东马努斯盆地高镁安山岩物质来源及演化过程——基于全岩主微量和同位素分析

发布时间：2018-05-03 03:01

本文选题：东马努斯盆地 + 高镁安山岩　；参考：《海洋与湖沼》2017年01期

【摘要】：对东马努斯盆地高镁安山岩做了全岩主微量和Sr-Nd-Pb同位素分析,并结合前人测试数据,探究了岩浆物质来源及演化过程。由主量元素[MgO、CaO、FeOT(全铁)、Al_2O_3、TiO_2和P_2O_5]含量随着硅含量的升高而降低和La/Sm随着La含量的升高而保持不变可知,岩浆在演化过程中只发生了矿物的分离结晶,分离的矿物可能为橄榄石、辉石、斜长石、钛铁矿和磷灰石。东马努斯盆地高镁安山岩的Pb和大离子亲石元素(K,Rb,Sr,Ba和U)的富集、高场强元素(Nb,Th,Ta和Ti)的亏损说明岩浆受到了俯冲板块脱水作用的影响。推测该区高镁安山岩是流体交代的地幔楔部分熔融形成的。由Sr-Nd同位素混合模拟结果可知东马努斯盆地高镁安山岩主要来源于马努斯MORB(洋中脊玄武岩),少量来自于太平洋蚀变洋壳和海底沉积物。根据Sr-Nd-Pb同位素特征推测岩浆混合作用发生在地幔源区,属于源区混染,岩浆在喷发的过程中没有发生同化混染作用,也没有加入其他体系的物质。
[Abstract]:The main trace and Sr-Nd-Pb isotopes of the high mafic andesite in the East Manus Basin are analyzed and the source and evolution process of the magmatic material are explored in combination with the previous data. The contents of principal element [MgO _ O _ 2O _ 3 tio _ 2 and P_2O_5] decreased with the increase of Si content, and La/Sm remained unchanged with the increase of La content. The magma had only separated and crystallized minerals during the evolution process, the separated minerals may be olivine and pyroxene, and the contents of the main element [MgO _ O _ (Cao)] _ (FeOT) _ _ _ Plagioclase, ilmenite and apatite. The enrichment of Pb and large ion lithophile elements K _ (RbN) _ (Sr _ (Ba) and U) in the high mafic andesite in the East Manus Basin, and the depletion of the high field strength elements (Nb _ (T) _ (Ta) and Ti) indicate that the magma is affected by the dehydration of the subduction plate. It is inferred that the high-mafic andesite was formed by partial melting of the fluid-metasomatic mantle wedge. The results of Sr-Nd isotopic mixing show that the high mafic andesites in the East Manus Basin are mainly derived from the Monus basalt (middle oceanic ridge basalt) and a small amount from the altered oceanic crust and submarine sediments in the Pacific Ocean. According to the characteristics of Sr-Nd-Pb isotopes, magmatic mixing occurs in mantle source region and belongs to mixed source region. There is no assimilation and contamination during the eruption of magma, and there is no material added into other systems.
【作者单位】：中国科学院海洋研究所海洋地质与环境重点实验室;中国科学院大学;国家海洋局第一海洋研究所海洋沉积与环境地质重点实验室;
【基金】：国家自然科学基金项目,41576055号
【分类号】：P588.144

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