Hostname: page-component-6d856f89d9-mhpxw Total loading time: 0 Render date: 2024-07-16T04:23:58.988Z Has data issue: false hasContentIssue false
  • English
  • Français

On the development of internal chemical zonation in small mafic dykes

Published online by Cambridge University Press:  17 July 2009

SOFYA CHISTYAKOVA  and
RAIS LATYPOV
SOFYA CHISTYAKOVA*
Affiliation:
Department of Geosciences, University of Oulu, Oulu, Finland
RAIS LATYPOV
Affiliation:
Department of Geosciences, University of Oulu, Oulu, Finland
*
*Author for correspondence: sofya.chistyakova@oulu.fi
Get access Rights & Permissions [Opens in a new window]

Abstract

Three dolerite dykes (Small, 3.2 cm; Middle, 13.5 cm; Thick, 50 cm) from Torsholma Island, SW Finland, reveal distinctly different internal zonation that becomes more complicated with increasing thickness of the dykes. The Small Dyke shows a systematic inward increase in normative Pl (An+Ab+Or) and a decrease in normative An (100*An/(An+Ab)), whole-rock MgO, Mg number (100*Mg/(Mg+Fetotal)), TiO2, K2O and Zr. The Middle Dyke exhibits the same compositional pattern at the margins, while the centre is distinguished by an abrupt increase in normative Pl and An, whole-rock Sr and Mg number. From the margins inwards, the Thick Dyke displays first a compositional pattern identical to that observed in the Small Dyke and the margins of the Middle Dyke. This is followed by a region where whole-rock MgO, Mg number and normative An start increasing inwards, while the transition to the centre of the dyke is characterized by a compositional pattern similar to that in the centre of Middle Dyke. The origin of chemical zonation in these dykes is attributed to the operation of three independent physico-chemical processes, namely: the Small Dyke formed exclusively by progressive changes in the composition of inflowing magma; the Middle Dyke by changes in composition of inflowing magma (margins) and concentration of plagioclase and olivine phenocrysts by flow differentiation (centre); the Thick Dyke by changes in composition of inflowing magma (margins), in situ cumulate growth against dyke sidewalls (middle) and flow differentiation (centre). Systematic changes in these processes and, as a result, in internal chemical zonation, likely take place in response to crystallization of magma under less supercooled conditions with increasing dyke thickness. A comprehensive geochemical study of the internal zonation of small mafic dykes worldwide is required to develop a complete understanding of the processes operating in mafic dykes.

