EXPERIMENTAL CONSTRAINTS ON THE DYNAMICS OF THE PARTIALLY MOLTEN UPPER-MANTLE .2. DEFORMATION IN THE DISLOCATION CREEP REGIME

被引:153
作者
HIRTH, G [1 ]
KOHLSTEDT, DL [1 ]
机构
[1] UNIV MINNESOTA, DEPT GEOL & GEOPHYS, MINNEAPOLIS, MN 55455 USA
关键词
D O I
10.1029/95JB01292
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
Experiments have been conducted to investigate the effect of melt on the creep behavior of water-free olivine aggregates deformed in the dislocation creep regime. The influence of the melt phase is modest at melt fractions less than similar to 0.04. However, at melt fractions > 0.04, the creep rate of melt-added samples is enhanced by more than an order of magnitude relative to melt-free aggregates. This unexpectedly large influence of melt on strain rate arises because deformation occurs by grain boundary sliding (GBS) accommodated by a dislocation creep process. Four observations support this hypothesis. (1) The strain rate enhancement observed in the dislocation creep regime can be related to the Stress concentration caused by the reduction in the solid-solid grain boundary area. (2) Both melt-free and melt-added samples exhibit strain rates indicating that deformation is limited by slip on (010)[100], the easiest slip system in olivine. (3) The GBS mechanism occurs near the transition between diffusion and dislocation creep. (4) Grains in specimens deformed in the GBS regime are not significantly flattened, even after similar to 50% shortening. in melt-free aggregates, a transition from the GBS mechanism to dislocation creep limited by slip on (010)[001], the hardest slip system, is observed with an increase in grain size. A transition to (010)[001] limited creep was not observed for partially molten aggregates because grain growth was inhibited by the presence of melt. The results of this study indicate that the viscosity of the upper mantle may decrease by at least an order of magnitude if the retained melt fraction exceeds 0.04 or if the onset of melting results in a reduction in grain size and a concomitant transition from (010)[001] to (010)[100] limited creep.
引用
收藏
页码:15441 / 15449
页数:9
相关论文
共 35 条
[1]   THEORIES OF NORMAL GRAIN-GROWTH IN PURE SINGLE-PHASE SYSTEMS [J].
ATKINSON, HV .
ACTA METALLURGICA, 1988, 36 (03) :469-491
[2]   HIGH-TEMPERATURE CREEP OF OLIVINE SINGLE-CRYSTALS .1. MECHANICAL RESULTS FOR BUFFERED SAMPLES [J].
BAI, Q ;
MACKWELL, SJ ;
KOHLSTEDT, DL .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1991, 96 (B2) :2441-2463
[3]   DEFORMATION OF FINE-GRAINED AGGREGATES OF OLIVINE PLUS MELT AT HIGH-TEMPERATURES AND PRESSURES [J].
BEEMAN, ML ;
KOHLSTEDT, DL .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1993, 98 (B4) :6443-6452
[4]  
Bussod GY, 1991, J PETROL, P17
[5]  
BUSSOD GY, 1991, EOS, V72, P508
[6]   STEADY-STATE POWER-LAW CREEP IN HETEROGENEOUS ALLOYS WITH COARSE MICROSTRUCTURES [J].
CHEN, IW ;
ARGON, AS .
ACTA METALLURGICA, 1979, 27 (05) :785-791
[7]   THE ROLE OF WATER IN THE DEFORMATION OF DUNITE [J].
CHOPRA, PN ;
PATERSON, MS .
JOURNAL OF GEOPHYSICAL RESEARCH, 1984, 89 (NB9) :7861-7876
[8]   SOLUTION-PRECIPITATION ENHANCED CREEP IN SOLID-LIQUID AGGREGATES WHICH DISPLAY A NON-ZERO DIHEDRAL ANGLE [J].
COOPER, RF ;
KOHLSTEDT, DL ;
CHYUNG, K .
ACTA METALLURGICA, 1989, 37 (07) :1759-1771
[9]   SINTERING OF OLIVINE AND OLIVINE-BASALT AGGREGATES [J].
COOPER, RF ;
KOHLSTEDT, DL .
PHYSICS AND CHEMISTRY OF MINERALS, 1984, 11 (01) :5-16
[10]   A LABORATORY STUDY OF MELT MIGRATION [J].
DAINES, MJ ;
KOHLSTEDT, DL .
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 1993, 342 (1663) :43-52