Staurolite|Bearing Gneiss and Re|Examination of Metamorphic

Total Page:16

File Type:pdf, Size:1020Kb

Staurolite|Bearing Gneiss and Re|Examination of Metamorphic Staurolite-bearingJournal gneiss of Mineralogical and re-examination and Petrological of metamorphic Sciences, zonal Volume mapping 99 ,of page the Higo1─ 18, metamorphic2004 terrane 1 Staurolite-bearing gneiss and re-examination of metamorphic zonal mapping of the Higo metamorphic terrane in the Kosa area, central Kyushu, Japan * * ** Kenshi MAKI , Yoshihisa ISHIZAKA and Tadao NISHIYAMA *Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan **Department of Earth Sciences, Faculty of Science, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan This paper describes the finding of staurolite-bearing gneiss from the Higo metamorphic terrane and proposes new mineral zones in the Kosa area, Kumamoto Prefecture. Previous mineral zones of the Higo metamorphic terrane proposed by Obata et al. (1994) consist of five zones: Zone A characterized by Chl + Ms, Zone B by Bt + Ms + And, Zone C by Kfs + Sil + Bt, Zone D by Grt + Crd + Bt, and Zone E by Opx in metapelites. They identified three zones from B to D in the Kosa area. However, we found that sillimanite appears together with Grt + Crd, hence this paper shows that Zone C is absent in the Kosa area. New finding of Opx in the southern- most part of the area made it possible to define three mineral zones; Bt zone, Grt-Crd zone, and Opx zone, in the order of increasing grade from north to south in the Kosa area. Analysis of staurolite-bearing assemblage in a KFMASH system together with textural evidence reveals that the following reactions occurred in the stauro- - lite bearing gneiss in the excess of Kfs, Qtz and H2O: [Sil] Str + Bt = Grt + Crd [Bt] Str = Grt + Crd + Sil Chemographic analysis of these reactions together with Grt-Bt geothermometers shows the metamorphic condition of P = 200 MPa and T = 600-620°C, which is much lower in pressure than that estimated by Osanai et al. (1996) in the Toyono area, about 10 km west of Kosa. Introduction phic rocks into three metamorphic zones with increasing grade from north to south based on mineralogy of metaba- The Higo terrane is located in the western part of central sites and axial color of hornblende. Nagakawa (1991) and Kyushu (Fig. 1) and is bordered to the south by the Usuki - Obata et al. (1994) presented a new zonal mapping, which Yatsushiro tectonic line. The terrane consists of Mano- defined five mineral zones based on pelitic mineral assem- tani metamorphic rocks, Higo metamorphic rocks, Higo blages (Fig. 1). The metamorphism was first considered plutonic rocks and Ryuhozan metamorphic rocks from to be of the andalusite-sillimanite type (Yamamoto, 1962; north to south, forming a narrow belt trending east-west Tsuji, 1967). However, several lines of evidence have (nomenclature of the rock units after Yamamoto, 1962). come out since then, showing the possibility of a medium The Manotani metamorphic rocks gradually change to P type metamorphism. Karakida and Yamamoto (1982) the Higo metamorphic rocks with no faults between them reported the occurrence of garnet amphibolite from the (Okamoto et al., 1989; Karakida et al., 1989), and they Higo metamorphic rocks in the Ogawa area, about 17 represent the lower grade part of the Higo metamorphic km west of Kosa, although it is not in itself a conclusive rocks (Karakida et al., 1989). In this paper, we discuss evidence of medium P. Osanai et al. (1995) reported the the nature of the metamorphism of the Higo metamorphic occurrence of staurolite inclusion in garnet porphyloblasts rocks. from the Toyono area, about 10 km west of Kosa. Kano Yamamoto (1962) first divided the Higo metamor- and Uruno (1995) reported the occurrence of kyanite from river sands in the Kosa area. These lines of evidence sug- K. Maki, [email protected]-u.ac.jp Corresponding author gest that the Higo metamorphic rocks may have suffered T. Nishiyama, [email protected]-u.ac.jp a medium P type metamorphism. Furthermore, Karakida 2 K. Maki, Y. Ishizaka and T. Nishiyama Staurolite-bearing gneiss and re-examination of metamorphic zonal mapping of the Higo metamorphic terrane 3 Figure 1. Metamorphic zonal mapping of the Higo metamorphic belt reprinted from Obata et al. (1994) with permission from Elsevier, Copy- right (1994). The study area is indicated by an envelope. et al. (1989) found occurrences of lawsonite and crossite microstructures from a garnet -biotite -cordierite gneiss from the Manotani metamorphic rocks, suggesting a high in Zone E (Obata et al., 1994) and interpreted the cores P / T metamorphism as a precursor of the low to medium and the rims as detrital zircons and recrystallized zircons, P type metamorphism. We therefore need further petro- respectively. They dated cores to be 2155-184 Ma U-Pb logical studies to clarify the nature of the