窑街煤田碳酸盐与突出气体的同位素组成特征

为探讨窑街煤矿突出CO₂气的成因与来源,对煤田中方解石、菱铁矿和水中溶解HCO₃-及沉淀碳酸盐的碳、氧同位素组成进行测试研究,并对“5.24”突出点涌出气的13C_CO2值和3He/4He值进行了测定.结果表明,煤田中CO₂气的碳同位素组成发生了复杂的分馏效应而和各种可能母质的碳同位素组成难以进行简单的对比;突出点气体的3He/4e值表明其为典型的壳源气;煤田中烧变岩可能为突出气的气源.

Isotope Compositions of Carbonate and Outburst Gas in Youjie Coalfield

The extraordinary outburst of CO₂ gas, coal and rocks happened on May 24, 1978 in aojie oalfield. The isotope compositions of the outburst gas and the carbonates relating to CO₂ gas. The results arc as follows: The δ13C values of the CO₂ gas are -0.55-4.81‰; and that of ealcitc veins are -15.88-+5.94‰ which are tending to be heavier with the. decrease of depth. The δ13O alues PDB. the same below) of the calcite distributed from-8.07 to-20.4‰; The values of δ13C and δ13 O of parry iron are-1.96-+2.66‰ and -8.55-11.97‰ respectively; The average δ13C value of HCO₃ in the barnt rock water is 2.325‰, and based on it, the calculated δ13C value of the primary CO₂ dissolved a the wanter is about -6‰, but that of free CO₂ released the solution is about -7‰; The δ13C can onate precipi-laied fron, the burnt rock water are 3.89-4.63‰, heavier than those of the HCO₃ dissolved in water. The above results show that there are isotope fractionation of carbon in the processes of the disselving and degassing of CO₂ gas and the precipitating of the carbonate. As the variation of the δ13C values of the CO, in the coal measures of the field is broad (The lightest is -43.44‰, it is difficult to simply of CO gas with the carberrates in their isolopic compositions. The He/4 He value of the gas in the outburst spot is (3.8±0.5)×108, showing that the outburst gas is a sypteal crust source gas. So it is necessary to strengthen the studying in geology and geochemistry er the eoalfitld ill itself for searching into the concrete source of the outburst gas.