博茨瓦纳Sua盐湖地下卤水来源及成因

单慧媚; 马腾; 谭婷; 罗朝晖; 祁志冲; 翟明哲; LekgoweOteng M.

doi:10.3799/dqkx.2013.061

博茨瓦纳Sua盐湖地下卤水来源及成因

doi: 10.3799/dqkx.2013.061

单慧媚^{1, 2,},
马腾^{1, 2, ,},
谭婷^{1, 2},
罗朝晖^{1, 2},
祁志冲^{1, 2},
翟明哲³,
LekgoweOteng M.⁴

1.
中国地质大学生物地质与环境地质国家重点实验室, 湖北武汉 430074
2.
中国地质大学环境学院, 湖北武汉 430074
3.
博茨瓦纳大学地质系, 哈博罗内 0022, 博茨瓦纳
4.
博茨瓦纳地质调查局, 哈博罗内 0014, 博茨瓦纳

基金项目:

国家自然科学基金项目 40872157

国家自然科学基金项目 40830748

教育部新世纪优秀人才支持计划 NCET-07-0773

中央高校基本科研业务费专项基金资助 CUGL100501

详细信息

作者简介:
单慧媚(1985-), 女, 博士, 主要从事同位素生物地球化学方面研究. E-mail: shanhuimei1985@163.com

通讯作者:
马腾, E-mail: mateng@cug.edu.cn

中图分类号: X142;P592
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- 被引次数: 0
出版历程
- 收稿日期: 2012-05-21
- 刊出日期: 2013-05-15

Sources and Genesis of Subsurface Brine in Sua Pan, Botswana

SHAN Hui-mei^{1, 2
,},
MA Teng^{1, 2
, ,},
TAN Ting^{1, 2},
LUO Zhao-hui^{1, 2},
QI Zhi-chong^{1, 2},
ZHAI Ming-zhe³,
Lekgowe Oteng M.⁴

1.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
2.
School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
3.
Department of Geology, University of Botswana, Gaborone 0022, Botswana
4.
Department of Geological Survey, Government of Botswana, Gaborone 0014, Botswana

摘要

摘要: Sua盐湖是博茨瓦纳面积最大的盐湖之一, 是南半球重要的天然碱资源.为进一步揭示该盐湖的成因, 对盐湖区地下水、地表水以及晒盐场盐结晶进行了常规阴阳离子含量、D、¹⁸O和³⁷Cl同位素组成及地下水¹⁴C年龄分析.水化学结果显示Sua盐湖的地下卤水具有富Na和K, 贫Ca和Mg的特征.氢氧同位素关系和³⁷Cl结果显示, 附近河流地表水与Sua盐湖地下卤水具有密切的水力联系, 而地下水对其补给作用较弱(³⁷Cl差异为0.04‰~0.06‰).TDS-γ_Na/γ_Cl关系揭示Sua盐湖地下卤水受到盐岩地层溶滤作用的影响(γ_Na/γ_Cl≈1), 而¹⁴C年龄(距今约2万年)表明古气候的波动变化是其重要影响因素.基于以上认识, 运用PHREEQC软件对Sua盐湖地下卤水进行反向地球化学模拟, 结果表明地表水的强烈蒸发浓缩以及附近地下水对盐岩地层的溶滤是控制Sua盐湖卤水形成的主要因素.
- 地下卤水 /
- 水化学特征 /
- 同位素 /
- 反向模拟 /
- 地球化学
Abstract: The salt lake of Sua Pan, one of the largest salt lakes in Botswana, is important resources of natural alkali. To identify the sources and genesis of subsurface brine in this salt lake, groundwater and surface water near this lake, in addition to subsurface brine water in the lake and salt crystals from solar salt field were collected and determined. The contents of major cation and anion, the isotope compositions of D, ¹⁸O and ³⁷Cl, and the ¹⁴C age of groundwater were calculated. It is found that the subsurface brine is characterized by enriched Na and K, and depleted Ca and Mg. Results of D, ¹⁸O and ³⁷Cl show that surface water is closely connected with subsurface brine in Sua Pan, while the role of groundwater recharge on it is weak (the difference of ³⁷Cl is 0.04‰-0.06‰). Relationships of TDS-γ_Na/γ_Cl indicate that leaching of halite affects the formation of this subsurface brine (γ_Na/γ_Cl≈1), and the age of ¹⁴C (about 20 000 years ago)indicates that the fluctuation of ancient climate is considered to be an important factor of the formation of Sua Pan. Based on the above knowledge, inverse simulation of subsurface brine in Sua Pan is modeled by PHREEQC software, which further verifies that salt lake of Sua Pan is mainly the result of strong evaporation and concentration of surface water and halite leaching by groundwater.
- subsurface brine /
- hydrogeochemical characteristics /
- isotopes /
- inverse simulation /
- geochemistry