metamorphism. ages and rims to be 116.5 ± 18.7 Ma U-Pb age by means The age of the Higo metamorphic and plutonic rocks of a SHRIMP. They interpreted that the Higo metamor- has been under debate. Nakajima (1995) dated biotites phic rocks reached the peak of metamorphism at 116.5 ± from both the Shiraishino granodiorite and the Higo meta- 18.7 Ma. This age is comparable with those of the Higo morphic rocks to be 100 -106 Ma by K -Ar dating. He plutonic rocks with a SHRIMP (Sakashima et al., 2003). also determined the same ages for these rocks by Rb-Sr This paper describes the finding of staurolite from whole rock isochron method. Osanai et al. (1996; 1998; the Kosa area and presents the result of a re -examina- 2001) dated zircons from garnet-cordierite-biotite tonal- tion of the metamorphic zonal mapping in the Kosa area ite to be about 250 Ma for the core by SHRIMP method based on new occurrences of orthopyroxene and garnet + and reported a similar age for garnet-orthopyroxene-bio- cordierite from metapelites. This paper also discusses the tite tonalite using a Rb -Sr whole rock isochron method. pressure-temperature condition of the metamorphism by They interpreted that the Higo metamorphic rocks reached considering breakdown reactions of staurolite and garnet- the peak of metamorphism at about 250 Ma and were then biotite geothermometers. locally re -heated by the intrusion of the Shiraishino granodiorite at about 120 Ma (the age after Kamei et al., Geological setting 1997). They stated that the age of 100 Ma reported by Nakajima (1995) represents the cooling age of the Shi- The Higo and the Manotani metamorphic rocks occur in raishino granodiorite and the Higo metamorphic rocks. the central part of the Kosa area, which is in fault contact On the contrary, Nagakawa et al. (1997) obtained very with the Mizukoshi Formation (Paleozoic) in northwest similar age (103-108 Ma) for biotite from Zones B to E (Fig. 2). A thin body of serpentinite occurs along the of Obata et al. (1994) using K -Ar dating. They stated fault. In the south of the Kosa area, the Shiraishino that this fact cannot be explained by the local re-heating granodiorite intrudes almost concordantly into the Higo suggested by Osanai et al. (1993) and concluded that the metamorphic rocks trending nearly east -west. The grano- peak of the Higo metamorphism was at about 105 Ma. diorite includes a pelitic xenolith of about 50 m in diam- Sakashima et al. (2003) found zircons with core -rim eter (Fig. 2). The metamorphic and plutonic complex is 2 K. Maki, Y. Ishizaka and T. Nishiyama Staurolite-bearing gneiss and re-examination of metamorphic zonal mapping of the Higo metamorphic terrane 3 Figure 2. Geologic map of the Higo terrane in the Kosa area. 4 K. Maki, Y. Ishizaka and T. Nishiyama Staurolite-bearing gneiss and re-examination of metamorphic zonal mapping of the Higo metamorphic terrane 5 Figure 3. Revised metamorphic zonal mapping of the Higo terrane in the Kosa area. Mineral abbreviations are after Kretz (1983). 4 K. Maki, Y. Ishizaka and T. Nishiyama Staurolite-bearing gneiss and re-examination of metamorphic zonal mapping of the Higo metamorphic terrane 5 locally covered by the Aso -4 pyroclastic flow deposits an accelerating voltage of 20 kV, a beam current of 0.6 nA (Quaternary) along the Midorikawa river and its branches. and a beam width of 2 μm. The Higo metamorphic rocks in the Kosa area consist mainly of psammitic -pelitic gneisses with small Biotite zone amounts of metabasites (amphibolites), marble and gneisses intermediate between pelitic and basic in com- The biotite zone is characterized by biotite + K-feldspar. positions. They show an east-west strike, dipping steeply Representative mineral assemblage of metapelites in the to the north. A large body of marble occurs in the central biotite zone is as follows: part of the Kosa area, which is in fault contact with the biotite + K-feldspar ± garnet + plagioclase + quartz (a) gneisses. Many small bodies of the marble occur as The biotite -rich melanocratic layer alternates with the lenses or as thin layers in the gneisses. quartz -rich leucocratic layer with distinct gneissosity. Biotite occurs as flaky crystal parallel to the gneissoisty. Metamorphic zonal mapping K-feldspar and plagioclase occur as anhedral crystals of about 0.1 mm in size. Myrmekite sometimes occurs be- The Higo metamorphic terrane has been divided into five tween K-feldspar and plagioclase. Muscovite shows two zones, A, B, C, D, and E in the order of increasing grade modes of occurrence in the Kosa area. One is flaky crys- form north to south based on mineral assemblages of tal parallel to the gneissosity, and the other is randomly pelitic and psammitic rocks (Obata et al., 1994). Zone A oriented crystal. We consider the former as primary and is characterized by chlorite and muscovite in metapelites, the latter as secondary phase.
