Metasomatic reaction bands at the Mt. Hochwart gneiss-peridotite contact (Ulten Zone, Italy): insights into fluid-rock interaction in subduction zones

Marocchi, Marta; Mair, Volkmar; Tropper, Peter; Bargossi, Giuseppe Maria

doi:10.1007/s00710-009-0043-8

Cited by 21 publications

(8 citation statements)

References 57 publications

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“…In these high temperature conditions, melt networks remain open for an extended time to allow for the physical concentration, or prolonged growth of zircon megacrysts in parts of the vein network. The textures and geochemistry of the megacrysts bear comparison with others reported from ultramafic hosts (Belousova et al 1998 ; Marocchi et al 2009 ) and suggest similar origins.…”

Section: Discussionsupporting

confidence: 79%

“…specimen from Iona in the Hunterian museum collections: GLAHM 148,080, and from Eilean Glas, Scalpay National Museums of Scotland: Dudgeon collection 74-49-245 and 246). Similar occurrences of large zircon in ultramafic rocks have also been noted elsewhere, including Greenland (Nilsson et al 2010 ), Italy (Marocchi et al 2009 ), and from kimberlites (Kresten et al 1975 ; Belousova et al 1998 ; Robles-Cruz et al 2012 ). However, the relationship of zircon to the ultramafic host is often uncertain.…”

Section: Introductionsupporting

confidence: 65%

“…Metasomatic mineral assemblages similar to those in the Lewisian complex are reported from various Alpine peridotites (Zanetti et al 1999 ; Markl et al 2003 ; Scambelluri et al 2006 ; Liati and Gebauer 2009 ) with interaction between the ultramafic rocks and crustal melts. In a similar context, Marocchi et al ( 2009 ) document zircon megacrysts associated with reactions between peridotite and adjacent crustal gneisses. Metasomatic interactions of this type should in theory be common at subduction zones with crustal slab-derived components infiltrating the mantle wedge from either partial melts or fluids derived from of the slab itself (Prouteau et al 2001 ) or from the introduction of subducted sediments (Currie et al 2007 ).…”

Section: Discussionmentioning

confidence: 96%

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Metasomatism and the crystallization of zircon megacrysts in Archaean peridotites from the Lewisian complex, NW Scotland

Faithfull

Dempster

MacDonald

et al. 2018

Contrib Mineral Petrol

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Zircon megacrysts are locally abundant in 1–40 cm-thick orthopyroxenite veins within peridotite host rocks in the Archaean Lewisian gneiss complex from NW Scotland. The veins formed by metasomatic interaction between the ultramafic host and Si-rich melts are derived from partial melting of the adjacent granulite-facies orthogneisses. The interaction produced abundant orthopyroxene and, within the thicker veins, phlogopite, pargasite and feldspathic bearing assemblages. Two generations of zircon are present with up to 1 cm megacrystic zircon and a later smaller equant population located around the megacryst margins. Patterns of zoning, rare earth element abundance and oxygen isotopic compositions indicate that the megacrysts crystallized from crustal melts, whereas the equant zircon represents new neocryst growth and partial replacement of the megacryst zircon within the ultramafic host. Both zircon types have U–Pb ages of ca. 2464 Ma, broadly contemporaneous with granulite-facies events in the adjacent gneisses. Zircon megacrysts locally form > 10% of the assemblage and may be associated to zones of localized nucleation or physically concentrated during movement of the siliceous melts. Their unusual size is linked to the suppression of zircon nucleation and increased Zr solubility in the Si-undersaturated melts. The metasomatism between crustal melts and peridotite may represent an analog for processes in the mantle wedge above subducting slabs. As such, the crystallization of abundant zircon in ultramafic host rocks has implications for geochemistry of melts generated in the mantle and the widely reported depletion of high field strength elements in arc magmas.

