Abstract
The Kelly's Mountain gneiss complex of Cape Breton Island, Nova Scotia, is a migmatitic paragneiss dominated by biotite- and cordierite-bearing assemblages. Metamorphic grade throughout the complex is in the upper amphibolite facies, with garnet absent and only retrograde muscovite present. In the high grade core of the complex the reaction biotite+andalusite+quartz=cordierite+K-feldspar+sillimanite+ilmenite+H2O is preserved. The pelitic migmatites contain cordierite- and K-feldspar-rich leucosomes and biotite-rich melanosomes. Minor clinopyroxene-bearing amphibolite in the complex does not show migmatitic textures. The migmatites are interpreted as in situ peraluminous partial melts on the basis of phase relations and textural criteria. Retrograde metamorphism under conditions of high fluid pressure locally produced muscovite after K-feldspar and muscovite+green biotite+chlorite after cordierite in paragneiss, and sphene after ilmenite in amphibolite. Peak metamorphic conditions of 1–3.5 kb and 580–700° C are estimated. The high geothermal gradient inferred from these conditions was probably caused by the intrusion of diorites associated with the gneiss complex. The Kelly's Mountain complex represents a rare example of migmatites formed in the low-pressure facies series, and illustrates some of the reactions involving melting in high grade pelitic rocks.
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References
Arzi AA (1978) Critical phenomena in the rheology of partially melted rocks. Tectonophysics 44:173–184
Atherton MP, Gribble CD (1983) Migmatites, melting, and metamorphism. Shiva Publishing Ltd., Nantwich, p 326
Abbott RN, Clarke DB (1979) Hypothetical liquidus relationships in the subsystems Al2O5-FeO-MgO projected from quartz, alkali feldspar and plagioclase for a (H2O)=1. Can Mineral 17:549–560
Althaus E (1967) The triple point andalusite-sillimanite-kyanite. Contrib Mineral Petrol 16:29–44
Barr SM, O'Reilly GA, O'Beirne AM (1982) Geology and geochemistry of selected granitoid plutons of Cape Breton Island. Nova Scotia Dept Mines Energy Pap 82-1, p 176
Berg JH, Docka JA (1983) Geothermometry in the Kiglapait contact aureole, Labrador. Am J Sci 283:414–434
Binns RA (1969) Hydrothermal investigations of the amphibolite-granulite facies boundary. Spec Publ Geol Soc Aust 2:341–344
Brown M, Earle MM (1983) Cordierite-bearing schists and gneisses from Timor, eastern Indonesia:P-T conditions of metamorphism and tectonic implications. J Metamorph Geol 1:183–203
Carmichael DM (1969) On the mechanism of prograde metamorphic reactions in quartz-bearing pelitic rocks. Contrib Mineral Petrol 20:244–267
Chappell BW, White AJR (1974) Two contrasting granite types. Pac Geol 8:173–174
Clarke DB (ed) (1981) Peraluminous granites. Can Mineral 19:12–216
Clemens JD, Wall VJ (1981) Origin and crystallization of some peraluminous (S-type) granitic magmas. Can Mineral 19:111–131
Day HW, Kumin HJ (1980) Thermodynamic analysis of the aluminum silicate triple point. Am J Sci 280:265–287
Ehlers EC (1972) The interpretation of geological phase diagrams. WH Freeman, San Francisco
Elias P (1983) Alteration of cordierite from Kelly's Mountain, Cape Breton Island. Unpublished report, Dalhousie University
Etheridge MA, Wall VJ, Vernon RH (1983) The role of the fluid phase during regional metamorphism and deformation. J Metamorph Geol 1:207–226
Flood RH, Shaw SE (1975) A cordierite-bearing granite suite from the New England batholith, NSW, Australia. Contrib Mineral Petrol 52:157–164
Fyfe WS, Price NJ, Thompson AB (1978) Fluids in the earth's crust. Elsevier, Amsterdam, p 383
Grambling JA (1981) Kyanite, andalusite, sillimanite, and related mineral assemblages in the Truchas Peaks region, New Mexico. Am Mineral 66:702–722
Grant JA (1983) Phase equilibria in low-pressure melting of pelitic rocks. In: Atherton MP, Gribble CD (ed) Migmatites, melting, and metamorphism. Shiva, Nantwich, p 292–293
Gupta LN, Johannes W (1982) Petrogenesis of a stromatic migmatite (Neulag, southern Norway). J Petrol 23:548–567
Haslam HW (1983) An Isotropic alteration product of cordierite. Mineral Mag 47:238–240
Helz RT (1973) Phase relations of basalts in their melting range at\(P_{H_2 O} = 5kb\) as a function of oxygen fugacity. Part I. Mafic phases. J Petrol 14:249–302
Hodges KV, Spear FS (1982) Geothermometry, geobarometry and the Al2SiO5 triple point at Mt. Moosilauke, New Hampshire. Am Mineral 67:1118–1134
Hoffer E (1976) The reaction sillimanite+biotite+quartz=cordierite+K-feldspar+H2O and partial melting in the system K2O-FeO-MgO-Al2O3-SiO2-H2O. Contrib Mineral Petrol 55:127–130
Holdaway MJ (1971) Stability of andalusite and the aluminum silicate phase diagram. Am J Sci 271:97–131
