Zircon U-Pb chronology, geochemistry and Lu-Hf isotope constraints on genesis of monzonitic granite from Harizha area in eastern section of East Kunlun region

摘要

The Harizha area is located in the eastern section of East Kunlun orogenic belt .The petrology, the zircon LA-ICP-MS U-Pb chronology and the petrogeochemistry of the monzonitic granite in the area were stud -ied.The results show that the formation age of the monzonitic granite in the Harizha area is 237.4 ±1.4 Ma, which belongs to Middle Triassic .The content of SiO 2 in the rock is 61.29％--63.30％, (K2 O +Na2 O) is 5.41％--5.84％, Al2 O3 is 14.80％-15.99％, the Mg# value is 46.33--48.33, and the aluminum saturation in-dex A/CNK is 0.87--0.91.Therefore, it can be concluded that the rock belongs to the I -type granite of quasi-aluminous high potassium Ca -alkaline series.The total REE content of the rock is 118.82 ×10-6-164.54 × 10 -6 , and the La /Yb ratios range from 7.77 to 10.13.Meanwhile, the rock does not show obvious Eu anoma -lies (δEu =0.61-0.75) and is characterized by enrichment of LREE and LILE such as Rb and K , relative de-pletion of HREE and HFSE such as Nb , Ti and Ta.Zircon Hf isotopic dating exhibits that the average εHf (t) is -2.4 and the average of two-stage model age (tDM2 ) is 1417 Ma, indicating that the source rocks are mainly crustal materials.It can be concluded from research findings and regional geological structural analysis that the monzonitic granite in the Harizha area originated from partial melting of the Mesoproterozoic mafic lower crust in the later stage of the subduction of the Paleo -Tethys Ocean.