马里亚纳海槽热液活动区玄武岩的岩石地球化学特征  

The Preliminary Study of Petrological Geochemistry of Basalts from Hydrothermal Activity Regions, Mariana Trough

作　　者：田丽艳[1] 赵广涛[1] 陈佐林[1] 王元领[1] 吴世迎[2] 

机构地区：[1]中国海洋大学海洋地球科学学院,青岛266003 [2]国家海洋局第一海洋研究所,青岛266061

出　　处：《青岛海洋大学学报（自然科学版）》2003年第3期405-412,共8页Journal of Ocean University of Qingdao

基　　金：国家自然科学基金 (4 990 3 0 0 3 ) ;国家重点基础研究发展规划项目(G2 0 0 0 0 785 0 3 )资助

摘　　要：对拖网采自马里亚纳海槽热液活动区 (18°N附近 )的 8个玄武质岩石样品进行岩石地球化学初步研究。岩石富集 L IL E和 L REE,稀土分布型式呈右倾图式 ,L a N=10 .6 8～ 2 2 .6 4 ,(L a/Yb) N=1.6 1～ 2 .4 7,并略显 Eu正异常。在相对于原始地幔的标准化微量元素分布图中 ,7个样品具较明显的 Nb亏损和 Zr、Hf富集 ,而 1个样品不具 Nb的亏损 ;HFSE/HFSE、L IL E/HFSE、L IL E/L IL E等微量元素比值大都在 N- MORB和 EMI2个地幔端员组分间变化。这表明岩浆起源于受俯冲组分改造或影响的上地幔 ,且地幔源区存在明显的化学不均一性。与冲绳海槽玄武岩相比 ,马里亚纳海槽玄武岩的 Nb亏损明显减弱 ,暗示俯冲组分对地幔源区的影响程度也随之减弱 ,这反映出处于弧后张裂阶段的冲绳海槽与处于从弧后张裂向海底扩张过渡阶段的马里亚纳海槽 。This paper reports the result of a petrological geochemistry study of eight basaltic samples from the Mariana Trough hydrothermal activity regions(near 18°N). The samples are basalt or basaltic andesite, belonging to cal alkalic series. They are enriched in LILE and LREE;REE patterns are right leaned( La N=10.68～22.64,(La/Yb) N=1.61～2.47),and have positive Eu abnormality. In the PM normalized plots seven samples are obviously depleted in Nb, and enriched in Zr and Hf; one is not depleted in Nb; the HFSE/HFSE, LILE/HFSE, LILE/LIFE values change between N MORB and EMI. It shows that the magma was derived from the upper mantle which was altered or affected by subduction composition, and the mantle source was of chemical inhomogeneity. Compared with basalts from the Okinawa Trough, the Nb depletion of basalts from the Mariana Trough is weaker, which implies that the influence of subduction composition is also weaker. This indicates that in the aspect of the origin and dynamics of magma, the Okinawa Trough which is now in the stage of back arc rifting is obviously different from the Mariana Trough which is now in the transitional phase from back arc rifting to seafloor spreading.

关 键 词：马里亚纳海槽 热液活动区 玄武质岩石 岩石研究 弧后张裂 化学特征 岩浆起源 岩浆动力学 

分 类 号：P736.3[天文地球—海洋地质]