Summary
Three types of mineralization are found in high-temperature lherzolite massifs of Southern Spain and Northern Morocco: (Cr) chromite, (Cr-Ni) chromite-nickel arsenide, (S-G) sulphide-graphite. The ore veins are distributed in this order from the plagioclase-lherzolite core to the garnet-lherzolite border of the massifs. These hightemperature ore assemblages (1200-600°C) have cumulate textures including orthopyroxene and/or cordierite as main silicate minerals.
High average PGE concentrations are present in the Cr-Ni ores (2000 ppb) in relation to the Ni-arsenide abundance. The Cr ores have only 900 ppb PGE, and the S-G ores are PGE-poor (350 ppb). Gold roughly follows the PGE distribution: 13,000 ppb in Cr-Ni ores, 570 ppb in Cr ores, and only 88 ppb in S-G ores. The chondrite normalized PGE patterns of the Cr-Ni ores are chondritic, whereas those of the Cr and S-G ores have respectively negative and positive slopes. The Pd/Ir ratio strongly increases from the Cr ores (0.39) to the Cr-Ni and the S-G ores (2.7 and 3.4)). There are some (Os, Ru)S2 inclusions in the chromite of the Cr ores. In the Cr-Ni ores, some minute Au, Au-Cu, and Au-Bi-Te grains are observed. No PGM have been found, except in a weathered Cr-Ni ore sample where abundant PGM (PtAs2, IrAsS) are present., suggesting that PGE may be hidden as solid solution in the Ni-arsenide.
The ore-forming magma probably has a mantle source-rock. The earliest chromites (Cr ores) contain Os-Ir-Ru mineral inclusions, whereas most of the gold and the remaining PGE with higher Pd/Ir ratio were partitioned into an immiscible As-S-liquid, which fractionated later into an earliest PGE-Au-rich NiAs-phase (Cr-Ni ores) and then a PGE-Au-poor MSS-phase (S-G ores).
Zusammenfassung
In den Hochtemperatur-Lherzolit Massiven von Süd-Spanien und Nord-Marokko kommen drei Typen von Vererzung vor: (Cr) Chromit, (Cr-Ni) Chromit-Nickelarsenid, (S-G) Sulfid-Graphit. Die Erzgänge sind in dieser Abfolge vom Plagioklas-Lherzolit Kern zum Granat-Lherzolit Rand der Massive angeordnet. Diese Hochtemperaturparagenesen (1200°-600° C) haben Kumulattexturen mit Orthopyroxen und/oder Cordierit als Hauptsilikatminerale.
Hohe Durchschnittsgehalte an PGE kommen in den Cr-Ni Erzen (2000 ppb) vor, und diese stehen in Beziehung zur Häufigkeit der Nickel-Arsenide. Die Cr-Erze führen nur 900 ppb PGE und die S-G Erze sind PGE-arm (350 ppb). Gold folgt in ungefähr der PGE-Verteilung: 13000 ppb in Cr-Ni Erzen, 570 ppb in Cr Erzen, und nur 88 ppb in S-G Erzen. Die Chondrit-normalisierten PGE Verteilungen der Chrom-Nickel Erze sind chondritisch, während jene der Cr- und S-G Erze negative, bzw. positive Neigungen zeigen. Das Pd/Ir Verhältnis nimmt von den Cr-Erzen (0, 39) zu den Cr-Ni und den S-G Erzen (2,7 und 3,4) deutlich zu. Es gibt einige (Os, Ru)S2 Einschlüsse in den Chromiten der Cr Erze. In den Cr-Ni Erzen, kommen winzige Einschlüsse von Au, Au-Cu und AuBi-Te Körnern vor. Keine PGM konnten nachgewiesen werden, mit Ausnahme eines verwitterten Cr-Ni Erzes wo reichlich PGM (PtAs2,1rAsS) vorliegen. Dies weist darauf hin, daß PGE in fester Lösung in den Nickel-Arseniden gebunden sein könnten.
Das erzbildende Magma dürfte dem Mantel entstammen. Die am frühesten gebildeten Chromite (Cr-Erze) enthalten Einschlüsse von Os-Ir-Ru Mineralen, während ein Großteil des Goldes und der verbleibenden PGE mit höheren Pd/Ir Verhältnissen in eine nicht mischbare As-S fluide Phase gingen; die letztere fraktionierte später in eine frühe PGE-Au-reiche NiAs-Phase (Cr-Ni Erze) und dann in eine PGE-Au-arme MSS-Phase (S-G Erze).
