Yunnan Lancang Old Factory Polymetallic Deposit Structure And Its Ore-control Study

Lancang lead deposit is one of important polymetallic deposits in south segment of Tri-rivers region in Yunnan province, China. The recent researches indicate that the genesises of Landcang ore deposit are compounded with Carboniferous volcano exhalative sedimentary and Himalayan concealed granite porphyry heated liquid. Based on the data collection and field survey, the regional tectonic features and tectonic evolvement and the relations to the systems of volcano exhalative sedimentary metallogenic and concealed granite porphyry metallogenic have been studied. Especially, the metallogenic system controlled by tectonic has been studied in detail.Since the late Paleozoic, the regional dynamic conditions have been changed in times. The evolution process of regional tectonic can be divided into 3 phases which are period of rift (D-P1), rift-close and lift (P2-K) and continental collision. Controlled by the complex tectonic conditions, the evolution process of the poly-metallogenic of Lancang ore deposit is also very complex. The in time sequence, when the tectonic was from rift to continental collision, the double metallogenic systems which processed from Carboniferous volcano exhalative sedimentary to Himalayan concealed granite porphyry heated liquid had been formed.In the research field, there are three folds including Shangyunshan anticline and Laochang anticline and Shuishishan syncline. The conformation of Laochang anticline is very complex and also an important ore-controlling structure. The faults are mainly spread in SN and NW directions and in NE and EW directions. The evolution process of the faults is very long and the activities of the faults can be observed in many stages which are at less including tension and squeeze and dextral strike slip. The faults in NE and EW directions are relative small.The Carboniferous volcano exhalative sedimentary controlled by tectonic in two aspects:the rift controls the metallogenic, the faults and the folds control the ore body. The boundary of the rift and the main fault are transfixion tectonics which is not only the channels for the magma ascending and eruption but also the space for the collection of rising metallogenic flow. The rift valley multi-stage basin in the rift is a good sedimentary depression for metallogenic and also helpful in the accumulation and sedimentary of minerals along the fault belt. During the process of rift close, the properties of faults reversed and many folds happened and the ore bodies lifted imbricately in phase of the deformation of stratum and can be enriched at the transition part of the folds. The continental collision of tectonic compression and strong regional uplift make the volcanic exhalation-sedimentary ore body deformed more.The porphyry metallogenic system is controlled by tectonic in two parts which are the space shape of concealed porphyry body and the ore body group related to the porphyry. According to the characters of the rock characteristics of occurrence, the concealed porphyry granite is controlled by Laochang anticline and faults F1 and F4. the shaft of the anticline locates the intersection of the two faults for the high intrusion of porphyry. Along the top the salience of porphyry and the rift belt, veins disseminated molybdenum(copper) ore body group has been formed. The nervation heated liquid filling ore body (IV orebody group) of Pb-Zn-Ag has been controlled by the main faults in NS direction such as F1 and F3 and F11and etc. In the secondary faults and fissures and cracks, there is not only low temperature heated liquid alteration but also many Pb-Zn-Ag ore body group(III orebody group) shaped in irregular nervation and lenticular.