摘要
对准噶尔盆地西北部克夏基性火山岩进行了系统的矿物学、岩石化学、微量元素、稀土元素和同位素地球化学研究。结果显示,克夏基性火山岩为亚碱性拉斑玄武岩系列,以低Ti、贫REE、LREE弱富集及LILE相对HFSE明显富集为特征,与岛弧拉斑玄武岩地球化学特征一致。克夏基性火山岩正的εNd(t)(+7.2^+7.4)和较低的(87Sr/86Sr)i(0.703717~0.704520)、明显较低的HFSE/LILE以及比大洋玄武岩和OIB陡的206Pb/204Pb-207Pb/204Pb相关线斜率,说明其是古洋盆闭合初期由俯冲洋壳之上亏损的岩石圈地幔楔较高程度部分熔融的结果,它形成于洋内弧环境。克夏基性火山岩与西准噶尔洋盆洋壳的俯冲消减有直接的成因联系,说明西准噶尔弧盆系向东延伸至盆地内部,盆地西部基底为洋陆俯冲形成的岛弧型增生地体。
Basic volcanic rocks from Ke-Xia region of northwestern Junggar Basin were investigated systematically in such aspects as petrology, mineralogy, trace elements and Nd-Sr-Pb isotope geochemistry. Ke-Xia basic volcanic rocks belong to tholeiitic series and are characterized by low abundance of Ti, poor REE, slight enrichment of LREE, and significant enrichment of LILE relative to HFSE in the spider diagram, consistent with features of island arc tholeiitic melts. Ke-Xia basic volcanic rocks have positive εNd（ t ）（ ＋ 7.2- ＋ 7.4）, low values of （87^Sr/86^Sr）i（0. 703 717-0. 704 520） and HFSE/LILE, and steeper 206^pb/204^pb- 207^pb/204^pb correlation gradient than that of MORB and OIB. These data show that Ke-Xia basic volcanic rocks might have been generated from the high-degree partial melting of depleted lithosphere mantle wedge above the subducted oceanic plate in the oceanic island arc, genetically related to the subduction of oceanic crust of western Junggar. It is thus considered that the western Junggar arc-basin system extends eastward into the Jungaer Basin, and that the basement crust in northwestern Junggar Basin is a island arc type accreted block formed by ocean-continent collision.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2006年第3期165-174,共10页
Acta Petrologica et Mineralogica
基金
新疆石油管理局基础研究项目(49873009)
