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Geochemistry of pink corundum-bearing feldspathic gneiss, Frenchvale quarry, Cape Breton Island, Canada: metamorphism of albitised, Fe-poor clastic rocks
- J. Victor Owen, Jacob J. Hanley, Mitchell J. Kerr, Matthew Stimson, Brandon Boucher
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- Mineralogical Magazine / Volume 83 / Issue 2 / April 2019
- Published online by Cambridge University Press:
- 14 January 2019, pp. 249-260
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Frenchvale quarry, once mined for dolomitic marble, contains pink corundum-bearing, quartz-free/-poor, feldspathic gneiss that is unusually sodic (~7% wt.% Na2O) and iron-poor (~0.6 wt.% Fe2O3), but has silica, alumina and immobile trace-element contents resembling those of suspended fluvial particulate matter (e.g. in the Congo River). The protolith of the gneiss, interpreted as a fine-grained clastic sediment deposited offshore, evidently was albitised prior to deformation and regional metamorphism. Variably-altered gneiss samples show a narrow range of δ18OVSMOW values (8.1 to 10.7‰) and no systematic differences in bulk O isotope composition as a function of alteration intensity. With the exception of an extensively fuchsitised zone adjacent to a thick (1.2 m), cross-cutting quartz vein that contains H2O–NaCl+CO2+CH4-bearing fluid inclusions, the O isotope data do not support interaction of the gneiss with an externally-derived fluid phase except at low fluid:rock ratio, even where granodiorite occurs in direct contact with the gneiss. Fluid inclusions in the quartz vein have bulk $X_{{\rm H}_2{\rm O}}$, $X_{{\rm C}{\rm O}_{\rm 2}}$ and $X_{{\rm C}{\rm H}_{\rm 4}}$ values (in mol.%) of 99.60, 0.14 and 0.26, respectively, as determined by gas chromatography. Although the protolith of the gneiss was associated with carbonate platformal rocks (now marble), corundum is confined to the feldspathic rocks. These feldspathic rocks lack calc-silicate minerals; they are not skarns. As such, they are distinct from well-known Himalayan sapphire and ruby deposits cited previously as analogues of the Frenchvale corundum occurrence.
Contrasting garnet parageneses in a composite Grenvillian granitoid pluton, Newfoundland
- J. Victor Owen, Robert A. Marr
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- Mineralogical Magazine / Volume 54 / Issue 376 / September 1990
- Published online by Cambridge University Press:
- 05 July 2018, pp. 367-380
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Almandine- and grossular-rich garnet occurs as both a coronitic and non-coronitic phase in ferruginous, Grenvillian (c. 1050 Ma) granitoid rocks of the composite Potato Hill pluton of the Long Range Inlier, Newfoundland. The country rock includes garnetiferous gneiss, but garnets in the pluton are compositionally distinct (higher Ca and Mn, lower Mg), so none are interpreted as xenocrysts from the Long Range gneiss complex.
Coronal garnet, quartz and hornblende separate primary pyroxene, ilmenite and hornblende from feldspar in two-pyroxene charnockite. Balanced mass-transfer reactions based on microprobe data and modes for the pyroxene-centred corona structures suggest that corona sites gained Fe and lost Na. The flux of Fe apparently controlled corona growth in the charnockite. The corona structures are attributed to subsolidus cooling of the pluton rather than to a metamorphic overprint because the coronas are obliterated in high strain zones cutting the charnockite. Temperature of formation is constrained at c. 775–630°C by two-pyroxene and garnet-hornblende thermometry. Compositionally-similar coronas in rare, Fe-rich enderbite of the Long Range gneiss complex probably formed during cooling after early, high-grade metamorphism or following the regional emplacement of the Grenvillian plutons.
Non-coronitic garnets occur in equigranular and megacrystic hornblende-biotite granite. Garnets in the equigranular granite are large, well-formed, and in some instances are associated with compositional layering of probable igneous origin. These garnets are enriched in grossular (XCa = 0.28), and are therefore interpreted as phenocrysts crystallized at high pressure (>9 kbar?). They would nevertheless have been stabilized to lower pressures by their moderate spessartine content (XMn = 0.13).
