Summary
Spinel occurs in the pyroxenitic, peridotitic and gabbroic layers of the Ivrea-Verbano layered igneous complex. Its composition varies between picotite and Mg-hercynite. Maximum Cr2O3 contents are found in the spinels of the dunitic cumulitic layers occurring at some height above the base of the complex. Chromium deposits are absent. The lack of chromite and of chromium deposits is attributed to the early fractionation of clinopyroxene (which depleted the residual liquid in chromium) instead of olivine, as a consequence of the relatively high pressure prevailing during crystallization (∼8 kb). The relationships betweenfO2-composition of spinel-composition of the silicate phases indicate thatfO2 exerted a major control on the internal stratigraphy of the single layers and on the pattern of fractionation. The variation offO2 are on their turn related to accidental variations of the pressure acting on the magma.
It is finally suggested that chromium deposits are limited to low pressure layered intrusions, where the magma has been emplaced rapidly into a shallow magma chamber. No chromium concentration is to be expected in those complexes that crystallized into deep-seated magma chambers and that fractionated at relatively high pressure, not markedly different from that at which the magma was produced. One of the major controls on the presence of chromium deposits results, therefore, to be the geotectonic environment of intrusion.
Zusammenfassung
Für die Spinelle der Pyroxenit-, Peridotit- und Gabbro-Lagen des Ivrea-Verbano-Intrusivkomplexes wurde eine Zusammensetzung im Bereich Picotit und Mg-Herzynit bestimmt. Die Dunit-Lagen im basalen Anteil des Komplexes führen Spinelie mit Cr2O3-Gehalten bis zu 30 Gew-%. Chromerz-Konzentrationen fehlen jedoch, was auf die fraktionierte Kristallisation von Klinopyroxen (und Entstehung Cr-Restschmelzen) an Stelle von Olivin, als Folge der bei relativ hohem Druck (8 kbar) erfolgten Intrusion, zurückzuführen ist. Die Beziehungen zwischen Sauerstoffpartialdruck und Spinell- und Silikat-Zusammensetzung zeigen den bedeutendenfO2-Einfluß auf den stratigraphischen Aufbau der einzelnen Gesteinslagen und auf die fraktionierenden Kristallisationsvorgänge. Die schwankendenfO2-Werter stehen in Zusammenhang mit den ebenfalls variierenden auf das Magma wirkenden Drücken.
Es ist anzunehmen, daß Chromerzkonzentrationen nur in geschichteten Intrusivkomplexen vorkommen, die sich unter niederem Druck bzw. in einer oberflächennahen Magma-Kammer bildeten, und nicht in jenen, die tiefer intrudierten und bei hohem Druck kristallisierten. Von großer Bedeutung für die Bildung von Chromerzlagerstätten ist also das geotektonische Milieu der Intrusion.
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References
Bigioggero, B., Boriani, A., Colombo, A., Gregnanin, A., 1978–1979a: The “Diorites” of the Ivrea Basic Complex (Central Alps, Italy). In: Proc. of the 2nd Symp. Ivrea-Verbano. Mem. Sc. Geo.33, 71–85.
Gigioggero, B., Brigo, L., Ferrario, A., Gregnanin, A., Montrasio, A., Zuffardi, P., 1978–1979b: Strona valley (Fe−Ni−Cu) and (Fe−Ba) ore deposits: Excursion book: In: Proc, of the 2nd Symp. Ivrea-Verbano. Mem. Sc. Geol.33, 33–39.
Burns, R. G., Huggins, F. E., Drickamer, H. G. 1972: Application of high-pressure Mössbauer spectroscopy to mantle mineralogy. Internat. Geol. Congr. 24th, sec. 14, 133–123.
Cameron E. N., 1971: Problems of the Eastern Bushveld Complex. Fortschr. Min.48, 86–108.
— 1977: Chromite in the central sector of the Eastern Bushveld Complex, South Africa. Amer. Min.62, 1082–1096.
— 1980: Evolution of the lower critical zone, central sector, Eastern Bushveld Complex, and its chromite deposits. Econ. Geol.75, 845–871.
—,Desborough, G. A., 1969: Occurrence and characteristics of chromite deposits —Eastern Bushveld Complex. Econ. Geol. Mon.4, 23–40.
Campbell, T. H. 1977: A study of macro-rhythmic layering and cumulate processes in the Jamberlana intrusion, Western Australia. Part I: Upper Layered Series. J. Petr.18, 83–215.
Capedri, S., Coradini, A., Fanucci, O., Garuti, G., Rivalenti, G., Rossi, A., 1977a: The origin of the Ivrea-Verbano Basic Formation (Italian Western Alps). Statistical approach to the peridotite problems. Rend. Soc. It. Min. Petr.33, 583–592.
