胶西北大尹格庄斑状花岗岩地球化学特征及地质意义

Geochemical Characteristics and Geological Significance of Porphyritic Granite in Dayingezhuang,Northwestern Jiaodong

郭家岭型花岗岩主要分布于胶西北北部的上庄、丛家、郭家岭一带,近年在大尹格庄金矿钻孔中发现了斑状花岗岩。本次研究采取大尹格庄斑状花岗岩样品,测试了岩石主量元素、微量元素和稀土元素含量。岩体具有高的Ba(1 187×10^(-6)~1 897×10^(-6))、Sr(931.25×10^(-6)~989.54×10^(-6))、轻稀土(113.17×10^(-6)~167.68×10^(-6))含量,低的Nb(3.81×10^(-6)~6.09×10^(-6))、Ta(0.18×10^(-6)~0.31×10^(-6))和重稀土(4.21×10^(-6)~5.63×10^(-6))含量,轻稀土富集、重稀土亏损(LREE/HREE=26.07~32.04),无明显Eu异常,亏损高场强元素Nb、Ta、P、Ti,与上庄岩体同属郭家岭型花岗岩。岩浆具有壳幔混合特点,成岩背景为活动大陆边缘。大型金矿附近都有郭家岭型花岗岩存在,金矿的形成与郭家岭型花岗岩相依;成岩时间早于金矿成矿时间5~10 Ma,与岩浆期后热液矿床成岩成矿时间差相符;郭家岭型花岗岩为金矿成矿提供了成矿物质、热源和矿化剂,胶东金矿的形成与郭家岭型花岗岩关系密切。

Guojialing granites are mainly distributed in Shangzhuang,Congjia and Guojialing in the northern part of northwestern Jiaodong.In recent years,porphyritic granites have been found in the drills of the Dayingezhuang gold deposit.In this study,Dayingezhuang porphyritic granite samples were used to test the contents of main element,trace elements,and rare earth elements.With high contents of Ba（1 187×10^-6 to 1 897×10^-6）,Sr（931.25×10^-6 to 989.54×10^-6）,and light rare earth（113.17×10^-6 to 167.68×10^-6）,low contents of Nb（3.81×10^-6 to6.09×10^-6）,Ta（0.18×10^-6 to 0.31×10^-6）and heavy rare earth（4.21×10^-6 to 5.63×10^-6）,enrichment of light rare earth,loss of heavy rare earth（LREE/HREE=26.07-32.04）,no obvious anomaly of Eu,and loss of high field strength elements Nb,Ta,P,Ti,the rock masses belong to the Guojialing type granite with Shangzhuang rock mass.The magma has the characteristics of crust-mantle mixing and the diagenetic background is the active continental margin.Guojialing granites exist near large gold deposits and the formation of gold deposits depends on the Guojialing granites.The diagenetic time is earlier than the 5-10 Ma gold mineralization time,and the diagenesis and mineralization time difference of the post-magmatic mineral deposits in the magmatic phase is consistent.Guojialing granites provide mineralization materials,heat sources,and mineralizers for gold mineralization.The formation of Jiaodong gold deposit is closely related to Guojialing granites.