Abstract
The occurrence of various types of mobilizates in the Baldissero spinel lherzolite is due to partial melting of the same body. The study of the relationships between the peridotite and its mobilizates demonstrates that olivine did not take an active part in the fusion. Estimates of the degree of partial melting vary from 10% for the average composition, to 20% for the most depleted samples. These values refer to an initial pyrolitic composition, and thus are relative, as they can vary depending on the actual primary composition.
The calculated composition of the liquid generated by partial melting is quite similar to that of a picritic basalt, and is practically the same irrespective of the 10% and 20% fusion. This fact provides strong evidence that melting took place at a unique invariant point of the natural system, producing a liquid with a remarkably constant composition.
Projection of the liquid in the fo-an-di-si diagram is fairly well aligned with the modal compositions of the solid residua, but does not coincide with the minimum of the simplified system. The proposed solution is based on the enlargement of the spinel field (at constant pressure), due to the Cr content in this phase. Therefore, the position of the invariant minimum is not fixed, but rather controlled by the Cr content of the spinel. Is is suggested that, by an increase in the Cr content, spinel might at a given moment become refractory. Thus, saturated or over-saturated magmas are produced depending on the phase relations between olivine, orthopyroxene and clinopyroxene. This would happen in the case of very advanced fusions or in the case of fusion of already depleted peridotites.
The relationships between mobilizates of different generations suggest a non adiabatic mantle upwelling.
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References
Berckhemer H (1969) Direct evidence for the composition of the lower crust and Moho. Tectonophysics 8:97–105
Bertolani M (1968) Fenomeni di trasformazione granulitica nella formazione basica Ivrea-Verbano (Alpi Occidentali Italiane). Schweiz Mineral Petrogr Mitt 48:21–30
Capedri S, Corradini 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 problem. Rend Soc Ital Mineral Petr 33:583–592
Capedri S, Garuti G, Rivalenti G, Rossi A (1977b) The origin of the Ivrea-Verbano basic formation. Pyroxenitic and gabbroic mobilizates as products of partial melting of mantle peridotite. Neues Jahrb Mineral, Monatsh H4:168–179
Cawthorn RG, Collerson KD (1974) The recalculation of pyroxene end-member parameters and the estimation of ferrous and ferric iron content from electron microprobe analyses. Am Mineral 59:1203–1208
Dickey JS Jr, Yoder HS Jr, Schairer JF (1971) Chromium in silicate-oxide systems. Carnegie Inst Washington Yearb 70:118–122
Ernst WG (1978) Petrochemical study of Iherzolitic rocks from the Western Alps. J Petrol 19:341–392
Etienne F (1971) La lherzolite rubanée de Baldissero Canavese (Piémont, Italie) — essai d'analyse structurale et de pétrogenèse. Thesis, 3rd cycle, Nancy, p 157
Fabriès J (1979) Spinel-olivine geothermometry in peridotites from ultramafic complexes. Contrib Mineral Petrol 69:329–336
Fenoglio M (1956) Limiti occidentali della zona Ivrea-Verbano e suoi rapporti con la zona del Canavese. Atti R Accad Sci Torino 90:284–286
Garuti G (1977) The origin of the Ivrea-Verbano basic formation (Italian Western Alps). Microstructural data on peridotites from the area of Sesia Valley. Rend Soc Ital Mineral Petr 33:601–616
Garuti G, Friolo R (1979) Textural features and olivine fabrics of peridotites from the Ivrea-Verbano zone. Mem Soc Geol Padova 33:111–125
Garuti G, Rivalenti G, Rossi A, Sinigoi S (1979) Mineral equilibria as geotectonic indicators in the ultramafics and related rocks of the Ivrea-Verbano basic complex (Italian Western Alps): Pyroxenes and olivine. Mem Soc Geol Padova 33:147–160
Giese P (1968) Die Struktur der Erdkruste im Bereich der Ivrea-Zone. Schweiz Mineral Petrogr Mitt 48:261–284
Giese P (1979) Crustal structure of the Ivrea zone within the frame of the Alpine crustal structure. Mem Soc Geol Padova 33:51–57
Green DH, Ringwood AE (1967) The genesis of basaltic magmas. Contrib Mineral Petrol 15:103–190
Herzberg CT (1972) Stability fields of plagioclase- and spinel-lherzolite. In: Progress in Experimental Petrology D 2:145–148
Herzberg CT (1978) The bearing of phase equilibria in simple and complex system on the origin and evolution of some well documented garnet-websterites (Preprint)
