Hostname: page-component-848d4c4894-wzw2p Total loading time: 0 Render date: 2024-06-02T10:25:23.146Z Has data issue: false hasContentIssue false
  • English
  • Français

Megacrysts and salic xenoliths in Scottish alkali basalts: derivatives of deep crustal intrusions and small-melt fractions from the upper mantle

Published online by Cambridge University Press:  05 July 2018

B. G. J. Upton ,
A. A. Finch  and
E. Słaby
B. G. J. Upton*
Affiliation:
School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh EH9 3JW, UK
A. A. Finch
Affiliation:
School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh EH9 3JW, UK
E. Słaby
Affiliation:
School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh EH9 3JW, UK
*
* E-mail: brian.upton@ed.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

Ca-poor and typically Na-rich feldspar megacrysts are common associates of spinel lherzolitic and pyroxenitic xenoliths in Scottish alkalic basalts. Associated megacrysts and composite megacrysts and salic xenoliths include apatite, magnetite, zircon, biotite, Fe-rich pyroxene(s) and corundum. The salic xenoliths and related megacrysts are referred to collectively as the ‘anorthoclasite suite': the majority of the samples are inferred to derive from the disaggregation of coarse-grained, typically Na-rich, syenitic protoliths at depth. Rare occurrences of euhedral anorthoclase megacrysts, together with zircon dating, imply that the suite crystallized at, or very shortly before, their entrainment by the basaltic host magmas. Some evidence suggests that the anorthoclasite suite protoliths lie within ultramafic (pyroxenitic) domains in the deep crust. The latter are inferred to be pegmatites, crystallized from carbonated trachytic magmas with widely variable Ca, Na, K, Ba and trace-element contents, and to have ranged from metaluminous to peraluminous. Crystal zonation and resorption textures within the salic xenoliths imply that the crystallization of the parent magmas was complex. Confirmation of this comes from cathodoluminescence studies of the feldspars showing that early ('primary’) anorthoclases and potassian albites exhibit partial replacement by a more potassic feldspar. A third generation of potassic feldspar (enriched in an assortment of trace elements and deduced to have crystallized from a carbonated high-K melt) forms transecting zoned veins in which carbonate fills the axial zone.

Whereas most of the anorthoclasite suite materials are inferred to have grown from metaluminous magmas, the occurrence of magmatic corundum in salic xenoliths indicates crystallization from magmas that were peraluminous. The corundum-bearing samples also contain Nb-rich oxide minerals and their associated feldspars have the highest rare-earth element (REE)contents. Accordingly, the peraluminous trachyte magmas are deduced to have been specifically enriched in high field-strength trace elements. It is proposed that formation of the anorthoclasite suite protoliths is a phenomenon closely related to that of salic glass ‘pockets', well known from spinel lherzolite xenoliths around the world. Not only are there compositional affinities, but both sets of phenomena appear to have closely pre-empted the ascent of alkali basalt (host) magmas. We propose that the two sets of phenomena are linked and that the anorthoclasite suite derived from coarse-grained sheets, generated by the aggregation of salic melt fractions rising from the shallow mantle and heralding the onset of basaltic magmatism.

