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The petrology of the Lugar Sill, SW Scotland

Published online by Cambridge University Press:  03 November 2011

C. M. B. Henderson  and
F. G. F. Gibb
C. M. B. Henderson
Affiliation:
Department of Geology, The University, Manchester M13 9PL, England.
F. G. F. Gibb
Affiliation:
Department of Geology, The University, Sheffield S1 3JD, England.
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Abstract

A 49 m complete section through the 288 Ma Lugar Sill obtained from drill cores can be subdivided into nine units. The uppermost four units are teschenitic and are mirror images of the bottom four. A 35 m thick central unit consists of theralite passing down into kaersutite theralite and then picrite. Marginal chilling 'of the units indicates multiple intrusion from the outside inwards. Olivine in the central unit (Fo88–90) encloses Cr-rich spinels and increases in amount inwards to over 50%. Clinopyroxene, kaersutite and biotite show symmetrically increasing Fe/Mg from the centre of the sill outwards. Most major and trace elements vary symmetrically throughout the sill with those in the central unit reflecting mainly olivine distribution but incompatible elements exhibit upward enrichment. Remarkably, the most-evolved rocks in the sill are at its margins. The sill was formed by multiple injections of successively less-evolved teschenitic magmas followed by a larger pulse of theralitic liquid carrying abundant olivine phenocrysts. The amount of olivine in this final pulse increased during emplacement. Subsequent in-situ differentiation in the central unit, with upward enrichment in residual liquid and volatiles, gave rise to lugarites. The various magmas were produced in a lower-level magma chamber by differentiation of a mantle-derived, alkali-rich picritic magma.

Keywords

Alkalinedifferentiated silllugaritemultiple intrusionPermo-Carboniferouspicriteteschenitetheralite
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 77 , Issue 4 , 1987 , pp. 325 - 347
Copyright
Copyright © Royal Society of Edinburgh 1987