Herzberg CT, Chapman NA (1976) Clinopyroxene geothermometry of spinel lherzolites. Am Mineral 61:626–637
Hytönen K, Schairer JF (1960) The system enstatite-diopside-anorthite. Carnegie Inst Washington Yearb 59:71–72
Irvine TN (1966) Chromian spinel as a petrogenetic indicator. Part 2. Petrologic applications. Can J Earth Sci 4:71–103
Jakobsson SP, Jonsson J, Shido F (1978) Petrology of the western Reykjanes Peninsula, Iceland. J Petrol 19:669–705
Keith ML (1954) Phase equilibria in the system MgO-Cr2O3-SiO2. J Am Ceram Soc 37:490
Kornprobst J (1970) Les péridotites et les pyroxénolites du massif ultrabasique des Beni Bouchera: une étude expérimentale entre 1,100° et 1,550° C, sous 15 à 30 kilobars de pression sèche. Contrib Mineral Petrol 29:290–309
Kushiro I (1969) The system forsterite-diopside-silica with and without water at high pressures. Am J Sci 267A:269–294
Kushiro I (1972) Determinations of liquidus relations in synthetic silicate system with electron probe analysis: the system forsterite-diopside-silica at 1 atmosphere. Am Mineral 57:1260–1271
Lensch G (1968) Die Ultramafitite der Zone von Ivrea und ihre geologische Interpretation. Schweiz Mineral Petrogr Mitt 48:91–102
Lensch G (1971) Die Ultramafitite der Zone von Ivrea. Ann Univ Saraviensis 9:5–146
Maaløe S, Printzlau I (1979) Natural partial melting of spinel lherzolite. J Petrol 20:727–741
MacGregor D (1967) Mineralogy of model mantle composition. In: Wyllie PJ (ed) Ultramafic and related rocks, pp 382–392
Mori T (1977) Geothermometry of spinel lherzolites. Contrib Mineral Petrol 62:129–139
Mysen BO (1974) The oxygen fugacity \((f_{{\text{O}}_{\text{2}} } )\) as a variable during partial melting of peridotite in the upper mantle. Carnegie Inst Washington Yearb 73:237–240
Mysen BO, Kushiro I (1977) Compositional variations of coexisting phases with degree of melting of peridotite in the upper mantle. Am Mineral 62:843–865
Nicolas A (1974) Mise en place des péridotites des Lanzo (Alpes Piémontaises); relation avec tectonique et métamorphisme alpins; conséquences géodynamiques. Schweiz Mineral Petrogr Mitt 54:449–460
Obata M (1976) The solubility of A12O3 in orthopyroxenes in spinel and plagioclase peridotites and spinel pyroxenite. Am Mineral 61:804–816
Osborn EF, Tait DB (1952) The system diopside-forsterite-anorthite. Am J Sci Bowen Vol:413–433
Panza GF, Mueller S (1979) The plate boundary between Eurasia and Africa in Alpine Area. Mem Soc Geol Padova 33:44–50
Presnall DC, Dixon SA, Dixon JR, O'Donnell TH, Brenner NL, Dycus DW (1978) Liquidus phase relations on the join diopsideforsterite-anorthite from 1 atm to 20 kbar: their bearing on the generation and crystallization of basaltic magma. Contrib Mineral Petrol 66:203–220
Presnall DC, Dixon JR, O'Donnell TH, Dixon SA (1979) Generation of Mid-ocean Ridge Tholeiites. J Petrol 20:3–35
Rivalenti G, Garuti G, Rossi A (1975) The origin of the Ivrea-Verbano basic formation (western Italian Alps). Whole rock geochemistry. Boll Soc Geol Ital 94:1149–1186
Rivalenti G, Garuti G, Rossi A, Sinigoi S (1979) Spinels as petrogenetic indicators in the Ivrea-Verbano basic complex (Italian Western Alps). Mem Soc Geol Padova 33:161–171
Roeder PL, Campbell IH, Jamieson HE (1979) A re-evaluation of the olivine-spinel geothermometer. Contrib Mineral Petrol 68:325–334
Shervais J (1979a) Ultramafic and mafic layers in the Alpine-type lherzolite massif at Balmuccia, NW Italy. Mem Soc Geol Padova 33:135–145
Shervais J (1979b) Thermal emplacement model for the Alpine lherzolite massif at Balmuccia, Italy. J Petrol 20:795–820
Thompson RN (1974) Primary basalt and magma genesis. Contrib Mineral Petrol 45:317–324
Wells PRA (1977) Pyroxene thermometry in simple and complex systems. Contrib Mineral Petrol 62:129–139
Wood BJ, Banno S (1973) Garnet-orthopyroxene and orthopyroxene-clinopyroxene relationships in simple and complex systems. Contrib Mineral Petrol 42:109–124
Yoder HS, Tilley CE (1962) Origin of basalt magmas: an experimental study of natural and synthetic rock systems. J Petrol 3:342–532
Yang HY (1973) Crystallization of iron-free pigeonite in the system anorthite-diopside-enstatite-silica at atmospheric pressure. Am J Sci 273:488–497
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Sinigoi, S., Comin-Chiaramonti, P. & Alberti, A.A. Phase relations in the partial melting of the Baldissero spinel-lherzolite (Ivrea-Verbano zone, Western Alps, Italy). Contr. Mineral. and Petrol. 75, 111–121 (1980). https://doi.org/10.1007/BF00389772
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DOI: https://doi.org/10.1007/BF00389772