Archean Rocks of Shoshonitic Affinities at Bijou Point, Northwestern Ontario

1974 ◽  
Vol 11 (10) ◽  
pp. 1407-1413 ◽  
Author(s):  
T. E. Smith ◽  
F. J. Longstaffe
Keyword(s):  
Trace Element ◽  
Chemical Characteristics ◽  
Island Arcs ◽  
Northwestern Ontario ◽  
Intrusive Rocks ◽  
Trace Element Contents ◽  
Greenstone Belts ◽  
Northwest Ontario ◽  
Late Stages ◽  
Shoshonitic Series

The Archean volcanic and intrusive rocks of Bijou Point, northwest Ontario show several chemical characteristics which suggest affinities to the alkali or shoshonitic series characteristic of late stages of evolution in modern island arcs. The rocks have unusually high total alkalis (7% at 58–65% SiO2), high Al2O3 and high trace element contents (Ba 800–2500 ppm, Rb 50–350 ppm, Sr 600–2000 ppm). The presence of such rocks in the greenstone belts of the Superior Province serves to further emphasize the similarities between these ancient volcanics and their modern counterparts.

Elemental abundances relevant to identification of magma sources

1984 ◽  
Vol 310 (1514) ◽  
pp. 535-547 ◽  
Keyword(s):  
Trace Element ◽  
Mantle Peridotite ◽  
Oceanic Island ◽  
Chemical Characteristics ◽  
Island Arcs ◽  
Oceanic Ridge ◽  
Aleutian Arc ◽  
Isotopic Evolution ◽  
Magma Sources ◽  
Back Arc

The search for chemical characteristics of magma sources is usually done by analysing the magmas themselves. This indirect approach has limitations: clearly the magma has only some of the source’s characteristics. What we require are process-independent chemical characteristics, analogous to the isotopic abundance of radiogenic daughter isotopes that have been used so successfully in defining magma sources. Process-independent chemical characteristics in mid-oceanic ridge, oceanic island and island-arc basalts (m.o.r.b., o.i.b., i.a.b.) have been used to identify contrasting chemical characteristics of mantle peridotite from these three tectonically distinct regions. As an example, the abundance ratios of one group of elements (e.g. Cs, K, Rb, Ba, U, and perhaps Th) relative to another group (e.g. light r.e.e., Zr, Hf) are found to be fractionation-independent during most shallow-level basalt fractionation. These ratios are presumed to reflect the chemical characteristics of the mantle source of basalt from the three tectonic environments. In particular the ratios indicate the large cation-depleted nature of all m.o.r.b. and most o.i.b. peridotite sources. In common with many other island arcs, the abundance ratios are consistently higher in mantle under the Aleutian arc than in adjacent non-arc mantle represented by oceanic ridge, oceanic island, and back-arc basalts. The contention that subduction of sediment could result in arc mantle sources with these high ratios is substantiated by trace element analyses of Ba and Cs-rich deep sea sediments of the type that are being subducted at present at the Aleutian trench. The importance of recycling of sediment into the mantle at island arcs as an important control on the trace element (and isotopic) evolution of the mantle is indicated.

Karroo basalts of southern Malawi and their regional petrogenetic significance

1983 ◽  
Vol 47 (344) ◽  
pp. 281-289 ◽  
Author(s):  
R. Macdonald ◽  
R. Crossley ◽  
K. S. Waterhouse
Keyword(s):  
Trace Element ◽  
Incompatible Trace Element ◽  
Chemical Characteristics ◽  
Southern Province ◽  
Mantle Sources ◽  
Heterogeneous Mantle ◽  
Trace Element Contents ◽  
Element Contents ◽  
Basaltic Lavas ◽  
Lower Group

AbstractKarroo basaltic lavas of southern Malawi are divided into two groups on the basis of stratigraphy, petrography, and the data from 20 newly analysed rocks. A lower group of porphyritic lavas is notably rich in plagioclase phenocrysts and has contents of K, Ti, P, Ba, and Zr unusually high for tholeiitic basalts. They are overlain by an upper group of aphyric or sparsely microphyric lavas whose chemistry is more normal for tholeiites and is comparable with that of the Karroo dolerite dykes in Malawi. Though they outcrop in the northern part of the Karroo province, the lavas and dykes have chemical characteristics more similar to southern province rocks, adding some complexity to the concept of geochemical provinces established by earlier workers. Inter-suite variations in incompatible trace element contents and ratios indicate that the basalts of each group were derived from heterogeneous mantle sources.