Recommended publications
  • Heat Capacity of High Pressure Minerals and Phase Equilibria of Cretan Blueschists
    Heat capacity of high pressure minerals and phase equilibria of Cretan blueschists by Matthew Rahn Manon A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Geology) in The University of Michigan 2008 Doctoral Committee: Professor Eric J. Essene, Chair Professor Rebecca Ann Lange Professor Youxue Zhang Associate Professor Steven M. Yalisove Matthew Rahn Manon 2008 Acknowledgments Cheers to all the grad students who have gone and come through CC-Little over the years. Zeb, Steven, Jim, Chris, Katy, Phillip, Franek, Eric, Tom, Darius, Sarah, Sara, Abir, Laura, Casey, Sam, John and anyone else I’ve been to learned something from, or argued something with. From early nights at Dominicks for subductology “seminars” through to the FWC, Michigan has been a fun place to live. Thanks to Anne Hudon, whos made sure I haven’t been able to place myself in inextricable holes. Thanks also to those from earlier in my life. College professors like Ken Hess or Barbara Nimmersheim who, in their very different ways inspired me to explore what it is I know. I’ll always remember time spent with Bob Wiebe who introduced me to the wild unknown of geology. Immeasurable thanks go to Eric Essene. The fieldtrips we took the first few years were good adventures. He’s always put aside his own issues to be there for me to talk to, especially when I didn’t deserve it. Eric’s scientific curiosity, and mental rigor are deservedly well known. His patience with me may be one of his great, unsung virtues.
    [Show full text]
  • 1 Revision 1 1 the High-Pressure Phase of Lawsonite
    1 Revision 1 2 The high-pressure phase of lawsonite: A single crystal study of a key mantle hydrous phase 3 4 Earl O’Bannon III,1* Christine M. Beavers1,2, Martin Kunz2, and Quentin Williams1 5 1Department of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High 6 Street, Santa Cruz, California 95064, U.S.A. 7 2Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, 8 U.S.A. 9 *Corresponding Author 10 1 11 Abstract 12 Lawsonite CaAl2Si2O7(OH)2·H2O is an important water carrier in subducting oceanic 13 crusts, and the primary hydrous phase in basalt at depths greater than ~80 km. We have 14 conducted high-pressure synchrotron single-crystal x-ray diffraction experiments on natural 15 lawsonite at room temperature up to ~10.0 GPa to study its high-pressure polymorphism. We 16 find that lawsonite remains orthorhombic with Cmcm symmetry up to ~9.3 GPa, and shows 17 nearly isotropic compression. Above ~9.3 GPa, lawsonite becomes monoclinic with P21/m 18 symmetry. Across the phase transition, the Ca polyhedron becomes markedly distorted, and 19 the average positions of the H2O molecules and hydroxyls change. The changes observed in the 20 H-atom positions under compression are different than the low temperature changes in this 21 material. We resolve for the first time the H-bonding configuration of the high-pressure 22 monoclinic phase of lawsonite. A bond valence approach is deployed to determine that the 23 phase transition from orthorhombic to monoclinic is primarily driven by the Si2O7 groups, and in 24 particular it's bridging oxygen atom (O1).
