摘要
河北承德的大庙斜长岩杂岩体是我国著名的岩体型斜长岩杂岩体,其苏长岩可分为两种类型,即早期苏长岩和晚期辉长—苏长岩。早期苏长岩已发生钠长绿帘角闪岩相变质;晚期辉长—苏长岩变质程度较弱,含有斜长石、斜方辉石和单斜辉石巨晶,主要呈岩墙、岩脉或小岩体侵入于斜长岩杂岩体中,与铁磷矿紧密相关。研究表明:晚期辉长—苏长岩主要由中性斜长石、反条纹长石、单斜辉石、斜方辉石、黑云母、磷灰石、钛磁铁矿和磁铁矿等组成,依矿物含量、成分和结构的差异可分为淡色辉长岩、单斜辉石苏长岩、斜方辉石辉长岩以及含铁磷矿对应岩石。其Ba、Sr和轻稀土富集、Eu弱负异常或无异常特征,表明晚期辉长—苏长岩岩浆不是形成斜长岩的基性岩浆,而是经斜长石分离结晶后的残余岩浆。Sr-Nd-Pb同位素地球化学特征显示晚期辉长—苏长岩可能源自EMI富集的岩石圈地幔,与岩体型斜长岩不存在同源岩浆分离结晶演化的关系。大庙地区晚期辉长—苏长岩的岩浆来源、演化和构造控制的特征对深化研究岩体型斜长岩杂岩体的成因有重要意义。
Damiao anorthosite complex is a typical massif-type anorthosite body in China, and its gabbo-norites can be divided into two types, early-staged norite and late-staged gabbro-norite. The early-staged norites have been transformed by albite-epidote-amphibolite facies metamorphism. The late-staged gabbro-norites with weak metamorphism intrude into the anorthosite and its surrounding rocks in dikes, sills or small intrusive bodies and have the close relationship with Fe-P ore deposits.The research shows that the late-staged gabbro-norites are composed of plagioclase, clinopyroxene,orthopyroxene, biotite, apatite, V-Ti-magnetite and magnetite, and can be divided into leuco-gabbro,Cpx-norite, Opx-gabbro and Fe-P ore-bearing gabbro-norite according to the difference of mineral content, composition and texture. The late-staged gabbro-norites have Ba, Sr and LREE enrichment,weakly negative or no Eu abnormality, which indicates that the late-staged noritic magma is not the evolving residue of anothosite-forming basic magma by the plagioclase fractionation. The Sr-Nd-Pb isotope geochemical characteristics show that the late-staged gabbro-norites may be derived from the EMI enriched lithospheric mantle, and have no relationship of comagmatic fractionation with the massif-type anorthosite. The magma source, evolution and structural control of the late-staged gabbro-norites in Damiao area is of great significance for deepening the genesis of the massif-type anorthosite complex.
作者
路智
刘永顺
聂保锋
王仁民
Lu Zhi;Liu Yongshun;Nie Baofeng;Wang Renmin(College of Resource,Environment and Tourism,Capital Normal University,Beijing 100048;School of Earth and Space Sciences,Peking University,Beijiing 100871)
出处
《地质科学》
CAS
CSCD
北大核心
2022年第1期243-261,共19页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金项目(编号:41641017)资助。