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

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.

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

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.

Granitoid complexes and the Archean tectonic record in the southern part of northwestern Ontario

1979 ◽  
Vol 16 (10) ◽  
pp. 1965-1977 ◽  
Author(s):  
W. M. Schwerdtner ◽  
D. Stone ◽  
K. Osadetz ◽  
J. Morgan ◽  
G. M. Stott
Keyword(s):  
Large Scale ◽  
Vertical Motion ◽  
Strike Slip ◽  
Horizontal Motion ◽  
Tectonic Deformation ◽  
Northwestern Ontario ◽  
Greenstone Belts ◽  
Second Period ◽  
Transcurrent Faults ◽  
Regional Compression

Two principal, possibly overlapping, periods of tectonic deformation can be distinguished in the Archean of northwestern Ontario, a period of dominantly vertical-motion tectonics and a period of dominantly horizontal-motion tectonics. Gigantic diapirs of foliated to gneissic tonalite–granodiorite developed during the first period and appear to be responsible for the gross structure of, and the major folds within, the metavolcanic–metasedimentary masses ("greenstone belts"). These diapirs are most likely due to mechanical remobilization of early tabular batholiths which originally intruded the oldest supracrustal rocks presently exposed. Later massive to foliated, dioritic to granitic plutons that vary from concordant, crescentic plutons to partly discordant plutons of various shapes and sizes were emplaced into the diapirs.The second period of tectonic deformation is characterized by large-scale dextral shearing and the development of major transcurrent faults under northwesterly regional compression. The strike-slip motions of this period outlasted the late plutonism, and led to the development of mylonitic zones which cut all Archean granitoid plutons.

Trace-Element Contents of Serum, Urine, and Kidney Stones in Urinary Stone Formers

Urolithiasis ◽  
1989 ◽  
pp. 229-231
Author(s):  
J. Hofbauer ◽  
I. Steffan ◽  
H. Schwetz ◽  
G. Vujicic ◽  
O. Zechner
Keyword(s):  
Trace Element ◽  
Kidney Stones ◽  
Urinary Stone ◽  
Stone Formers ◽  
Trace Element Contents ◽  
Element Contents

The implications of reworking on the mineralogy and chemistry of Lower Carboniferous K-bentonites

Clay Minerals ◽  
1996 ◽  
Vol 31 (3) ◽  
pp. 377-390 ◽  
Author(s):  
T. Clayton ◽  
J. E. Francis ◽  
S. J. Hillier ◽  
F. Hodson ◽  
R. A. Saunders ◽  
...  
Keyword(s):  
Trace Element ◽  
Volcanic Ash ◽  
Clay Fraction ◽  
Trace Element Content ◽  
Element Content ◽  
Heavy Minerals ◽  
Lower Carboniferous ◽  
Greenish Yellow ◽  
Trace Element Contents ◽  
Plastic Clays

AbstractPotassium-bentonites have been found in the Courceyan Lower Limestone Shales near Burrington Combe and Oakhill, Somerset, consisting of thin, greenish yellow, plastic clays interbedded within a mudrock and limestone sequence. Mineralogically, the clay fraction is composed of virtually monomineralic interstratified illite-smectite containing 7–10% smectite layers. The clay fraction of the surrounding mudrocks, however, consists of an illite-chlorite dominated assemblage. Their mineral composition, trace element content, and the relative abundance of zircon crystals suggest an origin from burial of montmorillonite originally formed from volcanic ash. The presence of anomalously high trace element contents with both euhedral and rounded zircon grains in the Oakhill K-bentonites suggests a secondary or reworked origin for these samples. In contrast, the presence of a non-anomalous trace element content and large (>100 μm) euhedral zircon grains suggests that the Burrington K-bentonite is primary in origin. Modelling of whole-rock rare-earth element (REE) patterns shows that the Oakhill REE pattern can be derived from the Burrington pattern by the addition of small contributions from zircon and monazite, two major heavy minerals present. These K-bentonites probably represent the oldest Carboniferous K-bentonites so far recorded in the British Isles.

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

2018 ◽  
Vol 158 (1) ◽  
pp. 143-157 ◽  
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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