Serpentinite with and without brucite: A reaction pathway analysis of a natural serpentinite in the Josephine ophiolite, California

Sonzogni, Y.; Treiman, Allan H.; Schwenzer, S. P.

doi:10.2465/jmps.160509

Cited by 16 publications

(7 citation statements)

References 82 publications

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“…The infiltration of Si-rich fluids into an ultramafic rock at low temperatures (<300 °C) tends to inhibit brucite precipitation (e.g., Bach et al, 2004;Sonzogni et al, 2017), and the absence of brucite in our specimens indicates that the olivine of ultramafic rocks in the Manlay Ophiolite reacted with Si-rich fluids to generate lizardite without brucite (Fig 4a-c).…”

Section: Olivine Water Silica Lizarditementioning

confidence: 84%

Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia

et al. 2021

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Serpentinization of ultramafic rocks in ophiolites is key to understanding the global cycle of elements and changes in the physical properties of lithospheric mantle. Mongolia, a central part of the Central Asian Orogenic Belt (CAOB), contains numerous ophiolite complexes, but the metamorphism of ultramafic rocks in these ophiolites has been little studied. Here we present the results of our study of the serpentinization of an ultramafic body in the Manlay Ophiolite, southern Mongolia. The ultramafic rocks were completely serpentinized, and no relics of olivine or orthopyroxene were found. The composition of Cr-spinels [Mg# = Mg/(Mg + Fe2+) = 0.54 and Cr# = Cr/(Cr + Al) = 0.56] and the bulk rock chemistry (Mg/Si = 1.21–1.24 and Al/Si < 0.018) of the serpentinites indicate their origin from a fore-arc setting. Lizardite occurs in the cores and rims of mesh texture (Mg# = 0.97) and chrysotile is found in various occurrences, including in bastite (Mg# = 0.95), mesh cores (Mg# = 0.92), mesh rims (Mg# = 0.96), and later-stage large veins (Mg# = 0.94). The presence of lizardite and chrysotile and the absence of antigorite suggests low-temperature serpentinization (<300 °C). The lack of brucite in the serpentinites implies infiltration of the ultramafic rocks of the Manlay Ophiolite by Si-rich fluids. Based on microtextures and mineral chemistry, the serpentinization of the ultramafic rocks in the Manlay Ophiolite took place in three stages: (1) replacement of olivine by lizardite, (2) chrysotile formation (bastite) after orthopyroxene and as a replacement of relics of olivine, and (3) the development of veins of chrysotile that cut across all previous textures. The complex texture of the serpentinites in the Manlay Ophiolite indicates multiple stages of fluid infiltration into the ultramafic parts of these ophiolites in southern Mongolia and the CAOB.

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Section: Olivine Water Silica Lizarditementioning

confidence: 84%

Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia

et al. 2021

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“…Serpentinites were collected from outcrops in southwestern Oregon at the Nolan Claim (N 42°10.003' W 123°42.709' and N 42°09.925' W 123°42.719') in Josephine County, OR, USA. These rocks are part of the Josephine Ophiolite in the Klamath Mountains [60,61], and were a sequence of ultrama c rocks (dunite and harzburgite) with a formation age of 157 million years. Fresh samples were taken along the Josephine creek, then powdered and analyzed by Raman, XRD, and XRF.…”

Section: Phosphorus Reactions and Speciationmentioning

confidence: 99%

Serpentinization as a route to liberating phosphorus on habitable worlds

Pasek¹,

Omran²,

Lang³

et al. 2020

Preprint

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Abstract Planetary habitability is in part governed by nutrient availability, including the availability of the element phosphorus. The nutrient phosphorus plays roles in various necessary biochemical functions, and its biogeochemical cycling has been proposed to be extremely slow due to a strong coupling to the rock cycle via mineral weathering. Here we show a route to P liberation from water-rock reactions that are thought to be common throughout the Solar System. We report the speciation of phosphorus in serpentinite rocks to include the ion phosphite (HPO32- with P3+) and show that reduction of phosphate to phosphite is predicted from thermodynamic models of serpentinization. As a result, as olivine in ultramafic rocks alters to serpentine minerals, phosphorus as soluble phosphite should be released under low redox conditions, liberating this key nutrient for life. Thus, this element may be accessible to developing life where water is in direct contact with ultramafic rock, providing a source of this nutrient to potentially habitable worlds.

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“…Hydrothermal alteration is recorded in the outcrop predominantly in the forms of serpentine and tremolite. Serpentine occurs as crosscutting veins and as a mesh texture replacing olivine (Figure 1) and is most likely lizardite or chrysotile, as seen elsewhere in the Josephine ophiolite (Coulton et al, 1995;Harper et al, 1996;Sonzogni et al, 2017). These low-temperature forms of serpentine are unstable at temperatures greater thañ 350°C (e.g., Evans, 2004;Schwartz et al, 2013) and are therefore unrelated to any hydration at ≥690°C.…”

Section: Evaluating Potential Sources Of Watermentioning

confidence: 99%

Evolution of the Josephine Peridotite Shear Zones: 1. Compositional Variation and Shear Initiation

Kumamoto

Warren

Hauri

2019

Geochem Geophys Geosyst

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Shear localization in the upper mantle, a necessity for plate tectonics, can have a number of causes, including shear heating, the presence of melt, the development of a strong crystal preferred orientation, and the presence of water. The Josephine Peridotite of southwestern Oregon contains shear zones that provide an excellent opportunity to examine the initiation of shear localization. These shear zones are relatively small scale and low strain compared to many shear zones in peridotite massifs, which typically have extreme grain size reduction indicating extensive deformation. We use major, trace, and volatile element analyses of a large suite of harzburgites from the Fresno Bench shear zones to evaluate the mechanisms leading to shear localization. Lithological evidence and geochemical transects across three shear zones show a complex history of melting, melt addition, and melt‐rock interaction. The distribution of aluminum and heavy rare earth elements across the shear zones suggest that melt flow was focused in the centers of the studied shear zones. Water concentrations in orthopyroxene grains of 180–334 ppm H2O indicate a comparatively high degree of hydration for nominally anhydrous minerals. The correlation of water with aluminum and ytterbium in orthopyroxene is consistent with a melt source for this hydration, suggesting that water equilibrated between the melt and peridotite. The presence of melt and hydration of the host rock provide mechanisms for initial weakening that lead to localized deformation.

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Serpentinite with and without brucite: A reaction pathway analysis of a natural serpentinite in the Josephine ophiolite, California

Cited by 16 publications

References 82 publications

Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia

Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia

Serpentinization as a route to liberating phosphorus on habitable worlds

Evolution of the Josephine Peridotite Shear Zones: 1. Compositional Variation and Shear Initiation

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