Fluid circulation along an oceanic detachment fault: insights from fluid inclusions in silicified brecciated fault rocks (Mid-Atlantic Ridge at 13°20'N)
Anne Verlaguet
(1)
,
D. Bonnemains
(2)
,
C. Mével
(2)
,
J. Escartin
(2, 3)
,
M. Andreani
(4)
,
F. Bourdelle
(5)
,
M-C Boiron
(6)
,
V. Chavagnac
(7)
1
iSTeP -
Institut des Sciences de la Terre de Paris
2 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
3 LGENS - Laboratoire de géologie de l'ENS
4 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
5 LGCgE - Laboratoire de Génie Civil et Géo-Environnement (LGCgE) - ULR 4515
6 GeoRessources
7 GET - Géosciences Environnement Toulouse
2 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
3 LGENS - Laboratoire de géologie de l'ENS
4 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
5 LGCgE - Laboratoire de Génie Civil et Géo-Environnement (LGCgE) - ULR 4515
6 GeoRessources
7 GET - Géosciences Environnement Toulouse
Anne Verlaguet
- Fonction : Auteur
- PersonId : 14521
- IdHAL : anne-verlaguet
- ORCID : 0000-0001-6302-5414
- IdRef : 111280338
J. Escartin
- Fonction : Auteur
- PersonId : 749242
- IdHAL : javier-escartin
- ORCID : 0000-0002-3416-6856
- IdRef : 126516839
M. Andreani
- Fonction : Auteur
- PersonId : 927029
- ORCID : 0000-0001-8043-0905
F. Bourdelle
- Fonction : Auteur
- PersonId : 745869
- IdHAL : franck-bourdelle
- ORCID : 0000-0002-7136-8692
- IdRef : 154210994
M-C Boiron
- Fonction : Auteur
- PersonId : 749084
- IdHAL : marie-christine-boiron
- ORCID : 0000-0001-7283-6200
V. Chavagnac
- Fonction : Auteur
- PersonId : 178961
- IdHAL : valerie-chavagnac
- ORCID : 0000-0002-7535-6568
- IdRef : 057671168
Résumé
The MAR 13°20′N corrugated detachment fault is composed of pervasively silicified mafic cataclastic breccias, instead of ultramafics and gabbros commonly found at other detachments. These breccias record overplating of hangingwall diabases, with syntectonic silicification due to important influx of silica‐iron‐rich fluids, able to leach alkalis and calcium. Fluids trapped in quartz inclusions show important salinity variations (2.1–10 wt.% NaCl eq.) indicating supercritical phase separation. Fluid inclusions also contain minor amounts of H2 ± CO2 ± CH4 ± H2S, with high H2/CO2 and H2/H2S ratios, signatures typical of ultramafic‐hosted vent fluids. We propose that seawater infiltrated the hangingwall upper crust at the axis adjacent to the active detachment, reaching a reaction zone at the dyke complex base (∼2 km). At >500°C, fluids become Si‐rich during diabase alteration (amphibolite‐facies alteration in clasts), and undergo phase separation. Brines, preferentially released in the nearby detachment fault during diabase brecciation, mix with serpentinite‐derived fluids bearing H2 and CH4. Cooling during detachment deformation and fluid upward migration triggers silica precipitation at greenschist‐facies conditions (quartz + Fe‐rich‐chlorite ± pyrite). Important variations in fluid inclusion salinity and gas composition at both sample and grain scales record heterogeneous fluid circulation at small spatial and short temporal scales. This heterogeneous fluid circulation operating at <2 km depth, extending both along‐axis and over time, is inconsistent with models of fluids channeled along detachments from heat sources at the base of the crust at the fault root. Present‐day venting at detachment footwall, including Irinovskoe, is instead likely underlain by fluid circulation within the footwall, with outflow crossing the inactive detachment fault near‐surface.
