冀东太平寨—娄子山太古宙麻粒岩相变质峰期流体研究  

Studies on Fluids of the Metamorphic Peak Time for the Archaean Granulite Series in the Taipingzhai-Lozishan District, Eastern Hebei Province

作　　者：卢良兆[1] 董永胜[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130026

出　　处：《高校地质学报》2000年第4期499-508,共10页Geological Journal of China Universities

基　　金：国家自然科学基金资助项目!(批准号 49772 144 )

摘　　要：冀东太平寨—娄子山地区太古宙麻粒岩系变质峰期流体包裹体首次见于夕线石中 ,按形态和产状可分三类 ,均形成于峰期至其稍后阶段。它们成分相似。特征是 :①富碳质 ,XCO2 +CH4 =0 64～ 0 93;②含少量H2 O ,XH2 O=0～ 0 2 2 ,且与峰期矿物组合平衡热力学计算的水活度 ( aH2 O=0 0 4～ 0 31)和含量 (XH2 O=0 0 3～ 0 2 2 )完全吻合 ;③有时含一定量H2 S和SO2 ;④盐水溶液中阴离子总量极低 ( 0 12～ 0 61mol/L)。石英和石榴石中也有特征相同的这期包裹体。峰期包裹体中CO2 均一温度多数为 - 2 8℃～ - 2 2℃ ,密度为 0 96～ 1 0 6g/cm3,包裹体整体密度应稍高 ,相应的压力为 0 60～ 0 70GPa。流体的氧逸度lgfO2 在 - 17～ - 15之间。峰期流体上述各种特征在空间上较均匀 ,相邻的不同岩石类型中 aH2 O值相似 ,结合地质和原岩特征分析 ,认为流体中CO2可能为深部地幔来源 。The fluid inclusions of the metamorphic peak time for the Archaean granulite series in the Taipingzhai Lozishan district, eastern Hebei Province were first found in sillimanite According to their shapes and occurrences, these inclusions can be subdivided into three types The earliest type is the isolated inclusions and inclusions in clusters with negative hexogonal, prismatic crystal forms. They are very rare and characterized by parallelism of their elongated direction with c axis of sillimanite; The second type is the inclusions with irregular shapes. They have no spatial relation to cleavage and (001) parting of host mineral; The third type is most common. The inclusions are usually square or rectangular. They occur along healed (001) parting perpendicular to c axis of sillimanite, and were entraped in the later stage of the metamorphic peak time. As a whole, the compositions of fluids in above mentioned three types are very similer All they are characterized by:①rich in carbonic materials, with X CO 2+CH 4 ≈0 64～0 93; ② low in water, with X H 2O ≈0～0 22, which coincides well with activity of H 2O (0 04～0 31) and mole percent of water ( X H 2O ≈0 03～0 22) based on thermodynamic calculation from equilibrium assemblage of peak metamorphism; ③with X H 2S,SO 2 <0 10～0 21 in some cases; ④very low content of anions in halogenic solution (mostly 0 12～0 61mol/L) These inclusions have also been found in garnet and quartz, but in the latter case, the inclusious are characterized by abundant two phase H 2O-CO 2 chemistry, with X H 2O >0 25～0 33 They were probably formed in the further late regressive stage under the low PT condition The homogenization temperature of CO 2 in fluid inclusions of peak stage ranges from -28℃ to -22℃ in most samples. The corresponding density is 0 96～1 06g/cm 3, and total fluid pressure ( P f ) is 0 60～0 70GPa This value is about 0 1～0 3GPa lower tha

关 键 词：变质峰期 麻粒岩相 太古宙 流体包裹体 成因 

分 类 号：P588.3[天文地球—岩石学]