Abstract
The fluorine content of Icelandic tholeiitic and alkaline basalts matches values found in similar rocks from other areas. Covariation between fluorine and incompatible minor elements such as potassium or phosphorus is found in evolved tholeiites and alkali basalts. Lack of such covariation in primitive olivine tholeiites indicates that fluorine and other incompatible minor and trace elements are not controlled by minerals such as amphibole, mica or apatite in the mantle residue, and that the covariation between these elements in the evolved basalts cannot be inherited from the mantle. Model calculations on rocks from the Langjökull area show that olivine tholeiite suites are, if derived by simple fractional crystallization, enriched in incompatible elements much in excess of the increase due to crystal removal. These observations are taken to indicate that the well documented covariation between fluorine and other incompatible elements is not established until evolution of the basaltic magma has started in crustal holding chambers. The constancy of element ratios and enrichment in excess of what can be accounted for by crystal fractionation or incremental addition of new batches of primitive magmas does indicate (1) mineral control involving amphibole, mica or apatite and (2) addition of fluorine, potassium and phosphorous from an external source. It is argued that this source is the crustal envelope of the holding chamber.
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References
Aoki K, Kanisawa S (1979) Fluorine contents of some hydrous minerals derived from upper mantle and lower crust. Lithos 12:167–171
Aoki K, Ishiwaka K, Kanisawa S (1981) Fluorine geochemistry of basaltic rocks from continental and oceanic regions and petrogenetic application. Contrib Mineral Petrol 76:53–59
Carmichael ISE, Turner FJ, Verhoogen J (1974) Igneous Petrology, McGraw Hill, New York
Hart SR, Aldrich LT (1967) Fractionation of K/Rb by amphiboles: implications regarding mantle composition. Science 155:325–327
Ingram BL (1970) Determination of fluoride in solicate rocks without separation of aluminum using a specific ion electrode. Anal Chem 42:1825–1827
Jeffery PG (1975) Chemical methods of rock analysis. Pergamon Press, Oxford
O'Hara MJ (1977) Geochemical evolution during fractional crystallization of a periodically refilled magma chamber. Nature 266:503–507
Óskarsson N (1980) The interaction between volcanic gases and tephra: Fluorine adhering to tephra of the 1970 Hekla eruption. J Volcanol Geotherm Res 8:251–266
Óskarsson N (1981) The chemistry of Icelandic lava incrustations and the latest stages of degassing. J Volcanol Geotherm Res 10:93–111
Óskarsson N, Sigvaldason GE, Steinthorsson S (1982) A dynamic model of rift zone petrogenesis and the regional petrology of Iceland. J Petrol 23:28–74
Rose HJ, Adler J, Flanagan FJ (1963) X.R.F.A. of light elements in rocks and minerals. Appl Spectrosc 17:4–81
Sigvaldason GE (1974) The petrology of Hekla and origin of silicic rocks in Iceland. Soc Sci Islandica. The Eruption of Hekla 1947–1948, 4:44
Sigvaldason GE, Óskarsson N (1976) Chlorine in basalts from Iceland. Geochim Cosmochim Acta 40:777–789
Smith JV (1981) Halogen and phosphorous storage in the Earth. Nature 289:762–765
Smith JV, Delaney JS, Hervig RI, Dawson JB (1981) Storage of F and Cl in the upper mantle: geochemical implications. Lithos 14:133–147
Thorarinsson S, Sigvaldason GE (1962) The eruption of Askja 1961: A preliminary report. Am J Sci 260:641–651
Thorarinsson S, Steinthorsson S, Einarsson Th, Kristmannsdottir H, Óskarsson N (1973) The eruption on Heimaey, Iceland. Nature 241:272–275
Yoder HS Jr (1976) Generation of Basaltic Magmas. Nat Acad Sci, Washington DC
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Sigvaldason, G.E., Óskarsson, N. Fluorine in basalts from Iceland. Contr. Mineral. and Petrol. 94, 263–271 (1986). https://doi.org/10.1007/BF00371435
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DOI: https://doi.org/10.1007/BF00371435