摘要
对汉诺坝地区的12个辉石岩和1个麻粒岩包体进行了Nd、Sr、Pb同位素测定,发现辉石岩组成有很大变化,143Nd/144Nd比值为0.51160—0.51314,87Sr/86Sr比值为0.7029—0.7086,206Pb/204Pb比值为15.942—18.683,207Pb/204Pb比值为15.264—15.569,208Pb/204Pb比值为36.213—38.744,显示了其复杂成因q推测具有高Sr、低Nd和低Pb同位素组成的辉石岩是地幔早期富集的产物,与麻粒岩、辉长岩包体有类似成因;具有弱至中等亏损的Nd。
Nd,Sr and Pb isotopic compositions of 12 pyroxenitic and 1 granulitic xenoliths in basalts from Hannuoba area,China were determined.The results show that they have wide variattions in composition( 143 Nd/ 144 Nd=0.51160—0.51314; 87 Sr/ 86 Sr=0.7029—0.70 86 ; 206 Pb/ 204 Pb=15.942—18.683; 207 Pb/ 204 Pb=15.264—15.569; 208 Pb/ 204 Pb=36.213—38.744)implying their sophisticated origin.It is postulated that pyroxenitic xenoliths which have high 87 Sr/ 86 Sr,low 143 Nd/ 144 Ndandlow 206 Pb/ 204 Pb ratios are products of mantle enrichment events at very early time probably in Archean or Proterozoic,and they have petrogenesis similar to gabbroic and granulite xenoliths.Pyroxenites with BSE or moderate depleted Nd and Sr and high radiogenic Pb isotopes are metasomatic or enriched products of evolved depleted mantle in recent time not very long before eruption.Most pyroxenites are probably located at shallower level in the lithospheric mantle compared to the lherzolites.
出处
《地球化学》
CAS
CSCD
北大核心
1997年第1期1-12,共12页
Geochimica
基金
国家自然科学基金
关键词
玄武岩
辉石岩
包裹体
钕
锶
同位素
pyroxenite xenoliths,Nd,Sr and Pb isotopes,mantle source,Hannuoba