THE EQUILIBRIUM GEOMETRY OF CARBONATE MELTS IN ROCKS OF MANTLE COMPOSITION
THE EQUILIBRIUM GEOMETRY OF CARBONATE MELTS IN ROCKS OF MANTLE COMPOSITION
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DOI：
10.1016/0012-821x(89)90059-9
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发表时间：
1989-04-01
影响因子：
5.3
通讯作者：
MCKENZIE, D
中科院分区：
文献类型：
--
作者：
HUNTER, RH;MCKENZIE, D
在3gpa的温度下进行了熔融实验，以确定橄榄石基体中白云岩熔体（近似成分：35% CO2, 20% CaO, 20% MgO, 6% FeO, 12% SiO2, 4% Al2O3）的平衡二面角。得到的值为28°，小于形成互连网络所需的60°。因此，由于它们的低粘度，富含碳酸盐的熔体可以在10 Ma的熔体分数低至0.02%时从它们的残留物中分离出来。这些熔体的任何运动都将支配地幔中不相容的微量元素分布，从而支配地壳和地幔的同位素系统。上涌的碳酸盐熔体在约1.8 GPa的压力下与橄榄石基体反应生成二氧化碳气体。由于游离co2的二面角大于60°，因此在孔隙度达到8%之前气体无法分离。到那时，它很可能会以爆炸式的方式这样做。当与基体发生反应时，基体会被碳酸盐熔体所携带的金属氧化物所交代。
A melting experiment was carried out at 3 GPa to determine the equilibrium dihedral angle for a dolomitic melt (approximate composition: 35% CO2, 20% CaO, 20% MgO, 6% FeO, 12% SiO2, 4% Al2O3) in an olivine matrix. The value obtained was 28°, and is less than the value of 60° required to form an interconnected network. Therefore, because of their low viscosity, carbonate-rich melts can separate from their residue at melt fractions as small as 0.02% in 10 Ma. Any movement of such melts will dominate the incompatible trace element distributions in the mantle and hence the isotopic systematics of the crust and mantle. Upwelling carbonate melts react with the olivine matrix at pressures of about 1.8 GPa to form CO2gas. The dihedral angle of free CO2is greater than 60°, and the gas will therefore be unable to separate until the porosity reaches 8%. It is then likely to do so explosively. Where the reaction with the matrix occurs, the matrix will be metasomatised by the metal oxides carried by the carbonate melt.