Kyanite Research Articles

Data for: Discovery of kyanite in typical cordierite/sillimanite-bearing low- to medium-pressure pelitic granulites: constraint on Paleoproterozoic plate tectonics

Data for: Discovery of kyanite in typical cordierite/sillimanite-bearing low- to medium-pressure pelitic granulites: constraint on Paleoproterozoic plate tectonics

Geothermobarometry of Al-silicate-bearing migmatites from the Variscan chain of NE Sardinia, Italy: a P-T pseudosection approach

This paper investigates Al-silicate-bearing migmatite from NE Sardinia by using the P-T pseudosection approach with the aim to determine the P-T conditions of partial melting and those of melt crystallization. P-T pseudosections were calculated in the NCKFMASH system within the P-T range 500-800 °C, 0.1-1.5 GPa by using the average compositions of metapelitic greywacke, average mesosome and average trondhjemitic leucosome, respectively. The P-T pseudosections calculated for the average metapelitic greywacke and for the average mesosome, contoured for melt volume %, Si/Al and Na/K molar ratios in melt point to P-T conditions ~ 700-740 °C, 1.1-1.3 GPa which are indicative of partial melting. The P-T pseudosection calculated for the average composition of trondhjemitic leucosomes, contoured for kyanite and biotite modal content and for X Mg ratio in biotite indicates P-T conditions of 660-730 °C, 0.75-0.90 GPa for the crystallization of the melt. The comparison between the Na/K and Si/Al ratios in leucosomes, and the same ratios modeled for the anatectic melt by an haplogranitic melt model is thus a powerful tool for the reconstruction of P-T conditions of partial melting also in pelitic rocks, provided that leucosomes represent pure melts and are not contaminated by restitic phases or feldspar cumulates.

DIFFERENT TECTONO-THERMAL EVOLUTIONARY PATHS IN ECLOGITIC ROCKS FROM THE AXIAL ZONE OF THE VARISCAN CHAIN IN SARDINIA (ITALY) COMPARED WITH THE LIGURIAN ALPS

The inner zone of the Sardinia Variscan segment consists of two metamorphic complexes: I) A polymetamorphic Migmatite Complex, with migmatites showing polyphase anatectic processes, in the presence of kyanite or sillimanite. The Migmatite complex preserved decametric lenses of eclogite relicts (eclogites A) affected by high T, high- to intermediate P recrystallization under granulite facies conditions The decompressional garnet + Ca-clinopyroxene + amphibole ± orthopyroxene-bearing assemblages developed in granoblastic textures generally in no stress conditions. In most cases, only symplectite textures provide evidence for the eclogitic event. II) A medium grade, mostly metapelitic complex consisting of Grt, Ky, Stau-bearing micaschists and paragneisses includes quartzites and garnet-bearing amphibolite boudins with N-MORB chemical affinity. Relicts of eclogite assemblages were locally found in the metabasite (eclogites B). In eclogites A, the geothermobarometric parameters yield temperatures in the range 690°-760°C for minimum pressure A1.3 GPa. Pyroxene compositions accord with temperatures in excess of 700°C. In eclogites B, the thermometric calibrations provide temperatures in the range 610°-700°C for pressures 1.3-1.5 GPa, based on the jadeite content. The temperatures are consistent with the biotite+muscovite+garnet+kyanite+staurolite assemblage in the host paragneisses, and with lack of anatectic processes. The age of 457±2 Ma, obtained by U/Pb dating on one sample of Type A eclogite is interpreted as a minimum estimate for the magmatism of the eclogite protolith. A second zircon population defined an age of 403±4 Ma interpreted as dating the zircon crystallization during the high-grade event. The relationships between Types A and B eclogites, and their bearing on the regional framework (Sardinia, Ligurian Alps) are discussed.

Kyanite from the Eastern Iratsu metagabbro mass in the Sambagawa metamorphic belt, central Shikoku, Japan

三波川帯は高圧型変成帯であるが藍晶石の産出は比較的まれであり, 四国中央部の高変成度部に分布するいくつかのテクトニック・ブロックから報告されているのみである(第1図). 今回, 四国中央部三波川変成帯の“いちのまつこ谷”上流の五良津東部岩体中から長径約16cmに達する藍晶石の巨晶が発見された(第2～5図). 五良津東部岩体は, 原岩が層状はんれい岩であり, グラニュライト相→高温のエクロジャイト相→藍閃石片岩相→低温のエクロジャイト相という変成履歴を経た後, 現位置にテクトニック・ブロックとしてもたらされ, 緑れん石角閃岩相の変成作用(三波川変成作用)を受けたと考えられている(Takasu, 1989). 藍晶石の巨晶は, 緑れん石角閃岩相の鉱物組合せよりなる岩石の片理面と斜交するすべり面上に形成されている. このことから, 藍晶石は五良津東部岩体が緑れん石角閃岩相の変成作用が進行していた三波川変成帯の現位置ヘテクトニック・ブロックとしてもたらされる前後の時期に形成されたといえる.

