摘要
青藏高原多条造山带发育富Li、B等资源元素的地热水,是尾闾盐湖矿床的重要物源。青藏高原富锂硼盐湖基本遵循热泉补给-河流携载运移-尾闾盐湖富集成矿的源-运-汇沉积模式。目前大多研究集中于高原南部地热及盐湖资源,缺乏对高原北部不同造山带地热水及尾闾盐湖卤水Li、B资源差异富集成矿的对比研究。柴达木盆地形成了南缘由东昆仑地热水补给的一里坪-东西台-(察尔汗盐湖)别勒滩区段盐湖卤水型锂矿床、柴北缘由大柴旦地热水补给的大柴旦盐湖固-液硼矿床,这些盐湖资源分别是中国重要的锂、硼矿资源储集地和开发基地,并为研究地热水及尾闾盐湖Li、B富集机制提供了独特的研究窗口。因此,本文系统讨论了柴达木盆地南北两侧对称的东昆仑和柴北缘地热水中Li、B差异富集机制及其对盐湖成矿的物源制约。通过对青藏高原地热水、河水、盐湖卤水及岩石的元素含量及H-O-Li-B同位素地球化学数据的分析,得出以下认识:(1)两大地热水及尾闾盐湖卤水的Cl^(-)含量和H-O同位素值揭示东昆仑与大柴旦地热水由大气降水(冰雪融水)与岩浆流体混合形成;(2)柴达木盆地南北两侧的地热水存在Li-B含量的差异特征,其物源补给差异控制着尾闾盐湖卤水Li-B资源矿床。东昆仑热泉水富Li-B(Li=96.00mg/L,B=180.00mg/L),而大柴旦热泉水富B(平均值B=41.54mg/L,Li=3.18mg/L);一里坪、东-西台吉乃尔盐湖和察尔汗盐湖别勒滩区段晶间卤水Li含量介于122.91~447.07mg/L之间,明显高于大柴旦盐湖卤水值(Li=117.00~187.00mg/L),而B含量则相反(大柴旦盐湖卤水B=513.00~706.00mg/L,一里坪等尾闾盐湖卤水B=143.50~329.71mg/L);(3)对比青藏高原地质背景与地热水、盐湖卤水Li-B含量关系发现,青藏高原地热水Li-B含量分别受到造山运动过程中岩浆作用和变质作用的控制。东昆仑岩浆作用形成富Li花岗岩(伟晶岩)或火山岩制约了布喀达坂峰热泉中的Li含量,祁连山变质作用形成的高压-超高压富B变质岩约束了大柴旦热泉B含量,即两大地热水及尾闾盐湖卤水中的Li-B主要来自围岩溶滤补给;(4)东昆仑低Li(<1mg/L)-高δ^(7)Li值(+29.45‰)的大气降水和高Li(928×10^(-6)~34,851×10^(-6))-低δ^(7)Li值(-3.39‰~+7.55‰)的伟晶岩约束了地热水和盐湖卤水的Li资源富集过程;柴北缘低B(<1mg/L)-高δ^(11)B值(+16.69‰)的大气降水和高B(32,000×10^(-6)~35,000×10^(-6))-低δ^(11)B值(-9.86‰~-3.75‰)的(高压-超高压变质岩)电气石约束了地热水和大柴旦盐湖卤水的B资源富集过程。本研究系统总结了青藏高原北部地热水Li-B资源元素的差异性富集机制,为理解高原地热水-尾闾盐湖资源成矿提供源-运-汇富集模式,反之地热水资源元素丰度可作为内生Li、B矿床的重要找矿标志。
The lithium(Li)-and boron(B)-rich geothermal waters developed on several orogenic belts on the Tibetan Plateau(TP)is often an important material source for brine mineralization of terminal salt lakes.The Li-B-rich salt lakes on the TP basically follow the basic pattern:recharge from hot springs-carrying and transporting by rivers-enrichment and mineralization in terminal salt lakes.Currently,most of the studies focus on the geothermal-salt lake resources in the southern TP,and there are fewer comparative studies on the Li-B enrichment mechanisms in the geothermal-salt lakes of different orogenic zones in the northern TP.The major resource bases for formation and utilization of Li resources in China are the brine-type Li deposits in the central salt lakes of the Qaidam Basin(QB),which are recharged by the geothermal water from East Kunlun Mountains(EK).The solid-liquid B deposits in the Da Qaidam Salt Lake(DQL)are replenished by the geothermal water from the southern Qilian Mountains(SQL).This study elucidates systematically the Li-B enrichment mechanism in the geothermal systems of the EK and SQL on the northern TP.Based on the analysis of geochemical data of the elemental contents and H-O-Li-B isotopes in geothermal water,river water,salt lake and surrounding rocks of the TP,the following conclusions are reached:(1)The Cl content of the two geothermal waters and H-O isotopes of the brines of the terminal salt lakes indicate that the geothermal waters of the EK and SQL geothermal systems are mixed by meteoric and magma water.