Skip to main content
SpringerLink
Log in

Monzo-anorthosite from the Tagueï ring-complex, Aïr, Niger: a hybrid rock with cumulus plagioclase and an infiltrated granitic intercumulus liquid?

  • Published:
Contributions to Mineralogy and Petrology Aims and scope Submit manuscript

Abstract

An unusual hybrid rock composed of cumulus plagioclase with the interstices occupied by abundant quartzo-feldspathic material occurs in the Tagueï ring complex, Niger. The monzo-anorthosite consists of about 75% plagioclase in large tabular to elongate crystals with interstices occupied in two stages, firstly by clinopyroxene, titanomagnetite and apatite and then by an intergrowth of quartz and alkali feldspar associated with brown-green amphibole and zircon. Secondary green amphibole, chlorite, epidote and calcite may occur. Four stages in the crystallization history were identified:

  1. (1)

    Cumulus stage represented by the cores of the plagioclase laths (An56-An66 with reversed oscillatory zoning) and rare clinopyroxene (T ∼1,150° C),

  2. (2)

    Early intercumulus stage with a wide overgrowth zone on plagioclase (An62-An15 with oscillatory zoning and increase in Or), clinopyroxene, apatite, titanomagnetite (T ∼1,150-1,050° C),

  3. (3)

    Late intercumulus stage with alkali feldspar, quartz, opaque oxide, brown-green amphibole, apatite and zircon (T ∼750-700° C). Alkali feldspar gave cryptoperthite on further cooling.

  4. (4)

    Deuteric stage with development of turbidity in the alkali feldspar and plagioclase rims, and formation of patch perthite with microcline and secondary minerals (T ∼400° C).

The contrast in mineralogy, the large gap of ∼300° C between the early and late cumulus stages and the great abundance of quartz and alkali feldspar (∼20%) suggest that the late-stage liquid of granitic composition which filled the interstices was not a simple residual liquid which crystallized in situ. From chemistry (including REE) it is almost identical to the later radial granite dykes. From gravity measurements the intrusion has the form of a pipe with less dense rocks below the present exposure level. We propose that a pulse of granite magma rose within the pipe just before complete consolidation of the leucogabbro and replaced by infiltration the denser residual intercumulus liquid.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  • Barrabé ML (1943) Sur la nature et le mode de gisement des gros massifs intrusifs de l'aire anticlinale du Cap Saint-André à Ma-dagascar, et leurs relations avec les grandes coulées volcaniques voisines. Bull Soc Fr Mineral Cristallogr 66:1–24

    Google Scholar 

  • Black R (1965) Sur la signification pétrogénétique de la découverte d'anorthosites associées aux complexes subvolcaniques du Niger. CR Acad Sci Fr 260(D):5829–5832

    Google Scholar 

  • Boulanger J (1959) Les anorthosites de Madagascar. Ann Géol Madagascar XXVI: 71

    Google Scholar 

  • Bridgwater D, Harry WT (1968) Anorthosite xenoliths and plagioclase megacrysts. In: Precambrian intrusions of South Greenland. Medd Grønland 185, n∘ 2, p 243

    Google Scholar 

  • Brown WL, Parsons I (1981) Towards a more practical two-feldspar geothermometer. Contrib Mineral Petrol 76:369–377

    Google Scholar 

  • Brown WL, Parsons I (1984a) Exsolution and coarsening mechanisms and kinetics in an ordered cryptoperthite series. Contrib Mineral Petrol 86:3–18

    Google Scholar 

  • Brown WL, Parsons I (1984b) The nature of potassium feldspar, exsolution microtextures and development of dislocations as a function of composition in perthitic alkali feldspars. Contrib Mineral Petrol 86:335–341

    Google Scholar 

  • Brown WL, Becker SM, Parsons I (1983) Cryptoperthite and cooling rate in a layered syenite pluton: a chemical and TEM study. Contrib Mineral Petrol 82:13–25

    Google Scholar 

  • Demaiffe D, Hertogen J (1981) Rare earth geochemistry and strontium isotopic composition of a massif-type anorthositic-charnockitic body: the Hidra massif (Rogaland, SW Norway). Geochim Cosmochim Acta 45:1545–1561

    Google Scholar 

  • Demaiffe D, Duchesne JC, Michot J, Pasteels P (1973) Le massif anorthosito-leuconoritique d'Hidra et son faciès de bordure. CR Acad Sci Paris 277(D):17–20

    Google Scholar 

  • Donnot M (1963) Les complexes intrusifs alcalins d'Ampasidava (Madagascar). Ann Géol Madagascar XXXIII: 81–87

    Google Scholar 

  • Duchesne JC (1984) Massif anorthosites: another partisan review. In: WL Brown (ed) Feldspar and Feldspathoids. D Reidel Co, Dordrecht, pp 411–433

    Google Scholar 

  • Emeleus CH, Upton BGJ (1976) The Gardar period in southern Greenland. In: Escher A and Watt S (ed) Geology of Green-land, The Geological Survey of Greenland, pp 152–181

  • Emslie RF (1978) Anorthosite massifs, rapakivi granites, and late Proterozoic rifting of North America. Precambr Res 7:61–98

    Google Scholar 

  • Finnerty AA, Boyd FR (1977) Pressuredependent solubility of calcium in fosterite coexisting with diopside and enstatite. Carnegie Inst Washington Yearb 77:713–717

