Abstract
The ultrabasic rocks which form the Beni Bouchera massif are schistose and folded isoclinally. They outcrop at the center of a late formed anticline under a series of granulite facies precambrian or lower paleozoic rocks. The ultrabasic rocks appear to have been in situ during the major structural development of the series and were emplaced at the time of metamorphism. The massif itself is essentially a peridotite, apparently layered, which contains pyroxenite bands (about 3% of the total volume of the massif). The peridotites are olivinerich containing two aluminous pyroxenes and spinel. The pyroxenites are however quite varied. They are frequently banded themselves and in several centimeters thickness can vary from enstatite rocks at the exterior of the layers to garnet clinopyroxenites at the center with websterite and garnet websterite as intermediate rock type. They are also present as monofacies bands of enstatite or garnet clinopyroxenite rock. Occasionally the minerals in these bands show exsolution features.
Thirty six new rock and mineral chemical analyses are presented here. An attempt is made to use these data correlated with abundant bibliographic material in order to evaluate the conditions of formation of the rock types. The temperature range is estimated to be 1100–1200° C, pressures between 15 and 20 kbs in the latest facies and 1400°C and 25 kbs for a primary phase represented by the pyroxenites showing marked exsolution features. Various arguments lead to the conclusion that the pyroxenite bands crystallized from a liquid which was in equilibrium with the solid lherzolite.
One sees in the Beni Bouchera the results of anatectic melting of an aluminous peridotite which originated in the upper mantle. This partial fusion was caused by the adiabatic upward movement of the mantle material toward the lower crust where tangential tectonic movements emplaced it as a solidified mass in an orogenic root zone under granulite facies conditions.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Pour un certain nombre de travaux antérieurs à 1967 cités dans le texte nous renvoyons le lecteur à la liste bibliographique publiée in: Ultramafic and related rocks (Wyllie, ed.), 1967.
Agard, J., G. Jouravsky et Y. Milliard: Les gîtes minéraux (graphite, vermiculite, magnésite, nickel, cuivre, chrome) liés aux roches ultrabasiques et métamorphiques des Beni Bouchera (Rif septentrional). Mines Géol. (Morocco) 8, 31–37 (1959).
Atlas, L.: The polymorphism of MgSiO3 and solid state equilibria in the system MgSiO3- CaMgSi2O6. J. Geol. 60, 125 (1952).
Babkine, J., F. Conquere et J. C. Vilminot: Les spinelles des basaltes de Monistrol d'Allier (chaîne du Devès, Haute Loire). Bull. Soc. Franç. Mineral. Crist. 88, 447–455 (1965).
—: Découverte d'une enclave d'ariégite à grenat dans l'absarokite du Pouget (Hérault). Compt. Rend. 267, 1266–1269 (1968).
Boyd, F. R., and J. L. England: The system enstatite-pyrope. Carnegie Inst. Wash. Year Bk. 63, 157–161 (1964).
Burnham, C. W.: Lattice constant refinement. Carnegie Inst. Wash. Year Bk. 61, 132–135 (1962).
Carswell, D. A.: Picritic magma-Residual Dunite relationships in garnet peridotite at Kalskaret near Tafjord, South Norway. Contr. Mineral. and Petrol. 19, 97–124 (1968).
Coquand, H.: Description géologique de la partie septentrionale de l'Empire du Maroc. Bull. Soc. Geol. France 4, 1188–1249 (1846–1847).
Davis, B. T. C., and J. F. Schairer: Melting relations in the join diopside-forsterite-pyrope at 40 kbs. and at one atmosphere. Carnegie Inst. Wash. Year Bk. 64, 123–126 (1965).
Deer, W. A., R. A. Howie, and J. Zussman: Rock forming minerals. London: Longmans 1962.
Fonteilles, M., G. Guitard et E. Raguin: Sur la présence de gneiss à disthène et cordiérite dans le massif du St. Barthélemy (Pyrénées de l'Ariége). Compt. Rend. 258, 3524–3525 (1964).
Gass, I. G.: The ultrabasic volcanic assemblage of the Troodos massif, Cyprus. Ultramafic and related rocks (Wyllie, ed.), p. 121–134 (1967).
Girod, M.: Données pétrographiques sur des pyroxénolites à grenat en enclaves dans des basaltes du Hoggar (Sahara central). Bull. Soc. Franç. Mineral. Crist. 90, 202–213 (1967).
Green, D. H.: The origin of the “Eclogites” from Salt Lake Crater, Hawaii. Earth and Planetary Sci. Letters 1, 414–420 (1966).
- High-temperature peridotite intrusions. Ultramafic and related rocks (Wyllie, ed.), p. 212–222 (1967).
