Hostname: page-component-78c5997874-s2hrs Total loading time: 0 Render date: 2024-11-10T07:39:17.006Z Has data issue: false hasContentIssue false
  • English
  • Français

Crystallization trend of titanomagnetites in an alkali basalt from Saint-Clément (Massif Central, France)

Published online by Cambridge University Press:  05 July 2018

M. Prévot  and
J. Mergoil
M. Prévot
Affiliation:
Laboratoire de Geomagnetisme, 4 avenue de Neptune, 94100 Saint-Maur, France
J. Mergoil
Affiliation:
Departement de Géologie et Minéralogie de l'U.E.R., Sciences Exactes et Naturelles, Université de Clermont-Ferrand, 5 rue Kessler, 63000, Clermont-Ferrand, France
Get access Rights & Permissions [Opens in a new window]

Summary

Three generations of homogeneous titanomagnetite in a hawaiite from Saint-Clément may be defined by differences in size, habit, or reflectance, and are believed to correspond to different crystallization stages of the lava. Chemical compositions were determined by electron microprobe, and by X-ray and thermomagnetic methods.

Larger crystals are of intratelluric origin and occur either as inclusions in phenocrysts of early clinopyroxene (generation 1) or separately in the groundmass (generation 2); in the latter case, they always show evidence of resorption. Post-eruptive titanomagnetite (generation 3) is smaller and so highly oxidized that it is better termed titanomaghemite. Since the maghemitization, which is a low temperature process, alters the metallic ratios (especially the Fe/Ti ratio) the metallic contents at the time of the high-temperature crystallization are exactly known only for the intratelluric titanomagnetites.

As intratelluric crystallization proceeds Ti content increases greatly (5 to 14%); Mn also increases (but slightly), A1 and Mg decrease, while results for Cr are inconclusive. Apparently these changes go on until the post-eruptive crystallization stage.

The titanium trend is contrary to common belief. However, it is in accordance with predictions from the Fe-Ti-O system and may be explained by a decrease in oxygen fugacity during magma ascent.

Type
Research Article
Information
Mineralogical Magazine , Volume 39 , Issue 304 , December 1973 , pp. 474 - 481
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1973

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

Anderson, (A. T.), 1968. Amer. Journ. Sci., 266, 704-27.CrossRefGoogle Scholar
Anderson, (A. T.) and Wright, (T. L.), I972. Amer. Min., 57, 188–;216.Google Scholar
Babkine, (J.), ConquéRé (F.), Vilminot, (J. C.), and Phan, (K. D.), 1965. Bull. Soc. franf. Min. Crist. 88, 447-55.Google Scholar
Babkine, (J.), ConquéRé (F.), Vilminot, (J. C.), and Phan, (K. D.) 1968. Ibid. 91, 141-50.CrossRefGoogle Scholar
Carmichael, (I. S. E.) and Nicholls, (J.), I967. Journ. Geophys. Res., 72, 4665-87.CrossRefGoogle Scholar
Darvich-Zad, (A.), 1971. Thése Doct. 3mecycle, Clermont, Fr., 160 p.Google Scholar
Huckenholz, , 1965. Beitr. Min. Petr., 11, 138-95.CrossRefGoogle Scholar
Marshall, (M.), and Cox, (A.), 1972. Journ. Geophys. Res., 77, 6459-69.CrossRefGoogle Scholar
O'Reilly, (W.) and Banerjee, (S. K.), I966. Nature, 211, 26-7.CrossRefGoogle Scholar
Ozlma, (M.) and Sakamoto, (N.), I97I. Journ. Geophys. Res., 76, 7035-46.Google Scholar
Prévot, (M.), Rémond, (G.), and Cave, (R.), 1968. Bull. Soc. fran. Min. Crist., 91, 65-74.Google Scholar
Prévot, (M.), Rémond, (G.), and Cave, (R.) 1971. Zeits. Geophys., 37, 339-47.Google Scholar
Prévot, (M.), Rémond, (G.), and Cave, (R.) and Poix, (P.), I97t. Journ. Geomagn. Geoelect., 23, 255-65.CrossRefGoogle Scholar
Prévot, (M.), Rémond, (G.), and Cave, (R.) and Mergoil, (J.), I973. In Travaux annuels ddpart, gdol. mindr., Clermont France, 142-74.Google Scholar
Taylor, (R. W.), I963. Journ. Amer. Ceram. Soc., 46, 276-9.CrossRefGoogle Scholar