中亚造山带核心区蛇绿混杂岩中洋岛玄武岩成因探讨

发布时间：2018-04-28 15:25

本文选题：洋岛玄武岩 + 海山　；参考：《科学通报》2016年34期

【摘要】：中亚造山带核心区(哈萨克斯坦山弯及翼部)发育新元古代晚期至早石炭世数条蛇绿混杂岩带,它们大多发育典型的海山岩石组合,即枕状玄武岩、火山角砾岩、礁灰岩、滑塌堆积岩、陆源碎屑岩等.结合其特有的构造特征,初步重建了中亚造山带核心区古海山火山地层格架.在地球化学上,构成古海山的火山岩主要为碱性玄武岩,TiO_2含量高,富集轻稀土元素,无明显Nb,Ta,Ti负异常,具有典型洋岛玄武岩特征.Nd,Sr及Pb同位素组成显示岩浆源区有富集组分的参与并受到流体交代的影响.总体上与地幔柱有关的典型海山Louisville,Ontong Java及Hawaiian的玄武岩地球化学特征一致,但不发育高镁苦橄岩或科马提质玄武岩.中亚造山带核心区洋岛玄武岩的来源可能至少有两种:(1)海山在俯冲带被刮削保留在增生楔中;(2)直接来自地幔交代岩的部分熔融,也不排除循环洋壳部分熔融和陆源沉积物参与的可能.可见中亚造山带洋岛玄武岩的物质来源多并发生复杂的壳幔相互作用,这与现代大洋中地幔柱活动及海山的发展演化类似.
[Abstract]:Several ophiolite melange belts developed from late Neoproterozoic to early Carboniferous in the core area of Central Asian orogenic belt (bend and wing of Kazakstan), most of which developed typical seamount rock assemblages, namely pillow basalt, volcanic breccia, reef limestone, etc. Tallies and accumulations, continental clastic rocks, etc. Combined with its unique structural characteristics, the volcanic stratigraphic framework of Paleoseamounts in the core area of the Central Asian orogenic belt was preliminarily reconstructed. Geochemically, the volcanic rocks that make up the paleoseamounts are mainly alkaline basalt with high tio _ 2 content, rich in light rare earth elements, and no obvious negative anomalies of NB ~ (2 +) Ta-Ti. The typical oceanic island basalt features. The isotopic compositions of Ndndln Sr and Pb indicate that the magmatic source area is enriched and affected by fluid metasomatism. The geochemical characteristics of the typical Louisvilleus Ontong Java and Hawaiian basalts related to mantle plumes are consistent in general, but there is no high mafic picrite or Komatite basalt. The source of oceanic island basalt in the central Asian orogenic belt may be at least two types: 1) the seamounts are scraped in the subduction zone and retained in the accretive wedge (2) directly derived from partial melting of mantle metasomatic rocks. Nor does it exclude the possibility of partial melting of the cyclic oceanic crust and the involvement of terrestrial sediments. It can be seen that the oceanic island basalt in the Central Asian orogenic belt has many material sources and complex crust-mantle interaction, which is similar to the modern oceanic mantle plume activity and the development and evolution of seamounts.
【作者单位】：长安大学地球科学与资源学院国土资源部岩浆作用成矿与找矿重点实验室;
【基金】：国家自然科学基金(41303027,41273033) 陕西省青年科技新星计划(2016KJXX-71) 中央高校基本科研业务费专项(310827153506,310827153407)资助
【分类号】：P588.145

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