Coesite and pure pyrope in high-grade blueschists of the Western Alps: a first record and some consequences

  title={Coesite and pure pyrope in high-grade blueschists of the Western Alps: a first record and some consequences},
  author={Christian Chopin},
  journal={Contributions to Mineralogy and Petrology},
  • C. Chopin
  • Published 1 May 1984
  • Geology
  • Contributions to Mineralogy and Petrology
A pyrope-quartzite originally described by Vialon (1966) from the Dora Maira massif was resampled and reinvestigated. Garnet (up to 25 cm in size), phengite, kyanite, talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz. The garnet is a pyrope-almandine solid solution with 90 to 98 mol % Mg end-member. It contains inclusions of coesite which has partially inverted to quartz, resulting in a typical radial cracking of the host garnet around the inclusions… 
First report of felsic whiteschist in the ultrahigh-pressure metamorphic belt of Dabie Shan, China
We report the first occurrence of a talc-kyanite assemblage typical of whiteschists in felsic ultrahigh-pressure metamorphic rocks of Dabie Shan, China. The whiteschist assemblage occurs in a
Microdiamond on Åreskutan confirms regional UHP metamorphism in the Seve Nappe Complex of the Scandinavian Caledonides
Metamorphic diamond in crustal rocks provides important information on the deep subduction of continental crust. Here, we present a new occurrence of diamond within the Seve Nappe Complex (SNC) of
Pohorje eclogites revisited: Evidence for ultrahigh-pressure metamorphic conditions
Kyanite eclogites from the Pohorje Mountains, Slovenia, are providing the first evidence of ultrahigh-pressure Eo-Alpine metamorphism in the Eastern Alps. Polycrystalline quartz inclusions in garnet,
Preservation of coesite in exhumed eclogite: insights from Raman mapping
Abundant coesite relics have been identified in a single thin section from a carbonate-bearing eclogite from the Saidenbach reservoir, Erzgebirge, German Variscides. The rock is only very slightly
The pyrope-coesite rocks and their country rocks at Parigi, Dora Maira Massif, Western Alps: detailed petrography, mineral chemistry and PT-path
Both the coarse- and fine-grained varieties of the partly coesite-bearing pyrope-quartzites, their interlayered jadeite-kyanite rocks, and the biotite-phengite gneiss country rock common to all of
The high-pressure to ultrahigh-pressure eclogite transition in the Western Gneiss Region, Norway
Mineralogical and textural criteria in high-pressure and ultrahigh-pressure metamorphic rocks in the Nordfjord-Stadlandet area of the Western Gneiss Region of Norway demonstrate in situ metamorphism
Phengite geobarometry based on the limiting assemblage with K-feldspar, phlogopite, and quartz
Following and extending the early work of Velde (1965) the pressure-temperature dependence of the compositions of potassic white micas coexisting with K-feldspar, quartz, and phlogopite in the model
Exsolution of Garnet and Clinopyroxene from High-Al Pyroxenes in Xugou Peridotite, Eastern China
Serpentinized massif peridotite in the Xugou, Su-Lu ultrahighpressure (UHP) metamorphic belt, eastern China, preserves texturally old (porphyroclastic) orthoand clinopyroxene with up to two
Paragonite eclogites from Dabie Shan, China: re-equilibration during exhumation?
Paragonite in textural equilibrium with garnet, omphacite and kyanite is found in two eclogites in the ultrahigh-pressure metamorphic terrane in Dabie Shan, China. Equilibrium reactions between


Three-stage metamorphic history of a whiteschist from Sar e Sang, Afghanistan, as part of a former evaporite deposit
Small volumes (in the cm3 range) of a talc-kyanite schist exhibit mosaic equilibria characterized by mineral assemblages conventionally attributed to vastly different pressure temperature conditions
40Ar-39Ar dating of high pressure metamorphic micas from the Gran Paradiso area (Western Alps): Evidence against the blocking temperature concept
The40Ar-39Ar method has been applied to high pressure (HP) white micas from the Gran Paradiso crystalline massif and from the overthrust Schistes Lustrés of its western slope. Preliminary
A unique magnesiochloritoid-bearing, high-pressure assemblage from the Monte Rosa, Western Alps: petrologic and 40Ar-39Ar radiometric study
AbstractA phengite-talc-chloritoid-chlorite-kyanite-quartz assemblage is reported from a nearly undeformed quartz-rich metapelite found in the Monte Rosa massif (Western Alps). Chloritoid contains up
The low‐high quartz and quartz‐coesite transition to 40 kbar between 600° and 1600°C and some reconnaissance data on the effect of NaAlO2 component on the low quartz‐coesite transition
The phase relations of low quartz, high quartz, and coesite were reinvestigated using extremely pure SiO2. The study was conducted with a piston-cylinder apparatus employing low-friction cells. While
Stability of pyrope-quartz in the system MgO-Al2O3-SiO2
Pyrope and quartz are stable with respect to aluminous enstatite and sillimanite at 1400 °C, 20 kb and at 1100 °C, 16 kb. The phase boundary limiting the coexistence of pyrope and quartz towards
Natural sodium phlogopite coexisting with potassium phlogopite and sodian aluminian talc in a metamorphic evaporite sequence from Derrag, Tell Atlas, Algeria
In its only natural occurrence known thus far sodium phlogopite is found in a dolomite containing large porphyroblasts of albite, three other magnesium phyllosilicates, dravite-uvite tourmaline,
The quartz‐coesite transition
The quartz–coesite transition curve has been determined over the temperature range 700° to 1700°C in the pressure range 20 to 40 kb. The equation for the curve is P = 19.5 + 0.0112T, where P is in