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References

Bhattacharji, S. & Smith, C. H. 1964. Flowage differentiation. SCIENCE, N.Y. 145, 150–3.CrossRefGoogle ScholarPubMed
Brooks, C. K. 1977. The Fe2O3/FeO ratio of basalt analyses: an appeal for a standardized procedure. BULL GEOL SOC DENMARK 25, 117–20.CrossRefGoogle Scholar
Brown, W. L. & Parsons, I. 1981. Towards a more practical two-feldspar geothermometer. CONTRIB MINERAL PETROL 76, 369–377.CrossRefGoogle Scholar
Bryan, W. B., Finger, L. W. & Chayes, F. 1969. Estimating proportions in petrographic mixing equations by least squares approximation. SCIENCE N.Y. 163, 1926–27.CrossRefGoogle ScholarPubMed
Buddington, A. F. & Lindsley, D. H. 1964. Iron-titanium oxide minerals and synthetic equivalents. J PETROL 5, 310–57.CrossRefGoogle Scholar
Burnham, C. W., Holloway, J. R. & Davis, N. F. 1969. Thermodynamic properties of water to 1,000°C and 10,000 bars. GEOL SOC AMER SPEC PAP 132.Google Scholar
Butcher, A. R. 1985. Channelled metasomatism in Rhum layered cumulates—evidence from late-stage veins. GEOL MAG 122, 503–18.CrossRefGoogle Scholar
Dickin, A. L., Henderson, C. M. B. & Gibb, F. G. F. 1984. Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland. MINERAL MAG 48, 311–22.CrossRefGoogle Scholar
Drever, H. I. & Johnston, R. 1958. The petrology of picritic rocks in minor intrusions—a Hebridean Group. TRANS R SOC EDINBURGH 63, 459–99.CrossRefGoogle Scholar
Drever, H. I. & Johnston, R. 1967. Picritic minor intrusions. In Wyllie, P. J. (ed.) Ultramafic and related rocks, 71–82. New York: J. Wiley.Google Scholar
Eby, G. N. 1984. Monteregian Hills. I. Petrography, major and trace element geochemistry, and Sr isotopic chemistry of the western intrusions: Mount Royal, St. Bruno, and Johnson. J PETROL 25, 421–52.CrossRefGoogle Scholar
Eyles, V. A., Simpson, J. B. & MacGregor, A. G. 1949. Geology of Central Ayrshire. MEM GEOL SURV SCOTLAND.Google Scholar
Faithfull, J. W. 1985. The Lower Eastern Layered Series of Rhum. GEOL MAG 122, 459–68.CrossRefGoogle Scholar
Flett, J. S., 1931. The Saline No. 1 Teschenite. SUMM PROGR GEOL SURV Pt II, 44–51.Google Scholar
Frey, F. A., Green, D. H. & Roy, S. D. 1978. Integrated models of basalt petrogenesis: a study of quartz tholeiites to olivine melilitites from South Australia utilizing geochemical and experimental petrological data. J PETROL 19, 463–513.CrossRefGoogle Scholar
Gamble, J. A. 1984. Petrology and geochemistry of differentiated teschenite intrusions from the Hunter Valley, New South Wales, Australia. CONTRIB MINERAL PETROL 88, 173–87.CrossRefGoogle Scholar
Gibb, F. G. F. 1973. The zoned clinopyroxenes of the Shiant Isles sill, Scotland. J PETROL 14, 203–30.CrossRefGoogle Scholar
Gibb, F. G. F. & Henderson, C. M. B. 1978a. The petrology of the Dippin sill, Isle of Arran. SCOTT J GEOL 14, 1–27.CrossRefGoogle Scholar
Gibb, F. G. F. & Henderson, C. M. B. 1978b. Possible higher pressure relics within titaniferous augites in a basic sill. GEOL MAG 115, 55–62.CrossRefGoogle Scholar
Gibb, F. G. F. & Henderson, C. M. B. 1984. The structure of the Shiant Isles sill complex, Outer Hebrides. SCOTT J GEOL 20, 21–9.CrossRefGoogle Scholar
Hamilton, D. L. & MacKenzie, W. S. 1965. Phase equilibria studies in the system NaAlSiO4 (nepheline)-KAlSiO4 (kalsilite)–SiO2–H2O. MINERAL MAG 34, 214–31.Google Scholar
Hatch, F. H., Wells, A. K. & Wells, M. K. 1972. Petrology of the igneous rocks, 13th edn. London: George Allen & Unwin.Google Scholar
Helz, R. T. 1982. Experimental studies of amphibole stability. REVS IN MINERAL (MIN SOC AMER) 9B, 279–353.Google Scholar
Henderson, C. M. B. & Gibb, F. G. F. 1972. Plagioclase-Ca-rich-nepheline intergrowths in a syenite from the Marangudzi complex. Rhodesia. MINERAL MAG 38, 670–7.CrossRefGoogle Scholar
Henderson, C. M. B. & Gibb, F. G. F. 1977. Formation of analcime in the Dippin sill, Isle of Arran. MINERAL MAG 41, 534–7.CrossRefGoogle Scholar
Henderson, C. M. B. & Gibb, F. G. F. 1983. Felsic mineral crystallization trends in differentiating alkaline basic magmas. CONTRIB MINERAL PETROL 84, 355–64.CrossRefGoogle Scholar
Henderson, C. M. B., Foland, K. A. & Gibb, F. G. F. 1987. The age of the Lugar sill and a discussion of the late-Carboniferous-Early-Permian sill complex of S.W. Scotland. GEOL J 22 (to appear).CrossRefGoogle Scholar
Ludington, S. 1978. The biotite-apatite geothermometer revisited. AMER MINERAL 63, 551–3.Google Scholar
Martin, D. J. 1985. Microstructure, geochemistry and differentiation of a primary teschenite sill. GEOL MAG 122, 335–50.CrossRefGoogle Scholar
Munoz, J. L. & Ludington, S. D. 1974. Fluorine-hydroxyl exchange in biotite. AMER J SCI 274, 396–413.CrossRefGoogle Scholar
Murata, K. J. & Richter, D. H. 1966. Chemistry of the lavas of the 1959–60 eruption of the Kilauea Volcano, Hawaii. US GEOL SURV PROF PAP 537–A.Google Scholar
Powell, M. & Powell, R. 1974. An olivine-clinopyroxene geothermometer. CONTRIB MINERAL PETROL 48, 249–63.CrossRefGoogle Scholar
Powell, R. & Powell, M. 1977. Geothermometry and oxygen barometry using coexisting iron-titanium oxides: a reappraisal. MINERAL MAG 41, 257–63.CrossRefGoogle Scholar
Roeder, P. L. & Emslie, R. F. 1970. Olivine-liquid equilibrium. CONTRIB MINERAL PETROL 29, 275–89.CrossRefGoogle Scholar
Sack, R. O. & Carmichael, I. S. E. 1984. Fe2 = Mg2 and TiAl2 = MgSi2 exchange reactions between clinopyroxene and silicate melts. CONTRIB MINERAL PETROL 85, 103–15.CrossRefGoogle Scholar
Simkin, T. 1967. Flow differentiation in the picritic sills of North Skye. In Wyllie, P. J. (ed.) Ultramafic and related rocks, 64–9. New York: J. Wiley.Google Scholar
Speer, J. A. 1984. Micas in igneous rocks. REVS IN MINERAL (MIN SOC AMER) 13, 299–356.Google Scholar
Stormer, J. C. 1975. A practical two-feldspar geothermometer. AMER MINERAL 60, 667–74.Google Scholar
Stormer, J. C. & Carmichael, I. S. E. 1971. Fluorine-hydroxyl exchange in apatite and biotite: a potential igneous geothermometer. CONTRIB MINERAL PETROL 31, 121–31.CrossRefGoogle Scholar
Tracy, R. J. & Robinson, P. 1977. Zoned titanian augite in alkali olivine basalt from Tahiti and the nature of titanium substitutions in augite. AMER MINERAL 62, 634–45.Google Scholar
Turner, F. J. & Verhoogen, J. 1960. Igneous and metamorphic petrology, 2nd edn. New York, Toronto, London: McGraw-Hill.Google Scholar
Tyrrell, G. W. 1917. The picrite-teschenite intrusion of Lugar (Ayrshire). Q J GEOL SOC LONDON 62, 84–131.Google Scholar
Tyrrell, G. W. 1948. A boring through the Lugar Sill. TRANS GEOL SOC GLASGOW 21, 157–202.CrossRefGoogle Scholar
Tyrrell, G. W. 1952. A second boring through the Lugar Sill. TRANS EDINBURGH GEOL SOC 15, 374–92.CrossRefGoogle Scholar
Wager, L. R. & Brown, G. M. 1968. Layered igneous rocks. 1st edn. Edinburgh: Oliver & Boyd.Google Scholar
Wones, D. R. 1981. Mafic silicates as indicators of intensive variables in granitic magmas. MINING GEOL 31, 191–212.Google Scholar
Wood, B. J. 1976. An olivine-clinopyroxene geothermometer: A discussion. CONTRIB MINERAL PETROL 56, 297–303.CrossRefGoogle Scholar
Worner, G. & Schmincke, H.-U. 1986. Petrogenesis of the zoned Laacher See tephra. J PETROL 25, 836–851.CrossRefGoogle Scholar
Yoder, H. S. & Tilley, C. E. 1962. Origin of basalt magmas: an experimental study of natural and synthetic rock systems. J PETROL 3, 342–532.CrossRefGoogle Scholar