Peridotite-gabbro-trondhjemite association of the Mid-Atlantic Ridge between 12°58′ and 14°45′N: Ashadze and Logachev hydrothermal vent fields

Silantyev, S. A.; Krasnova, E. D.; Cannat, Mathilde; Бортников, Н. С.; Kononkova, N. N.; Bel’tenev, V. E.

doi:10.1134/s0016702911040070

Cited by 34 publications

(11 citation statements)

References 13 publications

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“…Ultramafic rocks (lithological types 4a, b and c) are extensively altered into serpentine or talc (only 46 out of our 130 ultramafic thin sections contain olivine relicts). The composition of relicts of the primary peridotite mineralogy (olivine, orthopyroxene, uncommon clinopyroxene, and spinel; ) is consistent with a depleted residual harzburgitic protolith [ Silantyev et al , 2011].…”

Section: Sample Locations and Lithological Descriptionsmentioning

confidence: 99%

Deformation associated with the denudation of mantle‐derived rocks at the Mid‐Atlantic Ridge 13°–15°N: The role of magmatic injections and hydrothermal alteration

Picazo

Cannat

Delacour

et al. 2012

Geochem Geophys Geosyst

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[1] Outcrops of deeply derived ultramafic rocks and gabbros are widespread along slow spreading ridges where they are exposed in the footwall of detachment faults. We report on the microstructural and petrological characteristics of a large number of samples from ultramafic exposures in the walls of the Mid-Atlantic Ridge (MAR) axial valley at three distinct locations at lat. 13 N and 14 45′N. One of these locations corresponds to the footwall beneath a corrugated paleo-fault surface. Bearing in mind that dredging and ROV sampling may not preserve the most fragile lithologies (fault gouges), this study allows us to document a sequence of deformation, and the magmatic and hydrothermal history recorded in the footwall within a few hundred meters of the axial detachment fault. At the three sampled locations, we find that tremolitic amphiboles have localized deformation in the ultramafic rocks prior to the onset of serpentinization. We interpret these tremolites as hydrothermal alteration products after evolved gabbroic rocks intruded into the peridotites. We also document two types of brittle deformation in the ultramafic rocks, which we infer could produce the sustained low magnitude seismicity recorded at ridge axis detachment faults. The first type of brittle deformation affects fresh peridotite and is associated with the injection of the evolved gabbroic melts, and the second type affects serpentinized peridotites and is associated with the injection of Si-rich hydrothermal fluids that promote talc crystallization, leading to strain localization in thin talc shear zones. We also observed chlorite + serpentine shear zones but did not identify samples with serpentine-only shear zones. Although the proportion of magmatic injections in the ultramafic rocks is variable, these characteristics are found at each investigated location and are therefore proposed as fundamental components of the deformation in the footwall of the detachment faults associated with denudation of mantle-derived rocks at the MAR.

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Section: Sample Locations and Lithological Descriptionsmentioning

confidence: 99%

Deformation associated with the denudation of mantle‐derived rocks at the Mid‐Atlantic Ridge 13°–15°N: The role of magmatic injections and hydrothermal alteration

Picazo

Cannat

Delacour

et al. 2012

Geochem Geophys Geosyst

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“…4b). Among the major elements, SiO 2 and MgO are most mobile during the submarine weathering of abyssal peridotites (Snow and Dick, 1995;Bazylev, 1997;Silantyev et al, 2011). However, even in the most weathered serpentinites, the MgO content does not decrease below 30 wt % and 25 wt % in strongly carbonated varieties (Fig.…”

Section: Processes Of Peridotite Alteration In the Oceanic Crust: An mentioning

confidence: 95%

“…Titanite was found in sample DR37 8, although this mineral is not typical of oceanic serpentinites. However, this phase is often observed in vein gabbroids associating with abyssal peri dotites, where it replaces ilmenite or titanomagnetite (e.g., Silantyev et al, 2011). Perhaps, the serpentinized lherzolites of the Stalemate Fracture Zone contain thin veinlets of gabbroid material, the presence of which could be disguised by serpentinization.…”

