Genetic Mineralogy Of Cassiterite Placer And The Significant In Lailishan Area,Western YunNan

The Lailishan tin deposit is one of the famous tin polymetallic deposits in western Yun Nan.The main research object of this article is the Natural heavy sand minerals in the Lailishan tin mining area.Based on the typical research areas in the area,the relevant principles of genetic mineralogy,petrogeochemistry,and statistics are applied to the Natural heavy sand minerals collected in the field Observation,statistics and analysis are performed to extract the ore prospecting information of cassiterite heavy sand,to provide basic information for the establishment of a natural heavy sand ore prospecting model,and to serve the exploration and prospecting work.During the transportation of cassiterite heavy sand in the study area,the overall average particle size continued to decrease,the reporting rate of columnar cassiterite heavy sand gradually decreased,the reporting rate of granular cassiterite heavy sand gradually decreased,and the cone shaped cassiterite heavy sand gradually increased.The reported rate is basically stable;the overall grain size of cassiterite heavy sand is relatively small,which is consistent with the cassiterite cassiterite grain size characteristics;the crystal form and elongation coefficient of the cone shaped cassiterite are consistent with the characteristics of the cassiterite type cassiterite,and may form During the relatively high temperature and high temperature hydrothermal period,the crystal morphology and elongation coefficient of columnar cassiterite are in line with the characteristics of sulfide type cassiterite,and may be formed during the relatively low-temperature high-medium temperature hydrothermal period.The color of sand is divided into four types:colorless,brown,brown-red,and black-brown.The better the cylinder surface development of cassiterite,the larger the crystal elongation coefficient,and the lighter the color of cassiterite.Electronic probe analysis shows that there is a substitution relationship between Ta,Fe,and Sn in cassiterite;the darker the color of cassiterite,the higher the content of Ta₂O₅,Nb₂O₅,and Fe₂O₃^T;light(colorless,brown,brown-red)cassiterite The content distribution of Ta₂O₅,Nb₂O₅,and Fe₂O₃^T is similar and relatively continuous,and may be formed in a relatively continuous geological process.The content of black brown cassiterite Ta₂O₅,Nb₂O₅,and Fe₂O₃^T is significantly different from other three colors of cassiterite.The characteristics of the cassiterite-depleted Nb and Ta-rich in the study area indicate that its ore-forming hydrothermal fluid may originate from highly differentiated granitic magma,and cassiterite eventually formed in a weakly acidic environment.The content of Fe₂O₃^T in cassiterite is positively correlated with the formation temperature of cassiterite.The corresponding formation temperature of light-colored cassiterite corresponds to the uniform temperature of the ore-forming fluid of the Lailishan tin ore,indicating that the light-colored cassiterite originated from the Lailishan tin mine.And dark brown cassiterite has other sources.The research conclusions and related mapping results of the particle size,crystal form and color of cassiterite heavy sand in the study area show that light-colored cassiterite is formed in the high-medium temperature hydrothermal stage and belongs to sulfide-type cassiterite,mainly derived from the exploration Lailishan tin deposit;dark brown cassiterite formed in the relatively high-temperature high-temperature hydrothermal stage and belongs to the yunenite-type genetic cassiterite,indicating that there are still undiscovered yunnanite-type tin ore bodies in the area.