—, and A. E. Ringwood: The stability fields of aluminous pyroxene peridotite and garnet peridotite and their relevance in upper mantle structure. Earth and Planetary Sci. Letters 3, 151–160 (1967a).
—: The genesis of basaltic magmas. Contr. Mineral. and Petrol. 15, 103–190 (1967b).
Guitard, G., et E. Raguin: Sur la présence de gneiss à grenat et hypersthène (faciès d'Eskola) dans le massif de l'Agly (P.O.). Compt. Rend. 247, 2385–2388 (1958).
Harris, P. G.: Segregation processes in the upper mantle. Mantles of the earth and terrestrial planets. London: Intersci. publ. 1967.
Hernandez-Pacheco, A.: Estudio petrografico et geoquimico de macizo ultramafico de Ojen (Malaga). Estud. Geol. 23, 85–143 (1967).
Irvine, T. N.: The Duke-Island ultramafic complex, Southeastern Alaska. Ultramafic and related rocks (Wyllie, ed.), p. 84–97 (1967).
-, and C. H. Smith: The ultramafic rocks of the Muskox intrusion, Northwest Territories, Canada. Ultramafic and related rocks (Wyllie, ed.), p. 38–49 (1967).
Ito, K., and G. C. Kennedy: Melting and phase relations in a natural peridotite to 40 kbs. Am. J. Sci. 265, 519–539 (1967).
Knopoff, L.: Thermal convection in the earth's mantle. The earth's mantle (Gaskell, ed.), p. 171–196 (1967).
Kornprobst, J.: Observations sur la série métamorphique de la presqu'île de Ceuta (Rif septentrional — Maroc). Compt. Rend. 255, 2140–2142 (1962).
—: A propos des péridotites du massif des Beni Bouchera (Rif septentrional— Maroc). Bull. Soc. Franç. Mineral. Crist. 89, 399–404 (1966).
Kushiro, I.: Clinopyroxene solid solutions. Part I. The CaAl2SiO6 component. Japan. J. Geol. Geogr. 33, 213–220 (1962).
—: Compositions of magmas formed by partial zone melting of the earth's upper mantle. J. Geophys. Res. 73, 619–634 (1968).
—, and K. Aoki: Origin of some eclogite inclusions in kimberlite. Am. Mineralogist. 53, 1347–1367 (1968).
—, and H. S. Yoder Jr.: Anorthite-forsterite and anorthite-enstatite reactions and their bearing on the Basalt-Eclogite transformation. J. Petrol. 7, 337–362 (1966).
Lacroix, A.: Sur l'origine des brèches calcaires secondaires de l'Ariège; conséquence à en tirer au point de vue de l'âge de la lherzolite. Compt. Rend. 131, 396–398 (1900b).
- Contribution à la connaissance de la composition chimique et minéralogique des roches éruptives de l'Indochine. Bull. Serv. Geol. de Indochine, Hanoï (1933).
Lallemant, H. G. A.: Structural and petrofabric analysis of an “alpine-type” peridotite: the Lherzolite of the French Pyrenees. Leidse Geol. Mededel. 42, 1–57 (1967).
Lappin, M. A.: Structural and petrofabric studies of the dunites of Almklovdalen, Nordfjord, Norway. Ultramafic and related rocks (Wyllie, ed.), p. 183–190 (1967).
Marin, A.: Constitucion geologica y riqueza mineral de la zona de protectorado espanol en Marruecos. Bull. Soc. Geogr. Madrid 80, 103–104 (1930).
Melson, W. G., E. Jarosewich, U. T. Bowen, and G. Thompson: St. Peter and St. Paul rocks: a high-temperature, mantle-derived intrusion. Science 155, 1532–1535 (1967).
Mercy, E. L. P., and M. J. O'Hara: Nepheline normative eclogite from Loch Duich, Ross shire. Scot. J. Geol. 4, 1–9 (1968).
Milliard, Y.: Sur la présence d'assises carbonifères dans le massif paléozoïque interne du Rif. Compt. Rend. 249, 1688–1690 (1959b).
Miyashiro, A.: Orogeny, regional metamorphism, and magmatism in the Japanese Islands. Bull. Geol. Soc. Denmark 17, 390–446 (1968).
Mollat, H.: Die Geologie der Sierra Blanca und ihrer Umgebung (Westliche Betische Kordilleren). Diss. Bonn, inédit (1965).
Mottana, A., A. D. Edgar, and W. R. Church: Experimental studies on ariegites. Proceed. Can. Mineral. (1967).
