羌塘盆地热觉茶卡-藏夏河地区泉水水化学特征及其地质意义

Chemical characteristics of fountains in Rejuechaka-Zangxiahe area of the Qiangtang Basin and their geological implications

关键词:  羌塘盆地  泉水  水化学特征  氢氧同位素

Key words:  Qiangtang Basin  Fountains  hydrochemistry  hydrogen and oxygen isotopes

摘要:

泉水的水化学特征可以反映氧化-还原环境和水动力条件，近年来被广泛地用于石油、天然气以及天然气水合物的找矿工作中。本文对羌塘盆地热觉茶卡—藏夏河地区37处泉水和13件地表水进行了水化学特征、水溶性烃类气体特征和水中氢氧同位素特征分析，结果表明，羌塘盆地热觉茶卡—藏夏河地区的水型主要为Na₂SO₄型和MgCl₂型，其次为NaHCO₃型和CaCl₂型。矿化度普遍较高，说明该区具有较好的保存条件。铵根离子的平均含量为0.895μg/g，在藏夏河地区高达7.381μg/g，表明在藏夏河东部地区有机质相对较为丰富，这与区域上发育的富有机质页岩结果一致。氢氧同位素结果显示，该区水体的氢氧同位素落在了大气降水线附近，表明水体的来源主要受大气降水的补给。另外，采集的9个泉水样品中均检测出一定含量的水溶甲烷，在白云湖地区的甲烷含量相对较高，显示出较好的油气潜力。综合研究表明，藏夏河东和白云湖地区具有良好的油气烃源岩条件，保存条件较好，显示出良好的油气和天然气水合物资源前景。

Abstract:

Recent years, the chemical characteristics of fountains, which can reflect the redox environment and hydrodynamic conditions, have been widely used in prospecting for petroleum, natural gas and natural gas hydrate. In this paper, 37 samples of fountains and 13 samples of surface water have been collected from Rejuechaka-Zangxiahe areas of the Qiangtang Basin to analyze their chemical compositions, isotopic compositions of hydrogen and oxygen, and contents of aqueous hydrocarbon gases. The results show that the water types are mainly Na₂SO₄ type and MgCl₂ type, with subordinate NaHCO₃ type and CaCl₂ type. The general high mineralized degrees of the fountains reveal a good preservation condition in the area. The average content of the ammonium ion is 0.895 μg/g. In Zangxiahe area, the ammonium ion content is up to 7.381μg/g, which is consistent with the widespread organic-rich shale in the area, indicating the relatively high organic matter content. The isotopic results of hydrogen and oxygen show that the H and O isotopes of the water are near the precipitation line, indicating that the fountains originate from meteoric water. In addition, a certain content of aqueous methane has been detected in nine fountains, and the content is relatively high in Baiyun Lake area, showing a good hydrocarbon potential. The comprehensive study reveals that the Zangxiahe and Baiyun Lake areas in the Qiangtang Basin have good source rocks and good preservation conditions, showing a good prospect for oil, gas and gas hydrate resources.