Petrological Characteristics Of Ag - Pb - Zn Polymetallic Deposit In Lancang Old Factory, Western Yunnan, China

Laochang Ag Pb Zn polymetallic deposit is "Sanjiang" polymetallic sulfide deposit which is one of the most representative metallogenic belt,The mineralization is mainly through the volcanic exhalative sedimentary mineralization and joy of Early Carboniferous mountain stage concealed granite porphyry emplacement deposit,it has characteristics of polygenetic compound mineralization and parity.Wallrock alteration is strong,diverse, complex, can be divided into hydrothermal alteration associated with volcanic exhalative sedimentation system and concealed granite porphyry magmatic hydrothermal alteration related system.This paper mainly through the observation of the tunnel and drilling, logging, sample collection, microscopic identification of thin sections, electron microprobe analysis and typical sample element mass migration balance study after study of 1480 middle and ZK915 related to concealed granite porphyry altered rock, following conclusions are obtained:(1) the Laochang alteration zoning in the horizontal direction and the vertical have certain regularity:In the horizontal direction from rock to rock alteration types, followed by pyrite silk British rock, skarn and propylitization;The vertical from rock to rock, alteration types are as follows:pyrite silk British rock, skarn and propylitization.(2) Near pyrite silk British rock side, skarn show red brown color, and away from pyrite silk British rock, its color transition to celadon. Observation from hand specimen and under the microscope, the skarn is multi period containing molybdenite (Pyrite) with Shi Yingmai, show the early stage of skarn formation in the mineralization.(3) skarn belt altered minerals are garnet diopsidewollastonite; the garnet to Grossular andradite series, but the calcium aluminum garnet; pyroxene diopside and hedenbergite series, but mainly diopside.Wol+Hd+Ga combination displays skarn deposits are formed in high temperature under the condition of reduction; propylitization zone altered minerals are mainly pyrite, sericite+clinochlore, local containing calcium iron garnet zonation; pyrite silk British rock zone altered minerals are mainly pyrite sericite quartz, local containing albite polysynthetic twin elongated Shi Keli.(4) Concealed granite porphyry body (vein) and lower carboniferous in willow group (C1y) the existence of the volcanic rocks provides the mining area pyrite silk British rock and skarn, propylitization. Distribution of pyrite silk British rock also indicates the deep concealed porphyry intrusion of space, which is looking for porphyry-related deposit prospecting ideas and direction provided.(5) Through the research that the quality of element migration balance in the beresitization belt (P-S-Q), garnet diopside silicon card lithification belt (G-A-D), pyrite sericite chlorite azurite rock lithification belt (P-S-C),we found that Fe2O3, CaO were belt into in each alteration, Cu, Ni, Cr, Co enrich in pyrite silk British rock; Mo, zinc mainly occurred in skarn; Sr, Ba, Nb main enrich in propylitization. Through the study quality of altered rock element migration characteristics, it has important instruction significance for us to look for specific minerals and space which Granite porphyry emplaced.