Subduction-related rodingites from East Othris, Greece: Mineral reactions and physicochemical conditions of formation

Koutsovitis, Petros; Magganas, Andreas; Pomonis, Panagiotis; Ntaflos, Theodoros

doi:10.1016/j.lithos.2013.04.009

Cited by 50 publications

(90 citation statements)

References 86 publications

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“…Rodingites have been reported in ophiolites from various tectonic settings, mostly from the seafloor and rarely from the subduction zones (Koutsovitis et al 2013). Honnorez and Kirst (1975) reported rodingites from the mid-Atlantic fracture zones together with serpentinized ultramafics and fresh and metamorphosed basalts and gabbros.…”

Section: Tremolite Vein Formationmentioning

confidence: 99%

“…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: 99%

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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“…Crustal contamination processes most likely did not take place due to the tholeiitic affinity of the studied mafic rocks. On the other hand, the types of hydrogarnet and vesuvianite crystals found within the rodingites are indicative for the involvement of subduction-related fluids during the formation of the rodingites (Koutsovitis et al, 2013). In addition, the chemistry of spinels in serpentinites (TiO2=0.14-0.25 wt.%, Al2O3=35.1-35.21 wt.%, Cr#=37.38-38.87), shows that their harzburgitic protoliths plausibly resemble back-arc basin peridotites (Kamenetsky et al, 2001).…”

Section: Geotectonic Settingmentioning

confidence: 98%

“…Li et al (2008) explains the formation of hydrogarnet with clinopyroxene and water participation in the reaction with plagioclase, whereas Cr-bearing hydrogarnets formation is related with Cr release from serpentinites (Li et al, 2004). The vesuvianite was most likely formed in very low CO2 conditions with water rich fluids, at 300-400 ο C (Li et al, 2004, Hatzipanagiotou et al, 2003, Li et al, 2008, Koutsovitis et al, 2013. Nevertheless, in a lower T stage and during the ophicalcite formation the chemistry of pore waters were enriched in CO2.…”

Section: Metamorphic and Metasomatic Processesmentioning

confidence: 98%

“…Li et al, 2004;Tsikouras et al, 2009;Koutsovitis et al, 2013 Most garnets are hydroandradites, while there are some small sized Cr-bearing hydrogarnets crystals (Cr2O3= 10.34wt.%). Li et al (2008) explains the formation of hydrogarnet with clinopyroxene and water participation in the reaction with plagioclase, whereas Cr-bearing hydrogarnets formation is related with Cr release from serpentinites (Li et al, 2004).…”

Section: Metamorphic and Metasomatic Processesmentioning

confidence: 99%

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Petrological, Mineralogical and Geochemical Data From the Eohellenic Ophiolitic Nappe in the Island of Skyros, Greece

Karkalis¹,

Magganas²,

Koutsovitis³

2017

geosociety

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Deep carbon cycle recorded by calcium‐silicate rocks (rodingites) in a subduction‐related ophiolite

Dai

Wang

Liu

et al. 2016

Geophysical Research Letters

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Carbon cycling in subduction zones remains poorly constrained due to the lack of relevant geological records. Here we report magnesium isotope data (δ26MgDSM3) from calcium‐silicate rocks (rodingites) from the Xigaze ophiolite, southern Tibet, which is thought to represent remnants of Neo‐Tethyan oceanic lithosphere. Behaviors of immobile trace elements in rodingites resemble those of their mafic dike protoliths, showing subduction‐related signatures. The majority of rodingites exhibits low δ26Mg values of −0.72‰ to −0.33‰ with a weighted average of −0.47 ± 0.11‰ (2 SD), significantly lighter than that of their protoliths (−0.31 ± 0.03‰). This difference likely reflects the interaction of the protolith with isotopically light carbonate fluids. Modeling indicates that this hypothesis requires the input of 5 to 15 wt % carbonates during rodingitization. Our study suggests that rodingite may represent a previously unrecognized reservoir of dissolved Ca from subducted carbonates.

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Subduction-related rodingites from East Othris, Greece: Mineral reactions and physicochemical conditions of formation

Cited by 50 publications

References 86 publications

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

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

Petrological, Mineralogical and Geochemical Data From the Eohellenic Ophiolitic Nappe in the Island of Skyros, Greece

Deep carbon cycle recorded by calcium‐silicate rocks (rodingites) in a subduction‐related ophiolite

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