Holdaway MJ, Lee SM (1977) Fe-Mg cordierite stability in high grade pelitic rocks based on experimental, theoretical, and natural observations. Contrib Mineral Petrol 63:175–198
Jamieson RA (1982) The petrology of cordierite gneisses, Kelly's Mountain, Nova Scotia. Geol Assoc Can Progr Abstr 7:57
Jamieson RA (in press) Timing of tectonism in the Cape Breton Highlands — new evidence from Rb-Sn geochronology. Can J Earth Sci
Jamieson RA, Craw D (1983) Reconnaissance mapping of the southern Cape Breton Highlands — a preliminary report. Geol Surv Can Pap 83-1A:263–268
Johannes W, Gupta LN (1982) Origin and evolution of a migmatite. Contrib Mineral Petrol 79:114–123
Labotka TC (1981) Petrology of an andalusite-type regional metamorphic terrane, Panamint Mountains, California. J Petrol 22:261–296
Lee SM, Holdaway MJ (1976) Significance of Fe-Mg cordierite stability relations on temperature, pressure, and water pressure in cordierite granulites. In: Heacock JG (ed) The Earth's Crust: its Nature and Physical Properties. Am Geophys Union Mon 20:79–94
Lonker SW (1981) TheP-T-X relations of the cordierite-garnet-sillimanite-quartz equilibrium. Am J Sci 281:1056–1090
McLellan EL (1983) Contrasting textures in metamorphic and anatectic migmatites: an example from the Scottish Caledonides. J Metamorph Geol 1:241–262
Mehnert KR (1968) Migmatites and the origin of granitic rocks. Elsevier, Amsterdam, p 393
Milligan GC (1970) Geology of the George River Series, Cape Breton. Nova Scotia Dept Mines Mem 7:111
Moody JB, Meyer D, Jenkins JE (1983) Experimental characterization of the greenschist/amphibolite boundary in mafic systems. Am J Sci 283:48–92
Olsen SN (1977) Origin of the Baltimore Gneiss migmatites at Piney Creek, Maryland. Geol Soc Am Bull 88:1089–1101
Olsen SN (1982) Open- and closed-system migmatites in the Front Range, Colorado. Am J Sci 282:1596–1622
Olszewski WJ, Gaudette HE, Keppie JD, Donohoe HV (1981) Rb-Sr whole rock age of the Kelly's Mountain basement complex, Cape Breton Island. Geol Soc Am Abstr Progr 13:169
Phillips GN, Wall VJ, Clemens JD (1981) Petrology of the Strathbogie batholith: a cordierite-bearing granite. Can Mineral 19:47–63
Pichavant M (1981) An experimental study of the effect of boron on a water saturated haplogranite at 1 kbar vapour pressure. Contrib Mineral Petrol 76:430–439
Price RC (1983) Geochemistry of a peraluminous granitoid suite from north-eastern Victoria, south-eastern Australia. Geochim Cosmochim Acta 47:31–42
Richardson SW, Gilbert MC, Bell PM (1969) Experimental determination of kyanite-andalusite and andalusite-sillimanite equilibria: the aluminum silicate triple point. Am J Sci 267:259–272
Salje E, Werneke C (1982) The phase equilibrium between sillimanite and andalusite as determined from lattice vibrations. Contrib Mineral Petrol 79:56–67
Schreyer W, Yoder HS (1961) Petrographic guides to the experimental petrology of cordierite. Carnegie Inst Wash Yearb 60:147–152
Seifert F (1976) Stability of the assemblage cordierite+K-feldspar+quartz. Contrib Mineral Petrol 57:179–185
Selverstone J, Hollister LS (1980) Cordierite-bearing granulites from the Coast Ranges, British Columbia:P-T conditions of metamorphism. Can Mineral 18:119–129
Spear FS (1981) An experimental study of hornblende stability and compositional variation in amphibolite. Am J Sci 281:697–734
Thompson AB (1982) Dehydration melting of pelitic rocks and the generation of H2O-undersaturated granitic liquids. Am J Sci 282:1567–1595
Thompson AB, Algor JR (1977) Model systems for anatexis of pelitic rocks: I. Theory of melting reactions in the system KAlO2-NaAlO2-Al2O3-SiO2-H2O. Contrib Mineral Petrol 63:247–269
Thompson AB, Tracy RJ (1979) Model systems for anatexis of pelitic rocks: II. Facies series melting and reactions in the system CaO-KAlO2-NaAlO2-Al2O3-SiO2-H2O. Contrib Mineral Petrol 70:429–438
Thompson JB, Thompson AB (1976) A model system for mineral facies in pelitic schist. Contrib Mineral Petrol 58:243–277
Tracy RJ (1978) High grade metamorphic reactions and partial melting in pelitic schist, west-central Massachusetts. Am J Sci 278:150–178
Weill DS (1966) Stability relations in the Al2O3-SiO2 system calculated from solubilities in the Al2O3-SiO2-NaAlF system. Geochim Cosmochim Acta 30:223–277
Yardley BWD (1978) Genesis of the Skagit Gneiss migmatites, Washington, and the distinction between possible mechanisms of migmatization. Geol Soc Am Bull 89:941–951
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Jamieson, R.A. Low pressure cordierite-bearing migmatites from Kelly's Mountain, Nova Scotia. Contr. Mineral. and Petrol. 86, 309–320 (1984). https://doi.org/10.1007/BF01187136
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DOI: https://doi.org/10.1007/BF01187136