Temporal-spatial Framework Of The Pingchuan-Shuhe Tectono-magmatic-metallogenical Belt And Its Geologic Implications On The Western Margin Of The Yangtze Plate

The ELIP(Emeishan Large Igneous Province)is characterized by large-scale basalt eruptions,mafic and ultra-mafic intrusions.Lots of Fe-Ti-V deposits such as Panzhihua Fe-Ti-V deposit have been found in the Pan-Xi region which formed an N-S-trending metallogenic belt.The previous studies show that the regional tectonics of the ore-forming is Pan-Xi paleo-rift.Kuangshanliangzi iron ore deposit is a sub-volcanic-hosted iron ore depost in the Pingchuan-Shuhe area in the west of the Pan-Xi region.However,it is not well known that the relationship between structure and mineralization in this area.This thesis focus on the structural analysis of the kuangshanliangzi iron ore deposit for the N-S-trending tectonic belt,e.g.Jinhe—Qinghe fault,and the zircon U-Pb dating of main rocks.Some new improvements are as follows:1.Mineralization of the Kuangshanliangzi iron ore deposit is characterized by picritic porphyry intrusion and then the ore body emplacement.Moreover,picritic porphyries were passive emplaced in the deposit.In addition,the fractures were opened several times in metallogenic period showing that fractures and mineralization were pulsative during the metallogenic period.The ore-transmission structures are shown as combined constraint by NNE-trending faults and radial faults.The host structures are layered-sliding zones of limestone and some weak zones of structural breccias.Furthermore,structural collapse sites of the structures influence spacial expansion for the mineralization.2.Detailed field investigation shows that Jinhe-Qinghe fault and its secondary faults have experienced multistage activities in Late Permian,which are the typical tensional fracturing,and then undergone extensive compression deformation.Therefore the deformations have experienced two phrases from extension to compression.The zircon U-Pb ages for ultra-mafic,mafic and felsic intrusive rocks in Dabanshan area,and also for diabase dikes and porphyritic granite in Madigou area are all about 260Ma± representing(crystallization ages)emplacement ages of the main mass of rocks.The results demonstrate that there would be a bimodal assemblage of mafic and felsic plutonic rocks in the late Permian in this area,suggesting a characteristic of the rift setting.The results suggest that tectonics,magma and mineralization are all coupled together in the Pingchuan-Shuhe area.3.Based on field investigation and zircon U-Pb age analysis,here we confirm that iron ore deposits distributed in N-S-trending belts in the Pingchuan—Shuhe area can be compared with Pan-Xi region not only from the the characteristics of tectonic evolution but also from that of magmatism.Thus,Kuangshanliangzi style tectonic—magmatic—metallogenic sub-system may be above the Panzhihua style tectonic—magmatic—metallogenic system.The result may refer that we could find Panzhihua style Fe-Ti-V deposit under the Kuangshanliangzi style iron ore deposit.