Nicolas, A.: Le complexe Ophiolites-Schistes lustrés entre Dora Maira et Grand Paradis (Alpes Piémontaises). Trav. Fac. Sci. Nantes (1966).
O'Hara, M. J.: Mineral facies in ultrabasic rocks. Ultramafic and related rocks (Wyllie, ed.), p. 7–18 (1967a).
- Garnetiferous ultrabasic rocks of orogenic regions. Ultramafic and related rocks (Wyllie, ed.), p. 167–172 (1967b).
- Mineral paragenesis in ultrabasic rocks. Ultramafic and related rocks (Wyllie, ed.), p. 393–403 (1967c).
—: The bearing of phase equilibria studies in synthetic and natural systems on the origin and evolution of basic and ultrabasic rocks. Earth Sci. Rev. 4, 69–133 (1968).
—, and E. L. P. Mercy: Garnet-peridotite and eclogite from Bellinzona, Switzerland. Earth and Planetary Sci. Letters 1, 295–300 (1966a).
- - Lherzolite, ariegite and alkali basalt. Proc. Geol. Soc. London, 1637 (1967).
O'Hara, M. J., and H. S. Yoder Jr.: Formation and fractionation of basic magmas at high pressures. Scot. J. Geol. 3, 67–117 (1967).
Orueta, D. de: Estudios geologico y petrografico de la Serrania de Ronda. Mem. Inst. Geol. Espana (1917).
Peters, T. J.: Distribution of Mg, Fe, Al, Ca and Na in coexisting olivine, orthopyroxene and clinopyroxene in the Totalp serpentinite (Davos, Switzerland) and in the alpine metamorphosed Malenco serpentinite (N. Italy). Contr. Mineral. and Petrol. 18, 65–75 (1968).
Poldervaart, A., and H. H. Hess: Pyroxenes in the cristallisation of basaltic magma. J. Geol. 59, 472 (1951).
Ragan, D. M.: The Twin Sisters dunite, Washington. Ultramafic and related rocks (Wyllie, ed.), p. 160–166 (1967).
Saggerson, E. P.: Eclogites nodules associated with alkaline olivine basalts, Kenya. Geol. Rundschau 57, 890–903 (1968).
Sobolev, N. V., I. K. Kuznetzova, and N. Y. Zyuzin: The petrology of grospydite xenoliths from the Zagadochnaya kimberlite pipe in Yakutia. J. Petrol. 9, 253 (1968).
Tozer, D. C.: Towards a theory of thermal convection in the mantle. The earth's mantle (Gaskell, ed.), p. 325–353 (1967).
Velde, B.: Etude minéralogique d'une éclogite de Fay-de-Bretagne (Loire Atlantique). Bull. Soc. Franç. Mineral. Crist. 89, 385–393 (1966).
Vogel, D. E.: Petrology of an eclogite and pyrigarnite-bearing polymetamorphic rock complex at Cabo Ortegal, NW Spain. Leidse Geol. Mededel. 40, 121–213 (1967).
White, I. G.: Ultrabasic rocks and the composition of the upper mantle. Earth and Planetary Sci. Letters 3, 11–18 (1967).
Winchell, H.: The composition and physical properties of garnet. Am. Mineralogist 43, 595 (1958).
Yoder, H. S., and Th. G. Sahama: Olivine X-ray determinative curve. Am. Mineralogist 42, 475 (1957).
Zwaan, P. C.: On the determination of pyroxenes by X-ray powder diagrams. Leidse Geol. Mededel. 19, 167 (1954).
Author information
Authors and Affiliations
Additional information
Equipe de recherches associée au C.N.R.S.: ≪Pétrogenèse des roches éruptives et métamorphiques≫
Plusieurs missions sur le terrain ont été effectuées avec le concours du Service Géologique du Maroc et grâce, particulièrement, à G. Choubert, M. Diouri, Y. Ennadifi et A. FaureMuret. Les études pétrographiques ont été poursuivies à la Sorbonne sous la direction de J. Jung et de J. Ravier. Une aide inestimable m'a été apportée par M. J. O'Hara pour la rédaction de ce mémoire. A divers titres j'ai largement bénéficié des conseils et critiques de B. Azambre, F. Conquere, M. Durand-Delga, M. Fonteilles, J. R. Kienast, B. Velde, D. Velde et J. C. Vilminot
Rights and permissions
About this article
Cite this article
Kornprobst, J. Le massif ultrabasique des Beni Bouchera (Rif Interne, Maroc): Etude des péridotites de haute température et de haute pression, et des pyroxénolites, à grenat ou sans grenat, qui leur sont associées. Contr. Mineral. and Petrol. 23, 283–322 (1969). https://doi.org/10.1007/BF00371425
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00371425