Exploration Relationship Between The Metallogenic Geochemistry And Mineralization Of Basalt In Gold Polymetallic Ore Concentration Area In Beiya In Western Yunnan Province

The Beiya gold polymetallic deposit is located in the combination of the western margin of the Yangtze block and the "Three Rivers" Tethys Himalaya orogenic belt,which is a super large porphyry deposit with gold,iron,copper,lead,zinc and silver in the Jinsha River-Red River alkali-rich porphyry zone.On the basis of previous studies,through the systematic field investigation and cataloging of basalt in the surface and borehole of Beiya ore,this study conducted a detailed research on the geochemical characteristics of trace elements,rare earth elements and lead isotopes of basalt,as well as the difference between the basalt and the inner alkali rich porphyry and its output in the Wandongshan,Hongnitang,Bailian Village,Guochang River And Baxian Slope section of the mining area.The geochemical characteristics of basaltic rocks and their influence on their mineralization are mainly analyzed as well to conclude the following points:(1)Through field survey and typical borehole cataloging,it is found that basalt in this area mainly include: 1)dense massive basalt,in which chloritization,epidotization,peacock petrochemical,azurite mineralization and silicification can be seen.In the strong weathered and dense block basalt,in the southeast of the Baxian Slope mining area,there are spiegeleisen mineralization;2)almond basalt,the body of apricotis is filled with chlorite and epidote.Alteration is mainly chlorite and epidote,and peacock and azurite mineralization are visible locally.(2)The distribution of rare earth elements in beiya basalt is right type,and Eu has a weak negative anomaly.The distribution curve of trace elements is similar to that of OIB,but the element abundances of Rb and Ba have obvious fluctuations,suggesting that the basalt in the Beiya mining area has been strongly contaminated by the crust in the process of diagenesis,and the basalt in each mineral section is Y/Nb>1,which indicates that it belongs to alkaline basalt series.The characteristics of trace elements demonstrate that basalt in the area originated from type II enriched mantle source.(3)Through a comparative study of the distribution of metallogenic elements in the basalt in the mining area,it is found that: 1)the background value of the metallogenic elements in the basalt is generally higher than the Clark value,and it has the potential for providing material sources for the mineralization in this area;2)the related metallogenic elements in the horizontal and longitudinal aspects presents an "ore dilution" trend.In the process of polymetallic mineralization in this area,some ore forming minerals were extracted from the basalt near the ore.(4)The lead isotopes of ore was compared to basalt,alkali-rich porphyry and other surrounding rocks,and the results show that the ore and the basalt have similar isotopes,suggesting it contributed to the mineralization;while the basalt and the lead isotopes of the alkali rich porphyry are also similar,indicating that part of the northern alkali-rich porphyry may have assimilated part of the north basalt.The comprehensive research on the distribution characteristics of trace elements deems that the basalt of Beiya gold polymetallic mineralization provides some material source.At the same time,the extensive exposure of basalt around the center of the alkali-rich porphyry provides a "rock trap" for the migration of the Beiya metallogenic fluid,making the ore-forming fluid active and efficient in a small area,thus creating the formation of the Beiya super large gold polymetallic deposit.