论文部分内容阅读
对大别山双河和碧溪岭含柯石英榴辉岩和硬玉石英岩进行了详细的流体包裹体研究。根据流体包裹体的成分和盐度的不同 ,可以划分出至少五种类型不同的气液包裹体 :( 1) N2 包裹体 ;( 2 )高盐度流体包裹体 ;( 3) CO2 包裹体 ;( 4) CO2 -H2 O包裹体 ;( 5 )低盐度流体包裹体。N2 包裹体仅见于含柯石英榴辉岩 ,而高盐度流体包裹体则几乎存在于所有的榴辉岩和硬玉石英岩中。 CO2 包裹体沿榴辉岩中微剪切带分布 ,或存在于强变形的硬玉石英岩中 ,而低盐度流体包裹体分布较为局限。N2 和高盐度流体被认为是超高压变质作用平衡的产物 ,来源于变质前的古孔隙流体。而且榴辉岩中含有一系列盐度不同的流体显微域 ,其大小与矿物颗粒相当。在板块折返过程中 ,包裹体中流体可能发生迁移 ,但是不会超出寄主晶体的范围。CO2流体明显是外来的 ,可能来自共生大理岩或含碳酸盐的变质沉积岩。这与菱镁矿和柯石英等共生组合所指示的进变质过程中大理岩不存在脱碳反应的结论相一致。而低盐度流体则可能系顶峰变质矿物分解而成 ,或直接来源于围岩
A detailed fluid inclusion study was conducted on the coesite eclogite and jade quartzite in Shuanghe and Bixiling Mountains in the Dabie Mountains. Depending on the composition and salinity of the fluid inclusions, at least five different types of gas-liquid inclusions can be identified: (1) N2 inclusions; (2) high-salinity fluid inclusions; (3) CO2 inclusions; (4) CO2-H2O inclusions, and (5) low-salinity fluid inclusions. The N2 inclusions are found only in coesite-bearing eclogite, while the high-salinity fluid inclusions are found in nearly all eclogites and jadeite-quartzite. The CO2 inclusions distribute along the micro-shear zone in the eclogites, or exist in the strongly deformed jade quartzite, while the distribution of low-salinity fluid inclusions is more limited. N2 and high-salinity fluids are considered as the product of the balance of the UHP metamorphism and originated from the paleo-pore fluid before metamorphism. In addition, the eclogites contain a series of fluid microscopic domains with different salinities, which are comparable in size to mineral particles. During the plate foldback, the fluid in the inclusion may migrate but does not go beyond the host crystal. CO2 fluids are obviously extraneous, probably from symbiotic or carbonate-bearing metasedimentary rocks. This is consistent with the conclusion that there is no decarburization in marble during the metamorphic process as indicated by the symbiotic assemblages such as magnesite and coesite. The low-salinity fluid may be decomposed from the top metamorphic minerals, or directly from the surrounding rock