Evolution of Subduction Dynamics beneath West Avalonia in Middle to Late Ordovician Times

Abstract Middle to Upper Ordovician volcanic rocks in the Arisaig area of Nova Scotia, Canada, constitute the only known record of volcanism in West Avalonia during that interval. Hence, they have been extensively studied to test paleocontinental reconstructions that consistently show Avalonia as a drifting microcontinent during that period. Identification of volcanic rocks with an intermediate composition (the new Seaspray Cove Formation) between upper Darriwilian bimodal volcanic rocks of the Dunn Point Formation and Sandbian felsic pyroclastic rocks of the McGillivray Brook Formation has led to a reevaluation of magmatic relationships in the Ordovician volcanic suite at Arisaig. Although part of the same volcanic construction, the three formations are separated by significant time-gaps and are shown to belong to three distinct magmatic subsystems. The tectonostratigraphic context and trace element contents of the Dunn Point Formation basalts suggest that they were produced by the high-degree partial melting of an E-MORB type source in a back-arc extensional setting, whereas trace element contents in intermediate rocks of the Seaspray Cove Formation suggest that they were produced by the low-degree partial melting of a subduction-enriched source in an arc setting. The two formations are separated by a long interval of volcanic quiescence and deep weathering, during which time the back-arc region evolved from extension to shortening and was eventually onlapped by arc volcanic rocks. Based on limited field constraints, paleomagnetic and paleontological data, this progradation of arc onto back-arc volcanic rocks occurred from the north, where an increasingly young Iapetan oceanic plate was being subducted at an increasingly shallow angle. Partial subduction of the Iapetan oceanic ridge is thought to have subsequently generated slab window magmatism, thus marking the last pulse of subduction-related volcanism in both East and West Avalonia.

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Geochemistry and geochronology of OIB-type, Early Jurassic magmatism in the Zhangguangcai range, NE China, as a result of continental back-arc extension

Geological Magazine ◽

10.1017/s0016756818000705 ◽

2018 ◽

Vol 158 (1) ◽

pp. 143-157 ◽

Cited By ~ 4

Author(s):

Guangying Feng ◽

Yildirim Dilek ◽

Xiaolu Niu ◽

Fei Liu ◽

Jingsui Yang

Keyword(s):

East Asia ◽

Trace Element ◽

Partial Melting ◽

Early Jurassic ◽

Ne China ◽

Mafic Rocks ◽

Asthenospheric Mantle ◽

Trace Element Contents ◽

Pacific Slab ◽

Back Arc

AbstractThe Zhangguangcai Range in the Xing’an Mongolian Orogenic Belt, NE China, contains Early Jurassic (c. 188 Ma) Dabaizigou (DBZG) porphyritic dolerite. Compared with other island-arc mafic rocks, the DBZG dolerite is characterized by high trace-element contents, relatively weak Nb and Ta enrichments, and no Zr, Hf or Ti depletions, similar to OIB-type rocks. Analysed rocks have (87Sr/86Sr)i ratios of 0.7033–0.7044, relatively uniform positive ɛNd(t) values of 2.3–3.2 and positive ɛHf(t) values of 8.5–17.1. Trace-element and isotopic modelling indicates that the DBZG mafic rocks were generated by partial melting of asthenospheric mantle under garnet- to spinel-facies conditions. The occurrence of OIB-like mafic intrusion suggests significant upwelling of the asthenosphere in response to lithospheric attenuation caused by continental rifting. These processes occurred in an incipient continental back-arc environment in the upper plate of a palaeo-Pacific slab subducting W–NW beneath East Asia.

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Influence of volcanic activity and anthropic impact in the trace element contents of fishes from the North Patagonia in a global context

Environmental Monitoring and Assessment ◽

10.1007/s10661-015-4910-y ◽

2015 ◽

Vol 187 (11) ◽

Cited By ~ 3

Author(s):

D. F. Bubach ◽

P. J. Macchi ◽

S. Pérez Catán

Keyword(s):

Trace Element ◽

Volcanic Activity ◽

Anthropic Impact ◽

Global Context ◽

North Patagonia ◽

The North ◽

Trace Element Contents ◽

Element Contents

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Crustal assimilation in the Burnt Lake metavolcanics, Grenville Province, southeastern Ontario, and its tectonic significance

