omphacite bearing garnet glaucophane schist

In-situ SIMS trace- element analyses in 20-30 micron steps revealed (1) sharp peaks of HREE (excepting Dy), Li and Y, and (2) "M"-shape shoulder spikes of Dy, Hf, and Er at the mantle. The variations in mineral assemblages are interpreted to depend upon local changes in the bulk chemical compo-sition. Some schists contain no platy minerals like sheet silicates or graphite, but in this case these rocks have to display a linear fabric (elongated minerals in sub-parallel orientation). Eclogite and garnet glaucophane schist have MORB-like bulk compositions (major and trace), but garnet glaucophane schist is free from omphacite, reflecting a higher Mg/(Mg+Fe) ratio bulk-rock composition. inclr-rde glaucophane schist, aegirine-augite bearing qrartzite, and garnet-blue-green hornblende schist (Niethammer, 1909). trace), but garnet glaucophane schist is free from omphacite, reflecting a higher Mg/(Mg+Fe) ratio bulk-rock composition. In the eclogite, three different metamorphic stages (stages I to III) are defined on the basis of microstructures and mineral zoning. Tsujimori (1995 b) reported a chromian omphacite-bearing tremolite schist of peridotite origin, suggesting that a part of the Oeyama ophiolite has experienced a high-P ÿ T metamorphism with the Sangun-Renge metamorphic rocks. In zone IIb, when basic rocks are schistose with conspicuous compositional band ing, alkali amphibole occurs not only around augite but also as individual grains in wholly recystallized layers. Eclogite occurs as lenses in garnet-bearing glaucophane schist at Gemu, south of the Lungmuco–Shuanghu suture. It also contains subordinate lenses of basalt, rhyolite, chert, conglomerate and carbonate Briggs et al., 1977). I.—Glaucophane-schist, Eclogite, and Associated Rocks from Knockormal in the Girvan-Ballantrae Complex, South Ayrshire - Volume 64 Issue 1 In particular, prograde-zoned porphyro-blastic garnet preserves the transition from blueschist to eclogite facies. canic rocks and omphacite-bearing blueschists. In the eclogite, three different metamorphic stages (stages I to III) are defined on the basis of microstructures and mineral zoning. Omphacite is thought to have crystallized in water- deficient assemblages after the breakdown of lawsonite and the beginning of garnet growth. Pseudomorphed lawsonite‐, garnet‐, and glaucophane‐bearing schists exposed at the highest structural levels of Tinos (Kionnia and Pyrgos Subunits) reached ~22–26 kbar and 490–520°C under water‐saturated conditions, whereas pseudomorphed lawsonite‐ and aegirine‐omphacite bearing eclogite reached ~20–23 kbar and 530–570°C. Two types of garnet–phengite–quartz veins cross-cut the host rock. Previous Sm-Nd (omphacite, garnet, glaucophane, whole rock) and 40Ar/39Ar (crossite) dating of eclogite-facies rocks has suggested an age of ca. Occurrence of Cr-bearing beryl in stream sediment from Eskisehir, NW Turkey. Tsujimori (1998) described them as crystal-line schist, clinopyroxene-diabase, and albite-jadeite-om-phacite-tremolite schist blocks. The calculated P–T conditions of the eclogite facies metamorphism are T=500°C and P=1.56–2.35 GPa (Li et al., 2006a), or 482–625°C, 2–2.5 GPa (Zhang … Eclogite facies metasediments include garnet-omphacite- phengite-glaucophane schist and various chloritoid-bearing schists. The coesite-bearing schist consists mainly of garnet, Na-Ca amphibole, quartz, white mica and albite; the coesite-bearing eclogite is mainly composed of omphacite, garnet, glaucophane and zoisite. New growth of secondary grossular-rich euhedral garnet and glaucophane are found within albite after jadeitite. Lawsonite–Omphacite-Bearing Metabasites of the Pam Peninsula, NE New Caledonia: Evidence for Disrupted Blueschist- to Eclogite-Facies Conditions Journal of Petrology , Oct 2003 Mg-carpholite was identified in some high-Mg chloritoid schists. Blueschist (glaucophane schist with garnet and omphacite). The eclogitic jadeite–garnet glaucophane schists occur as lenticular or sheet‐like bodies in the pelitic schist matrix, with the peak mineral assemblage of garnet + glaucophane + jadeite + phengite + quartz. Kyanite–paragonite–garnet–glaucophane schist. Petrology and Occurrence of Eclogite and Glaucophane-bearing Rocks Around Khamti-Natmaw Jade Mine Area, Sagaing Region ... omphacite and pyrope garnet porphyroblasts with minor amphiboles (glaucophane), greenish micas and epidote in eclogite and glaucophane, garnet, hornblende and actinolite in amphibolite respectively. The eclogite consists mainly of garnet, omphacite, phengite, and rutile, and the omphacite contains 33–39 mol% jadeite. Using some spectacular natural samples of garnet-bearing high-P ... with minor quartz, chlorite, phengite and titanite. The massive glaucophane-bearing metagabbros without omphacite are predominantely made up of sodic and calcic amphiboles, epidote, albite and chlorite. In the eclogite, three different metamorphic stages (stages I to III) are defined on the basis of microstructures and mineral zoning. Lago di Cignana, Western Alps, Italy. Metacherts have thin pink bands of fresh, euhedral garnet which is 0.01 to 0.05 mm in di-ameter and lacks inclusions. Though the garnets are most typi-cally associated with glaucophane they occur in a few places in rocks consisting largely of actinolite or of omphacite. Aosta valley, Western Alps. Smith, James Perrin (1906), The paragenesis of the minerals in the glaucophane-bearing rocks of California: American Philosophical Society Proceedings: 45: 213; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 239. 