Cincinnatian Katian) age and occur in eastern Canada and the northeastern USA. Ctenodonta borealis Foerste is regarded as a subjective synonym of Nucularca lorrainensis. No new species names are proposed. The Nucularcidae includes the genera Nucularca and Sthenodonta Pojeta and Gilbert-Tomlinson (1977). Sthenodonta occurs in central Australia in rocks of Middle Ordovician (Darriwilian) age. The 12 family group names previously proposed for Ordovician palaeotaxodonts having taxodont dentition are reviewed and evaluated in the Appendix.

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.

scholarly journals Petrogenesis and Metallogenic Implications of Neoproterozoic Granodiorite in the Super-Large Shimensi Tungsten-Copper Deposit in Northern Jiangxi, South China

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 429 ◽  
Author(s):  
Wenfeng Wei ◽  
Chunkit Lai ◽  
Bing Yan ◽  
Xiaoxi Zhu ◽  
Shengqiong Song ◽  
...  
Keyword(s):  
South China ◽  
Copper Deposit ◽  
High Background ◽  
Granite Emplacement ◽  
High K ◽  
P Content ◽  
Continental Arc ◽  
Type Granite ◽  
Ree Patterns ◽  
Type Classification

The newly discovered Shimensi deposit is a super-large tungsten-copper (W–Cu) deposit with a metal reserve of 742.55 thousand tonnes (kt) W and 403.6 kt Cu. The orebodies are hosted in Mesozoic granites, which intruded the poorly documented Shimensi granodiorite belonging to the Jiuling batholith, the largest intrusion (outcrop > 2500 km2) in South China. Our new SHRIMP (Sensitive High Resolution Ion MicroProbe) zircon dating revealed that the granodiorite at Shimensi (ca. 830–827 Ma) was formed coeval (within analytical uncertainty) or slightly earlier than those in many other places (ca. 819–807 Ma) of the Jiuling batholith. The Neoproterozoic Shimensi granodiorite is peraluminous and high-K calc-alkaline, and contains low P content with no S-type trend (positive P2O5 vs. SiO2 correlation) displayed, thus best classified as peraluminous I-type. The I-type classification is also supported by the zircon REE patterns, largely (93%) positive εHf(t) (−0.87 to 6.60) and relatively low δ18O (5.8–7.7‰). The Neoproterozoic Shimensi granodiorite was formed after the continental arc magmatism (ca. 845–835 Ma), but before the post-collisional S-type granite emplacement (ca. 825–815 Ma) in the Jiangnan Orogen. Therefore, we propose that the Shimensi granodiorite was formed in a collisional/early post-collisional setting. The δ18O increase from the Shimensi granodiorite to many younger (ca. 819–807 Ma) granodiorites (6.0–8.5‰) in the Jiuling batholith probably reflects an increase of supracrustal rock-derived melts with the progress of collision. The Shimensi granodiorite contains low zircon Ce4+/Ce3+ and Eu/Eu*, suggesting a relatively reducing magma that does not favor porphyry Cu–Au mineralization. This left a high background Cu concentration (avg. 196 ppm) in the Neoproterozoic granodiorite, which may have contributed to the Mesozoic W–Cu mineralization, when the granodiorite is intruded and assimilated by the Mesozoic granites.

scholarly journals Geochemical Classification and Geotectonic Setting of Granitic Gneisses from Southeastern Margin of Western Nigeria Basement

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Mohammed Olatoye Adepoju ◽  
Yinusa Ayodele Asiwaju-Bello
Keyword(s):  
Inductively Coupled Plasma ◽  
Tectonic Setting ◽  
Calc Alkaline ◽  
Granitic Gneiss ◽  
Basement Complex ◽  
Southwestern Nigeria ◽  
Inductively Coupled ◽  
Continental Arc ◽  
Southeastern Margin ◽  
Geochemical Classification

Chemical whole-rock major oxides and some trace element analyses were done on granitic gneiss rocks located on the southeastern margin of western Nigeria Basement Complex, exposed in parts of Dagbala-Atte District, southwestern Nigeria. This was meant to classify the rocks and to understand the tectonic setting in order to evaluate their crustal evolution. The chemical analyses were done using inductively-coupled plasma mass spectrometer. From the results obtained, these rocks classified into calc-alkaline to shoshonite series with metaluminous to peraluminous varieties, they are I-type granitoids of feroan composition. The granitic gneisses formed from metamorphism of granite and granodiorite. Tectonically, most of the rock samples plotted in the field of island arc, continental arc and continental-collisional granitoids, which indicated that the protolith granite and granodiorite are orogenic and are arc related inferring arc tectonic setting.

scholarly journals Die Gattung Erratencrinurus Krueger, 1971 (Trilobita; Ordovizium) aus baltoskandischen Geschieben

Fossil Record ◽  
2004 ◽  
Vol 7 (1) ◽  
pp. 69-132
Author(s):  
H.-H. Krueger
Keyword(s):  
New Species ◽  
Hard Rock ◽  
Late Ordovician ◽  
Middle Ordovician ◽  
Different Types ◽  
Single Spine ◽  
Pore Canals ◽  
Different Parts

Aus der mittel- bis oberordovizischen Trilobitenfamilie Encrinuridae, die in Baltoskandia durch die Untergattungen <i>Erratencrinurus</i> und <i>Celtencrinurus</i> repräsentiert wird, werden achtzehn Arten beschrieben, darunter die vier neuen Arten <i>Erratencrinurus (E.) sellinensis, E. (E.) heinrichi, E. (E.) praecapricornu</i> und <i>E. (E.) rhebergeni</i>. Das überwiegende Material stammt aus dem schwer zu präparierenden Ostseekalk. Die Tripp'sche Tuberkelformel wurde der <i>Erratencrinurus</i>-Gruppe angepasst; innerhalb der <i>Erratencrinurus</i>-Gruppe können drei verschiedene Schilder-Typen des scutum rostrale nachgewiesen werden. Unterschiedliche Tuberkeltypen bis hin zu extremen Stacheln wurden beschrieben. Außerdem kann eine Reduzierung von drei Thoraxialstacheln im Mittelordovizium zu einem im oberen Oberordovizium festgestellt werden. Verschiedene Regionen des Panzers von <i>Erratencrinurus (E.) sellinensis</i>, die Porenkanäle besitzen, werden dargestellt. Ein neuer Häutungstyp kann an Panzerhemden von <i>Erratencrinurus (E.) seebachi</i> beschrieben werden. <br><br> In Baltoscandia the Middle to Late Ordovician trilobite family <i>Encrinurida</i> is represented by the two subgenera <i>Erratencrinurus</i> and <i>Celtencrinurus</i>. Out of these 18 species, four new species are described herein. Most of the material comes from the Ostseekalk which is an extremely hard rock and thus difficult to preparate. The tubercle formula after Tripp is applied to the <i>Erratencrinurus</i> group and led to the distinction of three different types of scutum rostrale shields. Various types of tubercles which may even pass into extreme spines are described. The number of thoracic spines becomes reduced from three spines in Middle Ordovician taxa to a single spine in youngest Ordovician species. Different parts of the carapace of <i>Erratencrinurus sellinensis</i> with pore canals are illustrated and a new moulting type of E. <i>seebachi</i> is introduced. New species are <i>E. sellinensis. E. heinrichi, E. praecapricornu and E. (E.) rhebergeni.</i> <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20040070106" target="_blank">10.1002/mmng.20040070106</a>

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

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