秘鲁MARIELA铁矿床的矿床特征与磁异常的分形解释

Geological characteristics and fractal interpretation of magnetic anomalies in MARIELA iron deposit,Peru

MARIELA磁铁矿矿床位于秘鲁南部成矿带上。矿体主要赋存于侏罗纪闪长岩体中,富矿体呈透镜状、脉状产出,而品位较低的矿石为浸染状和细脉状。矿石主要由阳起石(透辉石)-磁铁矿和磷灰石-磁铁矿组成,磁铁矿中V含量较高。该矿床具有玢岩型铁矿的特征,为岩浆期后热液交代充填成矿。运用多重分形理论建立模型,将地面磁异常分为低值异常与中值异常2级,它们分别作为一级找矿靶区和二级找矿靶区,较好地解释了已知矿体与磁异常的吻合关系,为下一步找矿提供了依据。

The MARIELA magnetite deposit is located in southern Peruian metallogenic belt,and its ore bodies are hosted in the Upper Jurassic dioritic body.Rich oresoccur as lensor veins while lower grade ores are in dissemination and veinlet forms.The ores are mainly of actinolite（diopside）-magnetite-apatite asemblage;the value of V in magnetite is high.The deposit has the typical characteristics of porphyry-type iron deposit,and ores were formed by post-magmatic hydrothermal metasomatism and filling mineralization.Based on the multifractal theory,the authors divided surface magnetic anomalies into low-value and medium-value anomalies which served respectively as prospecting targets of the main ore body and the secondary ore body.The coincident relationship between the known ore bodies and the magnetic anomalies has been well explained,and it is the prospecting guidance for the next step exploration work.