江南隆起带东段皖赣相邻区燕山期花岗岩类的成因及形成的地球动力学背景

GENESIS AND GEODYNAMIC BACKGROUND OF YANSHANIAN GRANITOIDS IN THE EASTERN JIANGNAN UPLIFT IN THE ADJECENT AREA OF ANHUI AND JIANGXI PROVINCES,CHINA

江南隆起带东段皖赣相邻区南(赣东北地区)、北(皖南地区)两侧发育花岗岩类,且与成矿关系密切。对花岗岩类的地质地球化学特征、地球物理、造山过程动力学及低Nd模式年龄分析表明,研究区至少存在两期规模较大的侵入岩浆活动,赣东北地区以燕山早—中期为主,皖南—浙西地区以燕山中—晚期为主。燕山早期两大动力学体系的转换(160Ma～170Ma),NE向赣东北深大断裂的线性拉张减薄作用,引起幔源岩浆上升并与地壳相互作用形成赣东北斑岩体;燕山中晚期(<145Ma),皖南与赣东北的动力学背景趋于一致,随着古太平洋板块对欧亚大陆的俯冲碰撞,挤压作用使上溪群或成分类似于上溪群的基底岩石部分熔融,形成皖南—浙西地区燕山期花岗岩、花岗斑岩和赣东北地区燕山期花岗岩。

Granitoids are well-developed in Gangdongbei(north Jiangxi Province),Wannan(south Anhui Province) and the south and north parts of the eastern Jiangnan Uplift.These granitoids have close relation with the Cu, Au and polymetallic mineralization. There exist at least two periods of large-scale magmatic activities: early- to middle Yanshanian in Gandongbei and middle- to late Yanshanian in Wannan and in Gandongbei. During the transition of the two dynamic systems(N-S to NNE- direction) in early Yanshanian(160 Ma^170 Ma), the linear extension along the Gangdongbei deep fault led to the thinning of lithosphere and the doming of the mantle, which resulted in the rising of mantle sourced magmas and the interaction with the crust rocks and the formation of porphyritic granitiods in Gangdongbei. Accompanying the collision between paleo-Pacific Block and the Eurasian Block in middle and late Yanshanian(<145 Ma), the two sides were in the same geodynamic background.Compressive processes caused by intra-continental orogeny led to the partial melting of basement of Shangxi Group to,and to the formation of granites and porphyritic granitiods in Wannan and granites in Gangdongbei.