Identification and discrimination of altered and metamorphosed volcanic rocks using immobile elements

Floyd, P. A.; Winchester, J. A.

doi:10.1016/0009-2541(78)90050-5

Cited by 435 publications

(214 citation statements)

References 33 publications

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“…This is supported by the strong correlation between negative Eu/Eu* anomaly magnitude and Zr/TiO 2 ratios (Fig. 6), which are sensitive to magmatic fractionation (Winchester & Floyd, 1977;Floyd & Winchester, 1978). It is unlikely that the anomalies are caused by processes during diagenesis and burial metamorphism (Eu is redox sensitive and can be mobilised under highly reducing conditions; Sverjensky, 1984;Wray, 1995) and more probable that they are a magmatic feature preserved, at least in part, in the unaltered apatite and zircon phenocrysts.…”

Section: Magmatic Parentage and Tectonic Settingmentioning

confidence: 80%

“…Spears & Kanaris-Sotiriou, 1979;Merriman & Roberts, 1990;Huff et al, 1993;Christidis et al, 1995). The major elements, which are routinely used to classify fresh or slightly altered volcanic rocks, are of limited use when classifying extensively altered volcanic rocks because several elements, including K and Na, are known to be mobile during weathering and diagenesis (Winchester & Floyd, 1977;Floyd & Winchester, 1978;Zielinski, 1982;Christidis, 1998). Instead, the classification of altered volcanic rocks relies on trace elements including Ti, the high-field-strength elements (HFSE) Hf, Nb, Ta, Zr and the rare-earth elements, which are generally considered to be immobile during most upper crustal processes and are also indicators of petrogenetic processes (Floyd & Winchester, 1978;Huff et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Pointon¹,

Chew²,

Delcambre³

et al. 2018

Geol. Belg.

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ABSTRACT. Several thin clay-rich horizons occur interbedded with Mississippian (Viséan) limestones in the Namur-Dinant Basin, southern Belgium. These have been interpreted as diagenetically altered volcanic ash layers (bentonites). Whole-rock geochemical analysis of several bentonites was undertaken to provide insight into their original magmatic composition. Ratios of several trace elements that are considered to be immobile during diagenetic alteration and indicators of petrogenetic processes suggest that most of the bentonites were originally trachyandesitic to trachytic ashes. Furthermore, the coarse grain size of euhedral zircon phenocrysts (up to 400 µm in length) suggests a proximal volcanic source. Zircon U-Pb isotopic ages and wholerock geochemical data from these bentonites were compared with literature data from volcanic and intrusive rocks in adjacent areas, and suggest that the bentonites were sourced from volcanoes within the Variscan orogenic belt.KEYWORDS: altered volcanic ash, cinerite, whole-rock geochemistry, trace element geochemistry, X-ray diffraction analysis.http://dx

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Section: Magmatic Parentage and Tectonic Settingmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Pointon¹,

Chew²,

Delcambre³

et al. 2018

Geol. Belg.

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“…Therefore, immobile elements, such as HFSE, are preferred for classification purposes (Winchester and Floyd 1976;Floyd and Winchester 1978). A popular diagram utilizing relatively immobile element ratios (Nb/Y vs. Zr/Ti) was proposed by Winchester and Floyd (1977).…”

Section: Ve-126 Světlík Olivine-pyroxene Porphyritic Metadoleritementioning

confidence: 99%

Metabasic rocks in the Varied Group of the Moldanubian Zone, southern Bohemia - their petrology, geochemical character and possible petrogenesis

Janoušek¹,

Vrána²,

Erban³

et al. 2012

J. Geosci.

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Metabasic rocks form an important constituent of the Chýnov and Český Krumlov units belonging to the Varied Group (Moldanubian Zone, south Bohemia). The amphibolites are dominated by amphibolite-facies mineral assemblages of mainly tschermakitic amphibole and plagioclase. Hornblendes show compositional variation with Si ~ 6.5 apfu, Mg/(Mg + Fe) ~ 0.5 and (Na + K) A ~ 0.5 apfu. Garnet with clinopyroxene are subordinate and occur in a few samples only. No relics of previous greenschist-or granulite-facies assemblages have been observed, most likely due to the relatively simple metamorphic history. The petrology indicates rather close correlation of the Chýnov and Český Krumlov units. The similarities include presence of dolomite in carbonate bodies, graphite schists, rocks with marialitic scapolite, locally also Ti-andradite (± magnetite, epidote) oxidic assemblages and thin layers of Mn-rich garnet-quartz rocks. However, there is a major difference in the oxidation state. Most Chýnov amphibolites have . This precludes closed-system crystallization from depleted mantle derived melts in Phanerozoic times. The exact age and nature of their parental magma remain enigmatic but any genetic link with the amphibolites in the structurally overlying Český Krumlov Varied Unit seems ruled out. Overall, the most likely tectonic setting of the magmatism was attenuated lithosphere, subjected to an Early Palaeozoic extension, leading eventually to fragmentation of the northern Gondwana margin. The minor OIB component preserved as alkali basalts as well as some contribution to the EMOR-like basaltic magmas was probably added by a rising mantle plume.

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“…The geochemical data showed that the amphibolites are undersaturated in silica. Major element compositions ( (Floyd & Winchester, 1978).…”

Section: Major Elementsmentioning

confidence: 99%

Geochemical Characteristics and Tectonic Setting of Amphibolites in Ifewara Area, Ife-Ilesha Schist Belt, Southwestern Nigeria

Bolarinwa¹,

Adepoju²

2016

ESR

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Trace and Rare Earth Elements (REEs) data are used to constrain the geochemical evolution of the amphibolites from Ifewara in the Ife-Ilesha schist belt of southwestern Nigeria. The amphibolites can be grouped into banded and sheared amphibolites. Major element data show SiO 2 (48.34%), Fe 2 O 3 (11.03-17.88%), MgO (5.76-9.90%), CaO (7.76-18.6%) and TiO 2 (0.44-1.77%) contents which are similar to amphibolites in other schist belts in Nigeria. The Al 2 O 3 (2.85-15.55%) content is varied, with the higher values suggesting alkali basalt protolith. Trace and rare earth elements composition reveal Sr (160-1077ppm), Rb (0.5-22.9ppm), Ni (4.7-10.2ppm), Co (12.2-50.9 ppm) and Cr (2-7ppm). Chondrite-normalized REE patterns show that the banded amphibolites have HREE depletion and both negative and positive Eu anomalies while the sheared variety showed slight LREE enrichment with no apparent Eu anomaly. The study amphibolites plot in the Mid Oceanic Ridge Basalts (MORB) and within plate basalt fields on the Zr/Y vs Zr discriminatory diagrams. They are further classified as volcanic arc basalt and E-type MORB on the Th-Hf/3-Ta and the Zr-Nb-Y diagrams. The amphibolites precursor is considered a tholeiitic suite that suffered crustal contamination, during emplacement in a rifted crust.

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Identification and discrimination of altered and metamorphosed volcanic rocks using immobile elements

Cited by 435 publications

References 33 publications

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Metabasic rocks in the Varied Group of the Moldanubian Zone, southern Bohemia - their petrology, geochemical character and possible petrogenesis

Geochemical Characteristics and Tectonic Setting of Amphibolites in Ifewara Area, Ife-Ilesha Schist Belt, Southwestern Nigeria

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