吉林夹皮沟金矿带的稀土元素地球化学研究

为了解吉林夹皮沟金矿带的成矿期次,利用稀土元素的示踪性,对夹皮沟金矿带含矿石英脉、花岗岩及变质地层斜长角闪岩等21个样品进行稀土元素含量测定。测定结果表明,石英脉ΣREE=19.12×10-6～147.57×10-6,δEu=0.61～1.22,平均值0.89,具弱的负Eu异常;太古代花岗岩ΣREE=121.40×10-6～157.32×10-6,δEu=0.87～1.09;中生代花岗岩ΣREE=69.78×10-6～90.95×10-6,δEu=0.94～1.02,LREE/HREE比值分别为11.51～14.12和14.16～16.73,后者轻重稀土分馏程度略高于前者;变质围岩ΣREE=22.40×10-6～275.86×10-6,δEu=0.75～5.79,平均值2.30,具明显的正Eu异常。三者都具有轻稀土富集的平滑稀土配分模型。结合其区域地质背景、流体包裹体和稀土元素特征,得出夹皮沟金矿存在两期成矿作用,分别对应于太古代成矿花岗岩岩浆作用及中生代燕山期花岗岩岩浆作用。太古代首次富集成矿,中生代燕山期叠加成矿并扩大成矿规模,成矿时代分别为2475～2469 Ma和170～160 Ma;结合稀土特征研究及包裹体研究,成矿流体以岩浆热液流体为主,遭受轻微地层变质热液混染,中生代成矿流体混染作用更强烈。

Geochemistry of Rare Earth Elements in Jiapigou Gold Belt,Jilin Province,China

Analyses of REEs in 21 samples collected from ore body,amphibolite and granite of Jiapigou gold belt in Jinlin province were conducted using ICP-MS.The results indicated that the ΣREE concentrations of ore bodies varied between 19.12×10-6~147.57×10-6 with low negative δEu anomaly,the value of δEu was 0.61~1.22 with an average value of 0.89.The ΣREE content of earlier granite varied from 121.40×10-6~157.32×10-6 with the δEu value of 0.87~1.09.The ΣREE content of later granite varied in a range of 69.78×10-6~90.95×10-6 with a value of δEu 0.94~1.02.The ratio of LREE/HREE of earlier granite(11.51~14.12) was higher than the latter(14.16~16.73).The ΣREE of amphibolite in altered rock were from 22.40×10-6 to 275.86×10-6,and the positive δEu anomaly was distinct,and the value was 0.75~5.79 with an average value of 2.30.The chondrite-normalized REE patterns of all these rocks were characterized by strong higher LREE than HREE.The Characteristics of geochemistry of REE of them suggested that there were two stages of metallogenesis contributed to the Jiapigou gold deposit correspond to the magmatisms in new Proterozoic era and Yanshanian of Mesozoic.An analysis of granite-normalized REE indicated that the element Au was concentrated and ore body was preliminarily formed in new Proterozoic era(2475~2469 Ma).In addition,it superimposed mineralization and enlarged the scale of ore body in Yanshanian of Mesozoic(170~160 Ma).Combined with the data of the inclusions geochemistry,the authors believe that the ore-forming fluids were mainly derived from magmatic hydrothermal fluids and magma contamination with altered rock was stronger in Mesozoic.