The Formation of Micro-Rodingites from IODP Hole U1309D: Key To Understanding the Process of Serpentinization

Frost, B. Ronald; Beard, James S.; McCaig, A. M.; Condliffe, Eric

doi:10.1093/petrology/egn038

Cited by 93 publications

(64 citation statements)

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“…They discussed that serpentinization took place in the deeper part of the oceanic crust and that rodingitization occurred simultaneously with the host serpentinization. Such rodingites from the ocean floor or from the oceanic lithosphere have also been reported by Frost et al (2008), Austrheim and Prestvick (2008), and Bach and Klein (2009). Subduction-related rodingites have been reported in East Othris, Greece, by Koutsovitis et al (2013) and in the Western Carpathians, Slovakia by Li et al (2014).…”

Section: Tremolite Vein Formationmentioning

confidence: 71%

“…Rodingites are not petrologically significant because their typical mineral assemblage of diopside + grossular provides little information about their formation conditions, such as pressure and temperature. However, rodingites have attracted attention of petrologists because of their role in fluid-rock interaction in oceanic lithospheres (Austrheim and Prestvik 2008;Frost et al 2008;Bach and Klein 2009) and subduction zone settings (Koutsovitis et al 2013;Li et al 2014). Rodingitization commonly occurs in Ca-rich and Si-deficient environments, although each rodingite has a unique formation setting.…”

Section: Introductionmentioning

confidence: 99%

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Interplay of irreversible reactions and deformation: a case of hydrofracturing in the rodingite–serpentinite system

Nishiyama

Shiosaki

Mori

et al. 2017

Prog. in Earth and Planet. Sci.

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The interplay of irreversible reactions and deformation during regional metamorphism was analyzed in the reaction zones between rodingite and serpentinite. Rodingites are leucocratic rocks found commonly in serpentinites and are considered metasomatic products of Ca-rich fluid. Rodingites occur ubiquitously in serpentinite from the Nomo metamorphic rocks, western Kyushu, a Cretaceous accretionary complex of greenschist to epidote-amphibolite facies condition. We used the singular value decomposition (SVD) method to analyze rodingitization reactions based on mineral compositions of a rodingite sample and a possible protolith (clinopyroxene gabbro). The resultant reaction implied that the rodingite was formed due to the addition of considerable amounts of CaO and H 2 O to the protolith, whereas other components such as SiO 2 , AF (Al 2 O 3 + Fe 2 O 3 ), and FM (FeO + MgO) were conserved. The Nomo rodingites are associated with reaction zones between serpentinite. A careful study on the compositional variations of diopside and chlorite in the rodingite, serpentinite, and the reaction zones between them showed a disequilibrium crystallization of diopside in the reaction zone. Diopside shows a serrated variation in composition across the reaction zone together with disequilibrium signature within grains (composite grain consisting of Fe-rich and Fe-poor parts). These features clearly indicate that diopside crystallized in a relatively short period compared to the metamorphism by irreversible reactions. Another conspicuous feature is that perovskite occurs in some reaction zones, whereas titanite is common in rodingites; this indicates that the reaction zone is poorer in SiO 2 . The tremolite veins are typically derived from the reaction zone into serpentinite; showing this is a good example of hydrofracturing associated with the formation of the reaction zone. All the reactions obtained by the SVD method that contribute to the formation of the reaction zones consumed CaO and evolved H 2 O, strongly suggesting that the hydrofracturing is caused by a rapid increment of fluid pressure during the progression of the reactions. The reactions consumed considerable amounts of SiO 2 in the reaction zone, which is consistent with the occurrence of perovskite, and the conservation of AF and FM components.

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Section: Tremolite Vein Formationmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Interplay of irreversible reactions and deformation: a case of hydrofracturing in the rodingite–serpentinite system

Nishiyama

Shiosaki

Mori

et al. 2017

Prog. in Earth and Planet. Sci.

