Formation characteristics of hot springs and its development prospects in mountain areas around the capital of China
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摘要: 【研究目的】环首都山区属于京津冀生态涵养区，包括集中连片特困区，温泉资源较丰富，但勘查开发程度较低，开展温泉分布规律和发育特征研究，对于山区地热资源的勘查开发具有一定的指导意义。【研究方法】本文在收集京津冀山区温泉和深部构造资料基础上，叠加分析，揭示了温泉分布与深部构造热背景的联系。结合补充调查、样品采集及综合研究，总结温泉发育特征，并深入探讨了温泉热源与成因，因地制宜提出研究区温泉开发利用前景。【研究结果】结果表明：温泉主要沿NE、EW向深大断裂呈带状或串珠状分布，研究区90%温泉分布在莫霍面深部构造变异带内。温泉温度与居里面埋深具有一定的相关性，燕山北部高温温泉区居里面埋深20 km左右，燕山与太行山交接带较高温温泉区居里面埋深22～24 km，太行山及燕山东南部低温温温泉区居里面埋深22～26 km；温泉热源主要来自地幔热或―低速-高导层‖，上地幔底辟体和深大断裂为深部热源的上涌提供了良好的通道；在区域尺度上，温泉出露温度与循环深度不存在直接对应关系，山间盆地沉积岩储层热储温度较低，温泉流量较大，最高可达约120 m3/h；变质岩热储温度一般大于100℃，流量较小。研究区温泉水普遍具有医疗开发利用价值，其中，燕山北部和山间盆地，具有较好的供暖潜力，承德七家-茅荆坝等地区可进一步向热电一体化方向发展。【结论】环首都山区温泉分布及发育特征受深部构造和区域地质结构影响明显，在燕山北部和山间盆地区具有较好的开发利用前景。Abstract: The paper is the result of geothermal geology survey engineering. [Objective]The mountainous areas surrounding the capital city belong to the ecological conservation area of Beijing-Tianjin-Hebei, including the contiguous areas of extreme poverty, and are rich in hot spring resources, but the degree of exploration and development is low. It is of certain guiding significance to carry out research on the distribution pattern and development characteristics of hot springs for the exploration and development of geothermal resources in mountainous areas. [Methods]In this paper, based on the collection of information on hot springs and deep tectonics in the mountainous areas of Beijing, Tianjin and Hebei, superimposed analysis reveals the connection between hot spring distribution and deep tectonic thermal background, and explores in depth the hot spring heat source and its formation. Combined with supplementary surveys, sample collection and comprehensive research, the development characteristics of hot springs were summarized, and prospects for hot spring development and utilization in the study area were proposed according to local conditions. [Results]The results show that hot springs are mainly distributed along NE and EW deep major fractures in the form of bands or beads, 90% of the hot springs are distributed within the deep structural variation zone of the Moho surface in the study area. The temperature of hot springs has a certain negative correlation with the depth of dwelling, the depth of dwelling in the high hot spring area in the northern Yanshan being about 20km, the depth of dwelling in the relatively high hot spring area in the Yanshan-Taihang Mountains junction zone being about 22~24 km and the depth of dwelling in the low hot spring area in the southeast Yanshan being 22~26 km; the heat source of hot springs mainly comes from the mantle heat or "low-velocity-high-conductivity layer", and the upper mantle diapirs and deep large faults provide good channels for the upwelling of deep heat sources; On the regional scale, there is no direct correspondence between the hot spring outcrop temperature and the depth of circulation, and the thermal reservoir temperature of sedimentary rock reservoirs in the intermountain basin is low, with a large flow rate of hot springs, up to about 120 m3/h. The thermal reservoir temperature of metamorphic rocks is generally greater than 100℃, with a smaller flow rate. The hot spring water in the study area generally has medical development and utilization value, among which, the northern Yanshan and intermountain basins, have a better potential for space heating, and areas such as Qijia-Maojingba can be further developed in the direction of thermol-electric integration. [Conclusions]The distribution and development characteristics of hot springs in the mountains area around the capital city are influenced by the deep tectonic and regional geological structure. The northern Yanshan Mountains and intermountain basins have good development and utilization prospects.
