广东省河源断裂带碳酸泉水化学特征及形成机制

The chemical characteristics and formation mechanisms of carbonate springs along Heyuan fault zone,Guangdong Province

为了解广东省河源断裂带碳酸泉的形成机理,全面认识碳酸泉形成过程,为碳酸泉的开发与管理提供科学依据,在河源断裂带地区采集了5组碳酸泉样品及18组非碳酸泉样品,开展了水化学特征分析及δD、δ^(18)O、^(14)C、δ^(13)C和~3He/~4He多种同位素分析。结果表明,碳酸泉主要水化学类型为Na-Ca-HCO_3型。δD、δ^(18)O同位素分别介于-43.32‰^-41.72‰和-7.06‰^-6.55‰,位于大气降水线附近,表明其补给来源于大气降水,补给高程在1 000~1 300 m。通过^(14)C法测年及修正后的δ^(13)C年龄校正模型计算得到碳酸泉的年龄在21~26 ka。碳酸泉点δ^(13)C的变化范围在-1‰~2‰之间,R/Ra(样品~3He/~4He与大气~3He/~4He之比)比值介于0~2.5,表明河源断裂带碳酸泉中的CO_2为幔源与变质混合成因,并以变质作用为主。

In order to understand the formation mechanisms of carbonated springs along Heyuan fault zone,Guangdong Province,comprehensively figure out their formation processes,and provide basic knowleges for their development and management,five groups of carbonated water samples and 18 groups non-carbonated water samples were collected along the Heyuan fault zone,Guangdong Province,and their hydrochemical characteristics,δD,δ18 O,14 C,δ13 C and 3He/4He isotopes were analyzed.The results showed that Na-Ca-HCO 3 is the main water chemistry type for the carbonated spring,andδD andδ18 O isotopes are between-43.32‰^-41.72‰and-7.06‰^-6.55‰,respectively.All the dots of groundwater smaples are located close to the atmospheric precipitation line,indicating that carbonated springs receive atmospheric precipitation recharging,and recharge elevation is between 1 000 m^1 300 m.The age of carbonated spring is calculated at 21~26 ka through the 14 C method dating and the revisedδ13 C age correction model.The range ofδ13 C of carbonated springs is between-1‰and 2‰,with the R/Ra(the ratio of 3He/4He in samples to 3He/4He in atmosphere)ratio between 0 and 2.5,which indicates that CO 2 gas in carbonated springs in the Heyuan fault zone is the source of mixing between mantle source and metamorphism,and is mainly based on metamorphism.