Keywords

Xenolithsmegacrystsanorthoclasecorundummantle salic glasses
Type
Research Article
Information
Mineralogical Magazine , Volume 73 , Issue 6 , December 2009 , pp. 943 - 956
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aspen, P., Upton, B.G.J. and Dickin, A.P. (1990) Anorthoclase, sanidine and associated megacrysts in Scottish alkali basalts: high-pressure syenitic debris from upper mantle sources? European Journal of Mineralogy, 2, 503—517.CrossRefGoogle Scholar
Bailey, D.K. (1972) Uplift, rifting and magmatism in continental plates. Journal of Earth Sciences, Leeds, 8, 225–239.Google Scholar
Bailey, D.K. (1987) Mantle metasomatism — perspective and propect. Pp. 1 — 13 in: Alkaline Igneous Rocks (Fitton, J. G. and Upton, B.G.J., editors). Special Publications, 30, The Geological Society, London.Google Scholar
Baker, M.B., Hirschmann, M.M., Ghiorso, M.S. and Stolper, E.M. (1995) Composition of near-solidus melts from experiments and thermodynamic calculations. Nature, 375, 308–311.CrossRefGoogle Scholar
Barlow, A.E. (1915) Corundum, its Occurrence, Distribution, Exploitation and Uses. Department of Mines. Canadian Geological Survey Memoir, 57, 377 pp.Google Scholar
Barr, S.M. and MacDonald, A.S. (1979) Palaeo-magnetism, age and geochemistry of the Denchai basalt, northern Thailand. Earth and Planetary Science Letters, 46, 113–124.CrossRefGoogle Scholar
Barr, S.M. and MacDonald, A.S. (1981) Geochemistry and geochronology of late Cenozoic basalts of Southeast Asia: Summary. Geological Society of America Bulletin, 92, 508–512.2.0.CO;2>CrossRefGoogle Scholar
Barron, B.J., Robertson, A.D. and Sutherland, F.L. (1996) Olivine ‘leucitites', their xenolith and megacryst suites, Hoskings Peak, north Queensland. Australian Journal of Earth Sciences, 43, 231–244.CrossRefGoogle Scholar
Beccaluva, L., Bonadiman, C., Coltorti, M., Salvini, L. and Siena, F. (2001) Depletion events, nature of metasomatising agent and timing of enrichment processes in lithospheric mantle xenoliths from the Veneto Volcanic Province. Journal of Petrology, 42, 173–187.CrossRefGoogle Scholar
Bodinier, J-L., Merlet, C, Bedini, R.M., Simien, F., Remaidi, M. and Garrido, CJ. (1996) Distribution of niobium, tantalum and other highly incompatible elements in the lithospheric mantle: the spinel paradox. Geochimica Cosmochimica Ada, 60, 545–550.CrossRefGoogle Scholar
Brooks, C.K. and Printzlau, I. (1978) Magma mixing in mafic alkaline volcanic rocks: the evidence from relict phenocryst phases and other inclusions. Journal of Volcanology and Geothermal Research, 4, 315–331.CrossRefGoogle Scholar
Brousse, R. and Varet, J. (1966) Les trachytes du Mont Dore et du Cantal septentrional et leurs enclaves. Bulletin de la Societe geologique de France, 8, 246–262.CrossRefGoogle Scholar
Chapman, N.A. (1976) Inclusions and megacrysts from under-saturated tuffs and basanites, East Fife, Scotland. Journal of Petrology, 17, 472–498.CrossRefGoogle Scholar
Chapman, N.A. and Powell, R. (1976) Origin of anorthoclase megacrysts in alkali basalts. Contributions to Mineralogy and Petrology, 58, 29–35.CrossRefGoogle Scholar
Coenraads, R.R. (1992) Surface feature on natural rubies and sapphires derived from volcanic provinces. Journal of Gemmology, 23, 151–160.CrossRefGoogle Scholar
Coenraads, R.R., Sutherland, F.L. and Kinny, P.D. (1990) The origin of sapphires: U-Pb dating of zircon inclusions sheds new light. Mineralogical Magazine, 54, 113–122.CrossRefGoogle Scholar
Coenraads, R.R., Vichit, P. and Sutherland, F.L. (1995) An unusual sapphire-zircon-magnetite xenolith from the Chonthaburi gem province, Thailand. Mineralogical Magazine, 59, 467–481.CrossRefGoogle Scholar