Canadian Journal of Earth Sciences ◽

10.1139/e17-101 ◽

1997 ◽

Vol 34 (9) ◽

pp. 1272-1285 ◽

Cited By ~ 5

Author(s):

T. E. Smith ◽

P. E. Holm ◽

N. M. Dennison ◽

M. J. Harris

Keyword(s):

Rare Earth ◽

Trace Element ◽

Partial Melting ◽

Continental Crust ◽

Fractional Crystallization ◽

Volcanic Rocks ◽

Lake Area ◽

Depleted Mantle ◽

Mafic Magmas ◽

Back Arc

Three intimately interbedded suites of volcanic rocks are identified geochemically in the Burnt Lake area of the Belmont Domain in the Central Metasedimentary Belt, and their petrogenesis is evaluated. The Burnt Lake back-arc tholeiitic suite comprises basalts similar in trace element signature to tholeiitic basalts emplaced in back-arc basins formed in continental crust. The Burnt Lake continental tholeiitic suite comprises basalts and andésites similar in trace element composition to continental tholeiitic sequences. The Burnt Lake felsic pyroclastic suite comprises rhyolitic pyroclastics having major and trace element compositions that suggest that they were derived from crustal melts. Rare earth element models suggest that the Burnt Lake back-arc tholeiitic rocks were formed by fractional crystallization of mafic magmas derived by approximately 5% partial melting of an amphibole-bearing depleted mantle, enriched in light rare earth elements by a subduction component. The modelling also suggests that the Burnt Lake continental tholeiitic rocks were formed by contamination – fractional crystallization of mixtures of mafic magmas, derived by ~3% partial melting of the subduction-modified source, and rhyolitic crustal melts. These models are consistent with the suggestion that the Belmont Domain of the Central Metasedimentary Belt formed as a back-arc basin by attenuation of preexisting continental crust above a westerly dipping subduction zone.

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Evolution of the trace element contents (Sr and Mn) of hemipelagic carbonates from the Zumaia Paleocene section (Gipuzkoa, Spain): implications for the knowledge of seawater chemistry during the Selandian

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.185.6.413 ◽

2014 ◽

Vol 185 (6) ◽

pp. 413-435 ◽

Cited By ~ 7

Author(s):

Laurence Le Callonnec ◽

Maurice Renard ◽

Marc De Rafélis ◽

Fabrice Minoletti ◽

Catherine Beltran ◽

...

Keyword(s):

Trace Element ◽

North Atlantic ◽

Absorption Spectrometry ◽

Minor Role ◽

Burial Diagenesis ◽

The North ◽

Trace Element Contents ◽

Mn Content ◽

The North Atlantic ◽

Element Contents

AbstractWell exposed and stratigraphically well constrained by numerous studies, the Zumaia section is one of the best places to conduct studies on the Palaeocene in basin facies. Thus, this section has been chosen [Schmitz et al., 2011] as a stratotype of Selandian basal and terminal limits (GSSP: Global boundary Stratotype Section and Point). The sediments consist of carbonate hemipelagites interbedded with fine carbonate (Maastrichtian to Selandian) and siliciclastic (Thanetian to Eocene) turbidites.The purpose of this work is to geochemically characterize the Selandian by trace element contents (strontium and manganese) and to try to assess the chemical composition of seawater during the Paleocene. Analysis of various separated granulometric fine fractions show that hemipelagic sediments from the Zumaia section present a high preservation quality of the original records of trace-element contents. Late burial diagenesis plays only a minor role and geochemical breaks are not reducible to a change in the nature of carbonate producers.The strontium contents of Paleocene sediments require that the Sr/Ca ratio of seawater was lower than that in the present ocean. The Selandian is characterized by a positive excursion of the strontium curve. This accident is also recognized in several worldwide sections and is related to the platform/basin carbonate sedimentation budget and the intensity of oceanic hydrothermalism.The Mn content of hemipelagites is very high and can reach 2500–3000 ppm in the Paleocene. A comparison of analyses by atomic absorption spectrometry (AAS) and electron paramagnetic resonance (EPR) shows that both Mn2+ (in the calcite lattice) and Mn4+ (as oxide micro nodules) coexist. The Mn content fluctuations are related to the opening phases of the North Atlantic during the Paleocene by submarine volcanism and hydrothermalism in the North Atlantic Igneous Province (NAIP).