The high-pressure granulites of the Bacariza Formation: an earlier stage in the exhumation of other eclogites in the Cabo Ortegal Complex (Hecynian belt, NW Spain)

This paper deals with the metamorphic evolution of the Bacariza Fm that outcrops in the two uppermost structural units of the Cabo Ortegal Complex (NW Iberian Massif). This formation includes ultramafic and mafic granulites, garnet amphibolites and garnet trondhjemitic gneisses. Although mineral associations characteristic of high pressure granulites predominate in the least retrogressed of these rocks, the presence of relic kyanite along with the fact that plagioclase only appears in symplectitic textures resulting from de-jadeitization of pyroxenes point to an earlier eclogite facies metamorphism. Thermobarometric estimations indicate higher P-T conditions for the rocks in the uppermost structural unit.

Reaction Sintering of Kyanite and Alumina to Form Mullite Composites

Submicron alumina was selected as the matrix to which the mineral kyanite was added to produce an aqueous alumina-kyanite suspension from which a green body could subsequently be cast and reaction-sintered. Naturally-occurring kyanite thermally decomposes above 1400°C to form mullite and free silica. By sintering the mineral in an alumina-rich matrix the silica subsequently reacts to form additional mullite, thereby forming an alumina-mullite composite. Characterisation techniques including sedimentation and rheology were employed to optimise aqueous processing conditions. The most stable dispersion pH for alumina-kyanite suspensions containing up to 20 vol% kyanite was 3.5. Composite green bodies were slip cast and sintered, and the products evaluated using X-ray diffraction, electron probe microanalysis, hardness, toughness and dielectric properties. The resulting 78% alumina-22% mullite material formed a fine-grained structure (∼1μ) with 14% decrease in shrinkage, 11% reduction in linear expansion coefficient and a 34% decrease in dielectric constant relative to alumina. © 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reservedRésuméOn a choisi l'alumine, ayant moins qu'un micromètre, comme matrice à laquelle on a ajouté le mineral cyanite pour la production d'une suspension aqueuse d'alumine-cyanite. À partir de cette suspension, on moule un corps vert et on le fritte par réaction. La cyanite naturelle se d é compose thermiquement, au-dessus de 1400°C, en mullite et en silice libre. En frittant le minéral dans une matrice riche en alumine, la silice reagit ensuite pour former de la mullite additionnelle, formant ainsi un compose d'alumine-mullite. On a employé des techniques de caractemploy érisation incluant la sédimentation et la rhéologie pour l'optimisation des conditions aqueuses de mise en forme. Le pH de dispersion le plus stable des suspensions d'alumine-cyanite contenant jusqu à 20% en volume de cyanite était de 3.5. Les corps verts composes ont été coules en barbotine puis frittes. On a utilise la diffraction des rayons x, la microanalyse par sonde électronique, la durete, la tenacite et les proprietes dielectriques pour evaluer les produits. Le materiel resultant, 78% alumine-22% mullite, formait une structure à grains fins (∼1 μ), avec une diminution de 14% du rétrecissement, une réduction de 11% du coefficient d'expansion linéaire et une diminution de 34% de la constante diélectrique relative à l'alumine. © 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved

Study and implication of the high-pressure felsic granulite in the Qinling complex of East Qinling

There is a typical assemblage of garnet + kyanite + microperthite + quartz + rutile in high-pressure (HP) felsic granulite of Qinling complex in Songshugou area. East Qinling. The HP granulite was formed at 800 -900℃ and 1.3 -1.6GPa and has experienced two stages of retrograde metamorphism at 600- 650 ℃, 0.8-1.0GPa and 500-600℃, 0.3-0.6GPa, forming two retrograde metamorphic assemblages of margarite + plagiodase (PlI)+quartz and sillimanite + biotite + plagioclase(PlII) + microdine+quartz, respectively. They construct a two-stage clockwise P-T path which shows down-pressure cooling in both early and late stage.

HRTEM-study of stacking faults and polytypism in kyanite

HRTEM-study of stacking faults and polytypism in kyanite

Metamoprhism of hydrotermally altered rocks in the volcanogenic massive sulfide deposits: the Palmeirópolis, Brazil, example

The PALMEIROPOLIS Cu-Zn (Pb) volcanogenic massive sulfide deposit, Brazil, consists of three ore bodies enclosed by hydrothermal alteration zones. The ore bodies and the alteration zones were metamorphosed under amphibolite fades conditions. The Palmeirdpolis alteration zones are characterized by a great diversity of bulk rock composition that originated a wide variety of low variance mineral assemblages. These assemblages are composed of orthoamphiboles (anthophyllite and gedrite), hornblende, biotite, garnet, staurolite, sillimanite, gahnite and, rarer, cordierite. Based on analyses of mineral chemistry aad mineral assemblages, temperatures are estimated to have been 550 - 625°C and pressures 2 - 5.5 kbar. The temperature of metamorphism that prevailed at the Palmeirdpolis deposit is comparable to other amphibolite fades massive sulfide deposits, such as Geco and Linda, Canada; Falun, Sweden; and Bleikvassli, Norway. The mineralogy of the alteration zones is similar in all these deposits even though they were metamorphosed at different pressure conditions, reflected by the crystallization of one of Al2 SiO5 phase (andalusite, sillimanite or kyanite).

