Study On Geochemistry And Petrology Of The Caledonian Granites In The Middle Section Of Wuyi Mountain

Since the formation of the continental crust in South China,it has undergone many tectonic movements.The geological tectonic background is extremely complex,and the magmatic activity is frequent.Large-scale granite rocks of different stages are exposed,accompanied by a large number of mineral resources such as rare metals and rare earths.Based on its exceptional traffic geography,geological features and lage scale of exposure,South China has become an important area for granite research in China and the world.After decades of unremitting research,the formation age,genetic type and tectonic environment of most rock masses have been recognized,but they have not formed a unified view.The Yanshanian granitoids have the largest scale of exposure and mineral resources,and the research level is the deepest.However,research on Caledonian granite is relatively weak,and there are also major differences in the types of genesis and the background of their construction.In this paper,the Shangqing,Lichuan and Ninghua rock masses of the middle Wuyi Mountains are selected as the research objects.Based on the field of geological survey of the system,its pathological characteristics,zircon U-Pb geochronology,zircon Hf isotope characteristics and whole rock geochemical characteristics are studied.In order to provide new data references for the genetic types and formation of the Caledonian granitoids in the middle section of the Wuyi Mountains in South China.The formation age of theShangqingrock masses 437.9±5.8 Ma(MSWD=0.59),which was obtained by LA-ICP-MS zircon U-Pb dating method,and it is a product of Caledonian early Silurian magmatism.The geochemical characteristics of the Shangqing rock mass show that it is characterized by high-potassium,alkali-rich,and titanium-depleted peraluminous to strongly peraluminousS-type granite,and has the characteristics of the K-type rock series.The characteristics of trace and rare earth elements show that the Shangqing rock mass has a medium negative anomaly of europium,enriching large ion lithophile elements such as Rb,Th,U,K,etc.,and depleting high field strength elements Nb,P,Ti,Ba,Sr,etc.element.Zircon Hf isotope characteristics show that the sample ?Hf(t)of the Shangqing rock mass is all less than zero and has an older crust model age.A small amount of acicular apatitequenching structure was observed under a polarizing microscope,indicating that the source may be mainly crustal material and a small amount of mantle material is mixed.The zircon U-Pb age of the Lichuan rock mass is 435.7±2.5Ma(MSWD=1.13),which is close to the time of the Shangqing rock mass,and belongs to the product of the early Silurian Caledonian magmatism.Geochemical characteristics of the Lichuan rock mass indicate that it has the characteristics of potassium-rich,alkali-rich and titanium-depleted peraluminous-strongly peraluminous S-type granite,and has certain characteristics of the K-type rock series.The results of rare earth and trace elements test show that the Lichuan rock has moderately negative europium,Enriched with large ion lithophile elements such as Rb,Th,U,and K,Ba and Sr have obvious losses.Zircon Hf isotope shows,the ?Hf(t)ofLichuanrock mass are also negative,indicating that they are derived from partial remelting of the crustal material.The zircon U-Pb dating results of the Ninghua rock mass show that the diagnostic age of the Ninghua rock mass is 416.0±5.5 Ma(MSWD=0.46),which should be formed by the late Silurian magmatism in the Caledonian period.Geochemical analysis of the Ninghua rock mass shows that the Ninghua rock mass is a weekly peraluminous-peraluminous calcium alkaline-high potassiumcalciumalk aline series granite,and reciprocates,alkali-rich and titanium-poor.In the analysis results of trace elements and rare earth elements,the Ninghua rock mass has different degrees of negative europium,which may be caused by the different degrees of crystallization of the plagioclase.And it also has the characteristics of enriching large ion lithophile elements with less high field strength elements,and is a lowBa and Sr continental crust-forming granite.In the results of zircon Hf isotope analysis,the?Hf(t)are all negative,indicating that the Ninghua rock mass is a source of crustal material.And it has a high zircon crystallization temperature,which may be affected by the mantle heat source.In combination with geology,the Caledonian granite is in an unconformity with the surrounding rock,lacking the characteristics of corresponding volcanic rocks.It is believed that the Shangqing and the Lichuan rock mass which in the early Silurian,and the Ninghua rock mass which in the early Silurian is formed in the extended collapse environment of the post-orogenic mountains.In the geological phenomenon,the Caledonian granite is in unconformity with the surrounding rock and lacks the corresponding characteristics of volcanic rocks.Combined with the tectonic environment discriminant map,it is believed that theShangqing and the Lichuan rock mass which in the early Silurian,and the Ninghua rock mass which in the early Silurian is formed in the extended collapse environment of the post-collision.