Summary
Corona textures between olivine and plagioclase or orthopyroxene and plagioclase are present in Hercynian gabbroic rocks from the Calabrian Sila Massif. They have been studied through optical and SEM investigations together with EDS and WDS analyses. Textural features indicate the existence of two extreme corona types formed during late magmatic stages or during subsolidus cooling. Magmatic coronas are characterized by an inner orthopyroxene layer and an outer orange-brown amphibole layer that might be in optical continuity with orthopyroxene and amphibole poikilites respectively. Subsolidus coronas consist of an inner layer of colourless amphibole and an outer layer of amphibole ± spinel. They sometimes form a collar also around plagioclase enclosed in olivine. A large spectrum in the composition of corona amphiboles from Ti-bearing pargasite to Mg-hornblende was observed. The variation in Ti content of amphibole was interpreted as a consequence of the different conditions of crystallization from late magmatic to subsolidus with temperatures ranging from 880°C to 580°C. The significant gahnite component in spinel possibly indicates that subsolidus reactions occurred in an open system. The pressure of formation constrained by the mineral assemblage of metamorphic basement rocks and by the neighbouring diorites has been estimated at 4 kbar.
Zusammenfassung
In herzynischen gabbroiden Gesteinen des Sila Massives in Kalabrien treten Korona-texturen zwischen Olivin und Plagioklas oder Orthopyroxen und Plagioklas auf. Diese wurden mittels optischer Methoden und SEM in Verbindung mit EDS und WDS Analytik untersucht. Textureile Kriterien belegen die Existenz zweier verschiedenartiger Koronatypen die während deospätmagmatischen Stadiums oderwährend der Abkühlung lung im Subsolidus Bereich gebildet wurden. Die magmatischen Koronatexturen sind durch eine innere Othopyrozenschicht und eine äußere orange-braune Ampkibolschicht gekennzeichnet, die in optischer Kontinuatät Orthopyroxen bzw. Amphibihol-poikilitn steht. Subsolidus-Koronas bestehen aus einer inneren Lage eines farblosen Amphiboles und einer äußeren Schicht von Amphibol ± Spinell. Bisweilen umgeben sie ringförmig in Olivin eingeschlossenen Plagioklos. Die Amphibolzusammensetzung in diesen Koronas variiert stark von Ti-führendem Pargasit bis Mg-Hornblende. Die Streubreite dumTi-Gehaltes der Amphibole wird durch unterschiedliche Kristallisations-bedingungen während des spätmagmatischen bis Subsolidusstadiums (880°C bis 550°C) interpretiert. Die signifikante (Gahnitkomponente des Spinells weist auf Subsolidusreaktionen in einem offenen System hin. Der Bildungsdruck, ablegeit aus der Mineral-vergesellschaftung der metamorphen Basementgetsteine und der benachbarten Diorite, wird mit 4kb abgeschätzt.
Similar content being viewed by others
References
Baltatzis E, Skounakis S (1990) Coronas in olivine-gabbros from Labanovo village, Northern Pindos, Greece. Chem Erde 50: 297–302
Boyle AP (1991) Simultaneous solution of geobarometers and geothermometers using a microcomputer spreadsheet. Computers Geosci 17: 1473–1479
Caggianelli A, Del Moro A, Piccarreta G (1991) Petrology of gabbros and diorites from Rovale. Abs Corgr Geol Basamento Ital, Siena 21–22 03/91: 112–114
— — — Petrology of basic and intermediate orogenic intrusives from the Sila Massif (Calabria, southern Italy) (in preparation)
Dubois R (1976) La suture Calabro-Apenninique Crétacé-Eocéne et l'ouverture Thyrremenne Néogéne; etude pétrographique et structurale de la Calabre Centrale. Thése Doct. Univ Pierre et Marie Curie Paris, 557pp
Esbensen KH (1978) Coronites from the Fongen gabbro complex, Trondheim Region, Norway, role of water in the olivine-plagioclase reaction. N Jahrb Mineral Abh 132: 113–135
Helz RT (1979) Alkali exchange between hornblende and melt: a temperature-sensitive reaction. Am Mineral 64: 953–965
Hodges KV, Crowley PD (1985) Error estimation and empirical geothermobarometry for pelitic systems. Am Mineral 70: 702–709
——Spear FS (1982) Geothermometry, geobarometry and the Al2SiO5 triple point at Moosilauke, New Hampshire. Am Mineral 67: 1118–1134
Hollister LS, Grissom GC, Peters EK, Stowell HH, Sisson VB (1987) Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons. Am Mineral 72: 231–239
Holloway JR, Burnham CW (1972) Melting relations of basalt with equilibrium water pressures less than total pressure. J Petrol 13: 1–29
Joesten R (1986) The role of magmatic reaction, diffusion and annealing in the evolution of coronitic microstructure in troctolitic gabbro from Risor, Norway. Mineral Mag 50: 441–469
Johnson CD, Carlson WD (1990) The origin of olivine-plagioclase coronas in metagabbros from the Adirondack Mountains, New York. J Metamorphic Geol 8: 697–717
Johnson MC, Rutherford MJ (1989) Experimental calibration of the aluminium-in-hornblende geobarometer with application to Long Valley Caldera (California) volcanic rocks. Geology 17: 837–841
van Lamoen H (1979) Coronas in olivine gabbros and iron ores from Susimaki and Riuttamaa, Finland. Contrib Mineral Petrol 68: 259–268
Lindsley DH (1983) Pyroxene thermometry. Am Mineral 68: 477–493
Massonne HJ, Schreyer W (1987) Phengite geobarometry based on the limiting assemblage with K-feldspar, phlogopite and quartz. Contrib Mineral Petrol 96: 212–224
Medaris LG (1969) Partitioning of Fe2+ and Mg2+ between coexisting synthetic olivine and orthopyroxene. Am J Sci 267: 945–968
Mongkoltip P, Ashworth JR (1983) Quantitative estimation of an open-system symplectiteforming reaction: restricted diffusion of Al and Si in coronas around olivine. J Petrol 24: 635–661
Montel JM, Weber C, Pichavant M (1986) Biotite-sillimanite-spinel assemblages in highgrade metamorphic rocks: occurrences, chemographic analysis and thermobarometric interest. Bull Mineral 109: 555–573
Otten MT (1984) The origin of brown hornblende in the Artîjallet gabbro and dolerite. Contrib Mineral Petrol 86: 189–199
Powell R, Holland TJB (1988) An internally consistent dataset with uncertainties and correlations: 3. Applications to geobarometry, worked examples and a computer program. J Metamorphic Petrol 6: 173–204
Rock NMS, Carroll GW (1990) MINTAB: a general purpose mineral recalculation and tabulation program for Mac microcomputers. Am Mineral 75: 424–430
Schenk V (1984) Petrology of felsic granulites, metapelites, metabasics, ultramafics and metacarbonates from Southern Calabria (Italy): prograde metamorphism, uplift and cooling of a former lower crust. J Petrol 25: 255–298
Schmidt MW (1992) Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblende barometer. Contrib Mineral Petrol 110: 304–310
Wyllie PJ (1983) Crustal anatexis: an experimental review. Tectonophysics 43: 41–77
Author information
Authors and Affiliations
Additional information
With 3 Figures
Rights and permissions
About this article
Cite this article
Acquafredda, P., Caggianelli, A. & Piccarreta, G. Late magmatic to subsolidus coronas in gabbroic rocks from the sila massif (Calabria, Italy). Mineralogy and Petrology 46, 229–238 (1992). https://doi.org/10.1007/BF01164648
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01164648