    [Show full text]
  • Activity 2: Crystal Form and Habit: Measuring Crystal Faces
    WARD'S GEO-logic®: Name:. Crystal Form Group: Activity Set Date: ACTIVITY 2: CRYSTAL FORM AND HABIT: MEASURING CRYSTAL FACES OBJECTIVE: To verify the relationship between interfacial angles and crystal form. BACKGROUND INFORMATION: The repeated patterns of the atomic structure for any mineral are re• flected by the consistency of certain features readily observed for that mineral. This similarity is exemplified by the constant angular relationship between similar sets of crystal faces on different specimens of any one mineral. Sample #105 is a representative of the hexagonal crystal system and thus exhibits a six-faced prismatic fomri. Although the faces on the crystal are of different sizes and shapes, the angles between them are al• ways exactly 120°. If you measure carefully, your readings should be accurate within ± 1 degree. MATERIALS: 6" ruler & protractor Sample #105 Sample #109 PROCEDURE: 1. Make a simple goniometer, the instrument used to measure the angle between crystal faces, by placing the ruler as shown over the protractor. Sample #105 2. Place the crystal of Sample #105 as shown. 3. Read the angle on the protractor that corresponds to the angle between crystal faces. 4. Measure each angle consecutively, holding the crystal against the protractor as shown, and record these angles below (you should have six readings). Angle #1 Angle #3 Angle #5 Angle #2 Angle #4 Angle #6 5. Compare and discuss your results with your classmates, and answer the Assessment questions that follow. Copymaster. Permission granted to make unlimited copies for use in any one © 2013 WARD'S Natural Science Establishment, Inc. school building.
    [Show full text]
  • Transition from Staurolite to Sillimanite Zone, Rangeley Quadrangle, Maine
    CHARLES V. GUIDOTTI Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706 Transition from Staurolite to Sillimanite Zone, Rangeley Quadrangle, Maine ABSTRACT GENERAL GEOLOGICAL SETTING Ordovician and Silurian to Devonian pelitic schist, conglomerate, quartzite, calc-silicate Study of pelitic schists in the Rangeley Figure 1 shows the location of the area granulite, and biotite schist. Post-tectonic, area, Maine, by means of petrographic, and a generalized geologic map of the shallow-dipping, adamellite sheets intrude x-ray, and electron-microprobe techniques southwestern third of the Rangeley quad- the metamorphosed strata. As illustrated in enables definition of the isogradic reaction rangle based upon Moench (1966, 1969, Figure 1, the isograds have a clear spacial relating the staurolite and lower sillimanite 1970a, 1970b, 1971). The rocks in this area relation to the distribution of the adamel- zones. The reaction is a discontinuous one consist of tightly folded, northeast-trending lites; but in a few cases, the adamellite and can be shown on an AFM projection as the tie line change from staurolite + chlorite to sillimanite 4- biotite. This topology change, in conjunction with the min- eralogical data provides the equation: Staur + Mg-Chte + Na-Musc + (Gam?) Sill + Bio + K-richer Muse + Ab + Qtz + H20. This reaction should result in a sharp isograd in the field but in fact is found to be spread out over a zone which is called the transition zone. It is proposed that this zene results from buffering of fH20 by means of the equation above. Buffering of fH.,o by continuous reactions also appears to be taking place in the lower sillimanite zone.
    [Show full text]
  • Geologic Evolution of Trail Ridge Eommn
    Geologic Evolution of Trail Ridge EoMmn Peat, Northern Florida AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the cur­ rent-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Sur­ vey publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available. Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated month­ ly, which is for sale in microfiche from the U.S. Geological Survey, Books and Open-File Reports Section, Federal Center, Box 25425, Denver, CO 80225. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL D , OVER THE COUNTER Books Books Professional Papers, Bulletins, Water-Supply Papers, Techniques of Water-Resources Investigations, Circulars, publications of general in- Books of the U.S. Geological Survey are available over the terest (such as leaflets, pamphlets, booklets), single copies of Earthquakes counter at the following Geological Survey Public Inquiries Offices, all & Volcanoes, Preliminary Determination of Epicenters, and some mis- of which are authorized agents of the Superintendent of Documents: cellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from WASHINGTON, D.C.-Main Interior Bldg., 2600 corridor, 18th and CSts.,NW.