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Section: Discussionsupporting

confidence: 79%

Section: Introductionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 96%

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Metasomatism and the crystallization of zircon megacrysts in Archaean peridotites from the Lewisian complex, NW Scotland

Faithfull

Dempster

MacDonald

et al. 2018

Contrib Mineral Petrol

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“…The contact between peridotites and country stromatic gneisses is often marked by metasomatic reaction zones with a composite structure consisting of an inner tremolite‐rich cm‐thick layer on the peridotite side and an outer phlogopite‐rich front toward the host gneiss (see also Marocchi et al., 2009, 2010; Tumiati & Martin, 2003; Tumiati et al., 2007).…”

Section: Resultsmentioning

confidence: 99%

Reaction‐Induced Mantle Weakening at High‐Pressure Conditions: An Example From Garnet Pyroxenites of Ulten Zone (Eastern Alps, N Italy)

Pellegrino¹,

Menegon

Zanchetta³

et al. 2021

JGR Solid Earth

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The deformational behavior of the upper mantle in response to the forces in the Earth's interior depends on several factors, including pressure, temperature, deviatoric stress, mineralogy, presence of fluids and/or melts, and the grain size of the deforming mantle rocks (e.g., Bürgmann & Dresen, 2008 and reference therein). Studies on both naturally and experimentally deformed mantle rocks indicate that most of the plastic deformation of the upper mantle is accommodated by grain size insensitive (GSI) deformation mechanisms, e.g., dislocation creep

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“…A great deal of petrological, geochemical, and geochronological studies have been devoted to orogenic peridotites, and crustal signatures have been increasingly recognized in them (e.g., Chen et al, ; Marocchi et al, ; Scambelluri et al, , , ; Vrijmoed et al, ; Zhang et al, ; Zheng, Yang, et al, ). This points to crust‐mantle interactions in subduction channels, which are referred to by Zheng () as crustal metasomatism.…”

Section: Introductionmentioning

confidence: 99%

Crustal Metasomatism at the Slab‐Mantle Interface in a Continental Subduction Channel: Geochemical Evidence From Orogenic Peridotite in the Sulu Orogen

Chen

Zheng

et al. 2018

JGR Solid Earth

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To understand crust‐mantle interactions in a continental subduction channel, we carried out a combined study of whole‐rock elements and Sr‐Nd isotopes, mineral elements, and whole‐rock and mineral O isotopes in orogenic peridotite and its host gneiss from the Sulu orogen in China. The results indicate that the peridotite originated from highly depleted subcontinental lithospheric mantle beneath the North China Craton and underwent three episodes of metasomatism via crustally derived fluids. The peridotite was offscraped from the subcontinental lithospheric mantle wedge base and experienced petrographic transformation from a spinel peridotite to a garnet peridotite during continental subduction from forearc to subarc depths. The peridotite underwent the first episode of metasomatism via aqueous solutions at high‐pressure conditions. Afterward, the peridotite underwent a second episode of metasomatism by carbonate melts at ultrahigh‐pressure conditions and a third episode of metasomatism by aqueous solutions at high‐pressure conditions. While the aqueous solution was derived from the metamorphic dehydration of the subducting/exhuming continental crust at the forearc depths, the carbonate melts were produced by partial melting of the ultrahigh‐pressure metasedimentary rocks in the exhuming continental crust at subarc depths. These metasomatic agents did not originate from the gneiss directly hosting the peridotite but from another part of the deeply subducted continental crust that was not in direct contact with the peridotite. Therefore, the orogenic peridotite recorded the geochemical transfer from the subducting crust into the mantle in the continental subduction zone.

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Metasomatic reaction bands at the Mt. Hochwart gneiss-peridotite contact (Ulten Zone, Italy): insights into fluid-rock interaction in subduction zones

Cited by 21 publications

References 57 publications

Metasomatism and the crystallization of zircon megacrysts in Archaean peridotites from the Lewisian complex, NW Scotland

Metasomatism and the crystallization of zircon megacrysts in Archaean peridotites from the Lewisian complex, NW Scotland

Reaction‐Induced Mantle Weakening at High‐Pressure Conditions: An Example From Garnet Pyroxenites of Ulten Zone (Eastern Alps, N Italy)

Crustal Metasomatism at the Slab‐Mantle Interface in a Continental Subduction Channel: Geochemical Evidence From Orogenic Peridotite in the Sulu Orogen

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