Coltorti, M., Bonadiman, C., Hinton, R.W., Siena, F. and Upton, B.G.J. (1999) Carbonatite metasomatism of the oceanic upper mantle: evidence from clinopyroxenes and glasses in ultramafic xenoliths of Grande Comore, Indian Ocean. Journal of Petrology, 40, 133–165.CrossRefGoogle Scholar
Coltorti, M., Beccaluva, L., Bonadiman, C., Salvini, L. and Siena, F. (2000) Glasses in mantle xenoliths as geochemical indicators of metasomatic agents. Earth and Planetary Science Letters, 183, 303–320.CrossRefGoogle Scholar
Downes, H. (1993) The nature of the lower continental crust of Europe: petrological and geochemical evidence from xenoliths. Physics of the Earth and Planetary Interiors, 79, 195–218.CrossRefGoogle Scholar
Downes, H., Upton, B.G.J., Handisyde, E. and Thirlwall, M.F. (2001) Geochemistry of mafic and ultramafic xenoliths from Fidra (Southern Uplands, Scotland): implications for lithosphere processes in Permo-Carboniferous times. Lithos, 58, 15–124.CrossRefGoogle Scholar
Draper, D.S. and Green, T.H. (1997) P-T phase relations of silicic, alkaline, aluminous mantle-xenolith glasses under anhydrous and C—O—H fluid-saturated conditions. Journal of Petrology, 38, 1187–1224.CrossRefGoogle Scholar
Duda, A. and Schmincke, H.-U. (1985) Polybaric differentiation of alkali basaltic magmas: evidence from green-core clinopyroxenes (Eifel, FRG). Contributions to Mineralogy and Petrology, 91, 340–353.CrossRefGoogle Scholar
Edgar, A.D., Lloyd, F.E., Forsyth, D.M. and Barnett, R.L. (1989) Origin of glass in upper mantle xenoliths from the Quaternary volcanics of Gees, West Eifel, Germany. Contributions to Mineralogy and Petrology, 103, 277–286.CrossRefGoogle Scholar
Finch, A.A. and Klein, J. (1999) The causes and petrological significance of cathodoluminescence emissions from alkali feldspar. Contributions to Mineralogy and Petrology, 135, 234–243.CrossRefGoogle Scholar
Gaillou, E. (2003) Les saphirs du Massif Central: etude mineralogique des saphirs du Sioulot, du Mont Coupet et du Menoyre. Determination de leur origine. Diplome d'Etude Approfondie, Universite Blaise-Pascal, Clermont-Ferrand, France, 45 pp.Google Scholar
Giuliani, G., Fallick, A., Ohnenstetter, D. and Pegere, G. (2009) Oxygen isotopes composition of sapphires from the French Massif Central: implications for the origin of gem corundum in basaltic fields. Mineralium Deposita, 44, 221–231.CrossRefGoogle Scholar
Graham, I., Sutherland, L., Zaw, Khin, Nechaev, V. and Khanchuk, A. (2008) Advances in our understanding of the gem corundum deposits of the West Pacific continental margins intraplate basaltic fields. Ore Geology Reviews, 34, 200–215.CrossRefGoogle Scholar
Guo, J., O'reilly, S.Y. and Griffin, W.L. (1996a) Zircon inclusions in corundum megacrysts: 1. Trace element geochemistry and clues to the origin of corundum megacrysts in alkali basalts. Geochimica Cosmochimica Ada, 60, 2347–2363.CrossRefGoogle Scholar
Guo, J., O'Reilly, S.Y. and Griffin, W.L. (1996b) Corundum from basaltic terrains: a mineral inclusion approach to the enigma. Contributions to Mineralogy and Petrology, 122, 368–386.CrossRefGoogle Scholar
Guzmics, T., Kodolanyi, J., Kovacs, I., Szabo, C., Bali, E. and Ntaflos, T. (2008) Primary carbonatite melt inclusions in apatite and in K-feldspar of clino-pyroxene-rich mantle xenoliths hosted in lampro-phyre dikes (Hungary). Mineralogy and Petrology, 94, 225–242.CrossRefGoogle Scholar
Hinton, R.W. and Upton, B.G.J. (1991) The chemistry of zircon: variations within and between large crystals from syenite and alkali basalt xenoliths. Geochimica Cosmochimica Ada, 55, 3287–3302.CrossRefGoogle Scholar
