北大别山上天梯珍珠岩地球化学特征、锆石U-Pb同位素年代学及地质意义  

EOCHEMICAL CHARACTERISTICS,ZIRCON U-Pb ISOTOPIC CHRONOLOGY AND GEOLOGICAL SIGNIFICANCE OF PERLITE IN SHANGTIANTI AREA,NORTHERN DABIE MOUNTAINS

作　　者：骆亚南[1] 王季伟[1] 许栋 余少华 史亮[1] 段留安 LUO Yanan;WANG Jiwei;XU Dong;YU Shaohua;SHI Liang;DUAN Liuan(NO.3 Institute of Geological and Mineral Resources Survey,Henan Geological Bureau,Xinyang,Henan 464000,China;Yantai Coastal Zone Geological Survey Center of China Geological Survey,Yantai,Shandong 264000,China)

机构地区：[1]河南省地质矿产勘查开发局第三地质矿产调查院,河南信阳464000 [2]中国地质调查局烟台海岸带地质调查中心,山东烟台264000

出　　处：《矿物岩石》2023年第2期39-49,共11页Mineralogy and Petrology

基　　金：国家重点研发计划“中东部地区金和铜矿床三维探测技术与增储示范”项目(编号:2022YFC2903605);河南省地质科研“大别山铜钼金银铅锌成矿系统与成矿预测研究”项目(编号:豫国土资函[2015]258号11)。

摘　　要：北大别山火山岩由于缺少精确的年代学资料和系统研究,其岩石成因背景和成岩成矿时代尚不清楚。通过对北大别山西段上天梯珍珠岩锆石U-Pb同位素定年和岩石主量、微量元素测试分析,表明上天梯酸性火山岩具有高硅(w(SiO_(2))介于71.82%~73.18%)、富碱(w(K_(2)O+Na_(2)O)介于7.97%~8.96%)、富钾贫钠(K_(2)O/Na_(2)O介于1.13~1.87)、弱过铝(A/NCK为1.00~1.15)等特点,属高钾钙碱性火山岩系列。岩石轻稀土强烈分馏、重稀土弱分馏,负Eu异常不明显(δ_(Eu)=0.81~1.16),稀土分布曲线呈左高右平向右倾斜的模式。利用LA-ICP-MS锆石U-Pb同位素定年测得上天梯成矿岩石珍珠岩加权平均年龄为145±1 Ma(n=18,MSWD=0.91),代表了火山岩的喷发年限和上天梯珍珠岩矿床形成年龄。研究认为,上天梯珍珠岩成因类型为Ⅰ型火山岩相在加厚下地壳物质熔融的产物。北大别山西段陈棚组火山岩具有多期次喷发活动,喷发时限在145~130 Ma之间,为早白垩世西太平洋板片持续俯冲,造成大别山区地壳加厚,下地壳部分物质熔融的后碰撞构造环境。Methods of geochronology and geochemistry are used to study the zircon U-Pb isotopic dating and the main and trace elements of perlite in the Shangtianti area of the western section of the Northern Dabie Mountains,for the purpose of solving the problem of unclear petrogenetic background and diagenetic and metallogenic age of the volcanic rocks.Analysis of zircon U-Pb isotope dating and rock main and trace element testing on perlite in Sahngtianti area at the western section of the Northern Dabie Mountains indicates that the Shangtianti acidic volcanic rocks are characterized by high silica(w(SiO_(2))=71.82%—73.18%),rich alkali(w(K_(2)O+Na_(2)O)=7.97%—8.96%),rich potassium and low sodium(K_(2)O/Na_(2)O=1.13—1.87),weak peraluminum(A/NCK=1.00—1.15),etc.,showing that the rock belongs to high potassium calc-alkaline volcanic rock series.The negative Eu anomaly is not obvious(δ_(Eu)=0.81—1.16),and the distribution curve of rare earth elements is high on the left,flat on the right and inclined to the right,with strong fractionation of light rare earths and weak fractionation of heavy rare earths in rocks.LA-ICP-MS zircon U-Pb isotopic dating shows that the weighted mean age of Shangtianti perlite rocks is 145±1 Ma(n=18,MSWD=0.91),which represents the eruption age of volcanic rocks and the formation age of Shangtianti perlite deposit.The genetic type of Shangtianti perlite is type I volcanic facies,which are resulted from the melting under the condition of crustal thickening.The volcanic rocks of the Chenpeng Formation in the western part of the Northern Dabie Mountains have experienced multiple periods of eruption activity,and the eruption time is between 145 and 130 Ma,which has resulted in a tectonic environment for the continuous subduction of western Pacific Plate at Early Cretaceous which led to the crust thickening in the Dabie Mountains and the post-collision of partially melted material from the lower crust.

关 键 词：珍珠岩 锆石U-PB年龄 地球化学 北大别山西段 上天梯 

分 类 号：P579[天文地球—矿物学]