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Trace Element Contents in Thyroid Cancer Investigated by Instrumental Neutron Activation Analysis

Journal of Oncology Research ◽

10.31829/2637-6148/jor2018-1(1)-102 ◽

2018 ◽

Vol 1 (1) ◽

pp. 1-13

Keyword(s):

Thyroid Cancer ◽

Neutron Activation Analysis ◽

Instrumental Neutron Activation Analysis ◽

Activation Analysis ◽

Neutron Activation ◽

Trace Element ◽

Thyroid Tissue ◽

Tissue Levels ◽

Trace Element Contents ◽

Element Contents

Background: Thyroid cancer is an internationally important health problem. The aim of this exploratory study was to evaluate whether significant changes in the thyroid tissue levels of Ag, Co, Cr, Fe, Hg, Rb, Sb, Sc, Se, and Zn exist in the malignantly transformed thyroid. Methods: Thyroid tissue levels of ten trace elements were prospectively evaluated in 41 patients with thyroid malignant tumors and 105 healthy inhabitants. Measurements were performed using non-destructive instrumental neutron activation analysis with high resolution spectrometry of long-lived radionuclides. Tissue samples were divided into two portions. One was used for morphological study while the other was intended for trace element analysis. Results: It was found that contents of Ag, Co, Cr, Hg, and Rb were significantly higher (approximately 12.8, 1.4, 1.6, 19.6, and 1.7 times, respectively) in cancerous tissues than in normal tissues. Conclusions: There are considerable changes in trace element contents in the malignantly transformed tissue of thyroid.

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The role of sulphur on the melting of Ca-poor sediment and on trace element transfer in subduction zones: an experimental investigation

Journal of Petrology ◽

10.1093/petrology/egab005 ◽

2021 ◽

Author(s):

Anne-Aziliz Pelleter ◽

Gaëlle Prouteau ◽

Bruno Scaillet

Keyword(s):

Trace Element ◽

Partial Melting ◽

Subduction Zones ◽

Sediment Flux ◽

Arc Magmas ◽

Trace Element Contents ◽

The Stability ◽

Element Transfer ◽

High Sediment

Abstract We performed phase equilibrium experiments on a natural Ca-poor pelite at 3 GPa, 750-1000 °C, under moderately oxidizing conditions, simulating the partial melting of such lithologies in subduction zones. Experiments investigated the effect of sulphur addition on phase equilibria and compositions, with S contents of up to ∼ 2.2 wt. %. Run products were characterized for their major and trace element contents, in order to shed light on the role of sulphur on the trace element patterns of melts produced by partial melting of oceanic Ca-poor sediments. Results show that sulphur addition leads to the replacement of phengite by biotite along with the progressive consumption of garnet, which is replaced by an orthopyroxene-kyanite assemblage at the highest sulphur content investigated. All Fe-Mg silicate phases produced with sulphur, including melt, have higher MgO/(MgO+FeO) ratios (relative to S-free/poor conditions), owing to Fe being primarily locked up by sulphide in the investigated redox range. Secular infiltration of the mantle wedge by such MgO and K2O-rich melts may have contributed to the Mg and K-rich character of the modern continental crust. Addition of sulphur does not affect significantly the stability of the main accessory phases controlling the behaviour of trace elements (monazite, rutile and zircon), although our results suggest that monazite solubility is sensitive to S content at the conditions investigated. The low temperature (∼ 800 °C) S-bearing and Ca-poor sediment sourced slab melts show Th and La abundances, Th/La systematics and HFSE signatures in agreement with the characteristics of sediment-rich arc magmas. Because high S contents diminish phengite and garnet stabilities, S-rich and Ca-poor sediment sourced slab melts have higher contents of Rb, B, Li (to a lesser extent), and HREE. The highest ratios of La/Yb are observed in sulphur-poor runs (with a high proportion of garnet, which retains HREE) and beyond the monazite out curve (which retains LREE). Sulphides appear to be relatively Pb-poor and impart high Pb/Ce ratio to coexisting melts, even at high S content. Overall, our results show that Phanerozoic arc magmas from high sediment flux margins owe their geochemical signature to the subduction of terrigenous, sometimes S-rich, sediments. In contrast, subduction of such lithologies during Archean appears unlikely or unrecorded.

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