    [Show full text]
  • A Systematic Nomenclature for Metamorphic Rocks
    A systematic nomenclature for metamorphic rocks: 1. HOW TO NAME A METAMORPHIC ROCK Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: Web version 1/4/04. Rolf Schmid1, Douglas Fettes2, Ben Harte3, Eleutheria Davis4, Jacqueline Desmons5, Hans- Joachim Meyer-Marsilius† and Jaakko Siivola6 1 Institut für Mineralogie und Petrographie, ETH-Centre, CH-8092, Zürich, Switzerland, [email protected] 2 British Geological Survey, Murchison House, West Mains Road, Edinburgh, United Kingdom, [email protected] 3 Grant Institute of Geology, Edinburgh, United Kingdom, [email protected] 4 Patission 339A, 11144 Athens, Greece 5 3, rue de Houdemont 54500, Vandoeuvre-lès-Nancy, France, [email protected] 6 Tasakalliontie 12c, 02760 Espoo, Finland ABSTRACT The usage of some common terms in metamorphic petrology has developed differently in different countries and a range of specialised rock names have been applied locally. The Subcommission on the Systematics of Metamorphic Rocks (SCMR) aims to provide systematic schemes for terminology and rock definitions that are widely acceptable and suitable for international use. This first paper explains the basic classification scheme for common metamorphic rocks proposed by the SCMR, and lays out the general principles which were used by the SCMR when defining terms for metamorphic rocks, their features, conditions of formation and processes. Subsequent papers discuss and present more detailed terminology for particular metamorphic rock groups and processes. The SCMR recognises the very wide usage of some rock names (for example, amphibolite, marble, hornfels) and the existence of many name sets related to specific types of metamorphism (for example, high P/T rocks, migmatites, impactites).
    [Show full text]
  • List of Abbreviations
    List of Abbreviations Ab albite Cbz chabazite Fa fayalite Acm acmite Cc chalcocite Fac ferroactinolite Act actinolite Ccl chrysocolla Fcp ferrocarpholite Adr andradite Ccn cancrinite Fed ferroedenite Agt aegirine-augite Ccp chalcopyrite Flt fluorite Ak akermanite Cel celadonite Fo forsterite Alm almandine Cen clinoenstatite Fpa ferropargasite Aln allanite Cfs clinoferrosilite Fs ferrosilite ( ortho) Als aluminosilicate Chl chlorite Fst fassite Am amphibole Chn chondrodite Fts ferrotscher- An anorthite Chr chromite makite And andalusite Chu clinohumite Gbs gibbsite Anh anhydrite Cld chloritoid Ged gedrite Ank ankerite Cls celestite Gh gehlenite Anl analcite Cp carpholite Gln glaucophane Ann annite Cpx Ca clinopyroxene Glt glauconite Ant anatase Crd cordierite Gn galena Ap apatite ern carnegieite Gp gypsum Apo apophyllite Crn corundum Gr graphite Apy arsenopyrite Crs cristroballite Grs grossular Arf arfvedsonite Cs coesite Grt garnet Arg aragonite Cst cassiterite Gru grunerite Atg antigorite Ctl chrysotile Gt goethite Ath anthophyllite Cum cummingtonite Hbl hornblende Aug augite Cv covellite He hercynite Ax axinite Czo clinozoisite Hd hedenbergite Bhm boehmite Dg diginite Hem hematite Bn bornite Di diopside Hl halite Brc brucite Dia diamond Hs hastingsite Brk brookite Dol dolomite Hu humite Brl beryl Drv dravite Hul heulandite Brt barite Dsp diaspore Hyn haiiyne Bst bustamite Eck eckermannite Ill illite Bt biotite Ed edenite Ilm ilmenite Cal calcite Elb elbaite Jd jadeite Cam Ca clinoamphi- En enstatite ( ortho) Jh johannsenite bole Ep epidote
    [Show full text]
  • What We Know About Subduction Zones from the Metamorphic Rock Record
    What we know about subduction zones from the metamorphic rock record Sarah Penniston-Dorland University of Maryland Subduction zones are complex We can learn a lot about processes occurring within active subduction zones by analysis of metamorphic rocks exhumed from ancient subduction zones Accreonary prism • Rocks are exhumed from a wide range of different parts of subduction zones. • Exhumed rocks from fossil subduction zones tell us about materials, conditions and processes within subduction zones • They provide complementary information to observations from active subduction systems Tatsumi, 2005 The subduction interface is more complex than we usually draw Mélange (Bebout, and Penniston-Dorland, 2015) Information from exhumed metamorphic rocks 1. Thermal structure The minerals in exhumed rocks of the subducted slab provide information about the thermal structure of subduction zones. 2. Fluids Metamorphism generates fluids. Fossil subduction zones preserve records of fluid-related processes. 3. Rheology and deformation Rocks from fossil subduction zones record deformation histories and provide information about the nature of the interface and the physical properties of rocks at the interface. 4. Geochemical cycling Metamorphism of the subducting slab plays a key role in the cycling of various elements through subduction zones. Thermal structure Equilibrium Thermodynamics provides the basis for estimating P-T conditions using mineral assemblages and compositions Systems act to minimize Gibbs Free Energy (chemical potential energy) Metamorphic facies and tectonic environment SubduconSubducon zone metamorphism zone metamorphism Regional metamorphism during collision Mid-ocean ridge metamorphism Contact metamorphism around plutons Determining P-T conditions from metamorphic rocks Assumption of chemical equilibrium Classic thermobarometry Based on equilibrium reactions for minerals in rocks, uses the compositions of those minerals and their thermodynamic properties e.g.
