黔西南冰洲石矿床地球化学研究

Geochemical study of iceland spar deposits in southwest guizhou

查明黔西南贞丰等地冰洲石矿床的成矿温度为１２６～１６０℃，成矿压力为（２６０～５２０）×１０５Ｐａ；成矿流体盐度（ＳＮａＣｌ）为１２．２％～１９．６％。研究了不同成矿阶段方解石、冰洲石的氢、氧、碳同位素组成及变化特征：其中冰洲石成矿阶段δ１８Ｏ值为１６．２４～１８．４８‰，平均１７．３６‰；Ｗ／Ｒ为０．１６～０．１８。而从薄层方解石阶段到冰洲石成矿阶段δＤＨ２Ｏ＝－４９～－６８‰。δ１３Ｃ（ＰＤＢ）＝－０．６０～０．７３‰，δ１３ＣＣＯ２（ＰＤＢ）为－０．３７～２．４３‰。计算出δ１３Ｃ∑Ｃ＝－２．０８～－２．４９‰。研究表明成矿流体来源于大气降水与加热的地下水的混合，碳来源于地层。探讨了冰洲石成矿时特定的物理化学条件及地质环境。

It has been established that the homogenization temperature of iceland spar deposits ranges from 126～160℃ and the ore forming pressure from 260～520×10 5 Pa in a certain location of Southwest Guizhou province.The salinity of ore forming fluid is measured in the range of 12.2～19.6%.Isotopic composition of oxygen,hydrogen and carbon has been studied.In this deposit,iceland spar has δ 18 O value of 16 24～18.48‰,on the average 17.36‰.W/R is 0.16～0.18,δD H 2O is -49‰～-68‰ from calcite to iceland spar stages.δ 13 C (PDB) is -0.60～0.73‰.δ 13 C CO 2 (PDB) is -0 37～2 43‰.The calculation is δ 13 C ∑C =-2 08～-2 49‰.The study shows that the ore forming fluid originates in comosite of meteoric water and heating underground water.Carbon comes from the limestone wallrock.The special physico chemical conditions and environment for forming iceland spar have been discussed.