—,Garuti, G., Rivalenti, G., Rossi, A., 1977b: The origin of the Ivrea-Verbano Basic Formation (Italian Western Alps). Pyroxenitic and gabbroic mobilisates as products of partial melting of mantle peridotite, N. Jb. Min. Mh.H4, 168–179.
Carmichael, I. S. E., Turner, F. J., Verhoogen, J. 1974: Igneous Petrology, 739 pp. McGraw-Hill Book Company, U.S.A.
Coertze, F. J. 1970: The geology of the western part of the Bushveld Complex. South Africa Geol. Survey, Spec. Publ.1, 5–22.
Dickey, J. S., Jr. (1975). A hypothesis of origin for podiform chromite deposits. Geochim. Cosmochim. Acta39, 1061–1074.
Evans, B. W., Frost, B. R. 1975: Chrome-spinel in progressive metamorphism — a preliminary analysis. Geochim. Cosmochim. Acta39, 959–972.
Garuti, G., Rivalenti, G., Rossi, A., Sinigoi, S., 1978–1979: Mineral equilibria as geotectonic indicators in the ultramafics and related rocks of the Ivrea-Verbano Basic Complex (Italian Western Alps): Pyroxenes and Olivine. In: Proc. of the 2nd Symp. Ivrea-Verbano. Mem. Sc. Geol.33, 147–160
Hamilton, D. L., Burnham, C. W., Osborn, E. F. 1964: The solubility of water and effects of oxygen fugacity and water content on crystallization of mafic magmas. J. Petr.5, 21–38.
Hess, H. H., 1960: Stillwater igneous complex, Montana: a quantitative mineralogical study. Geol. Soc. Amer. Mem.80, 230 pp.
Hill, R., Roeder, P. 1974: The crystallization of spinel from basatic liquid as a function of oxygen fugacity. J. Geol82, 709–729.
Hughes, C. J., 1970: Major rhythmic layering in ultramafic rocks of the Great Dyke of Rhodesia, with special reference to the Selukwe area. Geol. Soc. South Africa, Spec. Pub.1, 594–609.
Irvine, T. N., 1965: Chromian spinel as a petrogenetic indicator. Part I: Theory. Can. J. Earth Sci.2, 648–672.
Irvine, T. N., 1967: Chromian spinel as a petrogenetic indicator. Part II: Petrological application. Can. J. Earth Sci.4, 71–103.
— 1975: Crystallization sequences in the Muskox intrusion and other layered intrusions. II: Origin of chromite layers and similar deposits of other magmatic ores Geochim. Cosmochim. Acta39, 991–1020.
— 1977: Origin of chromitite layers in the Muskox intrusion and other stratiform intrusion: a new interpretation. Geology5, 273–277.
— 1978: Infiltration metasomatism adcumulus growth and secondary differentiation in the Muskox intrusion. Carnegie Inst. Washington Year Book1977–1978, 743–751.
— 1979: Rocks whose composition is determined by crystal accumulation and sorting. In: The Evolution of the Igneous Rocks, 50 th Anniversary Prospectives (Yoder, H. S., Jr. ed.). Princeton, New Jersey: Princeton University Press.
—,Smith, C. H., 1969: Primary oxide minerals in the layered series of the Muskox intrusion. Econ. Geol.4, 76–94.
Irving, A. J. 1980: Petrology and geochemistry of composite ultramafic xenoliths in alcalic basalts and implications for magmatic processes within the mantle. Amer. J. Sci.280A, 389–436.
Jackson, E. D., 1969: Chemical variations in coexisting chromite and olivine in chromitite zones of the Stillwater Complex. Econ. Geol. Mon.4, 41–71.
— 1970: The cyclic unit in layered intrusions. A comparison of repetitive stratigraphys in the ultramafic parts of the Stillwater, Muskox, Great Dyke and Bushveld Complexes. Geol. Soc. South Africa, Spec. Publ.1, 391–424.
Kadik, A. A., Eggler, D. H., 1974–1975: Melt-vapor relation in the join NaAlSi3O8−H2O−CO2. Carnegie Inst. Washington Year Book74, 479–484.
Kurat, G., Palmer, H., Spettel, B., Baddenhausen, H., Hofmeister, H., Palme, C., Wänke, H., 1980: Geochemistry of ultramafic xenoliths from Kapfenstein, Austria: Evidence for a variety of upper mantle processes. Geochim. Cosmochim. Acta,44, 45–60.
Lensch, G. 1971: Die Ultramafite der Zone von Ivrea. Ann. Univ. Saraviensis9, 5–146.
