EXPERIMENTAL INVESTIGATION OF THE DELAY IN NUCLEATION OF OLIVINE IN MAFIC MAGMAS

被引:95
作者
DONALDSON, CH
机构
[1] Department of Geology, University of St. Andrews, Fife, KY16 9ST, St. Andrews
关键词
D O I
10.1007/BF00375191
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The delay in nucleation of olivine in basaltic melts increases systematically with decreasing degree of supercooling, cooling rate, superheat, olivine content of the melt and with increasing melt viscosity. These findings imply homogeneous nucleation of olivine in melts run in the Pt-wire loop sample container used. Unlike plagioclase nucleation, the appearance of the first olivine crystal in a melt is predictable (to within 0.1-1 h of the event). The 'metastable region' (i.e., the minimum degree of supercooling necessary for nucleation) is less than 13 ° C. The cause of the delay in nucleation is discussed in terms of the finite growth rate of embryos and the progressive polymerization of the melt with decreasing temperature and increasing time. At degrees of superheat <18 ° the melts are inferred to be more highly disordered than expected. Some implications of the results for petrology and experimental petrology are discussed, including the possibility that continuous zoning may develop under isothermal conditions due to the sluggish attainment of equilibrium of melt structure following a sudden change in temperature. © 1979 Springer-Verlag.
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页码:21 / 32
页数:12
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