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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
引用本文:赵霞,黄朋,胡宁静,孔娟娟,廖仁强.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[J].海洋与湖沼,2017,48(1):8-21.
作者姓名:赵霞  黄朋  胡宁静  孔娟娟  廖仁强
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 青岛 266071;中国科学院大学 北京 100049,中国科学院海洋研究所海洋地质与环境重点实验室 青岛 266071,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 青岛 266061,中国科学院海洋研究所海洋地质与环境重点实验室 青岛 266071;中国科学院大学 北京 100049,中国科学院海洋研究所海洋地质与环境重点实验室 青岛 266071;中国科学院大学 北京 100049
基金项目:国家自然科学基金项目,41576055号。
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。

关 键 词:东马努斯盆地  高镁安山岩  地球化学特征  物质来源  演化过程
收稿时间:2016/7/27 0:00:00
修稿时间:2016/11/3 0:00:00

MAGMA SOURCE AND EVOLUTION OF HIGH-MG ANDESITE FROM EASTERN MANUS BASIN-GEOCHEMICAL AND ISOTOPIC CONSTRAINTS
ZHAO Xi,HUANG Peng,HU Ning-Jing,KONG Juan-Juan and LIAO Ren-Qiang.MAGMA SOURCE AND EVOLUTION OF HIGH-MG ANDESITE FROM EASTERN MANUS BASIN-GEOCHEMICAL AND ISOTOPIC CONSTRAINTS[J].Oceanologia Et Limnologia Sinica,2017,48(1):8-21.
Authors:ZHAO Xi  HUANG Peng  HU Ning-Jing  KONG Juan-Juan and LIAO Ren-Qiang
Institution:Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;University of Chinese Academy of Sciences, Beijing 100049, China,Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China,Key Laboratory of Marine Sedimentary and Environmental Geology, the First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China,Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;University of Chinese Academy of Sciences, Beijing 100049, China and Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;University of Chinese Academy of Sciences, Beijing 100049, China
Abstract:Bulk major and trace elements and Sr-Nd-Pb isotopic composition were analyzed for the high-Mg andesite from the Eastern Manus Basin, Papua New Guinea. We combined previous data with ours to explore the origination and evolution of the andesite. Results show that the contents of major elements (MgO, CaO, FeOT, MgO, Al2O3, TiO2, and P2O5) decrease as that of SiO2 increases, and La/Sm remains stable as the La content increases, reflecting the lavas was controlled by fractional crystallization (FC) but partial melting during magma evolution. The fractional minerals could be olivine, pyroxene, plagioclase, ilmenite, and apatite. The enrichments of Pb and LILEs (K, Rb, Sr, Ba, and U) and depletions of HFSEs (Nb, Th, Ta, and Ti) in the high-Mg andesite suggest that the magma has been influenced by fluids from a subducted slab. Therefore, we infer that the high-Mg andesite was formed by melting of a mantle wedge induced by water involvement. The magma sources were composed of mainly Manus MORB, some Pacific altered oceanic basalts, and abyssal sediments as indicated in the results of our simulation on mixing processes of Sr-Nd isotopic composition. In terms of Sr-Nd-Pb isotopic composition, we deduce that the subducted components have mixed homogeneously with the local mantle before the magma eruption and no subduction components added nor assimilation and fractional crystallization (AFC) occurred during magma upwelling.
Keywords:Eastern Manus Basin  high-Mg andesite  geochemical characteristic  magma source  evolution
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