Petrological Characteristics And Ore Potentiality Of Lianhuashan Alkali-rich Porphyry In Weishan, West Of Yunnan

Lianhuashan alkali-rich porphyry in Weishan of Western Yunnan, as one part ofalkali-rich intrusive rock belt of Jinshajiang-Honghe, is located in the south of thesanjiang region. In this paper, based on the structure-magma-mineralization theory, aseries of researches have been carried out systematically on lithological characteristics,lithogeochemical characteristics and ore potentiality.Lianhuashan alkali-rich porphyry is controlled by the NW-SE Weishan RiverFault, which is distributed on a smaller scale, but its lithofacies zonation is notobvious, and it is unconformity intrusion with the surrounding rocks. Rock types aremainly quartz monzonite porphyry and quartz syenite porphyry. Lithogeochemicalcharacteristics indicates that high SiO2, rich potassium, w(Na2O+K2O)>8%;Alkalinity is calc-alkaline; A/NKC=1and<1.1, are metaluminous-peraluminous rocks;Rb, Sr, Ba, Th, U, K and other LILE are rich, and Ta、Nb、Ce、P、Ti and other HFSEare poor. LREE concentrate, HREE disperse, and Eu negative anomaly is not obvious.Neutral-acid intrusive rocks in the study area belongs to A-type granites.According to trace elements illustration with elationship among Rb, Y, Nb and Ta,points fall into post-COLG. In the R1-R2illustration, points are centrally located inthe transition of orogenic late and post-COLG. In summary, the district alkali-richporphyry is produced in the tensile environment related to post-COLG. The trend oftrace element Standard curves is consistent, indicating that the alkali-rich porphyryhas the same magma source in the study area. Through field observations, theporphyry contains a number of porphyry MMEs, presumably originated in the mantlemagma source. REE distribution curve has a weak negative Eu anomalies, indicatingit is mixed with crustal material. Degree in the area of magma differentiation is stillnot enough, and still in the process of neutral acidic-acidic evolution.By the isotopic age, the age of diagenesis and mineralization is PaleogeneEocene in the work area. A investigation was done in Gantangzi whose mineralizationis good, indicating ore are mainly in porphyry and inner contact zone, however,outer contact zone and surrounding rock were weaker. Ore-forming elements such asAu、Cu has a industrial grade. Alterations of porphyry and surrounding rock focus on sericitization, kaolinization, chloritization, Hornfels, and potassic alteraction is notobvious. Due to significant changes in the ratio of K2O and Na2O, this paperspeculates that mineralization processes have a close relationship with ingredients ofK2O and Na2O. Stream sediment and soil geochemical survey also showe thatanomalie of Cu and Au is obvious in this area. As a result, there is probably exsitce ofgold mineralization in the contact zone of alkali-rich porphyry and surrounding rock,which is Worthy of further exploration development.