Domaines
Sciences du Vivant [q-bio]Format du dépôt | Fichier |
---|---|
Type de dépôt | Article dans une revue |
Titre |
en
Fluid circulation along an oceanic detachment fault: insights from fluid inclusions in silicified brecciated fault rocks (Mid-Atlantic Ridge at 13°20'N)
|
Résumé |
en
The MAR 13°20′N corrugated detachment fault is composed of pervasively silicified mafic cataclastic breccias, instead of ultramafics and gabbros commonly found at other detachments. These breccias record overplating of hangingwall diabases, with syntectonic silicification due to important influx of silica‐iron‐rich fluids, able to leach alkalis and calcium. Fluids trapped in quartz inclusions show important salinity variations (2.1–10 wt.% NaCl eq.) indicating supercritical phase separation. Fluid inclusions also contain minor amounts of H2 ± CO2 ± CH4 ± H2S, with high H2/CO2 and H2/H2S ratios, signatures typical of ultramafic‐hosted vent fluids. We propose that seawater infiltrated the hangingwall upper crust at the axis adjacent to the active detachment, reaching a reaction zone at the dyke complex base (∼2 km). At >500°C, fluids become Si‐rich during diabase alteration (amphibolite‐facies alteration in clasts), and undergo phase separation. Brines, preferentially released in the nearby detachment fault during diabase brecciation, mix with serpentinite‐derived fluids bearing H2 and CH4. Cooling during detachment deformation and fluid upward migration triggers silica precipitation at greenschist‐facies conditions (quartz + Fe‐rich‐chlorite ± pyrite). Important variations in fluid inclusion salinity and gas composition at both sample and grain scales record heterogeneous fluid circulation at small spatial and short temporal scales. This heterogeneous fluid circulation operating at <2 km depth, extending both along‐axis and over time, is inconsistent with models of fluids channeled along detachments from heat sources at the base of the crust at the fault root. Present‐day venting at detachment footwall, including Irinovskoe, is instead likely underlain by fluid circulation within the footwall, with outflow crossing the inactive detachment fault near‐surface.
|
Auteur(s) |
Anne Verlaguet
1
, D. Bonnemains
2
, C. Mével
2
, J. Escartin
2, 3
, M. Andreani
4
, F. Bourdelle
5
, M-C Boiron
6
, V. Chavagnac
7
1
iSTeP -
Institut des Sciences de la Terre de Paris
( 541927 )
- 4, place Jussieu BP CC129 75252 PARIS CEDEX 05
- France
2
IPGP (UMR_7154) -
Institut de Physique du Globe de Paris
( 1005035 )
- 1 rue Jussieu, 75238 Paris cedex 05 et Bât. Lamarck A case postale 7011, 75205 Paris CEDEX 13
- France
3
LGENS -
Laboratoire de géologie de l'ENS
( 1308 )
- 24 Rue Lhomond 75231 PARIS CEDEX 05
- France
4
LGL-TPE -
Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
( 153787 )
- Université Claude Bernard, Lyon1 - Campus de la Doua, bâtiment Géode - 2, rue Raphaël Dubois - 69622 Villeurbanne Cedex
École Normale Supérieure de Lyon - 46, Allée d'Italie - 69364 Lyon cedex 07
Université Jean Monnet - Faculté des Sciences et Techniques - 23 rue du Dr Paul Michalon - 42023 Saint Étienne Cedex 02
UMR CNRS 5276
- France
5
LGCgE -
Laboratoire de Génie Civil et Géo-Environnement (LGCgE) - ULR 4515
( 249848 )
- Université d'Artois - Technoparc FUTURA -
62400 BETHUNE
- France
6
GeoRessources
( 247127 )
- Université de Lorraine, Faculté des Sciences et Technologies, rue Jacques Callot, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex
- France
7
GET -
Géosciences Environnement Toulouse
( 151875 )
- Observatoire Midi-Pyrénées 14 Avenue Edouard Belin 31400 Toulouse
- France
|
Langue du document |
Anglais
|
Nom de la revue |
|
Vulgarisation |
Non
|
Comité de lecture |
Oui
|
Audience |
Internationale
|
Date de publication |
2021-01
|
Volume |
22
|
Numéro |
1
|
Domaine(s) |
|
DOI | 10.1029/2020GC009235 |
Origine :
Fichiers produits par l'(les) auteur(s)
Loading...