摘要
内蒙古中部发育的三条蛇绿岩带是华北板块和西伯利亚板块之间的缝合带。本文系统研究了其中的温都尔庙和巴彦敖包-交其尔两个蛇绿岩带中变质玄武岩的元素和 Sr、Nd、Pb 同位素地球化学。苏右旗温都尔庙碱性玄武岩为轻稀土富集型;岩石具有板内和大陆裂谷区玄武岩的特征,可能代表了600Ma 左右,温都尔庙地区开始发育的新洋盆。采自苏左旗的巴彦敖包-交其尔玄武岩分为两类,一类呈现轻稀土富集型,呈洋岛玄武岩特征;另一类具有明显的 Nb、Ta 负异常,显示大洋岛弧玄武岩特征,洋岛玄武岩的存在表明古亚洲洋曾经发育洋盆,大洋岛弧玄武岩的存在表明古亚洲洋内部有大洋岩石圈之间的俯冲。将本文的古亚洲洋洋岛玄武岩与中国西南地区的特提斯洋岛玄武岩进行系统的元素和同位素地球化学特征对比表明,古亚洲洋的洋岛玄武岩显示高 U/Pb(HU)和北大西洋和太平洋省的特征,而特提斯洋岛玄武岩属于印度洋省。这些说明古亚洲洋地幔域与特提斯地幔域是两个独立的构造域,它们代表了长期演化的两个不同的地幔地球化学域。
There are three ophiolites sited in central Inner Mongolia, representing the sutures between North China craton and Siberia plate. Elemental and Sr-Nd-Pb isotopic geochemistry of the meta-basaltic rocks in Wenduermian and Bayanaobao-Jiaoqier ophiolites were studied in this paper. The Wenduermiao alkli meta-basaltic rocks are enriched in light REE, showing the futures of within-ocean and intercongtinental rift basalt. This indicates possibly the early stage opening of a new ocean around 600Ma ago during the long-term evolution of Paleo-Asian Ocean. The Bayanaobao-Jiaoqier rocks collected from Suzuoqi are divided into two groups, the first group show ocean island basalt （OIB） features, with the light REE enrichment; the second have ocean island arc basalt （OIA） signature, displaying negative anomalies of Nb and Ta. These OIB and OIA basalts occurred in Bayanaobao-Jiaoqier ophiolite suggest the existence oceanic subduction related process within the Paleo-Asian Ocean around 400Ma ago. Systemic comparisons of elemental and isotopic geochemistry were made between the OIB in this study and that from the Tethyan Ocean in southwestern China. The results indicate that they have different features, the OIB in Paleo-Asian Ocean have the high U/Pb （HU） and north Atlantic and Pacific Ocean MORB province features, while the Tethys have the Indian Ocean MORB province feature. These results suggest that the mantle domains of Paleo-Asian Ocean and Tethys are two independent systems, each with different isotopic geochemical features.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第12期2889-2900,共12页
Acta Petrologica Sinica
基金
国家自然科学基金重点项目(No.40234052)
高等学校学科创新引智计划(E07011)
内蒙古国土资源厅[2005]院士6-20项目
中国科学院广州地化所同位素开放实验室基金
中国国家留学基金资助.
关键词
内蒙古
古亚洲洋
地幔域
洋岛玄武岩
岛弧
地球化学
Inner Mongolia, Paleo-Asian Ocean, Mantle domain, Ocean island basalt, Island arc, Geochemistry