Hirose, K. and Kawamoto, T. (1995) Partial melting of lherzolite at lGPa: the effect of H2O on the genesis of basaltic magmas. Earth and Planetary Science Letters, 133, 463–473.CrossRefGoogle Scholar
Hirschmann, M.M., Baker, M.B. and Stolper, E.M. (1998) The effect of alkalis on the silica content of mantle-derived fluids. Geochimica Cosmochimica Ada, 62, 883–902.CrossRefGoogle Scholar
Ionov, D.A., Hofmann, A.W. and Shimizu, N. (1994) Metasomatism-induced melting in mantle xenoliths from Mongolia. Journal of Petrology, 35, 753–785.CrossRefGoogle Scholar
Irving, AJ. (1974) Megacrysts from the Newer Basalts and other basaltic rocks of southeastern Australia. Geological Society of America Bulletin, 85, 1503–1514.2.0.CO;2>CrossRefGoogle Scholar
Irving, AJ. (1984) Polybaric mixing and fractionation of salic magmas: evidence from megacryst suites. EOS Transactions of the American Geophysical Union, 65, 1153.Google Scholar
Irving, AJ. (1986) Polybaric magma mixing in alkalic basalts and kimberlites: evidence from corundum, zircon and ilmenite deposits. Pp. 262—264 in: 4* International Kimberlite Conference, Perth, Extended Abstracts, Series 16, Geological Society of Australia, Sydney, Australia.Google Scholar
Irving, AJ. and Frey, F.A. (1984) Trace element abundances in megacrysts and their host basalts: Constraints on partition coefficients and megacryst genesis. Geochimica Cosmochimica Ada, 48, 1201–1221.CrossRefGoogle Scholar
Irving, AJ. and Price, R.C. (1981) Geochemistry and evolution of lherzolite-bearing phonolitic lavas from Nigeria, Australia and New Zealand. Geochimica Cosmochimica Ada, 45, 1309–1320.CrossRefGoogle Scholar
Macintyre, R.M., Cliff, R.A. and Chapman, N.A. (1981) Geochronological evidence for phased volcanic activity in Fife and Caithness necks, Scotland. Transactions of the Royal Society of Edinburgh, Earth Sciences, 72, 1–7.CrossRefGoogle Scholar
Marfunin, A.S. and Bershov, L.V. (1970) Electron-hole centers in feldspars and their possible crystal chemical and petrological significance. Doklady Akademii Nauka, 193, 412–414. (in Russian).Google Scholar
Marshall, D.J. (1988) Cathodoluminescence of Geological Materials, Unwin-Hyman, Boston, USA, 146 pp.Google Scholar
Monchoux, P., Fontan, F., De Parseval, P., Martin, R.F. and Wang, R.-C. (2006) Igneous albitite dikes in orogenic lherzolites, western Pyrenees, France: a possible source for corundum and alkali feldspar xenocrysts in basaltic terrains. I. Mineralogical associations. The Canadian Mineralogist, 44, 817–842.CrossRefGoogle Scholar
Morten, L. and De Francesco, A.M. (1993) Megacrysts in basanites from Monti Lessini, Veneto Region, northern Italy. Rendiconti Lincei, 94, 315–336.CrossRefGoogle Scholar
Navon, O. and Stolper, E. (1987) Chemical conse-quences of melt percolation: the upper mantle as a chromatographic column. Journal of Geology, 95, 285–307.CrossRefGoogle Scholar
Neumann, E.-R. and Wulff-Pedersen, E. (1996) The origins of the highly silicic glass in the mantle xenoliths from the Canary Islands. Journal of Petrology, 38, 1513–1540.CrossRefGoogle Scholar
O'Reilly, S.Y. and Griffin, W.L. (1987) Australia -4000 kilometres of mantle samples. Pp. 267—286 in: Mantle Xenoliths (Nixon, P. H., editor). John Wiley & Sons, New York.Google Scholar
Pilet, S., Hernandez, J. and Villemant, B. (2002) Evidence for high silicic melt circulation and metasomatic events in the mantle beneath alkaline provinces: the Na-Fe augitic green-core pyroxenes in the Tertiary alkali basalts of the Cantal massif (French Massif Central). Mineralogy and Petrology, 76, 39–62.CrossRefGoogle Scholar
