Solubility of carbon dioxide in melts of andesite, tholeiite, and olivine nephelinite composition to 30 kbar pressure
Solubility of carbon dioxide in melts of andesite, tholeiite, and olivine nephelinite composition to 30 kbar pressure
复制标题
在 30 kbar 压力下，二氧化碳在安山岩、拉斑玄武岩和橄榄石霞石组合物熔体中的溶解度
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发表时间：
1975
期刊：
影响因子：
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通讯作者：
D. Eggler
中科院分区：
文献类型：
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作者：
B. Mysen;R. Arculus;D. Eggler
采用碳-14 β径迹成像技术测定了天然安山岩（CA）、拉斑玄武岩（K 1921）和橄榄石霞石（OM 1）组成的无水含水硅酸盐熔体中二氧化碳的溶解度。CO2的溶解度随着压力、温度和硅酸盐熔体的二氧化硅欠饱和度的增加而增加。在1650° C下，CO2在CA中的溶解度从15 kbar下的1.48±0.05重量%增加到30 kbar下的1.95±0.03重量%。在OM 1中的相应溶解度为3.41±0.08重量%和7.11±0.10重量%。CO2在K1921中的溶解度介于CA和OM 1组合物的溶解度之间。在较低的温度下，这些硅酸盐熔体的CO2含量较低，并且溶解度的压力依赖性不太明显。H2O的存在也影响CO2的溶解度（在含水硅酸盐熔体中溶解的CO2比在无H2O的硅酸盐熔体中多20-30%）;溶解度曲线在挥发相的中等CO2/（CO2+H2O）组成处通过等温等压最大值。在碳酸盐矿物不稳定且存在CO2和H2O的上地幔条件下，必须存在气相。由于CO_2在硅酸盐熔体中的溶解度低于H_2O，在橄榄岩部分熔融过程中，挥发分必须在熔体和蒸汽之间破裂。已发表的相平衡数据表明，在20 kbar左右的压力下，随着温度的升高，橄榄岩+H2O+CO2母体熔体的组成顺序为安山岩-拉斑玄武岩-霞石。这种序列的例子可以在小安的列斯群岛和印度尼西亚岛弧中找到。
Carbon dioxide solubilities in H2O-free hydrous silicate melts of natural andesite (CA), tholeiite (K 1921), and olivine nephelinite (OM1) compositions have been determined employing carbon-14 beta-track mapping techniques. The CO2 solubility increases with increasing pressure, temperature, and degree of silica-undersaturation of the silicate melt. At 1650° C, CO2 solubility in CA increases from 1.48±0.05 wt % at 15 kbar to 1.95±0.03 wt % at 30 kbar. The respective solubilities in OM1 are 3.41±0.08 wt % and 7.11±0.10 wt %. The CO2 solubility in K1921 is intermediate between those of CA and OM1 compositions. At lower temperatures, the CO2 contents of these silicate melts are lower, and the pressure dependence of the solubility is less pronounced. The presence of H2O also affects the CO2 solubility (20–30% more CO2 dissolves in hydrous than in H2O-free silicate melts); the solubility curves pass through an isothermal, isobaric maximum at an intermediate CO2/(CO2+H2O) composition of the volatile phase.Under conditions within the upper mantle where carbonate minerals are not stable and CO2 and H2O are present a vapor phase must exist. Because the solubility of CO2 in silicate melts is lower than that of H2O, volatiles must fractionate between the melt and vapor during partial melting of peridotite. Initial low-temperature melts will be more H2O-rich than later high-temperature melts, provided vapor is present during the melting.Published phase equilibrium data indicate that the compositional sequence of melts from peridotite +H2O+CO2 parent will be andesite-tholeiite-nephelinite with increasing temperature at a pressure of about 20 kbar. Examples of this sequence may be found in the Lesser Antilles and in the Indonesian Island Arcs.