The Magmatic Formation And Evolution Of Taihua Complex In The Lushan Area,Southern Margin Of The North China Craton

The North China Craton as the largest and oldest craton in China,is an ideal region for investigating the magmatic activity and tectonic evolution of Archean,and has attracted considerable interest from many geologists in China.The Taihua Complex is an important part of the North China Craton,distrabuting in WWN-EES direction along its sourthern margin.In this study,we chose the Taihua Complex in the Lushan area,investigated detailed geological section,studied the Petrography,Geochemistry,Zircon U-Pb dating and Lu-Hf isotopes of amphibolite and TTG gneiss of Taihua complex,and discussed the magmatic formation and evolution of Taihua complex in this area.This research mainly obtains the following knowledge.(1)Zircon U-Pb dating of Taihua complex in the Southern margin of North China Craton,yield the weighted mean ²⁰⁷Pb/²⁰⁶Pb ages 2821?2776 Ma,2714?2680 Ma and?1900 Ma,representing the formation age,first stage metamorphic age,and second stage metamorphic age,respectively.(2)The study of Lu-Hf isotope shows that the?Hf(t)value range from-4.0 to 8.3,and its corresponding second stage model age mainly concentrated on 2800?3200 Ma,It is indicated that the original rock material is from the partial melting of the depleted mantle material during 2800?3200Ma,and the addition of a small amount of crustal material during upwelling emplacement process.(3)Through this study,together with previous works about geochemistry,and considered that the original rock of amphibolite is basic subalkaline basalt,namely tholeiite.The primary magma of the TTG gneiss was produced by the partial melting of subducted ocean plate with amphibole and garnet in the residue.Both of them are formed by the island arc setting.(4)Through this study,and together with previous works about zircon U-Pb dating,Nd and Hf isotope,analyzed and discussed the evolution of the southern margin of North China Craton:the remains of ancient crustal material(3700?3650 Ma),the ocean subduction causes the crustal growth(2850?2700 Ma),the crustal growth(2600?2450 Ma),the magmatic active period(2400?2250 Ma),the intracontinental rift(2200?2100 Ma),the collision period(2000?1850 Ma).This research is useful not only for interpretation of the magmatic formation,evolution and its geological significance of Taihua complex in Lushan area,but also provides new theoretical support for the further study of the formation and evolution of the southern margin of North China Craton,even the whole North China Craton.