ALKALINE ROCKS IN THE WUDANG-TONGBAI AREA SOUTHERN QINLING

Alkaline rocks in the Wudang-Tongbai area of the Southern Qinling Mountains can be divided into the southern and northern zones based on their spatial distribution. The alkalinity and Nb and REE abundances of the rocks in the southern zone are apparently higher than those in the northern zone. This paper focuses on the petrology, mineralogy, geochemistry, ages and petrogenesis of four alkaline rock bodies in the southern zone, which are the Huashanzhai nordmarkite, Guanzhishan jadeite-carcrinite syenite. Shaxiongdong alkaline amphibolite-cancrinite syenite-aegirine carbonatite complex and Miaoya syenite-biotite alvikiteankeritic carhonatite complex. Ages of the foar rock bodies have been determined with U-Ph, K-Ar and Rb-Sr methods to he 215—306 Ma, suggesting that they were formed in the Hercynian-Indosinian. On the basis of isotopic studies of ⁸⁷Sr/⁸⁸Sr, δ¹⁸O,δ¹³C and δD, it may be concluded that rock-forming materials of the Guanzhishan, Shaxiongdong and Miaoya rock bodies were derived from the upper mantle, while the genesis of the Huashanzhai rock body is mainly related to the lower crust materials.