邹平雪山二长岩年代学和Sr-Nd同位素研究及成因探讨  

Geochronology,Sr-Nd isotope and genesis of the Xueshan monzonite,Zouping County,Shandong Province

作　　者：王浩[1] 徐兆文[1] 李海勇[1] 赵增霞[1] 陆建军[1] 

机构地区：[1]内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210023

出　　处：《南京大学学报（自然科学版）》2015年第1期73-86,共14页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(41173050);教育部博士学科点专项基金(20110091110043)

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.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.

关 键 词：二长岩 岩石化学 SR-ND同位素 山东邹平 华北克拉通 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]