辽东宽甸钴矿勘查区变基性岩地球化学特征和年代学研究  

Whole-rock geochemistry and geochronology of meta-basic rocks from the cobalt exploration area in Kuandian,eastern Liaoning Province

作　　者：廉涛[1] 孙莉[1] 王舫[2] 刘福来[2] 邓文婷[1] LIAN Tao;SUN Li;WANG Fang;LIU Fu-lai;DENG Wen-ting(Liaoning Province Seventh Geological Brigade Co.,Ltd.,Dandong 118003,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]辽宁省第七地质大队有限责任公司,辽宁丹东118003 [2]中国地质科学院地质研究所,北京100037

出　　处：《岩石矿物学杂志》2024年第5期1281-1301,共21页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金项目(92062214);国家重点研发计划(2022YFC2903502);中国地质调查项目(DD20242528);中国地质科学院基本业务费项目(JB2304)。

摘　　要：以辽东宽甸钴矿勘查区南辽河群里尔峪组变基性岩为研究对象,通过全岩地球化学组成和锆石年代学研究,讨论了里尔峪组变基性岩形成的构造背景以及钴的来源。地球化学分析结果显示,钻孔中变基性岩为正斜长角闪岩,具有一致的稀土元素配分模式,弱Eu负异常,显示E-MORB的地球化学特征。详细的矿物化学分析和地质温压计算结果表明,含辉石斜长角闪岩(ZK2-1)记录了峰期高角闪岩相变质温压条件,p=0.82~1.00 GPa和t=712~751℃;(含辉石)斜长角闪岩(ZK1-1和ZK3-1)记录了峰后退变质阶段的温压条件,分别为p=0.42~0.81 GPa和t=688~759℃、p=0.59~0.85 GPa和t=703~739℃。锆石SHRIMP U-Pb定年结果表明,变基性岩中变质锆石记录的年龄为1857~1850 Ma。综合宽甸地区变基性岩地球化学和年代学结果,推测其原岩为古元古代中期拉斑玄武岩,形成于伸展环境,并且在其形成过程中岩浆经历了显著的地壳物质混染,暗示古元古代中期打开的洋盆规模可能有限。通过与南、北辽河群变基性岩全岩地球化学特征对比研究,认为宽甸地区变基性岩不是钴矿化的主要成矿物质来源,有关钴矿化的物质来源仍需进一步研究。In this study,the whole-rock geochemistry and zircon U-Pb ages are reported for the meta-basic rocks of the Li'eryu Formation of the South Liaohe Group from the cobalt exploration area in Kuandian.These data provide a significant insight into the tectonic background,as well as the source of cobalt.Geochemical features of the meta-basic rocks in boreholes show that they are orthorhombic amphibolite,and have similar rare-earth elements(REEs)patterns,with slightly negative Eu anomalies.REEs and trace elements compositions have affinity to those of E-MORB.Based on the mineral compositional analyses and p-t estimates using conventional geothermobarometers,the clinopyroxene-bearing amphibolite(ZK2-1)records p-t conditions of p=0.82~1.00 GPa and t=712~751℃,which probably constrained the peak high amphibolites-facies stage.The metamorphic p-t conditions of(clinopy-roxene-bearing)amphibolite(ZK1-1 and ZK3-1)are p=0.42~0.81 GPa,t=688~759℃and p=0.59~0.85 GPa,t=703~739℃,respectively,which represent the conditions of the retrograde stage.The metamorphic zircon from the meta-basic rocks yield the SHRIMP U-Pb ages of 1857~1850 Ma.The integrated study of geochemistry and zircon U-Pb dating reveals that their protoliths of the meta-basic rocks are mid-Paleoproterozoic tholeiitic basalt and formed in an extended tectonic environment.Their protoliths underwent significant crustal assimilation imply that the scale of the mid-Paleoproterozoic oceanic basin may be limited.By comparing the geochemical characteristics of meta-basic rocks in the North and South Liaohe groups,it is believed that meta-basic rocks in the Kuandian area are not the main source of cobalt mineralization.The material sources of cobalt mineralization still needs further research.

关 键 词：变基性岩 宽甸 里尔峪组 古元古代 变质事件 钴矿化 

分 类 号：P588.3[天文地球—岩石学]