Norwegian Garnet Websterites: Analogues for Mantle Metasomatism?

Simon Cuthbert, A. Qas-Cohen, C. Ballantyne, R. Burgess, G. Droop

Research output: Contribution to conferenceAbstract

Abstract

In the southern Norwegian Caledonides, garnet websterite forms small bodies enclosed in gneiss, or within layered complexes also comprising peridotite, clinopyroxenite and eclogite, probably originating as crustal, mafic-ultramafic
intrusions. Websterites are variably enriched in phlogopite and carbonate and have graphite-bearing fluid inclusions, and are frequently very coarse grained. Calculated pressures of 4-5GPa [1] are consistent with the presence of micro-diamond [3]. Bulk geochemistry suggests an olivine-rich protolith, but
subsequent enrichment in Si, C, K, P, other LIL and HFSE. Sr isotopic data for cpx [2] show unsupported, high radiogenic Sr, suggesting an influx of fluids from the enclosing gneisses. Interlayered eclogite is cut by veins of zircon- and apatite-rich glimmerite and coesite-garnetite with depletion haloes of
clinopyroxenite. Coarse magnesite is patchily distributed within the websterite. Near Molde [3] microdiamond-bearing garnetite, glimmerite and websterite form veins cutting peridotite, demonstrating fracture-metasomatism of an olivinerich
protolith. The Norwegian external garnet websterites therefore provide rare evidence for metasomatism of ultramafic rocks by siliceous, C-O-H-rich fluids/melts generated in the host gneisses under UHP conditions.
Characteristics of the websterites are similar to those of xenoliths attributed to metasomatism of mantle peridotite. Thus, importantly, they provide field-scale examples of metasomatic features not available in mantle xenoliths, and
could open new perspectives on mantle metasomatism, diamond genesis and crust-mantle interactions.
Original languageEnglish
Number of pages1
Publication statusPublished - Jun 2010
EventGoldschmidt Conference - Knoxville, United States
Duration: 13 Jun 201018 Jun 2010

Conference

ConferenceGoldschmidt Conference
CountryUnited States
CityKnoxville
Period13/06/1018/06/10

Fingerprint

metasomatism
garnet
peridotite
mantle
eclogite
diamond
coesite
magnesite
fluid
phlogopite
ultramafic rock
protolith
graphite
gneiss
fluid inclusion
apatite
olivine
zircon
geochemistry
melt

Cite this

Cuthbert, S., Qas-Cohen, A., Ballantyne, C., Burgess, R., & Droop, G. (2010). Norwegian Garnet Websterites: Analogues for Mantle Metasomatism?. Abstract from Goldschmidt Conference, Knoxville, United States.
Cuthbert, Simon ; Qas-Cohen, A. ; Ballantyne, C. ; Burgess, R. ; Droop, G. / Norwegian Garnet Websterites : Analogues for Mantle Metasomatism?. Abstract from Goldschmidt Conference, Knoxville, United States.1 p.
@conference{9845a3f2e11149f59f162a529d6a2ea2,
title = "Norwegian Garnet Websterites: Analogues for Mantle Metasomatism?",
abstract = "In the southern Norwegian Caledonides, garnet websterite forms small bodies enclosed in gneiss, or within layered complexes also comprising peridotite, clinopyroxenite and eclogite, probably originating as crustal, mafic-ultramaficintrusions. Websterites are variably enriched in phlogopite and carbonate and have graphite-bearing fluid inclusions, and are frequently very coarse grained. Calculated pressures of 4-5GPa [1] are consistent with the presence of micro-diamond [3]. Bulk geochemistry suggests an olivine-rich protolith, butsubsequent enrichment in Si, C, K, P, other LIL and HFSE. Sr isotopic data for cpx [2] show unsupported, high radiogenic Sr, suggesting an influx of fluids from the enclosing gneisses. Interlayered eclogite is cut by veins of zircon- and apatite-rich glimmerite and coesite-garnetite with depletion haloes ofclinopyroxenite. Coarse magnesite is patchily distributed within the websterite. Near Molde [3] microdiamond-bearing garnetite, glimmerite and websterite form veins cutting peridotite, demonstrating fracture-metasomatism of an olivinerichprotolith. The Norwegian external garnet websterites therefore provide rare evidence for metasomatism of ultramafic rocks by siliceous, C-O-H-rich fluids/melts generated in the host gneisses under UHP conditions.Characteristics of the websterites are similar to those of xenoliths attributed to metasomatism of mantle peridotite. Thus, importantly, they provide field-scale examples of metasomatic features not available in mantle xenoliths, andcould open new perspectives on mantle metasomatism, diamond genesis and crust-mantle interactions.",
author = "Simon Cuthbert and A. Qas-Cohen and C. Ballantyne and R. Burgess and G. Droop",
year = "2010",
month = "6",
language = "English",
note = "Goldschmidt Conference ; Conference date: 13-06-2010 Through 18-06-2010",

}

Cuthbert, S, Qas-Cohen, A, Ballantyne, C, Burgess, R & Droop, G 2010, 'Norwegian Garnet Websterites: Analogues for Mantle Metasomatism?' Goldschmidt Conference, Knoxville, United States, 13/06/10 - 18/06/10, .