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“…Sampling at different locations along the former detachment fault will allow us to evaluate records of fluid-rock interaction and metasomatism and test the hypothesis that exhumation faults serve as long-lived permeable pathways for hydrothermal flow that can feed moderate-to high-temperature hydrothermal vents (McCaig et al, 2007). In ultramafic/mafic systems, assemblages of talc-tremolite-chlorite form at >350°C (Boschi et al, 2006(Boschi et al, , 2008McCaig et al, 2010), typical of black smoker discharge zones, whereas serpentine-prehnite-hydrogarnet assemblages form at lower temperatures (Frost et al, 2008;Bach and Klein, 2009). Spatially constrained sampling of the Atlantis Massif detachment system gives us an opportunity to map these variations in metamorphic assemblages, which in combination with geochemical and isotopic studies will help constrain temperatures and fluid-rock ratios (Delacour et al, 2008d).…”

Section: Iodp Proceedingsmentioning

confidence: 99%

Expedition 357 summary

Früh-Green¹,

Orcutt²,

Green³

et al. 2017

Proceedings of the International Ocean Discovery Program

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Contents AbstractInternational Ocean Discovery Program (IODP) Expedition 357 successfully cored an east-west transect across the southern wall of Atlantis Massif on the western flank of the Mid-Atlantic Ridge (MAR) to study the links between serpentinization processes and microbial activity in the shallow subsurface of highly altered ultramafic and mafic sequences that have been uplifted to the seafloor along a major detachment fault zone. The primary goals of this expedition were to (1) examine the role of serpentinization in driving hydrothermal systems, sustaining microbial communities, and sequestering carbon; (2) characterize the tectonomagmatic processes that lead to lithospheric heterogeneities and detachment faulting; and (3) assess how abiotic and biotic processes change with variations in rock type and progressive exposure on the seafloor. To accomplish these objectives, we developed a coring and sampling strategy centered on the use of seabed drills-the first time that such systems have been used in the scientific ocean drilling programs. This technology was chosen in the hope of achieving high recovery of the carbonate cap sequences and intact contact and deformation relationships. The expedition plans also included several engineering developments to assess geochemical parameters during drilling; sample bottom water before, during, and after drilling; supply synthetic tracers during drilling for contamination assessment; acquire in situ electrical resistivity and magnetic susceptibility measurements for assessing fractures, fluid flow, and extent of serpentinization; and seal boreholes to provide opportunities for future experiments.Seventeen holes were drilled at nine sites across Atlantis Massif, with two sites on the eastern end of the southern wall (Sites M0068 and M0075), three sites in the central section of the southern wall north of the Lost City hydrothermal field (Sites M0069, M0072, and M0076), two sites on the western end (Sites M0071 and M0073), and two sites north of the southern wall in the direction of the central dome of the massif and Integrated Ocean Drilling Program Site U1309 (Sites M0070 and M0074). Use of seabed drills enabled collection of more than 57 m of core, with borehole penetration ranging from 1.30 to 16.44 meters below seafloor and core recoveries as high as 74.76% of total penetration. This high level of recovery of shallow mantle sequences is unprecedented in the history of ocean drilling. The cores recovered along the southern wall of Atlantis Massif have highly heterogeneous lithologies, types of alteration, and degrees of deformation. The ultramafic rocks are dominated by harzburgites with intervals of dunite and minor pyroxenite veins, as well as gabbroic rocks occurring as melt impregnations and veins, all of which provide information about early magmatic processes and the magmatic evolution in the southernmost portion of Atlantis Massif. Dolerite dikes and basaltic rocks represent the latest stage of magmatic activity. Overall, the ultramafic rocks recovered ...

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“…Alteration intensity is a function of time-integrated fluid flow, but also depends on the nature of the rocks. For instance, olivine gabbros and troctolites are more reactive than gabbro, because of the strong contrast in chemical potentials between olivine and plagioclase (e.g., Frost, Beard, McCaig, & Condliffe, 2008). Given the lithological heterogeneity of the basement at Site 1309, it is difficult to link the extent of alteration to the intensity of flow of seawater-derived fluids.…”

Section: Petrology and Alterationmentioning

confidence: 99%

“…Actinolitic hornblende and secondary plagioclase (±epidote) formed in the gabbros and oxide gabbros, whereas olivine-rich lithologies grew chloritetremolite(±talc) coronas along olivine-plagioclase grain boundaries. When the system had cooled to lower greenschist-facies temperatures, olivine underwent serpentinization, driving alteration of plagioclase to prehnite and hydrogrossular in olivine-rich lithologies (Frost et al, 2008). Chlorite-tremolite ± talc rocks are developed in the uppermost 25 m of basement, where strain localization took place along the detachment.…”

Section: Petrology and Alterationmentioning

confidence: 99%