浙江花岗岩类地球化学与地壳演化──Ⅱ.元古宙花岗岩类

GEOCHEMISTRY OF GRANITOIDS FROM ZHEJIANG PROVINCE AND CRUSTAL EVOLUTION-Ⅱ. PROTEROZOIC GRANITOIDS

浙江元古宙花岗岩类包括神功期（1．8－1．9Ga）和晋宁晚期（0．6—0．9Ga）。研究了浙江元古宙花岗岩类的主元素、微量元素、稀土元素和Rb、Sr同位素组成特征及岩石成因，探讨了浙江地壳的演化。浙江地壳形成于太古亩和元古宙，地壳增生的时期为2．6－2．7、0．8-1．1和0.1－0.12Ga。随时间演化浙江地壳组成有变化，但分异演化不明显。沿江-绍断裂分布的晋宁晚期慢源和壳幔混合中酸性岩是普宁期俯冲碰撞的证据。加里乐和印支期是两次规模不大的构造运动。

Proterozoic granitoids include Shenggong Period (1.8-1.9Ga) and Late Jinningian Period (0.6-0.9Ga) median-acid rocks. Compositions of major, trace, rare earth elements, Nd-Sr isotope and petrogenesis of graultoids were studied. Shenggong granites were formed by partial melting of the Badu Group. Late Jinningian median-acid rocks were derived from mantle or mixing of mantle and crust material.Using granite as a probe, crustal evolution in Zhejiang Province was discussed. Three periods of crustal growth at 2.6-2.7, 0.8-1.1 and 0.10-0.12Ga are recognized. The Archaean are considered as time of crust generation. Frahonation of crustal composition with time is not evident.