Geochemical Characteristics Of The Mesoproterozoic Shicheng Granite In Songshan Area

Songshan area is located in the southern margin of the North China Craton(NCC), and it is one of the typical areas to reserch the Precambrian geology. Magmatic activity that strongly mainly happens in the Neoarchaean and Mesoproterozoic in Songshan area. Many scholars have researched the Neoarchaean igneous rocks in Songshan area, so it is relatively high, but the study of the Mesoproterozoic igneous rocks is relatively weak. The Mesoproterozoic Shicheng granite is the largest rock body in Songshan area with low level of research.The research takes the Mesoproterozoic Shicheng granite in Songshan area, Henan province, and through research of petrography of the granite rock, geochemistry, geochronology, and tectonic environment,and the main geological results are obtained as follows:(1)The distribution of Shicheng granite is subject nearly east-westward, about 11 km long, about 5km wide, the exposed area approximately 55.5km2, and is the largest rock body in Songshan area. The main rock lithology is biotite syenogranite, pale yellow and pale red, medium to coarse grained granitic texture, porphyraccous texture and massive struvture, and the primary minerals are feldspar, quartz and biotite.(2)For the major elements in Shicheng granite, SiO2=66%, Al2O3=14.4%, Fe2O3= 5.7%, Ti O2=0.34%, P2O5=0.05%, CaO=0.51%, MgO=0.25%, K2O=9.5%, Na2O=1.63%, MnO=0.04%, overall with the a performance of high-silica, aluminum-rich, alkali-rich features and possess the features of metaluminous A-type granites and alkaline granites.(3)The REE are with the characteristics which are high ?REE(average ?REE=831.43×10-6), LREE enrichment(average ?LREE=784.74 × 10-6) and to HREE deficiency(average ?HREE=46.69 × 10-6), the fractionation of LREE and HREE is obvious and Eu anomaly with a strongly negative(?Eu=0.48~0.55).(4)The characteristics of the trace elements are rich with large ion lithophile element Rb, slightly enriched with K, Ba, and low with Sr; Rich with high field strength element Th, slightly enriched with Nb, Ta; and low with Zr, Hf, P. The overall performance of the trace elements are enrichment with large ion lithophile elements and loss high field strength elements.(5)The result through determining the age of the U-Pb zircon is 207Pb/206 Pb with the weighted mean age of 1857 ± 42 Ma Shicheng granite, belonging to Mesoproterozoic igneous rocks.(6)Combined geological features,Geochemistry characteristics with the formation time of the Shicheng granite, it forms under the tectonic environment that stretch and tension happens in the North China Craton to form intraplate continental rift. Some of continental crust which based on late Neoarchaean granites Melt to form Alkaline A-type granites. It is the result of rock recycling in the crust under the extensional system of Mesoproterozoic in the North China Craton.Densely distributed and large-scale REE mineralized rock forms are first discovered in the Shicheng granite during geological surveys, REE mineralized rock forms during the Post-magmatic evolution ore-bearing hydrothermal fills the fractures in late magmatic hydrothermal mineralization.