东太平洋海隆1°N洋中脊玄武岩斜长石斑晶的化学特征及其对岩浆作用的指示意义  

Chemical Characteristics of Plagioclase Phenocrysts in MORBs from the East Pacific Rise 1°N and Implication for Magmatic Processes

作　　者：李俊录 崔建军[2,3] 张维[4] LI Junlu;CUI Jianjun;ZHANG Wei(Geological Survey of Hebei Province,Langfang,Hebei 065000;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081;Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources,Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081;Institute of Oceanology, China Academic of Science,Qingdao,Shandong 266071)

机构地区：[1]河北省区域地质调查院,河北廊坊065000 [2]中国地质科学院地质力学研究所,北京100081 [3]自然资源部古地磁与古构造重建重点实验室中国地质科学院地质力学研究所,北京100081 [4]中国科学院海洋研究所,山东青岛266071

出　　处：《地质与勘探》2019年第2期562-569,共8页Geology and Exploration

基　　金：国家重点研发计划项目(编号:2017YFC0601402);国际海域资源调查与开发"十二五"前沿性课题(编号:DY125-22-QY-21)联合资助

摘　　要：东太平洋海隆为世界典型的扩张脊,其上的洋中脊玄武岩为研究快速扩张作用下的岩浆作用提供了机会。在东太平洋海隆1°N采集到的洋中脊玄武岩内发现了大量结晶状况良好的斜长石斑晶。基于玄武岩的常量元素测试分析,洋脊下部的原始岩浆经历了以橄榄石为主的结晶分离过程,并未发生大规模的斜长石结晶分离。对样品中斜长石斑晶的电子探针测试表明,这些斜长石斑晶为岩浆自生矿物,而非捕掳晶。部分环带斜长石斑晶成分的规律性的变化主要受控于原始岩浆温度的变化,而非岩浆混合作用。我们推测Galapagos三联点下部可能存在一个相对封闭的岩浆体系,为斜长石矿物的结晶提供了时间和空间条件。这些斜长石斑晶形成后并未分离成岩,而是被岩浆带至洋底喷发形成玄武岩。The East Pacific Rise( EPR) is a typical fast spreading ridge,which provides a good opportunity to further understanding of the magmatism under ridges. Mid Ocean Ridge Basalts( MORBs) from EPR 1°N were collected with amounts of well crystallized plagioclase phenocrysts. The major elements analysis on these MORBs show that the magma experienced fractional crystallization on olivine without plagioclase. The electron probe micro-analyzer( EPMA) analysis on these plagioclase indicates that these phenocrysts are authigenic minerals. Liner scan on some zoned plagioclases discovers relevant compositional changes,which are mainly the result of the temperature variation on magma rather than magma contamination. We infer the existence of a closed magmatism under the Galapagos triple junction,which provides conditions for crystallization of plagioclase minerals in space and time,leading to generation of the MORBs in the EPR 1°N.

关 键 词：东太平洋海隆 洋中脊玄武岩 斜长石 岩浆作用 

分 类 号：P588.145[天文地球—岩石学] P542.5[天文地球—地质学]