Existence of Different Peridotite Types and of a Layered Igneous Complex in the Ivrea Zone of the Western Alps

Rivalenti, Giorgio; Garuti, Giorgio; Rossi, A. P.; Siena, Franca; Sinigoi, S.

doi:10.1093/petrology/22.1.127

Cited by 139 publications

(58 citation statements)

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“…Coexisting Ca-poor pyroxenes have correspondingly high rag-values and AI contents, and low Cr20 3. Pyroxenes with similar mo-values and Cr and Ti contents also characterize pyroxenites occurring within ultramafic massifs from Etang de Lets, France (Dickey, 1970; Table 3, analysis a), and the Ivrea zone of the western Alps, Italy (Rivalenti et al, 1981; Table I.…”

Section: Mineralogymentioning

confidence: 92%

Garnet websterites and associated ultramafic inclusions from a nepheline mugearite in the Walcha area, New South Wales, Australia

Stolz¹

1984

Mineral. mag.

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ABSTRACT. A nepheline mugearite dyke in the Walcha area, New South Wales, contains xenoliths of Cr-diopside lherzolite, garnet-and spinel websterites, and twopyroxene-garnet granulites. The Cr-diopside lherzolite xenoliths are regarded as refractory upper mantle which finally equilibrated at c. 950-980 ~ The garnet websterites are considered to represent spinel websterite segregations from an Mg-rich olivine tholeiite magma at 14 16 kbar which on isobaric cooling to 1000 1050 ~ passed into the garnet pyroxenite stability field. Spinel-amphibole websterites which probably last equilibrated at c. 950 ~ and pressures of 9 12 kbar have dose mineralogical affinites with the Cr-diopside lherzolite xenoliths. The mafic granulites may represent metamorphosed crystal segregates resulting from relatively large degrees of crystallization of tholeiitic basaltic magma which finally equilibrated at c. 14 kbar and 1000 ~ Subcalcic dinopyroxene and spinel megacrysts crystallized from the host nepheline mugearite at c. 13 20 kbar.

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Section: Mineralogymentioning

confidence: 92%

Garnet websterites and associated ultramafic inclusions from a nepheline mugearite in the Walcha area, New South Wales, Australia

Stolz¹

1984

Mineral. mag.

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“…Quick et al 2003;Rivalenti et al 1975Rivalenti et al , 1981Sinigoi et al 1996). It was formed by magmatic underplating during the Permian extensional regime between ~ 290 and 280 Ma (e.g.…”

Section: Geological Settingmentioning

confidence: 99%

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Kunz

Regis

Engi

2018

Contrib Mineral Petrol

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Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U-Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P-T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U-Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure.

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“…The former unit is made up of layered gabbros intruded in the deep crust and re-equilibrated in granulite facies (Table 6B). Magmatic lithotypes varies from cumulitic peridotites, pyroxenites, gabbros, anorthosites and diorites (Rivalenti et al, 1980). The intrusion of this body occurs within the older Kinzigitic Complex in a general extensive regime which allow the creation of progressive enlarging magma chamber/s.…”

Section: -Lower Crustmentioning

confidence: 99%

“…The heat flux generating by the incoming basic magmas most probably caused the partial melting of the lower crust lithologies (crustal anatexis) which ultimately generated the acid intrusive and effusive magmas of the Serie dei Laghi (Table 6A). Few slices of subcontinental mantle occur at the base of the gabbroic intrusion near the tectonic contact with the Canavese Line (Balmuccia, Baldissero and Finero ultramafic complexes; Rivalenti et al, 1980;Coltorti and Siena, 1984;Mazzucchelli et al, 1992). The Kinzigitic Fm.…”

Section: -Lower Crustmentioning

confidence: 99%

U and Th content in the Central Apennines continental crust: A contribution to the determination of the geo-neutrinos flux at LNGS

Coltorti

Boraso

Mantovani

et al. 2011

Geochimica et Cosmochimica Acta

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Existence of Different Peridotite Types and of a Layered Igneous Complex in the Ivrea Zone of the Western Alps

Cited by 139 publications

References 0 publications

Garnet websterites and associated ultramafic inclusions from a nepheline mugearite in the Walcha area, New South Wales, Australia

Garnet websterites and associated ultramafic inclusions from a nepheline mugearite in the Walcha area, New South Wales, Australia

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

U and Th content in the Central Apennines continental crust: A contribution to the determination of the geo-neutrinos flux at LNGS

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