Eclogites and Eclogites: Their Differences and Similarities

Coleman, Robert G.; Lee, Donald E.; Beatty, L. B.; Brannock, Walter Wallace

doi:10.1130/0016-7606(1965)76[483:eaetda]2.0.co;2

Cited by 636 publications

(211 citation statements)

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“…Garnets from the Çetmi region are also almandine-grossular rich with Al 61-73 , Grs 18-24 , Prp 1-17 , Sps 0.9-12 mol%. Garnet composition of these eclogites fits the C-type of Coleman, Lee, Beatty, and Brannock (1965) classification (Figure 6(a)), typical of eclogites occurring in subduction complexes. These C-type eclogites are commonly associated with blueschist.…”

Section: Mineral Chemistry 71 Garnetsupporting

confidence: 58%

Petrology and geochemistry of eclogites from the Biga Peninsula, Northwest Turkey

et al. 2012

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The Biga Peninsula in northwest Turkey contains high-pressure metabasic eclogite that occur in two localities; as lenses within a 2 km long, 500 m thick quartz-phengite schist slice that is in turn found in the greenschist-facies metasedimentary rocks of the Çamlıca metamorphics, in Çamlıca area, and in two north-south elongated eclogites occurring as a tectonic slice between Kazdağ Massif and Çetmi Group, in Çetmi area. The P-T conditions under which these two exposures of eclogites formed are important to quantify the tectonic processes of subduction, exhumation and emplacement that highpressure rocks of the Biga Peninsula record. New geochemical data suggest that both protoliths were N-type MORB basalt with high TiO 2 and K 2 O-Na 2 O content and Nb/Y ratios. Most eclogite samples have tholeiitic signatures volcanic arc settings. ∑REE abundances range from 47.55 to 107.4 ppm. Europium anomalies are slightly variable (Eu/Eu * = 0.9-1.1) and trace element contents are similar to typical MORB based on tectonic discrimination diagrams. All eclogite protoliths were probably derived from depleted mantle source, modified by fluids within the subduction zone. The high-P mineral assemblage in eclogites from both regions is omphacite + garnet + glaucophane + phengite + epidote + zoisite + quartz. The inclusions in garnet are glaucophane, quartz, phengite, Ca-amphibole and rutile. P-T conditions are similar to each other and constrained at 550-700°C and 16-24 kbar. Geochemical data and mineral chemistry indicate that the eclogites in the Biga Peninsula represent oceanic crust processed at significant depths (50-80 km) within the subduction channel and were juxtaposed with greenschist facies as a tectonic slice in the accretionary complex at higher structural levels.

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Section: Mineral Chemistry 71 Garnetsupporting

confidence: 58%

Petrology and geochemistry of eclogites from the Biga Peninsula, Northwest Turkey

et al. 2012

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“…3a) reflecting their relatively higher bulk-rock Ca composition. Garnets plot in the field of group C as defined by Coleman et al (1965) (Fig. 3a).…”

Section: Garnetmentioning

confidence: 99%

Eclogite facies relics in metabasites from the Sierra de Guadarrama (Spanish Central System): P-T estimations and implications for the Hercynian evolution

Barbero

Villaseca

2000

Mineral. mag.

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Relics of HP-MT eclogitic assemblages related to the first metamorphic stage of the Hercynian nrr"TP'TlU in the Sierra de Guadarrama (Spanish Central SCS) are as boudins of IJi'-' -'JJLU-V metabasites enclosed by felsicTextures indicate a iHUUU--'H('Ll<.'-' metarnolrph the MT eclogite facies (as deduced from the presence of and rutile included in garnet) and through medium to Iow pressure and retrograde amphibolite-greenschist facies. Thermobarometric calculations in the ecIogitic yield pressures of -14 kbar for ternp,eraLtUlres in the range 725-775°C.for the indicates a Sl.ll� nlltlC,;m( drop in (P < 10 kbar) for similar temperatures vary from gab bro to lellCC)tonaJlltc:s showing the typical Fe enrichment of the tholeiitic series. Chemical characteristics indicate a derivation from low-pressure of tholeii tic melts more enriched than typical MORB compositions. Their original location far from continental margins as evidenced by the absence of ophiolitic material in the area and their association with platform sediments suggests that eclogitization was related to intracontinental crustal subduction and The P-T conditions estimated in the metabasites for the first metamorphic stage are similar to ones deduced for the metasediments and suggest that the Hercynian crust could have reached a thickness of -70-80 km, which is more than the double the present thickness.

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“…Garnet is typical of type C eclogite, which is defined by Coleman et al (1965) as crustally derived, relatively low-temperature eclogite. Garnet displays both prograde and sector zoning (Fig.…”

Section: Garnetmentioning

confidence: 99%

Geologic Setting of Eclogite-facies Assemblages in the St. Cyr Klippe, Yukon–Tanana Terrane, Yukon, Canada

Petrie

Gilotti

McClelland

et al. 2015

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SUMMARYThe St. Cyr area near Quiet Lake hosts well-preserved to variably retrogressed eclogite found as sub-metre to hundreds of metre-long lenses within quartzofeldspathic schist in southcentral Yukon, Canada. The St. Cyr klippe consists of structurally imbricated, polydeformed and polymetamorphosed units of continental arc crust and ultramafic-mafic rocks. Eclogite-bearing quartzofeldspathic schist forms thrust slices in a 30 km long by 6 km wide, northwest-striking outcrop belt. The schist unit comprises metasedimentary and felsic intrusive rocks that are intercalated on the metre to tens of metres scale. Ultramafic rocks, serpentinite and associated greenschist-facies metagabbro form imbricated tectonic slices within the eclogite-bearing quartzofeldspathic unit, which led to a previously held hypothesis that eclogite was exhumed within a tectonic mélange. The presence of phengite and Permian zircon crystallized under eclogite-facies metamorphic conditions in the quartzofeldspathic host rocks indicate that the eclogite was metamorphosed in situ together with the schist as a coherent unit that was part of the continental arc crust of the Yukon-Tanana terrane, rather than a mélange associated with the subduction of oceanic crust of the Slide Mountain terrane. Petrological, geochemical, geochronological and structural similarities link St. Cyr eclogite to other high-pressure localities within Yukon, indicating the high-pressure assemblages form a larger lithotectonic unit within the Yukon-Tanana terrane. Geoscience Canada, v. 42, http://www.dx

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Eclogites and Eclogites: Their Differences and Similarities

Cited by 636 publications

References 0 publications

Petrology and geochemistry of eclogites from the Biga Peninsula, Northwest Turkey

Petrology and geochemistry of eclogites from the Biga Peninsula, Northwest Turkey

Eclogite facies relics in metabasites from the Sierra de Guadarrama (Spanish Central System): P-T estimations and implications for the Hercynian evolution

Geologic Setting of Eclogite-facies Assemblages in the St. Cyr Klippe, Yukon–Tanana Terrane, Yukon, Canada

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