    [Show full text]
  • First Report and Significance of the Staurolite Metabasites Associated To
    Rev. Acad. Colomb. Cienc. 38(149):418-29, octubre-diciembre de 2014 Ciencias de la tierra First report and significance of the staurolite metabasites associated to a sequence of calc-silicate rocks from the Silgará Formation at the central Santander Massif, Colombia Carlos A. Ríos1,*, Oscar M. Castellanos2 1Grupo de Investigación en Geología Básica y Aplicada (GIGBA), Escuela de Geología, Universidad Industrial de Santander, Bucaramanga, Colombia 2Grupo de Investigación en Geofísica y Geología (PANGEA), Programa de Geología, Universidad de Pamplona, Pamplona, Colombia Abstract The Silgará Formation metamorphic rocks have been affected by a Barrovian-type of metamorphism, which has occurred under medium-pressure and high-temperature conditions. Scarce intercalations of metabasites from millimeter up to centimeter scale occur in reaction bands observed in the gradational contact between garnet-bearing pelitic and calc-silicate rocks. In this study, we report for the first time the presence of staurolite metabasites in the Santander Massif (Colombian Andes), which is of particular interest since it is an unusual occurrence, taking into account that staurolite is most commonly regarded as an index mineral in metapelites and is not very well known from other bulk compositions and pressure and temperature conditions. Staurolite metabasites contain plagioclase, hornblende and staurolite, suggesting a history of prograde metamorphism up to amphibolite facies conditions. The origin of staurolite can be associated to aluminium-rich metabasites and, therefore, it is strongly affected by bulk rock chemistry. Taking into account mineral assemblages and geothermobarometric calculations in pelitic rocks, we suggest that the staurolite + hornblende association can be formed at least at 400 to 600 °C and 6 kbar at the peak of prograde metamorphism.
    [Show full text]
  • Decomposition of Kyanite and Solubility of Al2o3 in Stishovite at High Pressure and High Temperature Conditions
    Phys Chem Minerals (2006) 33:711–721 DOI 10.1007/s00269-006-0122-x ORIGINAL PAPER Decomposition of kyanite and solubility of Al2O3 in stishovite at high pressure and high temperature conditions Xi Liu Æ Norimasa Nishiyama Æ Takeshi Sanehira Æ Toru Inoue Æ Yuji Higo Æ Shizue Sakamoto Received: 9 August 2006 / Accepted: 9 October 2006 / Published online: 3 November 2006 Ó Springer-Verlag 2006 Abstract In order to constrain the high-pressure Keywords Al2O3 solubility in stishovite Á Corundum Á behavior of kyanite, multi-anvil experiments have been Kyanite Á Phase equilibrium Á Stishovite carried out from 15 to 25 GPa, and 1,350 to 2,500°C. Both forward and reversal approaches to phase equi- libria were adopted in these experiments. We find that Introduction kyanite breaks down to stishovite + corundum at pressures above ~15 GPa, and stishovite + corundum Kyanite (Ky, Al2SiO5), commonly found in peralumi- should be the stable phase assemblage at the pressure– nous eclogites and amphibolites, has been soundly temperature conditions of the transition zone and the demonstrated to be an important constituent phase for uppermost part of the lower mantle of the Earth, the materials of continental crust and pelagic sediment in agreement with previous multi-anvil experimental at pressures from ~1 to 16 GPa (Irifune et al. 1994; studies and ab initio calculation results, but in dis- Schmidt et al. 2004). Its role at higher pressures, how- agreement with some of the diamond-anvil cell ever, remains unclear. With some preliminary experi- experimental studies in the literature. The Al2O3 sol- ments in a Bridgman–anvil apparatus, Ringwood and ubility in nominally dry stishovite has been tightly Reid (1969) tentatively suggested that Ky appears sta- bracketed by forward and reversal experiments; it is ble up to 15 GPa and 1,000°C.