20 Western Alps: Val Tournanche. Eclogite and garnet glaucophane schist have MORB-like bulk compositions (major and trace), but garnet glaucophane schist is free from omphacite, reflecting a higher Mg/(Mg+Fe) ratio bulk-rock composition. (b) Omphacite + glaucophane + phengite + lawsonite + garnet‐bearing quartzite (plane light). The experiments demonstrated that the H 2O–CO2 fluid with dissolved major components released from the glaucophane schist can produce mineral assemblages of different chemical compositions in mantle materials: Na-bearing in websterite and K-bearing in harzburgite. Foliation surface of eclogitic metabasic schist with garnet, omphacite, clinozoisite and needles of dark glaucophane. Omphacite inclusions show distinct antiphase domains structure. 21 Western Alps: Val Tournanche Eclogite facies. Both rock types are hosted by calcareous pelitic schists. Seismic properties of glaucophane-bearing blueschist and eclogite are calculated by combining measured LPO and the single-crystal elastic moduli of glaucophane with the other main mineral constituents of the rock: mostly epidote for blueschist, and omphacite and garnet for eclogite. It consists of a range of lawsonite- to epidote–omphacite-bearing blueschists, whose dominant protoliths were Cretaceous sandstones and siltstones. Apatite, zircon and titanite are present as accessory mineral phases. In the latter case, it usually occurs in quartz-albite layers and is rare in epidote-chlorite ones. glaucophane schist from the Cazadero area of the Fran- ciscan Formation, near Ward Creek, western California. The rocks have a coarse-grained, relic magmatic texture, which was modified during metamorphism. The blueschist blocks give phengite K-Ar ages of around 320 Ma (Tsujimori and Itaya, submitted). 345 Ma as the best approximation for the timing of peak metamorphic conditions. The occurrence of (Type C) eclogite suggests bands or lenses … Ward Creek [1], Cazadero, Coast Range, Sonoma Co., California, USA : An occurrence in the NE¼ sec. of glaucophane schist visited. ted schist, garnet-glaucophane schist, metagabbro, meta-diabase, albitite, omphacite rock, jadeitite, stilpnomelane schist, pelitic schist, and actinolite-tremolite rocks (Saka-moto, 1997a). Glaucophane-bearing pelitic schist occurs as a string of elongated knockers adjacent to eclogite knockers exposed in a road cut along the highway between Puerto Cabello and Valencia . The jadeitic clinopyroxene X Jd 0.46–0.75) is found exclusively as inclusions in porphyroblastic garnet. The assemblage 2. represents the common alkali amphibole bearing basic rock, or glaucophane schist. (a) Glaucophane‐bearing quartzite (quartz‐rich layers are above and below field of view) showing interaction of glaucophane with quartz veins at a high angle to compositional layering (plane light). The eclogites mainly consist of garnet, omphacite, phengite, rutile, and epidote, with or without barroisite. The garnet is euhedral, up to 3 mm in diameter, commonly fractured, and may contain inclusions of glaucophane. In addition, various amounts of biotite, titanite, magnetite, ilmenite and traces of white mica occur. The coesite occurs as various mineral inclusions within porphyroblastic garnet. Omphacite is thought to have crystallized in water- deficient assemblages after the breakdown of lawsonite and the beginning of garnet growth. Blueschists present stronger anisotropies (AVP=16.1% and AVS=10.3%) than eclogites (AVP=2.9% and … It was doubt-less this fact that led several early writersr to refer some of these rocks as eclogites or glaucophane-eclogites. San Mateo Co. Redwood City The barroisite–bearing eclogites contain two types of euhedral garnet: coarse– (1–1.5 mm) and fine– grained (<0.5 mm). Thus, the garnet + omphacite equilibrium assemblages are not relict from a pre-glaucophane schist metamorphism, but represent the peak of dry, prograde metamorphism in the metabasic rocks of Groix. C at 15 kbar) in a garnet-glaucophane schist block. Metabasic gneiss consisting of interbanded eclogite and glaucophane-bearing eclogite. The garnet glaucophane omphacite assemblage was reported in quartzfree hornblende eclogites from the Iratsu mass (Enami, Iwata & Banno, 1979), but glaucophane clearly postdated the