Mayer, H. O. A. 1975: Chromium and the genesis of diamond. Geochim. Cosmochim., Acta39, 929–936.
Medaris, L. G., Jr., 1975: Coexisting spinel and silicates in alpine peridotites of the granulite facies. Geochim. Cosmochim. Acta39, 947–958.
Morse, S. A., 1979: Reaction constants forEn-Fo-Sil equilibria: an adjustment and some applications. Amer. J. Sci.279, 1060–1069.
Muan, H., 1957: Phase equilibrium relationships at liquidus temperatures in the system FeO−Fe2O3−Al2O3. J. Amer. Ceram. Soc.40, 420–431.
Mysen, B., 1973: The oxygen fugacity (fO2) as a variable during partial melting of peridotite in the upper mantle.Carnegie Inst. Washington Year Book1973–1974, 237–240.
Osborn, E. F., 1969: Discussion ofUlmer, G. C., 1969. Experimental investigations of chromite spinels. Econ. Geol. Mon.4, 131.
— 1980: On the cause of the reversal of the normal fractionation trend — an addendum to the paper byE. N. Cameron, “Evolution of the Lower Critical Zone, Central Sector, Eastern Bushveld Complex, and Its Chromite Deposits” Econ. Geol.75, 872–875.
—,Watson, E. B., Rawson S. A., 1979: Composition of magnetite in subalkaline volcanic rocks. Carnegie Inst. Washington Year Book78, 475–481.
Presnall, D. C., Dixon, S. A., Dixon, S. A., Jr., O'Donnell, T. H., Brenner, N. L., Dycus, D. W., 1980: Liquidus phase relations on the join diopside-forsterite-anorthite from 1 atm to 20 kbar: their bearing on the generation and crystallization of basaltic magma. Contr. Min. Petr.66, 203–220.
Rivalenti, G., Garuti, G., Rossi, A., 1975: The origin of the Ivrea-Verbano Basic Formation (Western Italian Alps)-Whole rock geochemistry. Bol. Soc. Geol. It.94, 1149–1186.
Rivalenti, G., Garuti, G., Rossi, A., Sinigoi, S., 1978–1979: Spinels as petrogenetic indicators in the Ivrea-Verbano Basic Complex (Italian Western Alps). In: Proc. of the 2nd Symp. Ivrea-Verbano. Mem. Sci. Geol.33, 161–171.
————Siena, F., 1980: Existence of different peridotite types and of a layered igneous complex in the Ivrea Zone of Western Alps. J. Petr.22, 127–153.
Shervais, J. W. 1978–1979: Ultramafic and mafic layers in the alpine type lherzolite massif at Balmuccia, NW-Italy. In: Proc. of the 2nd Symp. Ivrea-Verbano. Mem. Sci. Geol.33, 135–145.
— 1979: Thermals emplacement model for the alpine lherzolite massif at Balmuccia, NW-Italy. J. Petr.20, 795–820.
Sinigoi, S., Comin Chiaramonti, P., Alberti, A., 1980: Phase relations, in the partial melting of the Baldissero spinel-lherzolite (Ivrea-Verbano Zone, Wester, Alps, Italy). Contr. Min. Petr.75, 111–121.
Smith, C. H., Kapp, H. E. 1963: The Muskox intrusion, a recently discovered layered intrusion in the Coppermine River area, northwest territories. Canad. Min. Soc. Am. Spec. Pap.1, 30–35.
Snethlage, R., Klemm, D. D. 1978: Intrinsic oxygen fugacity measurements on chromites from Bushveld Complex and their petrogenetics significance. Contr. Min. Petr.67, 127–138.
Speidel, D. H., 1967: Element distribution among coexisting phases in the system MgO−FeO−Fe2O3−SiO2 as a function of temperature and oxygen fugacity. Am. Min.52, 1139–1152.
Ulmer, G. C., 1969: Experimental investigation of chromite spinels. In: Magmatic ore deposits, a symposium (Wilson, Ch. D. B., ed.). Econ. Geol. Mon.4, 114–131.
Wager, L. R., Brown, G. M., 1967: Layered Igneous Rocks, 588 pp. London: Oliver and Boyd Ltd.
Yoder, H. S., Tilley, C. E., 1962: Origin of basalt magmas: an experimental study of natural and synthetic rock systems, J. Petr.3, 342–532.
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Rivalenti, G., Garuti, G., Rossi, A. et al. Chromian spinel in the Ivrea-Verbano layered igneous complex, western Alps, Italy. TMPM Tschermaks Petr. Mitt. 29, 33–53 (1981). https://doi.org/10.1007/BF01082813
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DOI: https://doi.org/10.1007/BF01082813