胶东地区早白垩世郭家岭期花岗岩

Study on Early Cretaceous Guojialing Granite in Jiaodong Area

摘要:

胶东地区早白垩世郭家岭期花岗岩指形成时代为早白垩世，形成年龄为123～135Ma的一期岩浆活动事件的产物，从西到东由莱州三山岛、招远上庄、招远北截、招远丛家、龙口七甲、栖霞郭家岭及蓬莱范家店7个岩体组成。主要岩性为二长花岗岩和花岗闪长岩，少量的石英二长岩和二长闪长岩，多数具有钾长石斑晶和暗色包体，为一套准铝质—过铝质高钾钙碱性岩系。该期花岗岩中的黑云母是在高氧逸度条件下结晶形成。同位素示踪及角闪石成分测试表明成岩物质既有以基性脉岩为特征的地幔物质，又有地壳物质的特征，是下地壳酸性岩浆与幔源基性岩浆混合作用的结果。利用角闪石的化学组分估算结晶深度在6~13km，郭家岭期花岗岩受构造控制的强力定位机制，岩体沿NEE向剪切作用所形成的剪切空间，在底劈和气球膨胀式侵位机制共同影响下，从小面积到大面积多次脉动侵位，是构造体制转换的产物,通过SHRIMP，LAICPMS锆石UPb定年，测得年龄范围（123±1）～（135±3）Ma，该期岩浆活动持续时间在12Myr左右，岩体中心部位年龄偏小，边部年龄偏大。

Abstract:

Theearly Cretaceous Guojialing granite is the product of a magmatic event with the formation age of 125~135 Ma in the early Early Cretaceous.From west to East,itiscomposed of 7plutons:Laizhou Sanshandao,Zhao yuan Shang zhuang,Zhaoyuan Beijie,Zhaoyuan Congjia,Longkou Qijia,Qixia guojialing and Penglai fanjiadian.The main lithology is monzonitic granite and granodiorite,a small amount of quartz monzonite and monzonitic diorite,and most of them have K-feldspar phenocrysts and dark enclaves.It is a set of quasi aluminous peraluminous and high potassium calc alkaline rock series.Biotite in the reformed granite is formed by crystallization under the condition of high oxygen fugacity.Isotopic tracing and amphibole composition testing shows that the diagenetic materials are characterized by both mantle materials and upper crust materials.It is the result of mixing of acidic magma and mantle derived basic magma in the lower crust.The chemical composition of amphibole estimates that the crystallization depth is 6~13 km.Strong positioning mechanism of Guojialing granite controlled by structure.The shear space formed by the nee direction shear of the granite body is multiple pulsating emplacement from small area to large area under the joint influence of the bottom splitting and balloon expansion emplacement mechanism. It is the product of structural system transformation. Zircon UPb dating by SHRIMP, LAICPMS show that the age range is （123±1）~（135±3）Ma, the duration of magmatic activity is about 12Myr.The age of the central part of the rock mass is relatively small, and the age of the edge is relatively large.