Notes on the inclusions in a greyish kyanite

Notes on the inclusions in a greyish kyanite

Chromium-bearing kyanite from Mozambique

Chromium-bearing kyanite from Mozambique

EPR of Fe3+ in andalusite and kyanite at V-band and the pair spectra

EPR spectra of Fe3+ in andalusite and kyanite (both having formula Al2SiO5) are remeasured at bands which included 60 GHz. Results, besides the unusually large b and other spin-Hamiltonian parameters, include also the (true) g-factors. The spectra due to Fe3+Fe3+ pairs are identified in andalusite and analysed. EPR-Spektren von Fe3+ in Andalusit and Kyanit (beide mit der Formel Al2SiO5) werden erneut bei Frequenzen gemessen, die 60 GHz einschliesen. Als Ergebnis werden, neben dem ungewohnlich grosen b-Wert und anderen Spin-Hamiltonparametern, die (wahren) g-Faktoren erhalten. Durch Fe3+Fe3+-Paare hervorgerufene Spektren werden in Andalusit identifiziert und analysiert.

The aluminium Kβ-band structure of andalusite, sillimanite and kyanite

The aluminium Kβ-band structure of andalusite, sillimanite and kyanite

Cyanite Occurrence in Massachusetts

Cyanite Occurrence in Massachusetts

Kyanites in Druses in Kyanite-Quartz-Veins from Saiho-ri in the Fukushinzan District, Korea

朝鮮江原道平康群縣内面細浦里の雲母片岩にともなう藍晶石・石英脈, 殊にその中にある晶洞を記載した。藍晶石・石英脈はこれまでに世界の多くの地方から記載されているが, そのなかに晶洞が報告されたことはないようである。この晶洞は藍晶石の生成條件も問題に關して,意義をもつている。

A Note on "Stress-Minerals"

It is the purpose of the present paper to criticize the hypothesis of stress-minerals proposed by Alfred Harker, to make it clear that it is unneccessary to use such a concept, and to attempt the explanation of metamorphic rock characteristics by regarding temperature, pressuer (hydrostatic), and concentration of components as the only essential factors controlling metamorphism., Petrological and physico-chemical considerations do not show the necessity of Harker's hypothesis of stress-minerals, in the present writers' view., All the minerals which Harker ranked in the category of stress-minerals, seem to be capable of formed under some conditions without stress., They may be divided into two groups, according to the condition of generation., The first group including kyanite, staurolite, almandine, and chloritoids, may be formed only under very high pressures., They all have very high density., They occur sometimes in ignenous rocks, pegmatitic veins, hornfelses, etc., which do not show any special evidence of stress., The second group, containing chlorite, muscovite, epidote, etc., may be formed only at low temperatures., This is shown by the fact that they are hydrothermal or deuteric minerals, the temperature of whose formation is much lower than that of ordinary pyrogenetic or thermal-metamorphic minerals., Harker's stress-minerals seem to be such as are formed only under conditions of lower temperatures and perhaps higher pressures than in ordinary hornfelses., Each of various kinds of metamorphism, such as thermal, regional, etc., takes place under a certain definite condition of temperature and pressure., The kinds of metamorphic minerals developed are determined by the prevailing temperature and pressure as well as by the chemical composition of the metamorphosed rocks., Therefore, each kind of metamorphism is distinguished from the others by a characteristic set of metamorphic minerals.,

RATE OF DECOMPOSITION OF KYANITE AT VARIOUS TEMPERATURES*

The rate at which North Carolina kyanite of various grain sizes decomposes into mullite and glass in the range 1350° to 1600 °C. is given. Kyanite from other sources is also discussed.

The origin of cyanite; discussion

The origin of cyanite; discussion

Origin of cyanite; reply

Origin of cyanite; reply

Kyanite in Virginia. Anna I. Jonas , Joel H. Watkins

Previous articleNext article No AccessReviewsKyanite in Virginia. Anna I. Jonas , Joel H. Watkins E. S. B.E. S. B. Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 42, Number 5Jul. - Aug., 1934 Article DOIhttps://doi.org/10.1086/624210 PDF download Crossref reports no articles citing this article.