Keywords

Small mafic dykesinternal zonationcompositional patternsdifferentiation processes
Type
Original Article
Information
Geological Magazine , Volume 147 , Issue 1 , January 2010 , pp. 1 - 12
Copyright
Copyright © Cambridge University Press 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bergman, L. 1986. Structure and mechanism of intrusion of postorogenic granites in the archipelago of southwestern Finland. Acta Academiae Aboensis (Series B) 46 (5), 74 pp.Google Scholar
Bhattacharji, S. 1967. Scale model experiments on flowage differentiation in sills. In Ultramafic and related rocks (ed. Wyllie, P. J.), pp. 69–70. New York, London, Sydney: John Wiley and Sons.Google Scholar
Bhattacharji, S. & Smith, C. H. 1964. Flowage differentiation. Science 145, 150–3.Google Scholar
Brouxel, M. 1991. Geochemical consequences of flow differentiation in a multiple injection dyke (Trinity ophiolite, N. California). Lithos 26, 245–52.Google Scholar
Chistyakova, S. Yu. & Latypov, R. M. 2009 a. Fine-scale chemical zonation in small mafic dykes, Kestiö Island, SW Finland. Geological Magazine 146, 485–96.Google Scholar
Chistyakova, S. Yu. & Latypov, R. M. 2009 b. Two independent processes responsible for compositional zonation in mafic dykes of the Åland–Åboland Dyke Swarm, Kestiö Island, SW Finland. Lithos (in press, http://dx.doi.org/10.1016/j.lithos.2009.03.037).CrossRefGoogle Scholar
Ehlers, C. & Ehlers, M. 1977. Shearing and multiple intrusions in the diabases of Åland archipelago, SW Finland. Geological Survey of Finland, Bulletin 289, 31 pp.Google Scholar
Eklund, O., Fröjdö, S. & Lindberg, B. 1994. Magma mixing, the petrogenetic link between anorthositic suites and rapakivi granites, Åland, SW Finland. Mineralogy and Petrology 50, 3–19.CrossRefGoogle Scholar
Ernst, R. & Bell, K. 1992. Petrology of the Great Abitibi Dyke, Superior Province, Canada. Journal of Petrology 33, 423–69.Google Scholar
Govindaraju, K. 1994. Compilation of working values and sample descriptions for 383 geostandards. Geostandards Newletter 18, 1–158.Google Scholar
Halama, R., Waight, T. & Markl, G. 2002. Geochemical and isotopic zoning patterns of plagioclase megacrysts in gabbroic dykes from the Gardar Province, South Greenland: implications for crystallization processes in anorthositic magmas. Contributions to Mineralogy and Petrology 144, 109–27.Google Scholar
Kretz, R., Hartree, R. & Garrett, D. 1985. Petrology of the Grenville swarm of gabbro dikes, Canadian Precambrian Shield. Canadian Journal of Earth Sciences 22, 53–71.Google Scholar
Laitakari, I. (ed.) 1991. Fennoscandian meeting excursion on Precambrian Dyke Swarm. IGCP-257 Technical Report 4.Google Scholar
Lindberg, B. & Eklund, O. 1990. The relation between Subjotnian diabases and rapakivi intrusions in southwestern Finland. Geologi 3, 44–7 (in Swedish).Google Scholar
Lindberg, B., Eklund, O. & Suominen, V. 1991. Middle Proterozoic, Subjotnian diabases and related mafic rocks in the archipelago of southwestern Finland. In IGCP-257 Fennoscandian Meeting and Excursion on Precambrian Dyke Swarms (ed. Laitakari, I.), pp. 18–30. IGCP-257 Technical Report 4.Google Scholar
Platten, I. M. 2000. Incremental dilation of magma filled fractures: evidence from dyke on the Isle of Skye, Scotland. Journal of Structural Geology 22, 1153–64.CrossRefGoogle Scholar
Platten, I. M. & Watterson, J. 1987. Magma flow and crystallization in dyke fissures. In Mafic dyke swarms (eds Halls, H. C. & Fahrig, W. F.), pp. 65–73. Geological Association of Canada, Special Paper no. 34.Google Scholar
Ragland, P. C., Rogers, J. J. W. & Justus, P. S. 1968. Origin and differentiation of Triassic dolerite magmas, North Carolina, USA. Contributions to Mineralogy and Petrology 20, 57–80.CrossRefGoogle Scholar
Rämö, O. T. & Haapala, I. 2005. Rapakivi granites. In Precambrian Geology of Finland – Key to the Evolution of the Fennoscandian Shield (eds Lehtinen, M., Nurmi, P. A. & Rämö, O. T.), pp. 533–62. Amsterdam: Elsevier B. V.CrossRefGoogle Scholar
Ross, M. E. 1986. Flow differentiation, phenocryst alignment, and compositional trends within a dolerite dike at Rockport, Massachusetts. Bulletin of the Geological Society of America 97, 232–40.2.0.CO;2>CrossRefGoogle Scholar
Ross, M. E. 1983. Chemical and mineralogic variations within four dikes of the Columbia River Basalt Group, southeastern Columbia Plateau. Bulletin of the Geological Society of America 94, 1117–26.Google Scholar
Ross, M. E. & Heimlich, R. A. 1972. Petrology of Precambrian Mafic Dikes from the Bald Mountain Area, Bighorn Mountains, Wyoming. Bulletin of the Geological Society of America 83, 1117–23.Google Scholar
Simkin, T. 1967. Flow differentiation in the picritic sills of north Skye. In Ultramafic and related rocks (ed. Wyllie, P. J.), pp. 64–9. New York, London, Sydney: John Wiley and Sons.Google Scholar
Steele, K. F. & Ragland, P. C. 1976. Model for the closed-system fractionation of a dike formed by two pulses of dolerite magma. Contributions to Mineralogy and Petrology 57, 305–16.CrossRefGoogle Scholar
Suominen, V. 1987. Mafic dyke rocks in southwestern Finland. In Diabases and other mafic dyke rocks in Finland (eds Aro, K. & Laitakari, I.), pp. 151–72. Geological Survey of Finland, Report Investigation 76 (in Finnish).Google Scholar
Suominen, V. 1991. The chronostratigraghy of southwestern Finland with special reference to Postjotnian and Subjotnian diabases. Geological Survey of Finland Bulletin 356, 100 pp.Google Scholar
Supplementary material: File

Chistyakova supplementary material

Table 1.doc

Download Chistyakova supplementary material(File)
File 106.5 KB
Supplementary material: File

Chistyakova supplementary material

Table 2.doc

Download Chistyakova supplementary material(File)
File 146.9 KB
Supplementary material: File

Chistyakova supplementary material

Table 3.doc

Download Chistyakova supplementary material(File)
File 378.4 KB