EVIDENCE FOR VARIABILITY OF MAGMATIC PROCESSES AND UPPER MANTLE HETEROGENEITY IN THE AXIAL REGION OF THE MID-ATLANTIC RIDGE NEAR 22-DEGREES AND 36-DEGREES-N

被引:48
作者
BOUGAULT, H
CAMBON, P
CORRE, O
JORON, JL
TREUIL, M
机构
[1] INST PHYS GLOBE PARIS,PARIS,FRANCE
[2] CENS,PIERRE SU LAB,SCI TERRE GRP,F-91190 GIF SUR YVETTE,FRANCE
关键词
D O I
10.1016/0040-1951(79)90333-0
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
Basalt samples at 36°N (FAMOUS area) and at 22°N (leg 45 and leg 46 of D.S.D.P.) are compared with particular reference to their trace element concentrations. The results are interpreted in terms of variability of magmatic processes and compositional heterogeneity of the upper mantle material. It is shown that the concentrations of elements such as nickel, chromium and cobalt, which have high partition coefficients, do not vary significantly either in the residue or in the liquid as a result of varying degrees of partial melting. The large variations of Ni and Cr, together with the narrow range of variation of Co in oceanic basalts provide valuable constraints for models of fractional crystallization. The concentrations of hygromagmaphile elements (low partition coefficient elements) in basalts and the ratios of two of these elements are a function of the initial values in the source material, partial melting and to a lesser extent crystallization processes. When a liquid is generated through partial melting, it is likely that the solid should be treated as a partial residue (previous melting) and not as fertile mantle material. The mantle sources at 22°N are the same both for sites 395 and 396 which are almost symmetric in relation to the ridge. The mantle source at 36°N is compositionally different. These sources (at 22°N and 36°N) can be considered either as original different sources constituting the upper mantle in both areas or as different residues of an initial homogeneous mantle. © 1979.
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页码:11 / 34
页数:24
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