Norwegian Garnet Websterites : Analogues for Mantle Metasomatism? / Cuthbert, Simon; Qas-Cohen, A.; Ballantyne, C.; Burgess, R.; Droop, G.

2010. Abstract from Goldschmidt Conference, Knoxville, United States.

Research output: Contribution to conferenceAbstract

TY - CONF

T1 - Norwegian Garnet Websterites

T2 - Analogues for Mantle Metasomatism?

AU - Cuthbert, Simon

AU - Qas-Cohen, A.

AU - Ballantyne, C.

AU - Burgess, R.

AU - Droop, G.

PY - 2010/6

Y1 - 2010/6

N2 - In the southern Norwegian Caledonides, garnet websterite forms small bodies enclosed in gneiss, or within layered complexes also comprising peridotite, clinopyroxenite and eclogite, probably originating as crustal, mafic-ultramaficintrusions. Websterites are variably enriched in phlogopite and carbonate and have graphite-bearing fluid inclusions, and are frequently very coarse grained. Calculated pressures of 4-5GPa [1] are consistent with the presence of micro-diamond [3]. Bulk geochemistry suggests an olivine-rich protolith, butsubsequent enrichment in Si, C, K, P, other LIL and HFSE. Sr isotopic data for cpx [2] show unsupported, high radiogenic Sr, suggesting an influx of fluids from the enclosing gneisses. Interlayered eclogite is cut by veins of zircon- and apatite-rich glimmerite and coesite-garnetite with depletion haloes ofclinopyroxenite. Coarse magnesite is patchily distributed within the websterite. Near Molde [3] microdiamond-bearing garnetite, glimmerite and websterite form veins cutting peridotite, demonstrating fracture-metasomatism of an olivinerichprotolith. The Norwegian external garnet websterites therefore provide rare evidence for metasomatism of ultramafic rocks by siliceous, C-O-H-rich fluids/melts generated in the host gneisses under UHP conditions.Characteristics of the websterites are similar to those of xenoliths attributed to metasomatism of mantle peridotite. Thus, importantly, they provide field-scale examples of metasomatic features not available in mantle xenoliths, andcould open new perspectives on mantle metasomatism, diamond genesis and crust-mantle interactions.

AB - In the southern Norwegian Caledonides, garnet websterite forms small bodies enclosed in gneiss, or within layered complexes also comprising peridotite, clinopyroxenite and eclogite, probably originating as crustal, mafic-ultramaficintrusions. Websterites are variably enriched in phlogopite and carbonate and have graphite-bearing fluid inclusions, and are frequently very coarse grained. Calculated pressures of 4-5GPa [1] are consistent with the presence of micro-diamond [3]. Bulk geochemistry suggests an olivine-rich protolith, butsubsequent enrichment in Si, C, K, P, other LIL and HFSE. Sr isotopic data for cpx [2] show unsupported, high radiogenic Sr, suggesting an influx of fluids from the enclosing gneisses. Interlayered eclogite is cut by veins of zircon- and apatite-rich glimmerite and coesite-garnetite with depletion haloes ofclinopyroxenite. Coarse magnesite is patchily distributed within the websterite. Near Molde [3] microdiamond-bearing garnetite, glimmerite and websterite form veins cutting peridotite, demonstrating fracture-metasomatism of an olivinerichprotolith. The Norwegian external garnet websterites therefore provide rare evidence for metasomatism of ultramafic rocks by siliceous, C-O-H-rich fluids/melts generated in the host gneisses under UHP conditions.Characteristics of the websterites are similar to those of xenoliths attributed to metasomatism of mantle peridotite. Thus, importantly, they provide field-scale examples of metasomatic features not available in mantle xenoliths, andcould open new perspectives on mantle metasomatism, diamond genesis and crust-mantle interactions.

M3 - Abstract

ER -

Cuthbert S, Qas-Cohen A, Ballantyne C, Burgess R, Droop G. Norwegian Garnet Websterites: Analogues for Mantle Metasomatism?. 2010. Abstract from Goldschmidt Conference, Knoxville, United States.