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1. 研究目的（Objective）
近年来，新疆阿尔金西段萤石找矿取得的重大突破。萤石矿主要分布于卡尔恰尔—阔什区域性大断裂（阿中断裂）以南的晚奥陶世碱长花岗岩侵入体内及其外接触带附近的富钙质岩系中，圈定了卡尔恰尔—小白河沟、盖吉克—亚干布阳、布拉克北—皮亚孜达坂、托盖里克东南—阿其克南4条沿北东向断裂分布的萤石矿带，整个远景区CaF2资源量已达3500万t以上。中国地质调查局西安矿产资源调查中心于2021—2023年对阿尔金西段小白河沟—克鲁求干道班一带开展了矿产调查评价，在小白河沟地区新发现热液充填型萤石矿产地1处，估算萤石的潜在资源达大型规模，对于拓展阿尔金地区萤石矿床具有借鉴意义。
2. 研究方法（Methods）
在对小白河沟地区以往地物化遥成果资料综合研究基础上，结合本次遥感蚀变异常提取和构造解译圈定了重点工作区，通过开展1∶10000地质草测、1∶10000岩石地球化学剖面测量、1∶500地质剖面测量、槽探及钻探等工作，在小白河沟共圈定萤石矿体21条，实现了找矿突破。通过典型矿床对比，总结了区内萤石矿成矿规律，初步建立了找矿模式，分析了区域萤石成矿潜力及找矿前景。
3. 研究结果（Results）
研究区出露地层基底主要为古元古界阿尔金岩群a岩组和b岩组，二者呈构造面理接触关系。阿尔金岩群a岩组为萤石主要赋矿地层，该岩组出露的岩石类型主要为黑云斜长片麻岩、黑云二长片麻岩、斜长变粒岩、石英岩、大理岩，局部夹有角闪斜长片麻岩（图1b）。区内断裂较为发育，期次较多，主要呈北北东向、北东向、南东东向，南东东向断裂主要与区内的萤石矿化关系密切。地层中岩脉极为发育，在接触带可见岩石具萤石化、钾长石化、碳酸盐化、绿帘石化、硅化等围岩蚀变。
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图 1 区域构造位置图（a）、矿区地质简图（b）、勘探线剖面图（c）及萤石矿岩心（d）Figure 1. Regional structure location map (a), brief geological diagram of ore district (b), prospecting line profile map (c) and cores specimen of fluorite deposit (d)在小白河沟共圈定萤石矿体21条（图1c），长100~1130 m，厚度0.7~4.68 m，矿体沿走向延续性较好，沿倾向呈透镜体状，断续产出，斜切岩体和变质岩，有“膨大缩小”变化，部分呈“透镜体”、“扁豆体”断续分布，主矿体旁侧发育少数分枝。矿体品位23.2%~82.4%，平均品位32.2%，钻孔深部验证效果良好。矿石主要以块状、纹层状为主，主要矿物为萤石，局部发育方解石、带云母和少量石英。萤石以紫色、紫黑色为主，少量呈白色或绿色，具粗晶结构、自形—半自形及他形粒状结构。矿石工业类型主要是CaF2型、CaF2–CaCO3型。围岩蚀变以碳酸盐化、带云母化、钾化、黄铁矿化、绿帘石化、角闪石化等为主。初步估算CaF2资源量117.42万t，具大型萤石矿床远景。
4. 结论（Conclusions）
（1）小白河沟萤石矿是阿尔金西段萤石找矿新发现，这一发现拓展了区内萤石矿向西延伸的空间，同时本次工作区内多数矿体走向和深部延伸均未封边，仍具有较大找矿潜力。
（2）本工作发现了品位较富的大型萤石矿，拓宽了区域找矿思路，具有重要借鉴意义，同时为阿尔金瓦石峡南—卡尔恰尔萤石锂大型资源基地建设提供了有力支撑。
5. 基金项目（Fund support）
本文为中国地质调查局项目（DD20190143、DD20211551、DD20243309）、陕西省自然科学基础研究计划项目（2023−JC−YB−241）、中国地质调查局自然资源综合调查指挥中心科技创新基金项目（KC20230011）联合资助的成果。
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