喜马拉雅东构造结地区地热成因分析

doi:10.19657/j.geoscience.1000-8527.2021.016

摘要/Abstract

摘要：

喜马拉雅东构造结地区是现今地球上构造活动最强烈、地貌演化最快的地区之一,属于地中海—喜马拉雅地热带,水热活动强烈。基于喜马拉雅东构造结的地热地质背景,采用野外调查、水化学和稳定同位素测试分析等手段,初步分析嘉黎地区深部地下热水发育特征及成因模式。结果表明,该区域地下热水均来自大气降水或冰雪融水,补给高程位于4 500 m以上,推测补给区位于研究区西北部片麻岩山区;区内地下热水均为未成熟水,热水补给水源沿断裂循环至深部热储,随后受热对流上升至地表出露成温泉,热水上升至浅表部与冷水发生混合,冷热水最大混合比可达91%;采用二氧化硅温度计、阳离子温度计以及硅-焓模型估算出热储温度最高达380 ℃,热水在雅鲁藏布江结合带内循环深度达到6 900 m。研究区深部热源主要来自雅鲁藏布江结合带及附近深大断裂,地表热显示主要受控于结合带两侧的次级张扭性断裂。本研究初步揭示了喜马拉雅东构造结嘉黎地区地热成因模式,可为该区重大工程建设和高温热害防治提供指导。

关键词: 地热成因, 水文地球化学, 热储温度, 循环机制, 喜马拉雅东构造结

Abstract:

The eastern Himalayan syntaxis is one of the regions with the strongest tectonic activity and the fastest geomorphic evolution on the Earth. It belongs to the Mediterranean-Himalayan tropics with strong hydrothermal activities. Based on the geological background, the development characteristics and genetic model of the deep underground hot water at Jiali are preliminarily explored through field survey, hydrochemical and stable isotope analyses. The results show that the origin of local geothermal water comes from meteoric precipitation or ice/snow melting, and the recharge altitude is above 4,500 m. It is speculated that the recharge area is located in the mountainous gneissic region in the northwest of the study area. The geothermal water in the area is immature. The geothermal water replenishment source circulates along the faults to the deep thermal reservoir, and then ascends by heating and convection until it is exposed as hot springs. The geothermal water rises to the shallow surface and mixes with cold water at a mixing ratio reaching 91%. SiO₂ thermometer, cation thermometer and silicon-enthalpy models are used to estimate the reservoir temperature, and the maximum reservoir temperature is 380 ℃. The depth of geothermal water circulation reaches 6,900 m in the Yarlung-Zangbo River junction zone. The local geothermal heat source comes mainly from the Yarlung-Zangbo River junction zone and the nearby deep faults, and the surface geothermal springs are mainly controlled by the secondary tensile and torsional faults on both sides of the junction zone. This study preliminarily revealed the geothermal genetic model at Jiali of the eastern Himalayan syntaxis, which can provide a scientific basis for the geothermal resource development and utilization, and for the planning and construction of major projects in the area.

Key words: geothermal origin, hydrogeochemistry, reservoir temperature, circulation mechanism, easternHimalayan syntaxis

中图分类号:

P642
P694

马鑫, 付雷, 李铁锋, 闫晶, 刘廷, 王明国, 邵炜. 喜马拉雅东构造结地区地热成因分析[J]. 现代地质, 2021, 35(01): 209-219.

MA Xin, FU Lei, LI Tiefeng, YAN Jing, LIU Ting, WANG Mingguo, SHAO Wei. Analysis of Geothermal Origin in Eastern Himalayan Syntaxis[J]. Geoscience, 2021, 35(01): 209-219.

图/表 13

图1 研究区地理位置及地质图

Fig.1 Geological map and location of the study area

图2 川西藏东地区大地热流值等值线分布图(据“全国大地热流数据汇编资料及调查成果”编制)[2,11]

Fig.2 Distribution map of geothermal heat flow value contours in western Sichuan and eastern Tibet (compiled according to “the compilation data and survey results of the national geothermal heat flow data” ) [2,11]

图3 长青温泉(a)与排龙温泉(b)

Fig.3 Photos of Changqing hot spring (a) and Pailong hot spring (b)