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Barnes SJ, Naldrett AJ, Gorton MP (1985) The origin of the fractionation of platinum-group elements in terrestrial magmas. Chem Geol 53: 303–323
Boudreau AE, Mathez EA, McCallum IS (1986) Halogen geochemistry of the Stillwater and Bushveld Complexes: evidence for transport of the platinum-group elements by Cl-rich fluids. J Petrol 27: 967–986
Cabri LJ (1981) The platinum-group minerals. Canadian Inst Mining Metallurgy Spec vol 23: 83–150
Campbell IH, Naldrett AJ, Barnes SJ (1983) A model for the origin of the platinum-rich sulfide horizons in the Bushveld and Stillwater complexes. J Petrol 24: 133–165
Darot M (1973) Cinématique de l'extrusion, á partir du manteau, des peridotites de la Sierra Bermeja (Serrania de Ronda, Espagna). C R Acad Sci Paris 278: 1673–1676
Dickey JS (1970) Partial fusion product in Alpine-type peridotites: Serrania de Ronda and other examples. Mineral Soc America, Spec Paper 3: 33–49
Elliott WC, Grandstaff DE, Ulmer GC, Buntin T, Gold DP (1982) An intrinsic oxygen fugacity study of Platinum-Carbon associations in layered intrusions. Econ Geol 77: 1491–1510
Frey FA, Suen CJ, Stockman HW (1985) The Ronda high temperature peridotite: Geochemistry and petrogenesis. Geochim Cosmochim Acta 48: 2469–2491
Gervilla F (1989) Mineralizaciones magmaticas ligadas a la evolucion de las rocas ultramaficas de la Serranie de Ronda (Malaga, Espana). Thesis Doct., Univ. Granada, Spain, 185p
—Leblanc M (1989) Exceptional magmatic ores in alpinotype lherzolite massifs (Ronda, Spain and Beni Boussera, Morocco). Econ Geol (in press)
—— (1987) Las mineralizaciones de Cr-Ni de los macizos ultrabasicos de la provincia de Malaga (Sur de Espana). Caracterizacion, tipos composicionales y relaciones con las facies de las rocas encajantes. Biol Geol Min XCVIIIIII: 357–375
Irvine TN, Keith DW Todd SG (1983) The JM platinum-palladium reef of the Stillwater Complex (Montana). Origin by double-diffusive convective magma mixing and implications for the Bushveld complex. Econ Geol 78: 1287–1334
Kornprobst J (1969) Le massif ultrabasique de Beni Bousera (Rif interne, Maroc): étude de péridotites de haute température et de haute pression, et des pyroxénites, á grenat ou sans grenat qui leur sont associées. Contrib Mineral Petrol 23: 283–322
Leblanc M (1986) Co-Ni arsenide deposits with accessory gold in ultrabasic rocks from Morocco. Can J Earth Sci 23(10): 1592–1602
—— (1988) Platinum group elements and Au distribution in Ni arsenide-chromite veins from the Rifo-Betico lherzolite massifs (Morocco/Spain). In:Prichard et al. (eds) Geoplatinum 87. Publ. Elsevier Applied Science, London, pp 181–198.
