大庙铁矿田——危机矿山还是潜在超大型铁矿基地

Is the Damiao ore field a crisis mine or a potential giant iron base?

笔者主要基于野外观察认为大庙铁矿田具有巨大的找矿勘探远景,有可能成为中国最大的铁矿资源基地。新的证据不支持大庙斜长岩杂岩体的各组成单元为同源岩浆演化产物的认识,也不支持大庙式铁矿的矿浆成因说。斜长岩至少比苏长岩多经历了两次构造变形,表明后者是在斜长岩冷却固结之后侵位的。大庙式铁矿的形成与苏长质岩浆密切相关,但含矿物质不是来自于苏长质岩浆的分异作用,而是同时侵位的透岩浆流体。含矿岩浆-流体混合物在地壳深部的排气作用导致了成矿物质在苏长岩中的富集,也导致了浅部脉状矿体上磷下铁的特点,主要矿体隐藏在斜长岩之下的苏长岩中。因此,大庙铁矿田仍具有巨大的找矿潜力。

Detailed field observations have revealed that the Damiao iron ore field obviously has excellent potential and is likely to become the largest base area of iron resources in China. New evidence supports neither the opinion that all the component igneous units in the Damiao anorthosite complex were evolutionary products of a unique primary magma nor the hypothesis that ore magma was responsible for the formation of the Damiao-type iron deposit. The anorthosite underwent at least two more times of deformation than the norite, suggesting that the norite was emplaced after the consolidation and cooling of the anorthosite. The generation of the Damiaotype iron deposit is closely related to the noritic magma. Nevertheless, the ore-forming materials were derived from the concurrently emplaced transmagmatic fluids instead of from the noritic magma differentiation. The degassing process of the ore magma-fluid mixed materials in the deep crust led to the concentration of the oreforming materials in the norite and the differentiation characteristics of the mineral veins, i.e., the apatite was concentrated in the shallow place, while the titanomagnetite became rich in the deeper part. The main ore bodies are huffed in the norite substrate beneath the anorthosite cover. Therefore, the Damiao iron ore field is a very promising area instead of a crisis mine.