Abstract:

Magmatic iron deposit, occurring in Panzhihua layered intrusion, is one of the most important iron resources in China and builds up Emeishan mantle plume. However, the metallogenic mechanism is still left controversial. In this article, the middle zone of Panzhihua intrusion in Zhujiabaobao mine is investigated. With the analysis of quantitative clinopyroxene texture, the genesis of layered iron bodies has been put forward based on field and microscopic observation. In the aspect of petrography, the textures of clinopyroxene and plagioclase in dissolved samples have been obviously changed by dissolution and the dissolved parts were occupied by oxide. Crystal Size Distribution diagrams show that dissolved samples have steeper CSD slopes and are more curved at small granularity with higher oxide than those of the original. It is explained that the dissolution results in a more steep CSD slope and a coarseninglike CSD diagram. Spatial Distribution Pattern shows that crystals in the upper part are better sorted, however the lower underwent compaction from the former. Sorting in magmatic processes have been recorded in the upper part and the lower are suffered from dissolution which results in bigger pore space. Rocks with larger space can not hold up the weight from the lower part so compaction trend is shown up. It is shown that fluid exists during oxide forming processes revealed by dissolution of rockforming minerals and fluidrich amphibole together with serpentine around the dissolved minerals and interstitial oxide. During the late magmatic stage of Panzhihua intrusion. Fluid rich in iron injected into the unsolidificated body, resulting in the dissolution, then filled the pore space. Iron formed when fluid escaped. Pervasive dissolution occurred in the lower part and ironrich fluid escaped by compaction, so poor bulk ore body came into being. In the upper part, fluid moved horizontally without compaction, so rich layered iron body formed. This oreforming pattern is similar to transmagmatic fuild metallogenic model.

Key words: Panzhihuatype iron deposit, quantitative texture analysis, dissolution, transmagmatic fluid, metallogenic model