滇中禄丰地区中元古代早期球颗玄武岩的锆石U-Pb年龄、地球化学特征及其大地构造意义  

The zircon U-Pb age,geochemical characteristics and tectonic significance of the spherical basalt in the early Mesoproterozoic in Lufeng area central Yunnan

作　　者：刘军平 孙柏东 王晓峰 刘伟[3] 马进华 关学卿 宋冬虎 吕勃烨 LIU Junping;SUN Baidong;WANG Xiaofeng;LIU Wei;MA Jinhua;GUAN Xueqing;SONG Donghu;LV Boye(Yunnan Institute of Geological Survey,Kunming,650216;MLR Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Kunming,650051;Chengdu Center,China Geological Survey,Chengdu,610081)

机构地区：[1]云南省地质调查院,昆明650216 [2]国土资源部三江成矿作用及资源勘查利用重点实验室,昆明650051 [3]中国地质调查局成都地质调查中心,成都610081

出　　处：《地质论评》2020年第1期35-51,共17页Geological Review

基　　金：云南省1:5 万撒马基幅、因民幅、贵城幅、舒姑幅区域地质调查(编号:D201905);云南1:5万二街、易门县、鸣矣河、上浦贝幅区域地质调查(编号:DD20160017);云南区域地质调查片区总结与服务产品开发项目(编号:121201102000150012-02)的成果~~

摘　　要：在1∶5万区域地质调查的基础上,在禄丰地区东川群黑山组新发现了球颗玄武岩及凝灰岩夹层。采用LA-ICP-MS技术测得球颗玄武岩和凝灰质板岩中锆石U-Pb加权平均年龄分别为1678±10 Ma和1572±19 Ma,表明黑山组沉积时代为中元古代早期;其中球颗玄武岩SiO2含量介于40.83%~52.56%,δEu正异常,大离子亲石元素Rb、Ba和高场强元素Nb、Ta、Th等强不相容元素相对富集,全岩地球化学显示为大陆板内低钛拉斑海相玄武岩,形成于伸展的构造环境,可能为Columbia超大陆裂解的产物。本次的发现,为准确地标定东川群时代、层序及大地构造属性提供新的参考依据,也为重塑整个滇中前寒武纪地层格架提供时代约束。Objectives: Based on the 1 ∶ 50000 regional geological survey,the authors have newly found intercalation of nodular basalts and tuff in Heishan formation of Dongchuan group in Lufeng area. In this study,the isotopic age of the newly found nodular basalts and tuff was determination for the first time in this area.Results: The weighted mean ages of zircon U-Pb in Spherical basalt and tuff were measured by LA-ICPMS technique to be 1678±10 Ma and 1572±19 Ma respectively. The SiO2 content of the Spherical basalt is between 40.83 and 52.56%,δEu has a positive anomaly,large ion lithophile elements Rb,Ba and high field strength elements Nb,Ta,Th and other incompatible elements are relatively enriched. The whole rock geochemistry is shown as lowtitanium-spotted marine basalt in the continental plate,formed in an extended structural environment.Conclusions: Our results indicate that Heishan Formation was deposited in early Middle Proterozoic,probably because of the splitting of the Columbia supercontinent. This study may provide a new evidence of the sedimentary age,sequence and tectonic setting of Dongchuan group,and provides an chronological constraint for the entire Precambrian stratigraphic framework in the central of Yunnan.

关 键 词：球颗玄武岩 凝灰岩 锆石U-PB测年 滇中 中元古代 Columbia超大陆 

分 类 号：P597.3[天文地球—地球化学] P588.14[天文地球—地质学] P548