摘要
沂沭断裂带内发育了大量的中生代火山岩,其成因研究对剖析断裂带活动规律具有重要意义。本文对断裂带北段潍坊、安丘、鄌郚地区中生代火山岩进行了详细的岩石学、锆石U-Pb年代学和主量元素、微量元素、Sr-Nd-Pb同位素分析。探讨了沂沭断裂带中生代火山岩成因及其形成的地球动力学过程。断裂带北段火山岩年龄集中在131~124Ma之间,喷发于早白垩世。岩石为一套高钾钙碱性火山岩,包括玄武安山岩、粗安岩、粗面岩、英安岩。火山岩富集Rb、Ba等大离子亲石元素,相对亏损Nb、Ta、Ti等高场强元素。稀土元素含量高(∑REE=140.5×10-6~433.1×10-6),富集轻稀土、亏损重稀土(∑LREE/∑HREE=9.8~31.0),无明显的Eu负异常。火山岩具有富集且变化范围较大的Sr-Nd-Pb同位素组成,(87Sr/86Sr)2i=0.708054~0.711692,εNd(t)值为-15.3^-7.4,(06Pb/204Pb)07i=17.213~17.962,(2Pb/204Pb)i=15.425~15.590,(208Pb/204Pb)i=37.597~38.365。研究表明,高钾钙碱性火山岩的源区与区域基性岩源区一致,均为富集岩石圈地幔。玄武安山岩、粗安岩、粗面岩经基性岩浆分离结晶作用形成,英安岩则遭受了华北下地壳强烈混染。三叠纪末期,由于扬子板块向华北克拉通俯冲,扬子地壳析出的流体/熔体交代了华北古老岩石圈地幔,形成富集岩石圈地幔。早白垩世,受古太平洋板块俯冲和后撤作用,富集岩石圈地幔部分熔融形成基性岩浆,岩浆在上升过程中发生分离结晶作用,受沂沭断裂深切作用影响,部分地区遭受华北下地壳混染,最终形成区内各类高钾钙碱性火山岩。
A large number of the Mesozoic volcanic rocks developed in the Yishu fault,whose origin are of great significance to analyze the activities of the fault. In this paper,the petrology,zircon U-Pb geochronology,major elements,trace elements and Sr-NdPb isotopes of the volcanic rocks in Weifang,Anqiu and Tangwu areas are studied,aimed to investigate the genesis and geodynamics of these volcanic rocks. Zircon U-Pb dating results of the volcanic rocks yield U-Pb ages concentrating at 131 ~ 124 Ma,indicating their eruption during the Early Cretaceous. The volcanic rocks are high-K calc-alkaline( HKCA) series,including basaltic andesite,trachyandensite,trachyte and dacite. They are enriched with large ion lithophilic elements such as Rb and Ba and relatively depleted in high field strengths such as Nb,Ta and Ti. The content of rare earth elements is high( ∑REE = 140. 5 × 10-6~ 433. 1 × 10-6),enrichment of light rare earth elements and depleted heavy rare earth elements( ∑LREE/∑HREE = 9. 8 ~ 31. 0),without obvious Eu negative anomaly. The volcanic rocks have rich and highly variable Sr-Nd-Pb isotopes,(87 Sr/86 Sr)i= 0. 708054 ~ 0. 711692,εNd( t)=-15. 3 ^-7. 4,(206 Pb/204 Pb)i= 17. 213 ~ 17. 962,(207 Pb/204 Pb)i= 15. 425 ~ 15. 590,(208 Pb/204 Pb)i= 37. 597 ~ 38. 365. It can be concluded that the HKCA volcanic rocks have the same magma source with the basic rocks in the Yishu fault. Both of them were derived from enriched lithosphere mantle. Basaltic andesite,trachyandensite and trachyte were formed by crystallization of basic magma. Dacite were suffered from strong contamination of the lower crust of North China Craton. Triassic,the ancient lithospheric mantle was subjected metasomatsim to form enriched lithosphere mantle by the fluid or melt from subducting Yangtze continental crust.Up to the Early Cretaceous,due to the subduction and rollback of the ancient Pacific plate towards Eurasian continent,the basic magma was generated by the partial melting of the enriched lithospheric mantle. HKCA volcanic rocks were f
作者
孟凡超
瞿志敬
崔岩
陈勇
张尚坤
周瑶琪
吴智平
刘嘉麒
MENG FanChao;QU ZhiJing;CUI Yan;CHEN Yong;ZHANG ShangKun;ZHOU YaoQi;WU ZhiPing;LIU JiaQi(School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;Dongxin Oil Production Plant,Shengli Oilfield Company,SINOPEC,Dongying 257000,China;Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology,Qingdao 266590,China;Shandong Institute of Geological Sciences,Ji'Nan 250013,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第11期3265-3286,共22页
Acta Petrologica Sinica
基金
山东省重大科技创新工程项目(2017CXGC1602、2017CXGC1608)
中国石油西南油气田(高校)盆地研究中心项目(XNS勘研院JS2020-059)
国家自然科学基金项目(42072169)联合资助。
