Magmatic Consanguinity And Tectonic Significance Of Zhongchuan Rock Group In Western Qinling

The Zhongchuan rock group in western Qinling orogenic belt have five monzograniterocks. They are Wuchaba rock body,Bojiazhuang rock body,Luzhouba rock body,Jiaochangbarock body and Lvjing rock body,commonly called as“Five golden flowers”. By the researthon chronology, major and trace elements, and structural character of important graniticintrusions in study area, this paper set up the temporal and spatial evolution framework ofgranite, discuss the tectonic setting and petrogenesis, analyze the relationship between graniteand mineralization, and provide information for the deployment of regional geologicalprospecting work. We divided stages of magmatic activity,and further clarified the structuralenvironment,material source and tectonic evolution.Based on previous work,combined with regional geological setting the granitoidmagmatism can be divided into four periods:the first stage is Wuchaba and Lvzhouba granite(232.9～248.8Ma), equivalent to early Triassic;the second stage is the main part of fivegranites(210～227Ma),equivalent to the middle Triassic;the third stage isBojiazhuang,Luzhoua and Lvjing granite(193.29Ma～208.5Ma);the forth stage is Wuchabaand Lvjing granite(181～181.5Ma), equivalent to early Jurassic.The Zhongchuan rock groupformed in Indo-Chinese and Yashanian epoch,which suggests that it was produced in theIndo-Chinese-Yanshanian magmatism event.The study on petrology and geochemical of5important granite show that they arehigh-K calc-alkaline series and rich in LREE.It reflect that was occured intensivedifferentiation by upper crust melt.Five granite have similar geochemical features,magmaeruption and inrusion,rich in LREE and depleted degree.We conclude that they have similarprocee of rock formation.Source magmas of the Zhongchuan rock group is continental granite that was relatedwith tectonic setting.It is high Sr granite.Geochemical study shows that they are the productof upper crust melt.The rock group include S-type and I-type,and the S-type is the main type.Based on the Sr-Yb content,the granite are included into Himalaya-type.The study area is a mixing tectonic unit by tectonic movement,magmatism andmetamorphism,meanwhile generating structural framework with N-S trend.Its basicly tectonicframework consists of series folds by the Himalayan thrust nappe movement.The Zhongchuanrock group is centre uplift,it presented annular distribution,the Bojiazhuang granite is in themiddle of them.Five granite located in a relatively dense of the structural line and NW-NEintersection belt.Liba-Suolongkou and Lixian-Taoping deep fault are passageway for ore fluid.Around ofthem,there are some small ore-controlling fracture.It controlled the distribution and scale ofgold deposit.In study area,there have Liba,Maquan,Minhua,Jinshan large and medium-sizedgold deposit,Yawan micro-dissemiated gole deposits.They are the product of consequence bydeep fault and magmatism.