马里亚纳海槽扩张轴(中心)玄武岩铂族元素特征

曹志敏; 安伟; 周美夫; 郑建斌; 漆亮

马里亚纳海槽扩张轴(中心)玄武岩铂族元素特征

1.
中国海洋大学, 海洋地球科学学院, 山东, 青岛, 266003
2.
中海石油环保服务有限公司, 天津, 塘沽, 300452
3.
香港大学, 地球科学系, 香港, 999077

基金项目: 国家自然科学基金(40273025);国家重点基础研究973项目(G2000078503)

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出版历程
- 收稿日期: 2005-05-01
- 修回日期: 2006-04-26

Characteristics of platinum-group elements in Mariana Trough basalts

1.
College of Marine Geosciences, Ocean University of China, Qingdao 266003, China
2.
China Offshow Environmental Sevice Ltd, Tanggu 300452, China
3.
Department of Earth Sciences, University of Hong Kong, Hong Kong, 999077, China

摘要

摘要: 马里亚纳海槽扩张轴中心玄武岩铂族元素(PGE)总量变化范围为0.418×10^-9~1.022×10^-9,其原始地幔标准化配分模式呈正倾斜型,表现出PPGE(包括Pt,Pd,Rh)和金的相对富集.与其他幔源岩石相比,该区玄武岩PGE总量较低,(Pd/Ir)N,(Pd/Pt)N,(Pd/Ru)N变化较大,表现出铂、铱的相对亏损和明显的铂负异常(Pt/Pt^*=0.01~0.15).PGE的分布特征一方面反映了该区地幔熔融度不高,另一方面,大离子亲石元素LILE(铷、锶、钾等)、铅和轻稀土LREE略富集,暗示扩张中心之下的软流圈地幔源受到了岛弧地幔的混染.上述特征反映了马里亚纳海槽玄武岩是MORB型与岛弧型地幔源不同程度混合后部分融熔的产物.
- 弧后盆地玄武岩 /
- 铂族元素(PGE) /
- 铂负异常 /
- 俯冲带
Abstract: Total platinum-group elements concentrations (ΣPGE) from Mariana Trough basalts ranged from 0.418 to 1.022 ng/g, and primitive mantle-normalized PGE concentration patterns are of positive slope with a clear Ptnegative anomaly (Pt/Pt^* = 0.01~0.15),showing the relative enrichment of PPGE and Au relative to IPGE.Compared with other mantleoriginated rocks, Mariana Trough basalts have lower PGE contents and wider ranges of (Pd/Ir) N, (Pd/Pt) N, (Pd/Ru) N.On the other hand, Mariana Trough basalts exhibited a relative Pt and Ir depletion.Characteristics of PGE patterns indicated that the studied Mariana Trough basalts were originated from low partial melting, and the MORB mantle beneath the spreading center had been contaminated byarcisland mantle.In the aspect of trace elements, Mariana Trough basalts showed the enrichment of LILE, Pb and LREE, indicating that they had been influenced by subduction compositions.All these demonstrated that Mariana Trough basalts are products of partial melting from amixed mantle (the contamination of MORB mantle by are-island mantle).
- Back-arc basin basalt /
- platinum-group elements /
- negative Pt anomaly /
- subduction zone

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