| Yunnan Pulang super-large porphyry copper deposit is one of the typical deposits in the Yidun Indosinian island arc belt of the southeastern part of the Sanjiang metallogenic belt and the most important porphyry copper deposit discovered in the beginning of this century.Pulang mining area is mainly composed of the first mining area and three peripheral ore section(respectively the northern,Eastern and southern periphery ore section).The previous researchers made a lot of research on the porphyry type and its petrology of the first mining area,chronology fruitful.In contrast,the study of petrology,geochemistry and chronology of the peripheral ore segments(?,?,?,?)is low.In recent years,the study of peripheral geology and mineral prospecting work gradually.In order to improve the metallogenic geological conditions and prospecting potential of peripheral ore deposits,In the practice of geological prospecting engineering in the northern part of the mining area,by taking ? porphyry of the north as research object,the author carried out geological and rock,geochemistry,rock,rock and zircon geochronology research comparing No.? rock body characteristics and No.? rock body,made a batch of new materials and new achievements,application of geological investigation,rock mineral identification,major,trace and rare earth elements analysis,LA-ICP-MS U-Pb zircon dating test and other methods.1.Based on the analysis of the characteristics of the rock mass and its contact with the surrounding rock,the detailed observation of the drill core and the systematic micro-petrography study,it is found that the main rock types of No.? composite porphyry body are diorite porphyry and quartz-monzonite porphyry.The diorite porphyry forms the main body of the rock mass,and the mineralization-alteration is weak.The quartz-monzonite porphyry with irregular dike-shaped intruded into diorite porphyrite rock,and mineralization-alteration is strong.It is the main metallogenic rock body.2.The representative samples were selected to study the composition of main elements,trace elements and rare earth elements.It is found that the SiO2 content of quartz-monzonite porphyry in No.? composite porphyry body is 60.30%?68.45%,with an average of 64.39%,which has the characteristics of typical intermediate acid rocks.The SiO2 content of diorite porphyry is 57.75%?59.71%,with an average of 58.73%,which belongs to the neutral rock.According to the chemical parameters of rock,diorite porphyry and quartz-monzonite porphyry show the characteristics of rich potassium and low sodium,which belong to calc alkaline rock series.The two types of rocks show the characteristics of rich large ionic lithophile element(LILE)such as Rb,K,Cs,Sr,Ba and low Nb,Ti,Zr,Ta and other high field strength elements(HFSE).In the rare earth elements,diorite porphyry and quartz-monzonite porphyry show that LREE enrichment and differentiation is relatively obvious,HREE characteristics and differentiation is not significant.The REE distribution patterns are very similar.3.LA-ICP-MS zircon U-Pb dating test analysis confirmed that diorite porphyry forming age ranged from 225.9±3.8Ma to 237.9 ± 7.2Ma,with an average of 230.6 ± 0.85Ma,and quartz-monzonite porphyry from 209.4 ± 0.9Ma to 221.2 ± 3.5Ma,with an average of 212.2 ±0.54Ma,indicating that they are the products of magmatic intrusion at different stages of the same period(Indosinian),and the diorite porphyry formation is relatively earlier than that of quartz-monzonite porphyry.4.The zircon typomorphic characteristics of diorite porphyry and quartz-monzonite porphyry were studied by means of stereoscopic microscope and scanning electron microscope.The results showed that both of the zircons developed well in the rhythmic zoning,and the magmatic genesis was obvious.The zircon is characterized by enrichment of HREE,loss of LREE,positive Ce anomaly and rare earth distribution curve.There are two main types of P and S,and the 12 subtypes.Zircon is formed in rich alkali low temperature environment,and the crystallization temperature is between 750?650 and C.In the evolution trend of zircon,it is located in the region of the earth mantle genetic calc alkaline granite.5.The diagenetic geological environment,rock assemblage,geochemistry,diagenetic age and zircon typomorphic characteristics and other aspects of information analysis,confirm:No.fll composite porphyry body is I type granite,that unweathered igneous rock melted to form granitic rock,is the product of the orogenic belt,with characteristics of shell mantle source.Tectonic environment for typical volcano arc,unlike typical adakite.6.The comprehensive comparison between No.? composite porphyry body and No.?composite porphyry body,two types of rock in the rock composition,chemical composition,trace element and REE composition,diagenetic age,petrogenesis and magmatic evolution and diagenetic tectonic environment has obvious similarities,with rock conditions of porphyry copper mineralization in the more favorable.However,compared with the No.? rock mass in the first mining area,quartz-monzonite porphyry of No.? composite porphyry body exposed on a small scale,the magma evolution time span is shorter.The differentiation of diorite porphyry and quartz-monzonite is not obvious. |
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