—— (1986) Un nouveau type de minéralisation platinifére: exemple des filons á arseniures de nickel et chromite du massif lherzolitique des Beni Boussera (Maroc). C R Acad Sci Paris 303: 163–166
—— (1989) Chromite pods in a Iherzolite massif (Collo, Algeria): evidence of oceanic-type mantle rocks along the West Mediterranean Alpine belt. Lithos 23: 153–162
Loumis TP (1972) Diapiric emplacement of the Ronda high temperature ultramafic intrusion, Southern Spain. Geol Soc Amer Bull 83: 2475–2496
—— (1975) Tertiary mantle diapirism, orogeny, and plate tectonics east of the Strait of Gilbraltar. Am J Sci 275: 1–30
Lorand JP (1987) Sur l'origine mantellaire de l'arsenic dans les roches du manteau: exemple des pyroxenites á grenat du massif lherzolitique des Beni-Bousera (Rif, Maroc). C R Acad Sci Paris 305: 383–386
Loubet M, Allegre C (1982) Trace elements in orogenic lherzolites reveal the complex history of the upper mantle. Nature 298: 809–814
Naldrett AJ (1981) Nickel sulfide deposits: classification, composition and genesis. Econ Geol 75: 628–655
—— (1980) Pt metals in magmatic sulfide ores; the occurrence of these metals is discussed in relation to the formation importance of these ores. Science 208: 1417–1424
—— (1982) Compositional variations within and between five Sudbury ore deposits. Econ Geol 77: 1579–1634
Obata M (1980) The Ronda peridotite: Garnet-Spinel-, and Plagioclase-Iherzolite facies and the P-T' trajectories of a high-temperature mantle intrusion. J Petrology 21(3): 533–572
Oen IS (1973) A peculiar type of Cr-Ni-mineralizations; cordierite- chromite- niccolite ore of Malaga, Spain, and their possible origin by liquid unmixing. Econ Geol 68: 831–842
—— (1971) Ni-arsenides, Ni-rich loellingite and (Fe-Co)rich gersdorfite in Cr-Ni-ores from Malaga province, Spain. N Jb Miner Abh 115: 123–139
—— (1973) Niccolite with pyrrhotite and cubanite exsolutions, Ni-Co-rich loellingite, and an Au-Cu alloy in Cr-Ni ores from Beni-Bousera, Morocco. Neues Jahrbuch Mineral 1974-1: 1–8
—— (1980) Orcelite and associated minerals in the Ni-FeAs system in chromitites and orthopyroxenites of Nebral, Spain. Bull Mineral 103: 198–208
Ouazzani-T'ouhami M (1986) Structures et recristallisations associées dans des zones de cisaillement: nappes de Mascate (Oman) et nappes de Federico (Rif interne, Maroc). Thesis 3d Cycle, Univ. Strasbourg, France, 163pp
Pearson WB (1967) A handbook of lattice spacings and structures of metals and alloys, Vol 2. Pergamon Press, New York, 1446pp
Polve M, Allegre CJ (1980) Orogenic lherzolite complexes studied by 87Rb-87Sr: a clue to understand the mantle convection processes. Earth Planet Sci Letters 51: 71–93.
Reuber I, Michard A, Chalouan A, Juteau TA, Jermoumi B (1982) Structures and emplacement of the alpine-type peridotites from Beni Bousera, Rif, Morocco: a polyphase tectonic interpretation. Tectonophysics 82: 231–254
Stockman HW (1982) Noble metals in the Ronda and Josephine peridotites. Ph.D., thesis, Massachusetts Institute of Technology, Cambridge, Mass., USA (unpubl.), 180pp
Suen CJ, Frey FA (1987) Origin of the mafic and ultramafic rocks in the Ronda peridotite. Earth Planet Sci Letters 85: 183–202
Todd SG, Keith DW LLe Roy LW, Schissel DJ, Mann EL, Irvine TN (1982) The JM platinum-palladium reef of the Stillwater Complex, Montana: Stratigraphy and Petrology. Econ Geol 77: 1456–1480
Torres-Roldan RL (1980) Plurifacial metamorphic evolution of the Sierra Bermeja peridotite aureole (Southern Spain). Estud Geol 37: 115–133
Tubia JM, Cuevas J (1986) High-temperature emplacements of Los Reales peridotite nappe (Betic Cordillera, Spain). J Struct Geol 8(3/4): 473–482
Vermaak CF (1976) The Merensky Reef: thoughts on its environment and genesis. Econ Geol 71: 1270–1298
Vinogradova RA, Kroutov GA, Mikhailov NP, Roudachevsky NS, Vialsov LN (1976) Sur les produits de transformation de la nickeline provenant des filons de chromite-nickeline du massif des Beni Bousera au Maroc du Nord. Mines et Géologie, Rabat, Morocco 39: 41–48
Zindler A, Staudiel M, Hart SR, Enders R, Goldstein S (1983) Nd and Sr isotope study of a mafic layer from Ronda ultramafic complex. Nature 304: 226–230
Author information
Authors and Affiliations
Additional information
With 6 Figures
Rights and permissions
About this article
Cite this article
Leblanc, M., Gervilla, F. & Jedwab, J. Noble metals segregation and fractionation in magmatic ores from Ronda and Beni Bousera Lherzolite Massifs (Spain, Morocco). Mineralogy and Petrology 42, 233–248 (1990). https://doi.org/10.1007/BF01162693
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01162693