    [Show full text]
  • Download the Scanned
    NOTES AND NEWS VIRGINIA STAUROLITBSAS GEMS Josnrn K. RosBnrs, Uniaersity of Virgi.nia. In Virginia well over a quarter of a century ago people began wearing staurolite crystals as watch charms, and pendants for neck- laces. This custom has grown until at the present time nearly every town in the state has one or more placeswhere the staurolites are for sale, some of which are genuine and some artificial. During the summers ol 1922 and 1923, the writer visited the better localities for collecting in Henry and Patrick Counties, Virginia. In the sum- mer of 1916 a collection was made at Ducktown, Tennessee,and in l9l7 a collection in Fannin County, Georgia. Being somewhat familiar with the mineral in its occurrence,and after seeingso many on the market, and some of the ways they are prepared, the pur- pose of this brief article is to call attention to the Virginia localities, and some of the ways the artificial stone is made and sold. Practi- cally all of the socalled staurolites sold as gems are of the right angle pattern. In Henry and Patrick Counties this form of twinning is rare compared to others, and since the cross of about 90 degrees is sold almost exclusively, the writer ofiers an explanation. The main locality in Virginia extends from near the city of Lynchburg southwestwardly into North Carolina, the better por- tion for collecting being in Henry and Patrick Counties. This belt lies in the portion of Virginia known as the Piedmont province, one of the natural divisions of the state. Its extent in Virginia is ap- proximately 60 miles with a maximum width of about 10 miles in the vicinity of Sanville, near the Patrick-Henry County line.
    [Show full text]
  • Minerals Found in Michigan Listed by County
    Michigan Minerals Listed by Mineral Name Based on MI DEQ GSD Bulletin 6 “Mineralogy of Michigan” Actinolite, Dickinson, Gogebic, Gratiot, and Anthonyite, Houghton County Marquette counties Anthophyllite, Dickinson, and Marquette counties Aegirinaugite, Marquette County Antigorite, Dickinson, and Marquette counties Aegirine, Marquette County Apatite, Baraga, Dickinson, Houghton, Iron, Albite, Dickinson, Gratiot, Houghton, Keweenaw, Kalkaska, Keweenaw, Marquette, and Monroe and Marquette counties counties Algodonite, Baraga, Houghton, Keweenaw, and Aphrosiderite, Gogebic, Iron, and Marquette Ontonagon counties counties Allanite, Gogebic, Iron, and Marquette counties Apophyllite, Houghton, and Keweenaw counties Almandite, Dickinson, Keweenaw, and Marquette Aragonite, Gogebic, Iron, Jackson, Marquette, and counties Monroe counties Alunite, Iron County Arsenopyrite, Marquette, and Menominee counties Analcite, Houghton, Keweenaw, and Ontonagon counties Atacamite, Houghton, Keweenaw, and Ontonagon counties Anatase, Gratiot, Houghton, Keweenaw, Marquette, and Ontonagon counties Augite, Dickinson, Genesee, Gratiot, Houghton, Iron, Keweenaw, Marquette, and Ontonagon counties Andalusite, Iron, and Marquette counties Awarurite, Marquette County Andesine, Keweenaw County Axinite, Gogebic, and Marquette counties Andradite, Dickinson County Azurite, Dickinson, Keweenaw, Marquette, and Anglesite, Marquette County Ontonagon counties Anhydrite, Bay, Berrien, Gratiot, Houghton, Babingtonite, Keweenaw County Isabella, Kalamazoo, Kent, Keweenaw, Macomb, Manistee,
    [Show full text]