摘要
湘东北中生代发育以辉绿岩类和煌斑岩类为代表的基性岩脉,属陆内拉斑玄武岩系,部分煌斑岩属于碱性系列。岩石富集LREE,δEu负异常不明显,其形成主要受软流圈地幔部分熔融作用制约。煌斑岩类微量元素总体上具有洋岛玄武岩(OIB)岩浆源区特征,富集Nd、P、Cs而K、Rb、Sr、U、Th等富集程度不明显,Ta、Nb略有富集。辉绿岩类表现出Ta、Nb、Ti亏损,但LILE并不富集,反映地壳混染程度的增强。基性岩脉形成于陆内拉张带的构造环境,岩浆活动未受到中生代大洋板块俯冲的影响。基性岩脉在时、空及物质组成上与湘东南玄武质岩石基本一致,属于整个湘东南岩石圈拉张-减薄带的一部分。
Mesozoic mafic dikes developed in No rtheastern Hunan Province were repr esented by the diabases and lamprophyres.Most of them belon g to tholeiite series,a part of lamprophyres belong to alkali basalt series.The petrological and geochemical characteristics show the natu re of tholeiite series within contin ental plate.The chondrite-normalized REE patterns are characterized by LREE enrichment.The negative Eu anomalies are not observed.The corr elation analysis of La /Sm -La shows t hat the mafic dikes were con-trolled by partial melting.The lamp rophyres are rich in LILE,Nd ,P,Cs ,but K,Rb,Sr ,U,Th and Ta,Nb are not enriched very obviously.The HFSE:Tb,Y,Yb and Lu are depleted,which have the general characteristics of OIB.The diabases show Ta,Nb and Ti depletion,but LILE are not enriched,so that Ta and Nb depletion expresses the continental matters h ydridization.The mafic dikes occur red in the tectonic setting of a intra-continental extension belt.The mag matic activity had been not influenced by the Mesozoic subducting oceanic plate.The mafic dikes corre sponded with the basaltic rocks at Southeastern Hunan Province in space and time as well as lithogeochemistry.It was the northeastern part of the lithospheric exten-sion-thinning belt of the whole Sout heastern Hunan Province and they should have a same magma source.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2002年第2期179-184,共6页
Geotectonica et Metallogenia
基金
中国科学院知识创新工程项目(KZCX2-102
KZCX2-209)
中国科学院边缘海与古环境开放实验室基金项目(BYH01A02)
中国科学院矿床地球化学开放研究实验室基金项目(2000)共同资助.
关键词
湖东北
中生代
基性岩脉
岩石地球化学
构造意义
Mafic dike
petrological geochemistry
intracontinental extension belt
northeastern Hunan Province
