皖中下地壳重熔型花岗岩类

The Anatectic Granitoids of Lower Crust in Central Anhui

安徽中部沿江地区北缘分布有洪镇、管店和滁县三个花岗岩类侵入体，各种岩石化学参数表明它们属于Ｉ型或同熔系列花岗岩类。但是，其Ｎｄ、Ｓｒ、Ｐｂ、Ｏ同位素比值均低，表明它们是古老麻粒岩相下地壳重熔的产物。这类花岗岩在已有的成因分类中未单独划出。

In Ahhui Province, there are three granitoid intrusions, namely Hongzhen, Guandian and Chuxian, distributed on the northern bank of the Yangtze River. Various petrochemical parameters show that they are of I-type. Nevertheless, their Nd, Sr and Pb isotopic ratios are all relatively low (∈ t Nd =-13.5—-15.5,I t Sr =0.7058—0.7065, 206 Pb/ 204 pb=16.50? ?6.99 , 207 Pb/ 204 Pb=15.29—15.37), suggesting that they are anatectic granitoids derived from Archean granulites in the lower crust. This granite type has not been included in known genetic classifications of granitoids.