摘要
于1994－1996年，采用高精度正热电离质谱测定氯同位素（δ37Cl）的方法，对青海柴达木盆地昆特依盐湖区的盐湖卤水、湖底盐类矿物、油田水以及该地区的盐类沉积物钻孔剖面的δ37Cl值进行了初步研究。结果表明，该地区的δ37Cl值（卤水）变化范围在-2．05‰—1．04‰，盐湖卤水的δ37Cl值较低，这与卤水的相对密度及pH值有关；盐类沉积钻孔剖面的δ37Cl值呈现自下而上逐渐降低的趋势，这一变化与该地区的古气候变化有关。盐类沉积的δ37Cl值研究将会对高原干旱、蒸发环境条件下湖相沉积古气候演化的研究提供一种新的手段。
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.
出处
《海洋与湖沼》
CAS
CSCD
北大核心
1998年第4期431-435,共5页
Oceanologia Et Limnologia Sinica
基金
国家自然科学基金!49173163
青海省自然科学基金!97-07-09
关键词
柴达木盆地
盐湖
氯同位素
古气候
Qaidam basin
Salt lake
Chlorine isotopic
Paleoclimate