C., Pin, Paquette, J.L., Monchoux, P. and Hammouda, T. (2001) First field-scale occurrence of Si-Al-Na-rich low-degree partial melts from the upper mantle. Geology, 29, 451–454.Google Scholar
Pin, C., Monchoux, P., Paquette, P., Azambre, B., Wang, R.-C. and Martin, R.F. (2006) Igneous albitite dikes in orogenic lherzolites, western Pyrenees: a possible source for corundum and alkali feldspar xenocrysts in basaltic terranes. II. Geochemical and petrogenetic considerations. The Canadian Mineralogist, 44, 843–856.CrossRefGoogle Scholar
Robertson, A.D.C. and Sutherland, F.L. (1992) Possible origins and ages for sapphire and diamond from the Central Queensland gem fields. Records of the Australian Museum, Supplement, 15, 45–54.CrossRefGoogle Scholar
Schiano, P. and Clocchiatti, R. (1994) Worldwide occurrences of silica-rich sub-continental and sub-oceanic mantle minerals. Nature, 368, 621–624.CrossRefGoogle Scholar
Schiano, P., Clocchiatti, R. and Joron, J.L. (1992) Melt and fluid inclusions in basalts and xenoliths from Tahaa Island, Society Archipelago: evidence for a metasomatized upper mantle. Earth and Planetary Science Letters, 111, 69–82.CrossRefGoogle Scholar
Schiano, P., Clocchiatti, R., Shimizu, N., Weiss, D. and Mattielli, N. (1994) Cogenetic silica-rich and carbonate-rich melts trapped in mantle minerals in Kerguelen ultramafic xenoliths: implications for metasomatism in the oceanic upper mantle. Earth and Planetary Science Letters, 123, 167–178.CrossRefGoogle Scholar
Schiano, P., Bourdon, B., Clocchiatti, R., Massare, D., Varela, M.E. and Bottinga, Y. (1998) Low-degree partial melting trends recorded in upper mantle minerals. Earth and Planetary Science Letters, 160, 537–550.CrossRefGoogle Scholar
Schultz, D.J. (1987) Megacrysts from alkalic volcanic rocks. Pp. 433–451 in: Mantle Xenoliths (Nixon, P. H., editor). John Wiley & Sons, New York.Google Scholar
Slaby, E., Gotze, J., Worner, G., Simon, K., Wrzalik, R. and Migielski, M. (2008) K-feldspar phenocrysts in microgranular magmatic enclaves: A cathodoluminescence and geochemical study of crystal growth as a marker of magma mingling dynamics. Lithos 105, 85–97.CrossRefGoogle Scholar
Stahle, V., Frenzel, G., Kober, B., Michard, A, Puchelt, H. and Schneider, W. (1990) Zircon syenite pegmatites in the Finero peridotite (Ivrea Zone): evidence for a syenite from a mantle source. Earth and Planetary Science Letters, 101, 196–205.CrossRefGoogle Scholar
Stephenson, P.J. (1976) Sapphire and zircon in some basaltic rocks from Queensland, Australia. Abstracts 25* International Geological Congress, 2, 602—603.Google Scholar
Stephenson, P.J. (1990) The geological context of sapphire occurrences in the Anakie region, Central Queensland. Geological Society of Australia, Abstract Series, 25, 232–233.Google Scholar
Sutherland, F.L. (1996) Alkaline rocks and gemstones, Australia: a review and synthesis. Australian Journal of Earth Sciences, 43, 323–343.CrossRefGoogle Scholar
Sutherland, F.L. and Coenraads, R.R. (1996) An unusual ruby-sapphire-sapphirine-spinel assemblage from the Tertiary Barrington volcanic province, New South Wales, Australia. Mineralogical Magazine, 60, 623–638.CrossRefGoogle Scholar
Sutherland, F.L., Hoskin, P.W.O., Fanning, C.M. and Coenraads, R.R. (1998) Models of corundum origin from alkali basaltic terrains: a reappraisal. Contributions to Mineralogy and Petrology, 133, 356–372.CrossRefGoogle Scholar
Sutherland, F.L., Bosshart, G., Fanning, C.M., Hoskin, P.W.O. and Coenraads, R.R. (2002a) Sapphire crystallization, age and origin, Ban Huai Sai, Laos: age based on zircon inclusions. Journal of Asian Earth Sciences, 20, 841–849.CrossRefGoogle Scholar
