吉林大学学报(地球科学版) ›› 2019, Vol. 49 ›› Issue (2): 414-424.doi: 10.13278/j.cnki.jjuese.20170127
伍锡昌, 初凤友, 王巍, 李正刚, 陈灵, 毕冬伟, 王建强
Wu Xichang, Chu Fengyou, Wang Wei, Li Zhenggang, Chen Ling, Bi Dongwei, Wang Jianqiang
摘要: 为了探讨俯冲沉积物与蚀变洋壳组分对弧后盆地岩浆作用的影响,利用独立成分分析从劳盆地、马努斯盆地,以及太平洋与印度洋共634组Sr-Nd-Pb同位素数据中提取了5个独立成分(IC1-IC5)。其中:IC1与87Sr/86Sr、Th/Nb值为负相关关系,表明其能够代表弧下地幔中的俯冲沉积物熔体组分的影响,能够很好地区别弧后盆地与洋中脊;弧后盆地IC5与Ba/Th值为负相关关系,暗示其能够反映弧下地幔中的俯冲蚀变洋壳脱水流体组分的影响;IC5与κ值(1.03Th/U)之间的关系,也说明洋中脊IC5可能与地幔中再循环蚀变洋壳的年龄有关。进而通过对比马努斯和劳盆地岩石中IC1与IC5间的差异,发现马努斯盆地东部裂谷(ER)表现出绝对值更高的IC1负异常以及与劳盆地相似的IC5特征,而马努斯盆地扩张中心与扩张转换带(MSC&ETZ)则表现出类似劳盆地的IC1特征以及更高的IC5正异常特征。两个盆地间的差异表明,ER更多地受到沉积物熔体组分影响,MSC&ETZ更少地受到俯冲洋壳脱水流体组分影响。其中,沉积物熔体组分影响可能与New Britain trench与Tonga trench巨大的沉积物厚度差异有关,而俯冲洋壳脱水流体组分影响可能受到了弧后扩张中心与俯冲带间距离的控制。
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