摘要
溶解度的临界异常现象是超临界流体萃取技术的理论基础,目前在食品、化工等领域已得到广泛应用,但在地质领域的应用相对较少。在地质流体临界区域内金属矿物溶解度的变化行为尚需实验查明。本文在34MPa 恒压、250℃～470℃条件下和420℃恒温、压力为20～50MP 条件下分别在快速淬火高压釜中实验测定了化学试剂白钨矿在4.0%NaCl 水溶液中的溶解度。4.0%NaCl 水溶液的临界温度和临界压力分别约为411℃和31.4MPa。在34MPa 恒压条件下,白钨矿的溶解度随体系温度的升高而缓慢增大,但在体系临界温度附近突然出现极大值现象。在34MPa 恒压和温度在250℃～400℃区间内白钨矿与 WO_3在4.0%NaCl 水溶液中的溶解度(单位为 mmol/L)基本相同,这表明溶解态钨在热液流体中的存在形式可能相同。在420℃恒温条件下,白钨矿的溶解度随体系压力的升高而增大,在体系临界压力附近可能出现涨落现象,有待进一步实验查证。在4.0%NaCl 水溶液临界区域内,白钨矿的溶解度对体系温度和压力的变化反应敏感,表明白钨矿的溶解度在热液流体临界区域内具有临界异常现象。结合前人研究结果发现,白钨矿、石英、WO_3、MoO_3等物质在热液流体中的溶解度变化行为基本相似,即溶解度随体系温度和压力的升高而增大,在临界区域内出现临界异常现象。矿物溶解度的临界异常现象对揭示热液型钨矿床成矿物质的萃取、迁移和沉淀富集机制具有重要意义。
Critical anomaly of solubility is the basic principle of supercritical fluid extraction, which is used widely in food and chemical engineering fields. But the application of supercritical fluid extraction to geological field is very few. The solubility behavior of metal minerals needs experimental determination in hydrothermal geofluids in critical region. Using rapid quench pressure vessel techniques, the scheelite solubilities of chemical reagent were experimental determined in 4.0% NaCl solution at 34MPa,250℃-470℃ and 420℃ 、20 -50MP. The critical temperature and pressure of 4.0% NaCl solution are about 411℃ and 31.4MPa. At 34 MPa, the solubility of scheelite increases with temperature slowly, but reaches the steep maximum value near the system＇s critical temperature. At constant pressure of 34 MPa and temperatures between 250℃ to 400℃, the solubilities of scheelite and WO3 are almost identical in mmoL/L unit in 4.0% NaCl solution, which indicates the soluble tungsten species of scheelite and WO3 in hydrothermal solution may be also identical. At 420℃, the solubility of scheelite increases with pressure, and solubility fluctuation maybe occurs near the system＇s critical pressure, which needs other experimental determinations. In the critical region of 4.0% NaCl solution, the solubility of scheelite is sensitive to the system＇s temperature and pressure, which indicates the critical anomaly of scheelite solubility emerged in the system＇s critical region. Combined with the former experimental results, we found the solubility behavior of scheelite, quartz, WO3 and MoO3 are similar in hydrothermal fluids. Their solubilities increase with the system＇s temperature and pressure in hydrothermal solution, and in the critical region emerged critical anomalies of their solubilities, which showed important implications for the ore-forming mechanism of hydrothermal tungsten deposits on the aspects of extraction, transportation and deposition of ore-forming minerals.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第12期3052-3058,共7页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40203006)的资助。
关键词
白钨矿
溶解度
超临界流体
临界异常
钨矿床
Seheelite, Solubility, Supercritical fluids, Critical anomaly, Tungsten deposit
