Summary
In the zoned clinopyroxene phenocrysts from the volcanic rocks of Almopia the Mg/Fe ratio and the contents of Mn, and mostly of Na, increase from the core towards the rim of the crystals, whereas the Fe3+/Fe2+ ratio, and in many cases the contents of Ca, decrease. On the contrary, the content of Si decreases from inside outwards or remains almost constant whereas Al and Ti increase.
The high Ca-content of the clinopyroxenes, low Ti, and limited Fe-enrichment, with a trend from Ca43.3: Mg47.0: (Fe + Mn)9.7 to Ca46.6: Mg42.2: (Fe + Mn)11.2, illustrate the shoshonitic to cale-alkaline nature of the parental magma.
The composition of the clinopyroxenes indicates that, of all possible controlling factors, the high water-vapour pressure is considered to play an important role for the AlIV fluctuations during the crystallization.
Zusammenfassung
Bei den zonierten Klinopyroxeneinsprenglingen der Vulkanite von Almopia nehmen das Mg/Fe-Verhältnis und die Gehalte an Mn und meistens an Na in den einzelnen Zonen vom Kern zum Rand zu, während das Fe3+/Fe2+-Verhältnis, und in vielen Fällen die Gehalte an Ca, abnehmen. Im Gegensatz dazu nimmt der Gehalt an Si von innen nach außen ab oder bleibt fast konstant, während Al und Ti zunehmen.
Der hohe Ca-Gehalt und gleichzeitig niedrige Ti-Gehalt der Klinopyroxene, zusammen mit ihrer begrenzten Fe-Anreicherung und einem Trend von Ca43.3: Mg47.0: (Fe + Mn)9.7 bis Ca46.6: Mg42.2: (Fe + Mn)11.2 weisen auf die shoshonitische bis kalk-alkalische Natur des Stammagmas hin. Die Zusammensetzung der Klinopyroxene weist darauf hin, daß der hohe Wasserdampfdruck im Magma auch eine wichtige Rolle für Schwankungen im AlIV-Gehalt während der Kristallisation darstellt.
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References
Bellon H, Jarrige JJ, Sorel D (1979) Les activités magmatiques égéennes de l'Oligocene à nos jours et leurs cadres géodynamiques. Données nouvelles et synthèse. Rev Géol Dyn Géorg Phys 21: 41–55
Best MG, Mercy ELP (1967) Composition and crystallization of mafic minerals in the Guadalupe igneous complex, California. Amer Min 52: 436–474
Boyd FR, England JL (1963) Some effects of pressure on phase relations in the system MgO-Al2O3-SiO2. Carnegie Inst Wash Year Book 62: 121–124
Hamilton DL, Anderson GM (1967) Effects of water and oxygen pressures on the crystallization of basaltic magmas. In:Hess HH, Poldervaart A (eds) Basalts, Vol 1. New York, pp 445–482
Joplin GA, Kiss E, Ware NG, Widdowson JR (1972) Some chemical data on members of the shoshonite association. Min Mag 38: 936–945
Kolios N, Innocenti F, Manetti P, Peccerillo A, Giuliani O (1980) The Pliocene volcanism of the Voras Mts (Central Macedonia, Greece). Bull Volcanol 43: 553–568
Kushiro I (1960) Si-Al relation in clinopyroxenes from igneous rocks. Amer J Sci 258: 548–554
——Yoder HS Jr (1964) Experimental studies on the Basal-Eclogite transformation. Carnegie Inst Wash Year Book 63: 108–114
Le Bas MJ (1962) The role of aluminum in igneous clinopyroxenes with relation to their parentage. Amer J Sci 260: 267–288
Morrison GW (1980) Characteristics and tectonic setting of the shoshonite rock association. Lithos 13: 97–108
Nicholls J, Carmichael ISE (1969) A commentary on the absarokite-shoshonite-banakite series of Wyoming, U.S.A. Schweiz Min Petrol Mitt 49: 47–64
Osborn EF (1962) Reaction series for subalkaline igneous rocks based on different oxygen pressure condition. Amer Min 47: 211–226
Papike JJ, Cameron K, Baldwin K (1974) Amphiboles and pyroxenes characterization of other than quadrilateral components and estimates of ferric iron from microprobe data. Geol Soc Am abstract with programs 6: 1053–1054
Poldervaart A, Hess HH (1951) Pyroxenes in the crystallization of basaltic magmas. J Geol 59: 472–489
Rittmann A (1973) Stable mineral assemblages of igneous rocks. Springer, Berlin Heidelberg, pp 262
Soldatos K (1961) Die jungen Vulkanite der griechischen Rhodopen und ihre provinziellen Verhältnisse. Vulkaninst Imm Friedlaeder Nr 8 Dissert (E.T.H.) Zürich, pp 102
Streckeisen A (1979) Classification and nomenclature of volcanic rocks, lamprophyres, carbonatites, and melilitic rocks: Recommendations and suggestions of the IUGS Subcommission of the Systematics of Igneous Rocks. Geology 7: 331–335
Thompson RN (1974) Some high-pressure pyroxenes. Min Mag 39: 768–787
Vieten K (1980) The minerals of the volcanic rock association of the Siebengebirge I. Clinopyroxenes 2. Variation of chemical composition of Ca-rich clinopyroxenes (salites) in the course of crystallization. N Jb Miner Abh 140: 54–88
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Eleftheriadis, G.E. Zoned clinopyroxenes from the volcanic rocks of almopia (Voras Mts), Central Macedonia, Greece. Mineralogy and Petrology 38, 117–126 (1988). https://doi.org/10.1007/BF01164316
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DOI: https://doi.org/10.1007/BF01164316