胶东地区早白垩世伟德山期花岗岩

Early Cretaceous Weideshan Period Granite in Jiaodong Area

伟德山期花岗岩代表了胶东地区中生代早白垩世晚期(110~123Ma)大规模岩浆事件,是中国东部中生代构造体制转换峰期事件产物;受区域构造控制,由二长闪长岩—二长岩—石英二长岩—花岗闪长岩—二长花岗岩类组成,斑晶发育,含大量的暗色闪长质微粒包体,以准铝质—弱过铝质的高钾钙碱性岩系为主,富集大离子亲石元素Rb、K、Ba,高场强元素U、Th,Nb、P、Ti元素亏损,Zr、Hf元素为正异常,具有高Ba-Sr花岗岩特征,为壳幔混合成因,壳源物质来源为新太古代TTG片麻岩及古元古代变质岩。该期花岗岩形成于岩浆弧构造环境,由于胶北地块与苏鲁造山带地壳结构差异,在岩石组合、地球化学特征及形成时代上略有差异,总体由西至东,年龄值逐渐变小,向偏碱性转变。

Weideshan granite represents a large scale magmatic event in late Mesozoic early Cretaceous(110~123Ma)in Jiaodong area.It is the product of the peak event of Mesozoic tectonic regime transformation in eastern China.Due to the control of regional structures,it is composed of monzodiorite monzolite quartz monzoite granodiorite monzogranite,and phenocryst is well developed containing a large number of dark diorite particle inclusions.The ore bodies are mainly quasi aluminous weak peraluminous high potassium calc alkaline rock series,and enriched with large ion lithophile elements Rb,K,Ba.High field strength elements,such as U,Th,Nb,P,Ti elements are deficiency,Zr and Hf elements are positive anomaly,and characterized by high Ba Sr granite.It is of crust mantle mixed origin,and the source of crust source material is Archean TTG gneiss and Proterozoic metamorphic rock.The granite in this period was formed in the magmatic arc tectonic environment.Due to the differences in crustal structure between Jiaobei block and Sulu orogenic belt,there are slight differences in rock assemblage,geochemical characteristics and formation age.Generally,from west to east,the age value gradually decreases and changes to alkaline.