Garnets in foliated megacrystic granite form tiny crystals depleted in Fe and Mg, and enriched in Mn and Ca, and in these respects are similar to garnet in deformed charnockite. These garnets are therefore interpreted to have formed (or re-equilibrated) during the late Grenvillian deformation. Garnet is absent in relatively magnesian Grenvillian granites (bulk XFe2+ = 0.50–0.85) elsewhere in the inlier. The restriction of garnet to the Potato Hill pluton (bulk XFe2+ = 0.88–0.94) therefore testifies to bulk compositional controls on the formation of both magmatic and subsolidus garnet in this intrusion.
Geochemistry of orbicular diorite from the Grenville Front zone, eastern Labrador
- J. Victor Owen
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- Journal:
- Mineralogical Magazine / Volume 56 / Issue 385 / December 1992
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- 05 July 2018, pp. 451-458
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Orbicules in diorite from the Grenville Front zone of eastern Labrador consist of biotite- and/or hornblende-studded, dioritic cores enclosed by fine-grained shell structures alternately enriched and depleted in biotite. The orbicules occur in a mesocratic, quartz-bearing matrix. Epidote of inferred magmatic origin occurs in all parts of the rock. Plagioclase in the matrix is relatively sodic, and biotite more ferroan than in the orbicules, suggesting that the matrix material has the most evolved composition, and crystallized last.
The diorite is unusually aluminous (orbicules: 24.9-27.4 wt.% Al2O3; matrix: 22.4-23.6% Al2O3) and calcic (orbicules: 7.0-8.4 wt.% CaO; matrix: 6.0-6.9% CaO); it shows a positive Eu anomaly, and has elevated Sr concentrations (1800-2500 ppm Sr), demonstrating that, compositionally, it resembles a plagioclase cumulate. Mass-balance calculations suggest that the orbicule cores had a crystal/melt ratio of ≤5. This accounts for the extreme fractionation of the rock (e.g., in orbicules, Zr <5 ppm). Compared with fractional crystallization patterns, variation diagrams show counter-trends (e.g. the siliceous matrix contains elevated TiO2) or scatter for several components, suggesting that the crystal/melt ratio governed some of the geochemical characteristics of the diorite.
The presence of coarse mafic clots containing primary epidote, biotite and/or hornblende testify to an elevated water content in the orbieule cores. The shell magma apparently formed as a result of the interaction of supercooled orbicule core fluids with the matrix magma, and tended to serve as a reservoir for alkalis and Fe. Alkalis and Ca diffused in opposite directions, possibly as a result of a temperature gradient at the orbicule/matrix interface. This, however, requires decoupling of the thermodiffusional behaviour of alkalis and femic components in hydrated intermediate magma, which contrasts with documented Soret diffusion in mafic systems.
The solidification of the shell magma prior, to the orbicule cores and matrix is attributed to dewatering, consistent with the fine grain size of the shell structures. Except where remobilized core material has disrupted the shells, the cores crystallized in isolation from the matrix, which fractionated toward a more evolved composition.
Significance of epidote in orbicular diorite from the Grenville Front zone, eastern Labrador
- J. Victor Owen
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- Mineralogical Magazine / Volume 55 / Issue 379 / June 1991
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- 05 July 2018, pp. 173-181
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Orbicules in diorite from the Grenville Front zone of eastern Labrador are defined by shell structures alternately enriched and depleted in biotite, epidote and magnetite. Hornblende occurs locally in orbicule cores and the matrix, but not in the shells. The shells enclose plagioclase-rich (An40–45), leucodioritic cores containing biotite, epidote, magnetite and/or hornblende-bearing mafic clots. The matrix of the orbicules is mineralogically-similar to the orbicule cores, but is mesocratic, and contains relatively sodic plagioclase and accessory quartz and K-feldspar. In places, hornblende contains quartz oikocrysts, implying the resorption of early-formed clinopyroxene, and is rimmed by biotite and epidote. The latter phases also occur as inclusions in quartz-free hornblende interpreted to have crystallized directly from the magma. Epidote has a pistacite content of 21 to 26 and occurs as (1) tiny, idiomorphic crystals (‘epidote I’) enclosed by plagioclase or hornblende, and (2) relatively large (to 1 mm) grains with vermicular textures (‘epidote II’), particularly where in mutual contact with biotite (or hornblende) and plagioclase. These microstructures suggest that epidote is a magmatic phase which formed by direct crystallization from the magma, and by reaction of previously-formed minerals with the magma.
