P-Tconditions during emplacement, and D2 regional metamorphism, of the Ben Vuirich Granite, Perthshire, Scotland

Mineralogical Magazine - Tập 64 Số 4 - Trang 737-753 - 2000
Y. Ahmed-Said1, Peter Tanner2
1PO Box 3671, Glasgow G42 9YA, UK
2Division of Earth Sciences, Gregory Building, University of Glasgow, Glasgow G12 8QQ, UK

Tóm tắt

AbstractThe 590±2 Ma Ben Vuirich Granite was intruded into late Proterozoic Dalradian rocks prior to the Grampian orogeny, during which it was affected by upper amphibolite facies regional metamorphism. Spotted cordierite and andalusite (chiastolite) hornfelses at the granite margin were altered to kyanite-and garnet-bearing assemblages during regional metamorphism. From the inferred mineralogy of the hornfels, together with the normative Qz–Ab–Or values of the granite and the application of a simple cooling model, we conclude that the country rocks immediately adjacent to the granite were hornfelsed atT= ∼600°C andP≤ 2 kbar.The hornfelsed rocks were subsequently metamorphosed during the regional D2 event to form an equilibrium mineral assemblage of muscovite + biotite + garnet + plagioclase + quartz + kyanite (after chiastolite). Garnet which grew during this event shows unusual reversed chemical zoning, with Ca increasing systematically from core to rim as Fe, Mg and Mn decrease. A study of element partitioning between coexisting phases in equilibrium (including zoned garnets), and use of an internally consistent thermodynamic dataset, suggest that isothermal (T= 577±42°C) compression (fromP= 6.2±1.6 kbar to 9.0±1.9 kbar) occurred during crustal thickening. K-feldspar-plagioclase-quartz veinlets found in the hornfels close the granite contact are demonstrated to be of igneous origin.

Từ khóa


Tài liệu tham khảo

Hollister, 1977, The reaction forming cordierite from garnet, the Khtada Lake metamorphic Complex, British Columbia, Canad. Mineral., 15, 217

10.2475/ajs.267.3.259

Ganguly, 1984, Mixing properties of aluminosilicate garnets: constraints from natural and experimental data, and application to geothermobarometry, Amer. Mineral., 69, 88

10.1017/S0016756800029757

Pantin, 1961, The stratigraphy and structure of the Blair Atholl-Ben a' Gloe area, Perthshire, Scotland, Trans. Roy. Soc. N.Z., 88, 597

10.2475/ajs.276.4.425

Moles, 1985, Metamorphic conditions and uplift history in central Perthshire: evidence from mineral equilibria in the Foss celsian-barite-sulphide deposit, Aberfeldy, J. Geol. Soc., 67, 1118

St-Onge, 1987, Zoned poikiloblastic garnets: P-T paths and syn-metamorphic uplift through 30 km of structural depth, Wopmay orogen, Canada, J. Geol., 28, 1

Bucker-Nurminen, 1990, Geological phase diagram software, Terra, 4, 401

Tracy, 1982, Characterization of Metamorphism through Mineral Equilibria, 355

10.1007/BF00372150

10.1111/j.1525-1314.1990.tb00495.x

10.1144/gsjgs.151.2.0209

10.1007/978-1-4612-5871-1_7

Kosiol, 1988, Redetermination of the anorthite beakdown reaction and improvement of the plagioclase-garnet-Al2SiO5 geobarometer, Amer. Mineral., 73, 216

10.1029/JZ069i004p00759

10.1093/petrology/13.1.147

Barrow, G. , Grant Wilson, J.S. and Cunningham Craig, B.A. (1905) The geology of the country round Blair Atholl, Pitlochry, and Aberfeldy (Explanation of Sheet 55). Memoir of the Geological Survey of Scotland.

10.1130/0091-7613(1990)018<0839:GARZIG>2.3.CO;2

Fuhrman, 1988, Ternary feldspar modelling and thermometry, Amer. Mineral., 73, 210

10.1016/0012-821X(76)90096-0

Holdaway, 1993, A reevaluation of the stability relations of andalusite: Thermochemical data and phase diagram for aluminium silicates, Amer. Mineral., 78, 298

10.1007/BF00324558

Stowell, 1996, Ca-metasomatism and chemical zonation of garnet in contact-metamorphic aureoles, Juneau gold belt, southe astern Alaska, Canad. Mineral., 34, 1195

Crawford, 1977, Calcium zoning in almandine garnet, Wissahickon formation, Philadelaph ia, Pennylvanna, Canad. Mineral., 15, 243

Dalmeyer, 1974, The role of crystal structure in controlling the partitioning of Mg and Fe+2 between coexisting garnet and biotite, Amer. Mineral., 59, 201

Ahmed-Said, Y. (1988) The geochemistry of thermal aureoles at Cashel, Co Galway (Ireland) and Comrie, Perthshire (Scotland). Unpubl. Ph.D Thesis, Univ. Glasgow, UK.

10.1007/BF00373040

Spear, 1993, Metamorphic Phase Equilibria and Phase-temperature Time Paths.

10.1144/sjg12020103

10.1144/gsjgs.146.5.0789

Tuttle, O.F. and Bowen, N.L. (1958) Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Mem. Geol. Soc. Amer., 74.

Holland, 1992, Plagioclase feldspars: activity-composition relations based upon Darken's Quadratic Formalism and Landau theory, Amer. Mineral., 77, 53

10.1111/j.1525-1314.1990.tb00458.x

10.1111/j.1525-1314.1985.tb00325.x

Powell, 1994, Optima geothermometry and geobarometry, Amer. Mineral., 79, 120

10.1017/S0016756800024547

10.1111/j.1525-1314.1997.00026.x

10.1144/sjg18020109

Indares, 1985, Biotite-garnet geothermometry in granulite facies: the influence of Ti and Al in biotite, Amer. Mineral., 70, 272

10.1007/BF01177588

10.1007/BF00398778

Spear, 1988, Evolution of Metamorphic Belts, 63

Deer, 1982, Rock-forming Minerals.

10.2475/ajs.291.10.917

10.2475/ajs.257.1.44

Hodges, 1982, Geothermometry, geobarometry and the Al2SiO5 triple point at Mt. Moosilauke, New Hampshire, Amer. Mineral., 67, 1118

10.1111/j.1525-1314.1986.tb00354.x

Berman, 1990, Mixing properties of Ca-Mg-Fe-Mn garnets, Amer. Mineral., 75, 328

Loomis, 1982, Kinetics and Equilibrium in Mineral Reaction, 1

10.1007/BF00373688

Piwinski, 1973, Experimental studies of igneous rock series, Central Sierra Nevada Batholith, California, part 2, Neues Jahrb. Mineral. Mh., 5, 193, 10.1127/njmm/1973/1973/193

Beddoe-Stephens, B. (1992) Pressures and temperatures of Dalradiam metamorphism, northeast Grampians: Dufftown-Keith area. British Geological Survey Technical Report WG/92/8.

Chinner, 1965, The kyanite isograde in Glen Clova, Angus, Scotland, Mineral. Mag., 34, 132

Thông tin
Thông tin xuất bản

Mineralogical Magazine

Tập 64 Số 4

737-753

Thông tin tác giả