【摘要】 尕林格大型矽卡岩铁矿位于祁漫塔格斑岩-矽卡岩成矿带内,发育一套典型的Ca质退化蚀变矽卡岩系列。其中,含黑柱石退化蚀变组合可以很好地反演流体交代热动力学过程。岩石学证据表明在早期退化蚀变阶段（StageⅠ）,黑柱石交代石榴子石和磁铁矿,该反应根据岩浆角闪石地质温压计设定最大压力条件50MPa,获得热动力学T=400～470°C和ΔlgfO₂（HM）=-4～-4.2;在晚期退化蚀变阶段（StageⅡ）,黑柱石和石英反应生成磁铁矿和铁阳起石,该反应发生在400～440°C和ΔlgfO₂（HM）=-4～-4.4热动力学条件范围内;到了方解石-石英-硫化物阶段（Stage Ⅲ）,黑柱石分解形成方解石、黄铁矿和铁阳起石,该反应发生温度随着X_CO2的升高而升高,在X_CO2=0.005-0.05范围内,分解反应条件为T=270-350°C和ΔlgfO₂（HM）<-5.2。随着黑柱石的连续演化,该热动力学模型完整地记录了退化蚀变反应的发生过程。除此之外,流体体系中Fe和Mg的含量会强烈影响黑柱石在矽卡岩体系中的稳定性。因此,黑柱石的岩石学和相变关系可以很好地指示不同类型矽卡岩矿床的交代反应过程。更多还原

【Abstract】 The ilvaite-bearing skarn associations in the Galinge skarn deposit were studied to determine their physicochemical formation conditions. A thermodynamic model setting pressure of 50 MPa（P_f=P_s=50 MPa） was set up to trace the skarn evolution. Petrographic evidence for replacement of garnet and magnetite by ilvaite in the early retrograde stage（Stage I） combined with thermodynamic modeling suggests that the alteration may have occurred at 400-470 °C under moderately high fO₂ with ΔlgfO₂（HM） ranges from-4 to-4.2. The model is based on a maximum pressure of 50 MPa calculated from magmatic amphibole geobarometer. The continuous breakdown of ilvaite with quartz to form ferro-actinolite and magnetite occur in the late retrograde stage（Stage Ⅱ）. The reactions occurred at 400-440°C under moderate fO₂（ΔlgfO₂（HM）:-4 to-4.4）. In Stage Ⅲ, the breakdown of ilvaite to form calcite, pyrite and ferroactinolite depends on X_CO2 which can be estimated to be in a range of 0.005 to 0.05, and the reaction would occur at higher temperatures with increasing X_CO2. Under these conditions, the breakdown occurs at 270-350 °C and low fO₂（ΔlgfO₂（HM）: up to-5.2）. The thermodynamic model for continuous evolution from Stage Ⅰ to Stage Ⅲ completely records the conditions of the retrograde alteration, which is inconsistent with the thermobarometry imprints of fluid inclusions. Therefore, the petrography and phase relations of ilvaite are useful indicators of reaction conditions in various skarn deposit types.更多还原