Sutherland, F.L., Graham, I.T., Pogson, G., Schwartz, D., Webb, G.B., Coenraads, R.R., Fanning, CM., Hollis, J.D. and Allen, T.C. (20026) The Tumbarumba basaltic gem field, New South Wales: in relation to sapphire-ruby deposits of Eastern Australia. Records of the Australian Museum, 54, 215–248.CrossRefGoogle Scholar
Thompson, R.N. (1974) Some high-pressure pyroxenes. Mineralogical Magazine, 39, 768–787.CrossRefGoogle Scholar
Tietz, O. and Biichner, J. (2007) Abundant in-situ zircon megacrysts in Cenozoic basaltic rocks in Saxony, Germany. Zeitschrift der Deutschen Gesellschqft fur Geowissenschaften. 158, 201–206.CrossRefGoogle Scholar
Ulrych, J. and Ujer, P. (1999) Low-hafnium zircon from alluvial and colluvial placers of northern Bohemia: composition and possible sources. Geologia Sudetica, 32, 139–146.Google Scholar
Upton, B.G.J., Aspen, P. and Chapman, N.A. (1983) The upper mantle and deep crust beneath the British Isles: evidence from inclusions in volcanic rocks. Journal of the Geological Society, London, 140, 105–121.CrossRefGoogle Scholar
Upton, B.G.J., Aspen, P., Rex, D.C., Melcher, F. and Kinny, P. (1998) Lower crustal and possible shallow mantle samples from beneath the Hebrides — evidence from a xenolithic dyke at Gribun, western Mull. Journal of the Geological Society, London, 155, 813–828.CrossRefGoogle Scholar
B.G.J., Upton, Hinton, R.W., Aspen, P., Finch, A. and Valley J.W. (1999) Megacrysts and associated xenoliths: evidence for migration of geochemically enriched melts in the upper mantle beneath Scotland. Journal of Petrology, 40, 935–956.Google Scholar
Witt-Eickschen, G., Kaminsky, W., Kramm, U. and Harte, B. (1998) The nature of young vein metasomatism in the lithosphere of the west Eifel (Germany): geochemical and isotopic constraints from composite mantle xenoliths from the Meerfelder Maar. Journal of Petrology, 39, 155–185.CrossRefGoogle Scholar
Wright, J.B. (1966) Olivine nodules in phonolite of the East Otago Alkaline Province, New Zealand. Nature, 210, 519–520.CrossRefGoogle Scholar
Wright, J.B. (1969) Olivine nodules and related inclusions in trachyte from the Jos Plateau, Nigeria. Mineralogical Magazine, 37, 370–374.CrossRefGoogle Scholar
Wright, J.B. (1970) High pressure phases in Nigerian Cenozoic lavas. Distribution and geotectonic setting. Bulletin ofVolcanology, 34, 833–847.CrossRefGoogle Scholar
Wulff-Pedersen, E., Neumann, E.-R. and Jensen, B.B. (1996) The upper mantle under La Palma, Canary Islands: formation of Si-K-Na rich melt and its importance as metasomatic agent. Contributions to Mineralogy and Petrology, 125, 113–139.CrossRefGoogle Scholar
Yoder, H.S. Jr. and Upton, B.G.J. (1971) Diopside-sanidine-H2O at 5 and 10 kb. Carnegie Institution of Washington Year Book, 70, 108–112.Google Scholar
Yui, T.-F., Wu, C.-M., Limtrakun, P., Sricharn, W. and Boonsoong, A. (2006) Oxygen isotope studies on placer sapphire and ruby in the Chanthaburi-Trat alkali basaltic gemfield, Thailand. Lithos, 86, 197–211.CrossRefGoogle Scholar
Zajacz, Z., Kovacs, I., Szabo, C., Halter, W. and Pettke, T. (2007) Evolution of mafic alkaline melts crystallized in the uppermost lithospheric mantle: a melt inclusion study of olivine-clinopyroxenite xenoliths, Northern Hungary. Journal of Petrology, 48, 853–883.CrossRefGoogle Scholar
Zaw, K., Sutherland, F.L., Dellapasqua, F., Ryan, C.G., Tzen-Fu Yui, Mernagh, T.P. and Duncan, D. (2006) Contrasts in gem corundum characteristics, eastern Australian basaltic fields: trace elements, fluid/melt inclusions and oxygen isotopes. Mineralogical Magazine, 70, 669–687.CrossRefGoogle Scholar