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图 1 马卡迪卡迪流域地理位置、地形和降雨量

Fig. 1. Makgadikgadi Pans showing locations, terrain and rainfall

下载: 全尺寸图片幻灯片

图 2 马卡迪卡迪流域水文模型及Sua盐湖采样点位置

Fig. 2. Hydrological model for the Makgadikgadi, locations and sampling sites of Sua Pan

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图 3 水样的Piper三线图

Fig. 3. Piper graph of water samples

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图 4 Sua盐湖水样氢氧同位素组成变化图(SMOW，标准平均大洋水)

Fig. 4. Variations of δD and δ¹⁸O values of water samples collected from Sua Pan

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图 5 Sua盐湖北部及附近水样γ_Na/γ_Cl与TDS分布

Fig. 5. Relationship between γ_Na/γ_Cl and TDS of water samples from northern part of Sua Pan

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表 1 Sua盐湖水样采集信息

Table 1. Water samples collected from Sua pan

样品编号	SW01	SW02	GW03	GW04	BW06	SW07
经纬度	26°11.224′E	26°22.055′E	26°27.126′E	26°28.373′E	25°57.871′E	26°14.439′E
	20°12.798′S	20°05.645′S	20°30.683′S	20°30.517′S	20°27.852′S	20°17.889′S
类型	地表水	地表水	地下水	地下水	地下卤水	地表水
地点	Nata河	Nata河	Dukwi地区	Dukwi地区	Sua盐湖	Nata国家公园
采样深度	0~30 cm	0~30 cm	＞36.93 m	＞34.50 m	约20 m	0~30 cm

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表 2 水样的水化学分析结果

Table 2. Results of hydrochemical analysis of water samples

指标	SW01	SW02	GW03	GW04	BW06	SW07
EC(μs/cm)	1 024.0	138.3	1 556.0	1 562.0	183 300.0	4 333.0
pH	8.80	8.89	7.16	7.08	9.50	8.83
温度(℃)	32.9	26.4	28.8	27.8	29.0	30.3
HCO₃^-(mg/L)	130.43	85.81	583.50	518.97	4 118.85	364.52
CO₃^2-(mg/L)	49.52	0.00	0.00	0.00	15 445.06	210.80
Cl^-(mg/L)	207.44	3.20	216.75	252.79	41 640.00	1 076.08
SO₄^2-(mg/L)	20.58	0.90	93.22	95.40	12 480.00	97.90
K⁺(mg/L)	14.91	6.33	4.81	4.14	2 108.90	49.23
Ca²⁺(mg/L)	16.81	16.26	23.08	16.34	7.30	10.64
Mg²⁺(mg/L)	3.05	2.78	35.22	30.94	3.50	0.78
Na⁺(mg/L)	185.30	5.43	269.76	296.44	46 278.01	1 028.80
TDS(g/L)	0.630	0.121	1.229	1.218	112.655	2.841
阴阳离子平衡(%)	0.981	4.486	1.548	0.017	4.371	4.808
库尔洛夫式	Cl·HCO₃-Na	HCO₃-Ca·Na	HCO₃·Cl-Na	HCO₃·Cl-Na	Na-Cl	Na-Cl

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表 3 样品的³⁷Cl测试结果

Table 3. δ³⁷Cl values of water and salt crystals samples from Sua Pan

样品	δ ³⁷Cl(‰)	d值(‰)
GW03	0.22	0.06
GW04	0.24	0.04
BW06	0.18	0.02
盐结晶	0.29	0.07

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表 4 Sua盐湖卤水的¹⁴C年龄

Table 4. ¹⁴C age of brine water from Sua Pan

编号	现代碳百分数(%)	¹⁴C年龄(ka)	校正后年龄(ka)
BW06	13.464	16.580±0.27	21.459

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表 5 Sua盐湖卤水演化的地球化学模型(单位：mol/L)

Table 5. Geochemistry models for the evolution of brines in Sua pan

起点	终点	H₂O	岩盐	方解石	钾长石	石膏	白云石	钠长石	CO₂
SW01	BW06	-1.261e+4	1.538e-1	-1.891e-1	-3.514e-2	1.220e-1	-2.844e-2	3.514e-2	3.779e-1
SW02	BW06	-7.794e+4	1.418	-6.526e-1	-1.756e-1	1.578e-1	-1.605e-1	1.756e-1	-6.335e-1
SW07	BW06	-2.567e+3	-	-1.320e-1	-7.751e-3	1.210e-1	-1.356e-3	7.751e-3	2.735e-1
	BW06	-2.578e+3	-	-1.302e-1	-	1.191e-1	-1.362e-3	-	-
GW03	BW06	-2.869e+3	1.271	-7.363e-2	4.542e-2	1.197e-1	-7.626e-2	-4.542e-2	-8.165e-2
GW04	BW06	-2.720e+3	1.242	-7.786e-2	4.661e-2	1.212e-1	-6.354e-2	-4.661e-2	-7.031e-2
注：负值表示从水溶液中迁移出来的摩尔量；正值表示进入水溶液的摩尔量.

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