CHARACTERISTICS OF CHLORINE ISOTOPES IN SALT LAKES OF KUNTEYI AND THEIR SIGNIFICANCE OF PALEOCLIMATE
CHARACTERISTICS OF CHLORINE ISOTOPES IN SALT LAKES OF KUNTEYI AND THEIR SIGNIFICANCE OF PALEOCLIMATE
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发表时间：
1998
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通讯作者：
Liu Wei-gu
中科院分区：
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作者：
Liu Wei-gu
氯有两种稳定的同位素，37 Cl和35 Cl。根据氯同位素的高精度测定方法，确定了天然水体中氯的同位素分馏。本文研究了青海昆特依地区盐湖的氯同位素特征。用Ba-阳离子树脂和H-阳离子树脂分离卤水、油田水和盐存款中的氯，用Cs_2CO_3溶液调pH至3，生成CsCl。供试品溶液的氯浓度约为5 mg/ ml。本文在Cs_2Cl ~+离子测定的基础上，用正热电离质谱法测定了昆特依盐湖卤水、油田水和钻井盐矿物中的氯同位素组成。将2μl含10μg CsCl形式的氯化物的试验溶液加载到灯丝上，通过收集在团状物上的达拉来进行氯的同位素测量。301（133 Cs235 Cl）和303（133 Cs237 Cl+）。结果表明，在120° 26 ′ E，21°50 ′ N的海水中，氯的同位素组成为δ37 Cl（‰），δ37 Cl值在-2.05‰ ~ 1.19‰之间，比油田水低。卤水的氯同位素组成与卤水的密度和pH值有关。低pH值、高浓度卤水由于蒸发作用，Cl值较低。当盐水蒸发到饱和时，在盐沉淀过程中，~（37）Cl优先掺入到盐矿物中，导致卤水中~（37）Cl相对于~（35）Cl的贫化。在盐沉淀过程中，卤水发生同位素分馏，导致盐存款中氯同位素组成的连续变化。由上而下递减，呈现八个周期性变化。δ ~（37）Cl值的这种变化反映了古气候环境的变化。因此，盐湖沉积物δ ~（37）Cl值的系统变化对干旱和强蒸发地区的古气候研究是有用的。
Chlorine has two stable isotopes, 37Cl and 35Cl. The isotopc fractionation of chlorine in natural environmnts has been identified on the basis of the procedures for high-precision measarement of chlorine isotopes. In this parer, the feature of chlorine isotopes in the salt lakes of Kunteyi area, Qinghai, has been studied. The chiorine in the samples, including brine, oil-field warer and saline deposit, was separated using Ba-cation resin and H-cation resin to form CsCl by adjustion to pH 3 using a Cs2CO3 solution. The chlorine concentration of test solutions is around 5mg / ml. The isotopic compositions of chiorine in the brine, oil-field water and saline mineral derived from drilling in the Kunteyi salt lakes have been determined by positive thermal ionization mass spectromeny, based on the measarement of Cs2Cl+ ion.The Ta filaments were beated with a 2.5μl graphite slurry, and 2μl of test solution containing 10μg of chloride in the form of CsCl were loaded on the filament The isotopic measarements of chlorine were carried out by collecting dara on messes 301 (133Cs235Cl) and 303(133Cs2 37Cl+). The isotopc compositions of chlorine in the studied samples are expressed asδ37 Cl (‰), in relation to a reference standard seawater collected at 120°26'E,21°50' N.The results show tha δ37 Cl values vary from -2.05‰ to 1.19‰ and the brines have lower δ37Cl compared to the oil-field water. The chlorine isotopic compositions of brine are associated with the density and pH value of brine. The brines with low pH values and high densihes have low Cl values due to evaporation of brine. When brines are evaporated to saturation, Preferential incorporation of the 37Cl into the saline mineral causes depletion of 37Cl in relation tO 35Cl in the brine during the precipitation of salt The brine is subected to an isotpoical fractionation during the precipitation of the salt which causes continuous changes in the isotopic composition chlorine in the saline deposit The δ337Cl value of salt deposits from the Kunteyi bore holes decreases from the upper part towards the lower part and exhibits eight cyclical changes. Such chanes in the ‰δ37Cl value represent changes in the paleoclimate environment Therefore, the systomatic variation in δ37Cl of saline deposits is useful for the study of paleoclimate in dronght and strongly evaporated areas.