 |
| Titel |
Carbonation of Peridotite by CO2-rich Fluids: Insights from Listvenites in the Advocate Ophiolite (Newfoundland) |
| VerfasserIn |
Manuel Menzel, Carlos J. Garrido, Claudio Marchesi, Vicente López Sánchez-Vizcaíno, Károly Hidas, Monica P. Escayola, Bjørn Jamtveit |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144828
|
| Publikation (Nr.) |
 EGU/EGU2017-8699.pdf |
|
|
|
|
|
| Zusammenfassung |
| Listvenites are the result of a sequence of reactions of CO2-rich hydrothermal fluids with
serpentinite that forms magnesite-quartz rocks in the last reaction step. Listvenites are
natural analogues for carbon sequestration by mineral carbonation, fixing large
quantities of carbon in relatively small, confined zones of intense reactive fluid flux
within serpentinite. The association of listvenite (magnesite-quartz), soapstone
(talc-magnesite) and carbonated serpentinite in the mantle section of the Advocate
ophiolite complex in Newfoundland (Canada) is an ideal natural example to study
the carbonation of serpentinites because the reaction progress is recorded by the
differently carbonated assemblages. The Advocate listvenites crop out in a 20-30 m
wide zone that can be followed for about 1 km, surrounded by serpentinite and
harzburgite. Quartz and magnesite veins are widespread in the central listvenite
domain. This mobilization of silica into a vein network is reflected in a depletion
of silica in the most carbonated lithologies, whereas most other major elements
remain unchanged over a wide range of CO2-contents. Notably, there is a sharp
decrease in bulk rock Fe3+/Fetotal from 0.65 – 0.8 in lizardite-chrysotile serpentinites
to 0.1 – 0.3 in talc-magnesite rocks and listvenites. High Cr and Ni contents and
preserved red-brown Cr-spinel in the carbonated lithologies demonstrate the mantle
peridotites provenance of the listvenites. The presence of thin veins of Cr-mica
(fuchsite) suggests that Cr was mobilized to some degree. Fine dispersed magnetite
trails in magnesite trace serpentine pseudomorphs after olivine, indicating that no
deformation occurred in some domains during the carbonation, while deformation was
concentrated in talc-rich lithologies. The rheological contrasts of serpentinites, soapstones
and listvenites and, in consequence, the formation of veins in response to shear-
or extensional fractures may result in a re-opening of pathways for the influx of
very CO2-rich fluids that are needed for the formation of listvenites. Carbonated
mantle rocks like the Advocate listvenites may represent the best accessible natural
analogue for carbonation of serpentinites through bend faulting at the outer rise of
trenches, since hydrothermal fluids in those systems may become more CO2-rich due
to percolation through overlying sediments, thus allowing for localized intense
carbonation.
Funding: We acknowledge funding from the People programme (Marie Curie
Actions - ITN) of the European Union FP7 under REA Grant Agreement n˚ 608001. |
|
|
|
|
|
|