温度、质量浓度对富氟流体中Hf高温高压水解行为的影响

Effect of Temperature and Mass Concentration on the Hydrolysis of Fluorine-rich Hafnium Complex in High Temperature and High Pressure Fluids

Hf是一种高场强元素,在地壳中的丰度较低,往往以类质同象的形式进入锆石中。以氟铪酸钾(K_2HfF_6)络合物为研究对象,观察它们在富水热液中的水解程度,进而研究Hf元素在地质过程中的迁移行为。结果表明:K_2HfF_6络合物在热液条件下能发生一定程度的水解反应,总体趋势为络合物的初始质量浓度越低且反应的温度越高,其水解程度越剧烈,络合物的稳定性也就越低;获得了高温高压条件下K_2HfF_6络合物的累积水解平衡常数。同时运用实验模拟的方法,根据提取液中Hf元素含量来推测矿物结晶时富氟流体中Hf元素含量,若以K_2HfF_6络合物最高配位的离子团形迁移时,Hf与F元素之间的质量浓度比值为1.6,据此可以计算成矿流体所需的最小F元素含量。

Hf is a high field strength element (HFSE) with low abundance in the earth s crust, and often enters zircon in the form of isomorphism. The migration behavior of Hf in natural geological processes was studied by observing the hydrolysis degree of K 2HfF 6 complex in hydrothermal solution. The results show that K 2HfF 6 complex could undergo hydrolysis reaction to a certain extent under hydrothermal conditions, and the general trend is that the lower the initial mass concentration of the complex and the higher the reaction temperature, the more severe the hydrolysis degree and the lower the stability of the complex;the cumulative hydrolysis equilibrium constant of K 2HfF 6 complex under high temperature and high pressure is obtained. At the same time, according to the content of Hf in the extraction solution, the content of Hf in the fluoride-rich fluid can be estimated based on the method of experimental simulation;if the ion group migrates with the highest coordination of K 2HfF 6 , the ratio of mass concentrations between Hf and F is 1.6, so the minimum content of F required for the mineralization fluid can be calculated.