The following approximate paragenetic sequence has been inferred for orbicule cores and the matrix: clinopyroxene (clinopyroxene resorbed [→ poikilitic hornblende]), epidote I, Ca-Na plagioclase, biotite, hornblende (biotite and/or hornblende ± plagioclase resorbed [→ epidote II]), quartz + K-feldspar. Biotite compositions became progressively more Fe-rich during crystallization (XMg ⋍ 0.6 → 0.4), and the first-formed plagioclase (inclusions in quartz-free hornblende in orbicule cores) is more calcic (An51) than the last (matrix grains: An35).
The appearance of epidote early in the crystallization history of the diorite testifies to elevated PH2O and PTotal (PT). The most aluminous hornblende indicates maximum PT of 5 to 6 kbar. Orbicule shell structures are interpreted to have crystallized from supercooled boundary layers enclosing water-saturated globules within the dioritic magma. Although sufficient to suppress the formation of hornblende in the shell structures, the extent of magma supercooling did not permit the development of comb layering in the orbicules. Supercooling is attributed to an influx into the magma of water from an unidentified source.
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- By Rose Teteki Abbey, K. C. Abraham, David Tuesday Adamo, LeRoy H. Aden, Efrain Agosto, Victor Aguilan, Gillian T. W. Ahlgren, Charanjit Kaur AjitSingh, Dorothy B E A Akoto, Giuseppe Alberigo, Daniel E. Albrecht, Ruth Albrecht, Daniel O. Aleshire, Urs Altermatt, Anand Amaladass, Michael Amaladoss, James N. Amanze, Lesley G. Anderson, Thomas C. Anderson, Victor Anderson, Hope S. Antone, María Pilar Aquino, Paula Arai, Victorio Araya Guillén, S. Wesley Ariarajah, Ellen T. Armour, Brett Gregory Armstrong, Atsuhiro Asano, Naim Stifan Ateek, Mahmoud Ayoub, John Alembillah Azumah, Mercedes L. García Bachmann, Irena Backus, J. Wayne Baker, Mieke Bal, Lewis V. Baldwin, William Barbieri, António Barbosa da Silva, David Basinger, Bolaji Olukemi Bateye, Oswald Bayer, Daniel H. Bays, Rosalie Beck, Nancy Elizabeth Bedford, Guy-Thomas Bedouelle, Chorbishop Seely Beggiani, Wolfgang Behringer, Christopher M. Bellitto, Byard Bennett, Harold V. Bennett, Teresa Berger, Miguel A. Bernad, Henley Bernard, Alan E. Bernstein, Jon L. Berquist, Johannes Beutler, Ana María Bidegain, Matthew P. Binkewicz, Jennifer Bird, Joseph Blenkinsopp, Dmytro Bondarenko, Paulo Bonfatti, Riet en Pim Bons-Storm, Jessica A. Boon, Marcus J. Borg, Mark Bosco, Peter C. Bouteneff, François Bovon, William D. Bowman, Paul S. Boyer, David Brakke, Richard E. Brantley, Marcus Braybrooke, Ian Breward, Ênio José da Costa Brito, Jewel Spears Brooker, Johannes Brosseder, Nicholas Canfield Read Brown, Robert F. Brown, Pamela K. Brubaker, Walter Brueggemann, Bishop Colin O. Buchanan, Stanley M. Burgess, Amy Nelson Burnett, J. Patout Burns, David B. Burrell, David Buttrick, James P. Byrd, Lavinia Byrne, Gerado Caetano, Marcos Caldas, Alkiviadis Calivas, William J. Callahan, Salvatore Calomino, Euan K. Cameron, William S. Campbell, Marcelo Ayres Camurça, Daniel F. Caner, Paul E. Capetz, Carlos F. Cardoza-Orlandi, Patrick W. Carey, Barbara Carvill, Hal Cauthron, Subhadra Mitra Channa, Mark D. Chapman, James H. Charlesworth, Kenneth R. Chase, Chen Zemin, Luciano Chianeque, Philip Chia Phin Yin, Francisca H. Chimhanda, Daniel Chiquete, John T. Chirban, Soobin