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在热液矿床中铁的氧化物和硫化物(赤铁矿-磁铁矿-磁黄铁矿-黄铁矿)的垂直分带和连续系列可以做为开放的热力学体系中的变化来进行研究:f(P,T,a_A,a_B,……a_N)=O,式中T为温度,P为压力,a_A,a_B,a_N……为体系组分的活度。碱度(pH),氧化电位(Eh)、硫(a_(ΣS))和氧(a_(ΣO))的活度可以通过热力学称以活度表示。因此体系的状态将为f(P,T,pH,Eh,a_(ΣO),a_(ΣS))=O。 铁的氧化物和硫化物的这一序列见于保加利亚西南部的奥索哥沃山(Ossogovo)。据该矿床的资料和有关参数的推导,上式可简化为:a_(ΣS)=f(T,pH,Eh)。 这意味着热液的演变取决于T,pH,Eh诸因素。这种溶液最初的特征是酸性弱,氧化电位和温度都较高。因此,硫的活度较低,故氧化物被沉淀下来。后来pH逐渐增高,Eh降低,这就使溶液液相中HS~-的浓度和活度增高。与此同时,在较氧化的环境和温度较低的情况下,随着硫化物稳定性的提高为硫化物代替氧化物沉淀创造了条件。
The vertical zoning and continuous series of iron oxides and sulfides (hematite - magnetite - pyrrhotite - pyrite) in hydrothermal deposits can be studied as a change in an open thermodynamic system: f (P, T, a_A, a_B, ... a_N) = O, where T is the temperature, P is the pressure, a_A, a_B, a_N ... is the activity of the system components. The activity of alkalinity (pH), oxidation potential (Eh), sulfur (a_ (ΣS)) and oxygen (a_ (ΣO)) can be expressed in terms of activity by thermodynamics. So the state of the system will be f (P, T, pH, Eh, a_ (ΣO), a_ (ΣS)) = O. This sequence of iron oxides and sulfides is found in Ossogovo in southwestern Bulgaria. According to the information of the deposit and the derivation of relevant parameters, the above formula can be simplified as: a_ (ΣS) = f (T, pH, Eh). This means that the evolution of hydrothermal fluids depends on factors such as T, pH and Eh. The initial characteristics of this solution is weak acidity, oxidation potential and temperature are higher. Therefore, sulfur activity is low, so the oxide is precipitated. Later, the pH gradually increased, Eh decreased, which makes the liquid phase HS ~ - concentration and activity increased. At the same time, sulfides replace oxide precipitates as the stability of sulfides improves at lower oxidation temperatures and temperatures.