| 西藏加查象牙泉水文地球化学特征及成因 |
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| 引用本文： | 章旭,郝红兵,刘康林,毛武林,肖尧.西藏加查象牙泉水文地球化学特征及成因[J].水文地质工程地质,2019,0(4):1-9. |
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| 作者姓名： | 章旭 郝红兵 刘康林 毛武林 肖尧 |
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| 作者单位： | 1.中国地质科学院探矿工艺研究所，四川 成都611734；2.四川省地质矿产勘查开发局成都水文地质工程地质中心，四川 成都610081 |
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| 基金项目： | 中国地质调查局地质调查项目（121201019000161305） |
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| 摘 要： | 象牙泉地处青藏高原高寒地区，因其钙华沉积酷似“象牙”而闻名。开展象牙泉形成机理的研究，有助于钙华景观的地质环境保护，对雅鲁藏布江构造带古环境演化、新构造活动的研究具有重要意义。文章以象牙源泉及其钙华沉积为研究对象，通过钙华成分、泉水水化学组分、氢氧同位素及相关性分析，探讨了象牙泉及钙华景观的形成机制，估算了钙华形成年代，讨论了钙华景观演化趋势。结果表明:象牙泉出露高程3 208 m，温度16.1 ℃，pH值6.06～6.64，溶解性总固体1 521.1～1 524.2 mg/L，为中偏弱酸性微咸水；阳离子以钠和钙为主，阴离子以碳酸氢根和氯离子为主，水化学类型为重碳酸钙型水；象牙泉具有较高的氯、钠及稍高的溶解性总固体特征，其氢氧同位素分布于全球大气降水方程线附近，说明象牙泉主要为大气降水补给，具有较长的径流途径和缓慢的循环速度，水岩作用强烈。象牙泉为溶解沉淀型，其化学组分来源于水岩相互作用过程碳酸盐岩矿物、硅酸盐岩矿物的溶解。象牙泉钙华沉积的化学成分主要为碳酸钙，占63.07%；次要成分为二氧化硅，占10.19%；属钙华为主、硅华次之的常温泉类钙华。钙均衡估算表明，象牙泉钙华形成于1.38万年前，其沉积速率约为0.27 mm/a。
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| 关 键 词： | 西藏加查 象牙泉 钙华 水文地球化学 沉积速率 |
| 收稿时间： | 2018-09-20 |
| 修稿时间： | 2018-12-22 |
Hydrogeochemical characteristics and formation of the Ivory Spring in Jiacha County of Tibet |
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| ZHANG Xu,HAO Hongbing,LIU Kanglin,MAO Wulin,XIAO Yao.Hydrogeochemical characteristics and formation of the Ivory Spring in Jiacha County of Tibet[J].Hydrogeology and Engineering Geology,2019,0(4):1-9. |
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| Authors: | ZHANG Xu HAO Hongbing LIU Kanglin MAO Wulin XIAO Yao |
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| Affiliation: | 1.Institute of Exploration Technology, CAGS, Chengdu, Sichuan611734, China；2.Chengdu Center of Hydrogeology & Engineering Geology, Sichuan Bureau of Geology & Mineral Exploration & Development, Chengdu，Sichuan610081, China |
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| Abstract: | Located in the alpine region of the Qinghai-Tibet Plateau, the Ivory spring is famous for its travertine deposition resembling an “ivory”. Research on the formation mechanism of the Ivory spring is helpful for the geological environment protection of travertine landscapes, and is of great significance to the studies of paleoenvironmental evolution and neotectonic activities in the Yarlungzangbo tectonic belt. Taking the Ivory spring and its travertine as the research object, this paper discusses the formation mechanism of the Ivory spring and its travertine landscape, estimates the age of travertine formation, and describes the evolution trend of the travertine landscape through the compositions of the travertine, the chemical compositions of the spring water and hydrogen and oxygen isotopes through correlation analyses. The results show that the elevation of the ivory spring is 3 208 m, the temperature, 16.1 ℃, the pH value, 6.06-6.64, and the total dissolved solid, 1 521.1-1 524.2 mg/L. The spring water is weakly acidic and brackish water. The cations are dominated by sodium and calcium, and the anions by bicarbonate and chloride, and the water is of HCO3-Ca type. The Ivory spring has relatively high concentration of Cl and Na, and slightly higher total dissolved solids. Data points of hydrogen and oxygen isotopes fall near the global meteoric water line, indicating that the Ivory spring is mainly of meteoric origin, with long runoff route and slow circulation speed, and undergoes strong water-rock interactions. The Ivory spring is of dissolved and precipitated type, and its chemical compositions are derived from the dissolution of carbonate minerals and silicate minerals in the process of water-rock interactions. The chemical compositions of the Ivory spring’s travertine is mainly calcium carbonate, accounting for 63.07% and the secondary component is silicon dioxide, accounting for 10.19% . The Ivory springs is a normal-temperature spring type with the calcification and silicidation as the supplement. Estimation of calcium balance indicates that the Ivory spring’s travertine was formed at 13,800 years ago and its deposition rate is about 0.27 mm/a. |
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