Crustal Formation And Evolution Of The Provenance In Laoha River Over Band Sediment, Chifeng City Of Inner Mongolia

In this paper, we applied the U-Pb geochronology, Lu-Hf isotopic compositions, main elements, trace elements, heavy mineral identification and particle size analysising to study the over band sediments of Laoha River in Chifeng City, Inner Mongolia, and we draw the following conclusions:1. The U-Pb ages of detrital zircons in the Laoha River over band sediments are divided into three groups:119-405 Ma (accounting for 54%),1727-2087 Ma(accounting for 36%), and 2202-2598 Ma(accounting for 10%),lack of 500-1600 Ma. So the over band sediments mainly originated from the northern margin of the North China Craton.2. The main peak of the first age group is 230 Ma, may be relevant of stretching after collision of the North China Block and the Mongolia hyperplasia fold belt in southern edge of Siberia, and may be on behalf of the subduction of the Paleo-Asian Ocean to the North China Craton; Secondary peak is 123Ma, it is mainly representative of the North China Craton destruction event; The main peak of the second group is 1845Ma when the North China Craton had completed cratonization; The main peak of the third group is 2504Ma, it is the formation time of continental crust basement of the North China Craton.3.2933-2500Ma is the crust-mantle differentiation stage of source area; From 2500Ma, continental crust growth rate started to slow down, until 1000Ma the continental crust of the Laoha River’s provenance is basically stabilized, volume of continental crust is almost identical to the volume of present continental crust.4. The provenance exists the middle-Archean geological bodies, about 2700Ma, there are a relatively strong crust-mantle differentiation event; 2202-2598Ma magmatic materials mainly came from the depleted mantle; 1727-2087Ma detrital zircons mainly came from ancient crust remelting which formed in 2202-2598Ma; During 1700-1500Ma, a lot of depleted mantle materials added in this area.5. The youngest model age before Laoha River confluxing is 1269Ma, releaved that the melting of mantle-derived rocks which underplated at Middle Proterozoic occurred in Late Palaeozoic, it was caused by the Paleo-Asian Ocean closed; The youngest model age after Laoha River confluxing is 502Ma, and the North China Craton exists model ages after 500Ma.