冀东金矿带中生代岩浆作用及其成矿意义——来自锆石矿物学证据  

Mesozoic magmatism and metallogenic significance in eastern Hebei gold belt:Evidence from zircon mineralogy

作　　者：张岱岳 王树志 曹冲 王涛[2] 郭志华 ZHANG Daiyue;WANG Shuzhi;CAO Chong;WANG Tao;GUO Zhihua(School of Mining Engineering,North China University of Science and Technology,Tangshan,Hebei,063210;Chinese Academy of Geological Sciences,Beijing,100037)

机构地区：[1]华北理工大学,河北唐山063210 [2]中国地质科学院,北京100037

出　　处：《地质论评》2022年第4期1361-1374,共14页Geological Review

基　　金：国家自然科学基金资助项目(编号:42002098);河北省自然科学基金资助项目(编号:2019209531,D2020209017)的成果。

摘　　要：冀东金厂峪金矿被认为与青山口花岗岩体侵入有关,而同样距离矿区较近的腰岭子花岗闪长岩体则研究较少,由于两岩体在岩性、构造背景等方面有很大的相似性,因此有必要探讨两成矿条件和成矿潜力差异的可能原因。本文对腰岭子和青山口岩体中的锆石进行透射光和阴极发光(CL)图像分析、晶体形态学以及统计学分析,结果显示两岩体的形成温度相差不大,分别为650~800℃和650~850℃。较高的岩浆热水含量和富碱环境可能是青山口岩体成矿的必要条件。应用LA-ICP-MS方法对腰岭子花岗闪长岩中的锆石进行U-Pb年代学测试,其结晶年龄为161.5±0.9 Ma,与峪耳崖金矿区内的闪长岩脉年龄相近,且两者在含矿岩体特征方面有很大的相似性,因此认为腰岭子岩体的成金潜力较大。两岩体稀土元素地球化学特征显示轻稀土相对亏损而重稀土相对富集。同时,有明显的Ce正异常和微弱的Eu负异常,结合野外地质观察,认为两岩体可能经历了壳幔混合作用。结合前人对青山口岩体年龄的测试结果及大地构造背景认为两岩体可能为来自同一岩浆房不同阶段侵位的产物。Objectives:The Jinchangyu gold deposit in eastern Hebei Province is considered to be related to the Qingshankou granodiorite intrusive.However,the Yaolingzi granodiorite intrusive is less studied in spite of closing to the mining area.Due to the great similarity between the two intrusives in lithology and tectonic setting,it is necessary to discuss the possible reasons for the difference in metallogenic conditions and metallogenic potential.Methods:Based on detailed field observations of Yaolingzi and Qingshankou intrusives,the methods of transmitted light,cathodoluminescence(CL)image,crystal morphology and statistical analysis were used for granodiorite and monzogranite so as to explain conditions of magmatism.The U-Pb isotopic dating by LA-ICP-MS was conducted for the granodiorite in order to determine the igneous intrusion age.Moreover,rare earth element(REEs)geochemistry of zircons was conducted for granodiorite and monzogranite for discussing magmatism,mineralization and tectonic background in the region.Results:The results show that the formation temperature of the two zircons are 650~800℃and 650~850℃,respectively.The crystallization age of granodiorite from Yaolingzi is 161.5±0.9 Ma.Obvious mafic microgranular enclaves are found in the two intrusives in the field.The REEs geochemical features of the two intrusives show that LREE is relatively depleted while HREE is relatively enriched with obvious positive Ce anomaly and negative Eu anomaly at the same time.Conclusions:Large amount of magmatic water and alkaline-riched environment may be the necessary conditions for the Qingshankou intrusive mineralization.The ore-forming features of granodiorite as well as crystallization age in Yaolingzi area are similar to the diorite in Yuerya gold deposit area.Therefore,we consider that granodiorite intrusive in Yaolingzi have great gold-forming potential.Field geological observations and REEs geochemical analysis indicate that the two intrusions may have experienced crust—mantle mixing.Combined with the result

关 键 词：锆石形态 岩浆演化 锆石U-Pb年龄 成矿潜力 冀东地区 

分 类 号：P618.51[天文地球—矿床学]