    Google Scholar 

  • Ghiorso MS (1984) Activity/composition relations in the ternary feldspars. Contrib Mineral Petrol 87:282–296

    Google Scholar 

  • Grove TL, Baker MB, Kinzler RJ (1984) Coupled CaAl-NaSi diffusion in plagioclase feldspar: experiments and applications to cooling rate speedometry. Geochim Cosmochim Acta 48:2113–2121

    Google Scholar 

  • Husch JM (1982) Geology, petrology and geochemistry of anorthositic and other rocks associated with hypabyssal ring-complexes, Aïr massif, Republic of Niger. Unpublished, Ph D, Princeton Univ, p 231

  • Husch JM, Moreau C (1982) Geology and major element geochemistry of anorthositic rocks associated with Paleozoic hypoabyssal ring-complexes, Republic of Niger, West Africa. J Volcanol Geotherm Res 14:47–66

    Google Scholar 

  • Irvine TN (1982) Terminology for layered intrusions. J Petrol 23:127–162

    Google Scholar 

  • Jaeger JC (1968) Cooling and solidification of igneous rocks. In: Hess HH, Poldervaart A (eds) Basalts. Wiley, New York, pp 503–536

    Google Scholar 

  • Kushiro I (1973) The system Diopside-Anorthite-Albite: determination of compositions of coexisting phases. Carnegie Inst Washington Yearb 72:502–507

    Google Scholar 

  • Lindsley D (1983) Pyroxene thermometry. Am Mineral 68:477–493

    Google Scholar 

  • Luth WC (1976) Granitic rocks. In: Bailey WL, Macdonald R (eds) The Evolution of the Crystalline Rocks, London, Academic Press, pp 335–417

    Google Scholar 

  • Miyashiro A (1978) Nature of alkalic rock series. Contrib Mineral Petrol 66:91–104

    Google Scholar 

  • Moreau C (1982) Les complexes annulaires anorogéniques à suites anorthositiques de l'Aïr central et septentrional (Niger). Doctoral Thesis, University of Nancy, p 356

  • Moreau C, Karche JP, Trichet J (1978) Remarques sur les anorthosites des complexes subvolcaniques de l'Aïr (Niger). C R Som Soc Géol Fr 1:21–23

    Google Scholar 

  • Morse SA (1982) A partisan review of Proterozoic anorthosites. Am Mineral 67:1087–1100

    Google Scholar 

  • Murphy (1977) An experimental study of solid-liquid equilibria in the albite-anorthite-diopside system. MS Thesis, University of Oregon

  • Obata M, Banno S, Mori T (1974) The iron-magnesium partitioning between naturally occurring coexisting olivine and Carich clinopyroxene: an application of the simple mixture model to olivine solid solution. Bull Soc Fr Mineral Cristallogr 97:101–107

    Google Scholar 

  • Parsons I (1978) Feldspars and fluids in cooling plutons. Mineral Mag 42:1–17

    Google Scholar 

  • Sparks RSJ, Huppert HE (1984) Density changes during the fractional crystallization of basaltic magmas: fluid dynamic implications. Contrib Mineral Petrol 85:300–309

    Google Scholar 

  • Sparks RSJ, Huppert HE, Turner JS (1984) The fluid dynamics of evolving magma chambers. Philos Trans R Soc London A 310:511–534

    Google Scholar 

  • Simkin T, Smith JV (1970) Minor-element distribution in olivine. J Geol 78:304–325

    Google Scholar 

  • Tait SR, Huppert HE, Sparks RSJ (1984) The role of compositional convection in the formation of adcumulate rocks. Lithos 17:139–146

    Google Scholar 

  • Wager LR, Brown GM (1968) Layered igneous rocks. Oliver and Boyd, London, p 588

    Google Scholar 

  • Wager LR, Brown GM, Wadsworth WJ (1960) Types of igneous cumulates. J Petrol 1:73–85

    Google Scholar 

  • Wright JB (1975) Anorthosite — first occurrence in Nigeria and relevance to Younger Granite genesis. Mineral Mag 40:193–196

    Google Scholar 

  • Weill DF, Hon R, Navrotsky A (1980) The igneous system CaMg- Si2O6-CaAl2Si2O8-NaAlSi3O8: variations on a classic theme by Bowen. In: Hargraves RB (ed) Physics of magmatic processes, Princeton University Press, pp 49–92

Download references

Author information

Authors and Affiliations

  1. Département de Géologie, Faculté des Sciences, Dakar-Fann, Sénégal

    Christian Moreau

  2. CRPG, BP 20, 54501, Vandoeuvre-lès-Nancy Cédex, France

    William L. Brown

  3. Faculté des Sciences, Laboratoire de Pétrographie, 25030, Besançon Cédex, France

    Jean -Paul Karche

Authors
  1. Christian Moreau
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. William L. Brown
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Jean -Paul Karche
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Moreau, C., Brown, W.L. & Karche, J.P. Monzo-anorthosite from the Tagueï ring-complex, Aïr, Niger: a hybrid rock with cumulus plagioclase and an infiltrated granitic intercumulus liquid?. Contr. Mineral. and Petrol. 95, 32–43 (1987). https://doi.org/10.1007/BF00518028

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF00518028

Keywords

Search

Navigation