Granite Zircon Dating, Geochemistry, Tectonic Setting And Prospecting Significance In Muchang, Zhenkang

Through the study of geology, petrology, zircon U-Pb geochronology and geochemical characteristics of Muchang granite in Zhen Kang, Yunnan province.Following results can be gotten in combination with the regional data analysis:(1) Muchang granite is characterized by high Si O2 low Ca O, the total alkali content(K2O+Na2O) is 7.38%–8.94%, the ratio of K2O/Na2 O is 0.90-1.16, Nb, Ta, P, Zr, Ti and other high field strength elements displays obvious negative anomalies, and Rb, La, Nd, Y, K and other large-ion lithophile elements have obvious positive anomalies, the content of high REE is 342.58-1264.219 μ g/g, Moderately enriched in LREE[(La/Yb)N=3.02-6.79],with obvious moderately negative abnormal Eu(σEu=0.17-0.19).The granite belongs to met-aluminous-high K calc-alkaline series. The formation of granite may be related to the partial melting of mafic lower crust, besides the degree of separation and crystallization of the granite is high.(2) Using SHRIMP zircon U-Pb isotopic dating to get the magma crystallization age of Muchang granite: the 207Pb/238 U weighted average age of sample IMCZK603-01 is 235.0±3.5Ma,MSWD=0.89,and the 207Pb/238 U weighted average age of sample IMCZK603-02 is 241.7.0±4.6Ma,MSWD=0.53. The results showed that: the diagenetic era of Muchang granite is late Early Triassic(3)On the Al2O3/(Fe O+Mg O-Ca O/(Mg O+Fe O) discrimination diagram: All the samples of Muchang granite fell into the metamorphosed mudstone region, what indicates that the source rock of granite is mudstone component. According to the zirconium concentration saturated thermometer, we can calculate the formation temperature of granite is 675-803℃; On the Hf-Rb-Ta Trace Elements discrimination diagram: The samples distribute mainly in the intra-plate region. On the R1-R2 graphic:All the samples distribute in the non-orogenic A-type granites region.(4)The trace element concentration sequence of Muchang granite is Sn(23.17)�'Zn(9.41)�'Bi(8.30)�'F(6.82)�'W(6.44)�'Sb(6.03)�'Pb(5.29)�'Mo(3.75)�'As(3.02)�'B(2.16)�'Au(1.23). Elements highly enriched(K≥5):Sn、Zn、Bi、F、W、Sb、Pb; Elements enriched(5≥K≥1.2):Mo、As、B、Au; elements depleted(K≤0.8):Cu、Cr、Ni、Co.(5)20 component of Muchang alkaline granite can be divided into five mutually orthogonal factorcombination:F1:Sb-Zn-Sn-Bi;F2:B-F-As-K2O-Na2O-[Si O2];F3: W-Ni-Cu-Au;F4:Cr-Mo-Pb-Ag;F5: V-Co。...