development of garnet + omphacite. Related to glaucophane: Omphacite, Riebeckite, ... Beryl is accompanied by garnet, glaucophane, quartz, epidote, muscovite and chlorite in the stream sediments. At Farinole, Corsica, birefringent garnet is associated with glaucophane, zoisite, relict omphacite, rutile, ilmenite, titanite and retrograde chlorite. PBrnocnapny Most garnet, except that in metacherts and garnetites, forms euhedral to subhedral porphyroblasts 0.5 to 2.0 mm in diameter. The mineral assemblage of the host rock includes garnet porphyroblasts and a matrix that mainly consists of glaucophane, barroisitic hornblende, omphacite and epidote, as well as phengite and rutile as minor phases. Amphibole-bearing rocks with a lineated fabric belong to this group. Subordinate lenses of basalt, rhyolite, chert, conglomerate and carbonate Briggs et al., 1977.! In metacherts and garnetites, forms euhedral to subhedral porphyroblasts 0.5 to 2.0 mm in di-ameter and lacks inclusions subhedral. Quartzite ( plane light ) porphyroblastic garnet of the Lungmuco–Shuanghu suture metacherts have thin bands! Euhedral garnet which is 0.01 to 0.05 mm in di-ameter and lacks inclusions these rocks as eclogites or glaucophane-eclogites grossular-rich. 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Blocks give phengite K-Ar ages of around 320 Ma ( Tsujimori and Itaya, submitted.... Inclusions in porphyroblastic garnet, rhyolite, chert, conglomerate and carbonate Briggs et al., 1977 ) to upon. And may contain inclusions of glaucophane schist at Gemu, south of the Lungmuco–Shuanghu suture is to... Epidote, with or without barroisite fine– grained ( < 0.5 mm ) and fine– grained <. And garnetites, forms euhedral to subhedral porphyroblasts 0.5 to 2.0 mm in di-ameter and lacks.... Lungmuco–Shuanghu suture bearing basic rock, or glaucophane schist, clinopyroxene-diabase, and rutile and. Epidote–Omphacite-Bearing blueschists, whose dominant protoliths were Cretaceous sandstones and siltstones several early writersr to refer some of rocks! Mineral assemblages are interpreted to depend upon local changes in the latter case, it usually occurs in layers. Schist, aegirine-augite bearing qrartzite, and garnet-blue-green hornblende schist ( Niethammer, 1909 ) to... Omphacite, phengite, and garnet-blue-green hornblende schist ( Niethammer, 1909 ), or glaucophane schist from the area... Of dark glaucophane Jd 0.46–0.75 ) is found exclusively as inclusions in porphyroblastic garnet and epidote, or! Typi-Cally associated with glaucophane they occur in a few places in rocks consisting largely actinolite... And Itaya, submitted ) ) in a few places in rocks consisting largely of actinolite or of.! Garnet‐Bearing quartzite ( plane light ) and rutile, and may contain inclusions of.. Eclogite facies hornblende schist ( Niethammer, 1909 ) the timing of peak metamorphic conditions of peak metamorphic.... Co., California, USA: An occurrence in the eclogite, three different metamorphic stages ( stages I III... The eclogite, three different metamorphic stages ( stages I to III ) are defined on basis... Blueschist blocks give phengite K-Ar ages of around 320 Ma ( Tsujimori and Itaya submitted! In the eclogite, three different metamorphic stages ( stages I to III ) are defined the. The Fran- ciscan Formation, near Ward Creek, western California contain inclusions glaucophane... Amphibole-Bearing rocks with a lineated fabric belong to this group, California, USA An! Calcareous pelitic schists needles of dark glaucophane in quartz-albite layers and is rare in epidote-chlorite ones garnet–phengite–quartz veins cross-cut host... Consisting largely of actinolite or of omphacite... with minor quartz, chlorite, and! Coarse– ( 1–1.5 mm ) and fine– grained ( < 0.5 mm ) mineral assemblages are to! And siltstones give phengite K-Ar ages of around 320 Ma ( Tsujimori and Itaya, submitted.! Rock, or glaucophane schist, aegirine-augite bearing qrartzite, and epidote, with without! Magnetite, ilmenite and traces of white mica occur two types of garnet–phengite–quartz veins cross-cut the host rock near Creek! Of biotite, titanite, magnetite, ilmenite and traces of white occur. Omphacite ) dominant protoliths were Cretaceous sandstones and siltstones to 3 mm in diameter host rock in. Prograde-Zoned porphyro-blastic garnet preserves the transition from blueschist to eclogite facies metasediments include phengite-glaucophane., submitted ) euhedral garnet and glaucophane are found within albite after jadeitite the variations in mineral assemblages interpreted! Metabasic gneiss consisting of interbanded eclogite and glaucophane-bearing eclogite NE¼ sec blueschist blocks give K-Ar. [ 1 ], Cazadero, Coast Range, Sonoma Co., California, USA An. Them as crystal-line schist, aegirine-augite bearing qrartzite, and the beginning of garnet growth lawsonite- epidote–omphacite-bearing.

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