Choi, Robert Choquette, Mita Choudhury, Gerald Christianson, John Chryssavgis, Sejong Chun, Esther Chung-Kim, Charles M. A. Clark, Elizabeth A. Clark, Sathianathan Clarke, Fred Cloud, John B. Cobb, W. Owen Cole, John A Coleman, John J. Collins, Sylvia Collins-Mayo, Paul K. Conkin, Beth A. Conklin, Sean Connolly, Demetrios J. Constantelos, Michael A. Conway, Paula M. Cooey, Austin Cooper, Michael L. Cooper-White, Pamela Cooper-White, L. William Countryman, Sérgio Coutinho, Pamela Couture, Shannon Craigo-Snell, James L. Crenshaw, David Crowner, Humberto Horacio Cucchetti, Lawrence S. Cunningham, Elizabeth Mason Currier, Emmanuel Cutrone, Mary L. Daniel, David D. Daniels, Robert Darden, Rolf Darge, Isaiah Dau, Jeffry C. Davis, Jane Dawson, Valentin Dedji, John W. de Gruchy, Paul DeHart, Wendy J. Deichmann Edwards, Miguel A. De La Torre, George E. Demacopoulos, Thomas de Mayo, Leah DeVun, Beatriz de Vasconcellos Dias, Dennis C. Dickerson, John M. Dillon, Luis Miguel Donatello, Igor Dorfmann-Lazarev, Susanna Drake, Jonathan A. Draper, N. Dreher Martin, Otto Dreydoppel, Angelyn Dries, A. J. Droge, Francis X. D'Sa, Marilyn Dunn, Nicole Wilkinson Duran, Rifaat Ebied, Mark J. Edwards, William H. Edwards, Leonard H. Ehrlich, Nancy L. Eiesland, Martin Elbel, J. Harold Ellens, Stephen Ellingson, Marvin M. Ellison, Robert Ellsberg, Jean Bethke Elshtain, Eldon Jay Epp, Peter C. Erb, Tassilo Erhardt, Maria Erling, Noel Leo Erskine, Gillian R. Evans, Virginia Fabella, Michael A. Fahey, Edward Farley, Margaret A. Farley, Wendy Farley, Robert Fastiggi, Seena Fazel, Duncan S. Ferguson, Helwar Figueroa, Paul Corby Finney, Kyriaki Karidoyanes FitzGerald, Thomas E. FitzGerald, John R. Fitzmier, Marie Therese Flanagan, Sabina Flanagan, Claude Flipo, Ronald B. Flowers, Carole Fontaine, David Ford, Mary Ford, Stephanie A. Ford, Jim Forest, William Franke, Robert M. Franklin, Ruth Franzén, Edward H. Friedman, Samuel Frouisou, Lorelei F. Fuchs, Jojo M. Fung, Inger Furseth, Richard R. Gaillardetz, Brandon Gallaher, China Galland, Mark Galli, Ismael García, Tharscisse Gatwa, Jean-Marie Gaudeul, Luis María Gavilanes del Castillo, Pavel L. Gavrilyuk, Volney P. Gay, Metropolitan Athanasios Geevargis, Kondothra M. George, Mary Gerhart, Simon Gikandi, Maurice Gilbert, Michael J. Gillgannon, Verónica Giménez Beliveau, Terryl Givens, Beth Glazier-McDonald, Philip Gleason, Menghun Goh, Brian Golding, Bishop Hilario M. Gomez, Michelle A. Gonzalez, Donald K. Gorrell, Roy Gottfried, Tamara Grdzelidze, Joel B. Green, Niels Henrik Gregersen, Cristina Grenholm, Herbert Griffiths, Eric W. Gritsch, Erich S. Gruen, Christoffer H. Grundmann, Paul H. Gundani, Jon P. Gunnemann, Petre Guran, Vidar L. Haanes, Jeremiah M. 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Yee, Viktor Yelensky, Yeo Khiok-Khng, Gustav K. K. Yeung, Angela Yiu, Amos Yong, Yong Ting Jin, You Bin, Youhanna Nessim Youssef, Eliana Yunes, Robert Michael Zaller, Valarie H. Ziegler, Barbara Brown Zikmund, Joyce Ann Zimmerman, Aurora Zlotnik, Zhuo Xinping
- Edited by Daniel Patte, Vanderbilt University, Tennessee
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- The Cambridge Dictionary of Christianity
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- 05 August 2012
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- 20 September 2010, pp xi-xliv
