辽东中—新生代玄武岩的橄榄石斑晶和捕虏晶氧同位素组成及其岩石圈地幔演化启示  

Oxygen isotopic composition of olivine phenocryst and xenocryst from Mesozoic-Cenozoic basalts in Liaodong Peninsula and its implications for lithospheric mantle evolution

作　　者：张超[1] 马强[1] 郑建平[1] 洪路兵 庞崇进 王翠翠[4] 毋雅京 朱律运 ZHANG Chao;MA Qiang;ZHENG Jianping;HONG Lubing;PANG Chongjing;WANG Cuicui;WU Yajing;ZHU Luyun(School of Earth Sciences,State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan,Hubei 430074,China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,College of Earth Sciences,Guilin University of Technology,Guilin,Guangxi 541004,China;Guilin University of Technology,Provincial Ministry Collaborative Innovation Centre for Non-ferrous Metal Mineral Exploration and Efficient Resource Utilization,Guilin,Guangxi 541004,China;China Geological Survey Urumqi Natural Resources Integrated Survey Centre,Urumqi,Xinjiang830000,China;Zijin College of Geology and Mining,Fuzhou University,Fuzhou,Fujian 350108,China)

机构地区：[1]中国地质大学(武汉)地球科学学院,地质过程与矿产资源国家重点实验室,湖北武汉430074 [2]桂林理工大学地球科学学院,广西隐伏金属矿产勘查重点实验室,广西桂林541004 [3]桂林理工大学,有色金属矿产勘查与资源高效利用省部共建协同创新中心,广西桂林541004 [4]中国地质调查局乌鲁木齐自然资源综合调查中心,新疆乌鲁木齐830000 [5]福州大学,紫金地质与矿业学院,福建福州350108

出　　处：《地质学报》2022年第12期4211-4223,共13页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41973050,42288201)资助的成果。

摘　　要：华北克拉通东部岩石圈地幔性质在中—新生代时期发生了重大转变,但细节还不清楚。本文对辽东半岛早白垩世(克拉通破坏峰期)小岭组玄武岩和第四纪(克拉通破坏后)宽甸玄武岩中橄榄石斑晶/捕虏晶进行了主量元素和氧同位素组成研究。早白垩世小岭组玄武岩斑晶橄榄石Fo为79~88,CaO>0.1%,具有高Ni/Mg(0.4~1.2)、低Mn/Fe(1.3~1.6)和低Ca/Fe比值(0.2~1.5)的特征,指示岩浆源区是辉石岩和橄榄岩混合的岩石圈地幔;高于正常地幔橄榄石的δ^(18)O(4.77‰~5.96‰,平均值5.4‰)显示低温热液蚀变洋壳熔体/流体组分对地幔源区的影响。第四纪宽甸玄武岩捕虏晶橄榄石Fo值为88~92(平均值90),具有高NiO(0.3%~0.4%)和低CaO(<0.1%)、MnO(0.1%~0.2%)含量,显示主体饱满、与少量过渡型和难熔型并存的地幔组成特征;其δ^(18)O(4.58‰~5.38‰,平均值5.3‰)与正常地幔值接近。结合华北其他地区地幔橄榄石氧同位素数据,发现早白垩世破坏峰期有较多俯冲洋壳来源的熔/流体交代岩石圈地幔,而新生代岩石圈地幔则为破坏后的残余和新增生产物,我们认为古太平洋板块俯冲和后撤—撕裂引起的熔体/流体交代作用对华北克拉通岩石圈地幔的弱化、侵蚀和最终置换起了重要作用。The properties of subcontinental lithospheric mantle beneath the eastern North China Craton changed significantly in the Mesozoic-Cenozoic,but details are sketchy.In this study,we report major element and oxygen isotopic compositions of olivine phenocrysts from early Cretaceous Xiaoling basalts and olivine xenocrysts from Quaternary Kuandian basalts.The olivine phenocrysts from the Xiaoling basalts show relatively low Fo values(79~88),Mn/Fe(1.3~1.6)and Ca/Fe ratios(0.2~1.5),but relatively high CaO(greater than 0.1%)and Ni/Mg values(0.4~1.2),indicating that the Xiaoling basalts were derived from a hybrid source of peridotite and pyroxenite within the lithoshperic mantle.Theirδ18 O(4.77‰~5.96‰,mean 5.4‰)values significantly higher than those of the normal mantle value,further demonstrate the influence of cryogenic hydrothermal alteration oceanic crust melt/fluid components in the mantle source.The olivine xenocrysts from the Kuandian basalts have Fo values ranging from 88to 92,together with high NiO(0.3%~0.4%)and low CaO(<0.1%)and MnO contents(0.1%~0.2%),indicating the coexistence of fertile and refractory lithospheric mantle beneath the eastern North China Craton in the Quaternary.Theirδ^(18)O values(4.58‰~5.38‰,mean 5.3‰)are close to the normal mantle value.Combined with previous olivine oxygen isotope data from different regions in North China Craton,we find that destruction of the North China Craton reached the peak in the Early Cretaceous,accompanied by a large number of crust-derived melts/fluids metasomatized the lithospheric mantle.Whereas the Cenozoic lithospheric mantle is juvenile and residual after destruction.We suggest that the metasomatism caused by the melts/fluids resulting from subduction and retreat-tearing of Paleo-Pacific plate played an important role in the weakening,erosion and final replacement of the lithospheric mantle beneath the North China Craton.

关 键 词：岩石圈地幔 橄榄石 氧同位素 早白垩世—新生代 再循环蚀变洋壳 华北克拉通破坏 

分 类 号：P588.145[天文地球—岩石学] P542.5[天文地球—地质学]