Geochemistry and SHRIMP Zircon U‐Pb Age of Post‐Collisional Granites in the Southwest Tianshan Orogenic Belt of China: Examples from the Heiyingshan and Laohutai Plutons

Abstract

Abstract: The Heiyingshan granite and the Laohutai granite plutons exposed in the Southwest Tianshan resemble A‐type granites geochemically. Analysis shows that the both are ferron calc‐alkalic peraluminous or ferron alkali‐calcic peraluminous with a relatively high concentration of SiO 2 (>70%), high alkali contents (Na 2 O + K 2 O = 7.14%‐8.56%; K 2 O>N 2 O; A/CNK = 0.99‐1.20), and pronounced negative anomales in Eu, Ba, Sr, P and Ti. A SHRIMP zircon U‐Pb age of 285±4 Ma was obtained for the Heiyingshan hornblende biotite granite intrusion. The geochemical and age dating data reported in this paper indicate that these granites were formed during the post‐collisional crustal extension of the Southwest Tianshan orogenic belt, in agreement with the published data for the granites in the South Tianshan.