表1 水样水化学及同位素测试结果

Table 1 Hydrochemical and isotope measurement results of water samples

送样编号	温度/℃	Na⁺/ (mg/L)	K⁺/ (mg/L)	Ca²⁺/ (mg/L)	Mg²⁺/ (mg/L)	Cl^-/ (mg/L)	SO₄^2-/ (mg/L)	CO₃^2-/ (mg/L)
Q1	95.0	598.72	98.39	<3.00	<3.00	368.40	252.86	336.78
Q2	77.5	324.50	45.32	148.46	16.09	111.40	494.02	<5.00
Q3	40.2	113.54	25.55	154.79	28.25	87.84	143.82	<5.00
ZK1	19.2	7.57	14.65	385.57	27.28	0.44	999.15	<5.00
ZK2	53.1	233.13	24.13	180.84	29.51	168.50	165.85	<5.00
S1	4.2	1.07	0.59	<3.00	<3.00	1.67	0.17	<5.00
S2	7.6	54.20	<0.05	21.80	<3.00	5.80	102.80	<5.00
S3	8.5	51.70	<0.05	22.60	<3.00	6.40	376.02	<5.00
Y1	8.6	0.76	0.25	<3.00	<3.00	1.45	0.63	<5.00
送样编号	pH	HCO₃^-/ (mg/L)	偏硅酸/ (mg/L)	Li⁺/ (mg/L)	F^-/ (mg/L)	Sr²⁺/ (mg/L)	矿化度/ (mg/L)	水化学类型
Q1	9.79	38.52	345.30	2.532	7.98	0.252	1 688	CO₃·Cl-Na
Q2	7.95	643.76	225.53	0.408	3.70	0.817	1 467	HCO₃·SO₄-Na·Ca
Q3	7.63	673.66	159.39	0.445	1.33	1.029	894	HCO₃-Ca·Na
ZK1	7.59	181.23	41.86	0.017	0.35	6.876	1 529	SO₄-Ca
ZK2	7.97	821.50	44.82	0.374	0.28	2.156	1 267	HCO₃-Ca·Na
S1	6.91	15.26	<0.06		0.01		103	HCO₃-Na
S2	7.78	60.80	<0.06		0.01		224	HCO₃·SO₄-Na·Ca
S3	7.62	36.20	<0.06		0.02		621	SO₄-Na·Ca
Y1	6.87	10.98	<0.06		0		33	HCO₃-Na

图4 水化学三线图(单位:%)

Fig.4 Trilinear chart of water samples(unit: %)

图5 温泉及河流水样氢氧稳定同位素分布特征

Fig.5 δD vs. δ18O plot of geothermal water and river water

表2 研究区地下热水氢氧同位素组成与补给高程

Table 2 Estimated altitude, δD and δ18O of the thermal water samples from the study area

取样点	采样高程/m	样品δ¹⁸O/‰	样品δD/‰	降水δD/‰	ρ/(‰/hm)	补给高程/m
Q1(长青温泉)	1 982	-9.82	-93.28	-20.85	-2.5	4 879.2
Q2(排龙温泉)	2 033	-11.43	-83.51	-20.85	-2.5	4 539.4
Q3(拉月温泉)	2 265	-11.91	-87.70	-20.85	-2.5	4 939.0
ZK2(测温孔)	2 650	-11.91	-86.94	-20.85	-2.5	5 293.6

表3 研究区深部热储温度计算结果(℃)

Table 3 Calculation results of reservoir temperatures in the study area(℃)

水样编号	T	石英¹温标	石英²温标	石英³温标	玉髓温标	K-Mg温标	Na-K温标	Na-K-Ca温标
Q1	95.0	182.07	181.41	169.33	160.52	147.20	275.33	259.05
Q2	77.5	154.22	153.97	146.75	129.24	97.62	260.46	192.57
Q3	40.2	135.33	135.17	131.01	108.25	75.85	306.58	199.55

图6 研究区水样离子相关性图

Fig.6 Relations between Cl- and H-O isotopes in thermal water samples from the study area

图7 研究区温泉水样Na-K-Mg三角图(单位: %)

Fig.7 Ternary diagram of Na-K-Mg for thermal water samples from the study area(unit: %)

图8 温泉水样硅-焓模型图解

Fig.8 Diagrams of silica-enthalpy model for thermal watersamples

图9 东喜马拉雅构造结边界断裂带变形构造 (a1)拉月—迫隆乡段运动学特征;(b1)鲁朗—拉月段运动学特征;(c1)嘎马—米林段运动学特征;(a2)甘登—加拉萨段运动学特征;(b2)旁辛—达木段运动特征;(c2)阿尼桥—希让段运动学特征;据董汉文等[9]修改

Fig.9 Boundary fault deformation of the eastern Himalayan syntaxis

图10 喜马拉雅东构造地区地热系统成因模式

Fig.10 Genetic model of the eastern Himalayan syntaxis geothermal system

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