Magmatic response to lithospheric thinning of the North China Craton—evidence from the Daqingshan granite
The magmatic activities of the Yanshan period in North China Craton are an ideal carrier for studying the mechanism of craton destruction. In this paper,the Daqingshan granite was selected for LA-ICP-MS zircon U-Pb dating and geochemical analysis to investigate the rock genesis and its implications for the Mesozoic tectonic-magmatic evolution in the northern margin of the central North China Craton. The results show that the granite consists mainly of phenocryst adamellite,with a zircon U-Pb age of (139±1) Ma(MSWD=0. 28,N=12),indicating an early Cretaceous magmatic event. The geochemistry of the genesis indicates that it is highly silicic,alkali-rich,relatively potassium-rich,peraluminous,and magnesium-tita-nium-phosphorus-calcium poor. The genesis was classified as a highly differentiated type I granite of pera-luminous for the results of NK/A,saturation temperature of zircon and the value of P2O5,Zr and FeOT.The granite is enriched in large ion lithophile elements (Rb,Th,K) and depleted in high field-strength el-ements (Ba,Sr,P,Ti). The total rare earth element contents are low (∑REE ranges from 84. 5×10-6 to 216. 0×10-6),with a strong fractionation between light and heavy rare earth elements and significant neg-ative Eu anomalies (δEu=0. 08～0. 56),showing a four-group pattern. The genesis exhibits obvious char-acteristics of crustal source and intrusion age coincides with the peak period of magmatic activity in the North China Craton,representing a shallow magma response to craton thinning,closely related to the re-treat of the ancient Pacific plate.
Craton destructiongeochemistrypetrogenesisDaqingshan graniteNorth China Craton
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