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Hydrothermal mineralization and fluid inclusion study on the Heishan iron deposit,Chengde County,Hebei Province,China

2010; Science Press; Linguagem: Inglês

2095-8927

Li Li, Mlr Key,

earthquake and tectonic studies

The Heishan Fe-Ti-P deposit,hosted in the Damiao Proterozoic massif-type anorthosites,is one of the most important Damiao-type iron deposits in Chengde County,Hebei Province. It was generally considered that the ore magma of the Heishan iron deposit,who injected into the anorthosites,result from fractional crystallization or immiscibility of magma. However,at field,Fe-P and Fe-sulphide veins which injected into the anorthosites show that hydrothermal mineralization is ubiquitous. So,it is indicated that the mineralization was not only associated with the magmatic process but also with hydrothermal process. A series of petrographic,microthermometric and laser Raman spectroscopic studies on fluid inclusions in the apatite of the Fe-Ti-P ores and the quartz of the hydrothermal mineralizing stage from Heishan deposit have been carried out in this paper. Five types of fluid inclusions have been identified in the apatite and quartz. They are aqueous,CO2-bearing aqueous,daughter mineral-bearing aqueous,pure aqueous,pure CO2 fluid inclusions respectively. The homogenization temperatures of the fluid inclusions in the apatite vary remarkably from 180℃ to 420℃. The salinities of fluid are mainly in ranges between 6.2% and 38.9% NaCleq. Laser Raman spectroscopy of fluid inclusions in the apatite indicate that the gas components are mainly CO2,N2 and CH4,the liquid component is H2O and the daughter mineral components are calcite,salt,dolomite and iron oxides. The homogenization temperatures of the fluid inclusions in the quartz vary from 149℃ to 422℃. The salinities of fluid are mainly in ranges between 5.7% and 22.9% NaCleq. Laser Raman spectroscopy of fluid inclusions in the quartz indicate that the gas components are mainly CO2,N2 and CH4,the liquid component is H2O and the daughter mineral component is calcite. The relation between homogenization temperatures and salinities is positive correlation. Ore-forming fluid is likely composed of CaCl2-NaCl-H2O-CO2. The primary fluid inclusions in apatite of the Fe-P ores have the characteristics of high salinities,several kinds of daughter minerals,and being rich in CO2 and CH4. All of these characteristics indicate that the ore-forming fluid belongs mainly to magmatic hydrothermal fluid. The meteoric fluid maybe plays an important role during the ore-forming process by diluting the magmatic hydrothermal fluid.