摘要
本文研究的科马提岩位于大兴安岭北段吉峰地区。地质 地球化学研究表明 ,科马提岩系列由超镁铁质科马提岩、玄武质科马提岩、拉斑玄武岩和辉长岩等组成 ,稀土配分型式为球粒陨石型。 8件科马提岩、辉长岩和拉斑玄武岩样品的Sm Nd同位素数据构成一条相关性较好的等时线 ,其Nd模式年龄多数为 15 89～ 1799Ma ,等时线年龄为 (172 7± 74 .7)Ma ,INd=0 .5 10 72 5± 0 .0 0 0 0 798,εNd(t) =6 .94± 1.5 6 ,表明该区科马提岩形成于中元古代早期 ,来源于亏损地幔源区。
The Jifeng komatiites are situated in the north Da Hinggan Ling. Their geological and geochemical feature indicate that the komatiite series consists of the ultramafic komatiite,basaltic komatiite,tholeiite and gabbro.The REE patterns of the komatiite is similar to chondrite.The eight samples composed of komatiite,tholeiite and gabbro yield a reasonable good isochron age of ( 1727± 74.7)Ma(2 σ ) with I Nd =0.510725±0.0000798, ε Nd ( t )=6.94±1.56.Their Nd model ages mainly range from 1 589 Ma to 1 799 Ma.Such a case shows the Jifeng komatiites derived from the depleted theosphere mantle in the early Middle Proterozoic. This crustal accretion event would be associated with the Songnen Massif splitting from the southorn continental margin of the Xibailiya Massif.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2003年第5期405-408,共4页
Acta Geoscientica Sinica
基金
地质调查项目"六十林场幅和阿里河幅 1:2 0万填图"资助