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COMMISSION 16: PHYSICAL STUDY OF PLANETS AND SATELLITES
- Guy J. Consolmagno, Regis Courtin, Dale P. Cruikshank, Carlo Blanco, Dale P. Cruikshank, Leonid V. Ksanfomality, Melissa A. McGrath, David Morrison, David Morrison, Keith S. Noll, Tobias C. Owen, Maarten C. Roos-Serote, John R. Spencer, Victor G. Tejfel
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- Proceedings of the International Astronomical Union / Volume 3 / Issue T26B / December 2007
- Published online by Cambridge University Press:
- 18 November 2008, pp. 133-135
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- December 2007
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Commission 16 held its business meeting during the General Assembly in Prague, on Wednesday August 23, 2006, with nine members present. The meeting was called to order at 14:00 hr by president Guy Consolmagno. A moment of silence was observed in memory of those Commission (or Division) members deceased since the last General Assembly. They are Joseph W. Chamberlain, Michel Festou, Thomas Gold, Cornell H. Mayer, Vasilij I. Moroz, William M. Sinton, Willem Wamsteker, James A. Westphal, and Fred L. Whipple.
7 - Dehydroepiandrosterone in aging and mental health
- from Part II - Hormones and mental health in the elderly
- Edited by Mary F. Morrison, University of Pennsylvania
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- Hormones, Gender and the Aging Brain
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- 18 September 2009
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- 04 May 2000, pp 144-167
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Summary
Introduction
Dehydroepiandrosterone (DHEA) and its sulfated metabolite, DHEA-S (together abbreviated DHEA(S)), are quantitatively the most important adrenal corticosteroids in man, although their physiological roles are unknown. These steroids have captured widespread scientific and public attention in recent years due to three key observations. First, circulating levels of these steroids progressively decline from young adulthood through the end of the lifespan; they also decrease in response to chronic stress or illness. Second, preclinical studies suggest that DHEA(S) protects against certain pathological processes seen in illness and with aging. Third, some epidemiological studies in man suggest that relatively higher DHEA(S) levels are associated with enhanced physical and mental well-being. Such findings have raised hope that replacement dosing with pharmaceutical DHEA may enhance and prolong life, although very limited clinical data exist to support this. This chapter will review preclinical and clinical data regarding the effects of DHEA(S) in the central nervous system, its biological role in aging and mental health and its possible efficacy in treating neuropsychiatric illness in the middle-aged and elderly.
DHEA(S) as a neurosteroid
DHEA(S) is synthesized in situ in brain, with glial cells playing a major role in its formation and metabolism; it has therefore, been termed a neurosteroid (Baulieu, 1997). Accumulation of DHEA(S) in rat brain is largely independent of adrenal and gonadal synthesis, remaining constant after orchiectomy, adrenalectomy and dexamethasone administration (Robel & Baulieu, 1995; Corpechot et al., 1981).