南太行山平顺辉长岩体锆石SHRIMP U-Pb年龄、地球化学特征及构造意义  

SHRIMP U-Pb dating, geochemistry and tectonic implications of Pingshun gabbros in southern Taihang Mountain

作　　者：杨金昆 张海东[1] 刘建朝[1] 彭素霞[1] 王得权[1] YANG JinKun;ZHANG HaiDong;LIU JianChao;PENG SuXia;WANG DeQuan(Chang＇an University,Xian 710054,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710064

出　　处：《矿床地质》2018年第4期854-867,共14页Mineral Deposits

基　　金：国家自然科学基金(编号:41040020;41073027);中央高校基金(编号:CHD2011ZY005;CHD2011JC168)的联合资助

摘　　要：南太行山平顺辉长岩体主要造岩矿物为斜长石、单斜辉石、普通角闪石和橄榄石等。锆石SHRIMP U-Pb同位素定年结果表明,辉长岩体形成于(123.4±1.7)Ma,为早白垩世华北板块内岩浆活动的产物。平顺辉长岩w(SiO_2)为42.82%~49.74%,w(Al_2O_3)为11.91%~16.54%,w(MgO)为6.79%~14.57%,w(TiO_2)为0.36%~1.53%,w(Fe_2O_3T)为4.02%~15.03%,w(CaO)为7.45%~18.70%,w(K_2O+Na_2O)为2.42%~3.81%,Mg#为56.53~81.68,LREE富集,HREE亏损,略显微弱的正Eu异常,以富集LILE、LREE元素和亏损Nb-Ta等高场强元素为特征。辉长岩^(206)Pb/^(204)Pb为17.062~18.295,^(207)Pb/^(204)Pb为15.354~15.422,^(208)Pb/^(204)Pb为37.185~37.298,ISr为0.7046~0.7051,εNd(125 Ma)为-14.03^-13.00,表明平顺辉长岩起源于EMⅠ富集地幔,并受到少量地壳物质的混染,可能是早白垩世华北克拉通破坏事件在太行山地区的岩浆活动产物。The major petrogenetic minerals in the Pingshun gabbros located in southern Taihang Mountain are plagioclase, clinopyroxene, hornblende and olivine. As the SHRIMP zircon U-Pb dating results show, diagenetic age of gabbros is （123.4±1.7） Ma, which indicates that the gabbros were formed by Early Cretaceous magmatism in the North China craton. The major oxides of the Pingshun gabbros are w（SiO2） 42.82%～49.74%, w（Al2O3） 11.91%～16.54%, w（MgO） 6.79%～14.57%, w（TiO2） 0.36%～1.53%, w（Fe2O3） 4.02%～15.03%, w（CaO） 7.45%～18.70%, w（K2O＋Na2O） 2.42%～3.81% and Mg# 56.53～81.68. LREE are enriched, and HREE are depleted, coupled with no or a weak positive Eu anomalies. Moreover, the rocks are characterized by high abundances of LILE and LREE, and low abundances of HFSE （such as Nb and Ta）. The 206Pb/204Pb ratios of gabbros range from 17.062 to 18.295, 207Pb/204Pb ratios from 15.354 to 15.422, and 208Pb/204Pb ratios from 37.185 to 37.298. ISr=0.7046～0.7051 and εNd（125 Ma）=-14.03～-13.00. These data suggest that Pingshun gabbroic magma originated from the EMⅠ, and was contaminated by minor crustal composition.Hence it might have been formed by early Cretaceous magmatism in Taihang Mountain area resulting from the destruction of the North China Craton.

关 键 词：地球化学 岩浆活动 EMI 平顺辉长岩 南太行山 

分 类 号：P588.124[天文地球—岩石学]