长江中下游富钠闪长岩类与铁矿系列的成因联系

长江中下游成矿带内,铁矿系列与中生代燕山期岩浆活动有十分密切的关系,其形成主要与富钠闪长岩类成岩过程中发育的钠硅质异常演变相联系。富钠闪长岩类和与其密切相伴的矿浆贯入-残浆气液交代充填-接触交代(矽卡岩)-热液交代充填型铁矿系列,是深部同源岩浆顺序演化的产物。

Genetic relationship between sodium-rich dioritoids and iron ore series in the Middle-Lower valley of the Yangtze River

The most important iron ore series in the Middle-Lower valley of the Yangtze River, which include series of ore-magma type-contact metasomatic(skarn) type-hydrothermal metasomatic and filling type deposits and series of ore magma type-residual magma to pneumato-hydrothermal metasomatic and filling type-contact metasomatic type-hydrothermal metasomatic and filling type deposits, are closely related to sodium-rich dioritoids in space, time and genesis. Metallization of iron deposits proceeded through the whole process of thediagenetic evolution of the sodium-rich basic-intermediate magma and the post-magmatic hydrothermal activities, associated mainly with abnormal evolution and concentration of sodium and silica during diagenesis. These processes are evidently demonstrated by the regular variations in mineral constituents of the rocks and major chemical composition (Table 2 and Fig.1) as well as by the correlationship between the main mineral phases (Fig. 3) which appeared during the diagenetic process. The generation and separation of the iron ore-magma seem to have started at the early stage fractional crystallization of the sodium-rich magma, with the prerequisite being high alkalinity, rich sodium, abundant volatiles(especially halogen), and relatively stable environment suitable for abnormal evolution and enrichment of sodium and silica. The ore-bearing hydrothermal solution must have been generated and separated under the similar condition, only the formation time was somewhat later. Orebodies formed by ore-magma and cre-bearing hydrothermal solution generally show no regular sequence and their distribution patterns are also varied.