Section: Petrographic and Mineralogical Characteristicsmentioning

confidence: 96%

“…High chro mium contents in chlorite from the serpentinites of the Mid Atlantic Ridge (MAR) have been reported in many publication on oceanic core complexes (e.g., Bazylev, 1997;Silantyev et al, 2011). Serpentine from the serpentinized lherzolites of the Stalemate Fracture Zone is chemically similar to serpentinized peridotites from the oceanic core complexes of the MAR (e.g., Silantyev et al, 2011) and shows variable Al 2 O 3 (0.34-2.3 wt % and 0.95-3.3 wt % in two samples) and a pos itive correlation between Fe and Cl contents. The find ing of clinozoisite in a sample of tectonically affected banded serpentinite (DR37 16) may indicate the pres ence of plagioclase in this rock.…”

Section: Petrographic and Mineralogical Characteristicsmentioning

confidence: 96%

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Silicification of peridotites at the stalemate fracture zone (Northwestern Pacific): Reconstruction of the conditions of low-temperature weathering and tectonic interpretation

et al. 2012

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During cruise SO201 1b of the joint Russian-German expedition on the R/V Sonne in 2009, mantle peridotites affected by varying secondary alteration were dredged on the eastern slope of the north western segment of the Stalemate transverse ridge adjacent to the eponymous fracture zone. The collection discussed in this paper included four samples of silicified serpentinites after dunites and 11 lherzolite samples serpentinized to a varying degree. The abundance of amorphous silica and quartz, very high SiO 2 content (up to 88.7 wt %), and unusually low MgO (up to 1.4 wt %) in the serpentinized dunites strongly distinguish these rocks from the known products of hydrothermal alteration and low temperature (seafloor) weathering of peridotites in the oceanic crust. In order to determine the conditions and processes resulting in the silicifica tion of peridotites at the Stalemate Fracture Zone, thermodynamic modeling accounting for the kinetics of mineral dissolution implemented in the GEOCHEQ program package was used in this study. The results of modeling allowed us to suppose that the geochemical and mineralogical effects observed in the silicified ser pentinized dunites of the Stalemate Fracture Zone are consequences of low temperature deserpentinization of oceanic materials under subaerial conditions.

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“…11) evidenced about their involving in deformation processes. Thus, according to data available, the most OCCs Smith et al, 2008;MacLeod et al, 2009: Silantyev et al, 2011 and references therein), as well as ophiolite assemblages (Knipper et al, 2002;Dilek and Furnes, 2011), have the similar structure and composition of lower crust and lithospheric mantle. So, the structure of the studied area represents common type of the shallow oceanic lithosphere and we can discuss some general problems of origin and functioning of slow-spreading ridges on its example.…”

Section: Origin Of Lower Oceanic Crust: Evidence From Sierra Leone Areamentioning

confidence: 99%

Cyclic Development of Axial Parts of Slow-Spreading Ridges: Evidence from Sierra Leone Area, the Mid-Atlantic Ridge, 5-7°N

Шарков¹

2012

Tectonics - Recent Advances

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Peridotite-gabbro-trondhjemite association of the Mid-Atlantic Ridge between 12°58′ and 14°45′N: Ashadze and Logachev hydrothermal vent fields

Cited by 34 publications

References 13 publications

Deformation associated with the denudation of mantle‐derived rocks at the Mid‐Atlantic Ridge 13°–15°N: The role of magmatic injections and hydrothermal alteration

Deformation associated with the denudation of mantle‐derived rocks at the Mid‐Atlantic Ridge 13°–15°N: The role of magmatic injections and hydrothermal alteration

Silicification of peridotites at the stalemate fracture zone (Northwestern Pacific): Reconstruction of the conditions of low-temperature weathering and tectonic interpretation

Cyclic Development of Axial Parts of Slow-Spreading Ridges: Evidence from Sierra Leone Area, the Mid-Atlantic Ridge, 5-7°N

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