(2)There are significant differences in the Li-B concentrations of the hot spring water and brine of the terminal salt lakes in the two geothermal systems located in the north and south orogenic belts of the QB.The EK hot spring water enriched in Li-B(Li=96mg/L,B=180mg/L),while the SQL hot spring harbors high B(B=41.54mg/L,average Li=3.18mg/L).The Li concentrations of the intercrystalline brines in Yiliping,Dong-Xitaijinaier and Qarhan salt lakes(122.91~447.07mg/L)are obviously higher than that of the DQL(Li=117.00~187.00mg/L),while the opposite occurred in the B content of the DQL(513.00~706.00mg/L).(3)Comparison of the relationship between the geologic background of the TP and Li-B in geothermal waters and salt lakes reveals that Li-B in the geothermal system of the TP is controlled by magmatism and metamorphism during orogeny.The Li-rich granites(igneous rocks)widely spread in the EK constrained the Li content of the hot springs in Bukadaban Peak,and the HP-UHP B-rich metamorphic rocks formed by the Qilian Mountain orogenic movement constrained the B content in the DQ hot springs.(4)Low Li(<1mg/L)-highδ^(7)Li(+29.45‰)for meteoric water and high Li(928×10^(-6)~34,851×10^(-6))-lowδ^(7)Li(-3.39‰~+7.55‰)for pegmatites around the EK geothermal system are responsible for the Li cycling process of geothermal water and salt lakes.Low B(<1mg/L)-highδ11 B(+16.69‰)for meteoric water and high B(32,000×10^(-6)~35,000×10^(-6))-lowδ^(11)B(-9.86‰~+3.75‰)tourmaline(metamorphic rocks)of the DQ geothermal system constrains B cycling process on the geothermal water and salt lakes.The Li-B in the geothermal water and terminal salt lakes of the two geothermal system are mainly derived from leaching from the host rock reservoirs.This study provides a source-transport-sink enrichment model for understanding the mineralization of geothermal water-terminal salt lake resources on the TP,which can reversely be a reference for tracing the mineralization of rocks in orogenic belt(hard rock lithium or B-rich rocks)through the variations in Li-B contents of geothermal waters.
作者
韩春梅
樊启顺
吴蝉
王建萍
李庆宽
陈天源
杨浩田
秦占杰
HAN ChunMei;FAN QiShun;WU Chan;WAN JianPing;LI QingKuan;CHEN TianYuan;YANG HaoTian;QIN ZhanJie(Key Laboratory of Green and High-end Utilization of Salt Lake Resources,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,China;Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes,Xining 810008,China;University of Chinese Academy of Sciences,Beijing 100049,China;Qinghai CITIC Guoan Lithium Development Co.Ltd,Golmud 816000,China)
出处
《岩石学报》
北大核心
2025年第3期950-967,共18页
Acta Petrologica Sinica
基金
第二次青藏高原综合考察项目(2019QZKK0805)
国家自然科学联合基金重点项目(U21A2018)
青海省自然科学青年基金项目(2023-ZJ-954Q)联合资助.
关键词
地热水
青藏高原
锂-硼的富集机制
地质构造
Geothermal systems
Tibetan Plateau
Lithium-boron enrichment mechanisms
Geological tectonics
