【摘要】 山东邹平雪山二长岩岩体位于华北克拉通东南部邹平火山岩盆地内.本文通过对雪山二长岩年代学、岩石地球化学、同位素地球化学的研究,探讨邹平地区早白垩世岩浆作用.LA-ICP-MS锆石U-Pb加权平均年龄为(128.5±1.2)Ma,属于燕山晚期岩浆活动产物.二长岩具有富碱(K2O+Na2O=9.92~10.35 wt.%)、富镁(Mg#=42.89~51.22),准铝质(ACNK=0.78~0.82)和钾玄质;轻稀土富集、重稀土亏损[(La/Yb)N=5.19~7.19],无明显Eu异常(δEu=0.82~0.99);大离子亲石元素元素(Rb,Ba等)富集,高场强元素(Nb、Ta、Ti等)亏损等特征.二长岩具有较低的(87Sr/86Sr)i比值(0.705188~0.705661),εNd(t)值(-14.79~-13.46)和老的两阶段Nd模式年龄TDM2(2.02~2.12Ga).早白垩世俯冲的太平洋板片后撤拉张,软流圈上涌加热鲁西EM1型富集岩石圈地幔,岩石圈地幔部分熔融产生的玄武质岩浆,经橄榄石、辉石结晶分异形成了雪山二长岩.更多还原

【Abstract】 A combined study of petrochemistry,Sr-Nd isotopes and zircon U-Pb ages of the late Mesozoic Xueshan monzonite in the Zouping volcanic basin,Shangdong Province,North China Craton(NCC),was carried out.The zircon U-Pb dating results reveal that the Xueshan monzonite was emplaced in Early Cretaceous((128.5±1.2)Ma).The Xueshan monzonite is alkaline(K2O+Na2O=9.92~10.35 wt.%),magnesium-rich(Mg#=42.89~51.22),metaluminous(ACNK=0.78~0.82)and shoshonitic in composition,and enriched in large ion lithophile elements(e.g.,Rb and Ba)and light rare earth elements((La/Yb)N =5.19~7.19),depleted in high field strength elements(e.g.,Nb,Ta,and Ti)and heavy rare earth elements,and have no Eu anomalies(δEu=0.82~0.99).Relatively low(87Sr/86Sr)iratios(0.705188~0.705661)andεNd(t)values(-14.79~-13.46)indicate that the monzonitic magma was likely to be derived from partial melting of the Luxi EM1-type enriched lithospheric mantle and underwent frac-tional crystallization of olivine and pyroxene.The tectonic triggered the late Mesozoic large scale magmatism in eastern NCC,might be accompanied with the roll-back of the subducted paleo-Pacific plate.更多还原