山东汞丹山地区新太古代变基性岩地球化学特征及其构造意义  

Geochemical characteristics and tectonic significance of Neoarchean meta-mafic rocks in Gongdanshan area,Shandong Province

作　　者：季志刚 宋宗超 宋志刚 JI Zhigang;SONG Zongchao;SONG Zhigang(College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Qingdao Geological Exploration Institute of China Metallurgical Geology Bureau,Qingdao 266109,China;The Second Prospecting Team of Shandong Coal Geology Bureau,Jining 272007,China)

机构地区：[1]山东科技大学地球科学与工程学院,山东青岛266590 [2]中国冶金地质总局青岛地质勘查院,山东青岛266109 [3]山东省煤田地质局第二勘探队,山东济宁272007

出　　处：《山东科技大学学报（自然科学版）》2023年第3期14-25,共12页Journal of Shandong University of Science and Technology(Natural Science)

基　　金：山东省自然科学基金项目(ZR2019PD001)。

摘　　要：为探讨华北克拉通鲁西地区前板块构造与板块构造体制转换时间问题,利用LA-ICP-MS锆石U-Pb测年和全岩主微量元素特征对山东沂水地区汞丹山一带的新太古代变基性岩进行了年代学和地球化学分析。汞丹山变基性岩为斜长角闪岩,具有较强的面理化特征,主要由角闪石和斜长石组成,其原岩(玄武岩/安山岩)的结晶年龄为2626±28 Ma,可划分为拉斑系列和钙碱性系列,拉斑系列的岩浆源区可能为亏损地幔,且形成过程中有俯冲流体/熔体的参与,而钙碱性系列与太古宙硅质高镁玄武岩具有相似的地球化学特征,是俯冲板片流体或含水熔体交代的地幔楔在相对较浅的条件下发生较高程度部分熔融的产物。汞丹山变基性岩以及华北克拉通已识别出的一系列新太古代晚期玄武质-安山质岩浆岩均存在明显的Nb、Ta、P、Ti亏损,与岛弧玄武岩的特征一致,表明华北克拉通在新太古代晚期经历了大规模的俯冲作用。To discuss the conversion time of pre-plate tectonic and plate tectonic systems of Western Shandong Province in the North China Craton,we present chronological and geochemical studies of Neoarchean meta-mafic rocks in the Gongdanshan area of Yishui Country,Shandong Province,by using the methods of LA-ICP-MS zircon U-Pb dating and whole-rock major and trace elemental analysis.The Gongdanshan meta-mafic rocks are amphibolites mainly composed of hornblende and plagioclase with obvious characteristics of foliation.The protolith for the Gongdanshan meta-mafic rocks(basalt/andesite),with a crystallization age of 2626±28 Ma,can be divided into tholeiitic series and calc-alkiline series.The magmatic source of tholeiitic samples is probably a depleted mantle and subduction-related fluids/melts may have been involved in the generation of the tholeiitic rocks.The calc-alkiline samples have similar geochemical characteristics with Archean siliceous high magnesium basalt.The magmas that formed the calc-alkiline samples were generated by a relatively higher degree of partial melting of a mantle wedge that was previously metasomatized by slab-derived fluids or melts at a relatively lower level.The Gongdanshan meta-mafic rocks,as well as other identified Late Neoarchean basaltic-andesitic magmatic rocks in the North China Craton,show obvious depletion of Nb,Ta,P,and Ti,which is consistent with those island arc basalt,implying that large-scale oceanic subduction would take place in the NCC during the Late Neoarchean.

关 键 词：华北克拉通 鲁西地区 柳杭岩组 太古宙 构造演化 

分 类 号：P581[天文地球—岩石学]