摘要
自始新世以来,西菲律宾海板块经历了复杂的地质演化过程,在盆地形成过程中伴随有大量板内火山岩形成,板内火山岩主要表现为洋底高原,这些板内火山岩之间的联系一直是研究关注的重点。其中,本哈姆隆起和乌尔达内塔两个洋底高原因其构造位置特殊是研究西菲律宾海盆内板内火山岩相互关系的良好切入点。本次研究对在乌尔达内塔高原获得的10个火山岩样品进行了电子探针矿物分析,全岩主量元素、微量元素及同位素分析。分析结果表明我们获得的乌尔达内塔高原火山岩为碱性玄武岩,其地幔归一化微量元素模式具有典型洋岛玄武岩特征;具有较高的(Sm/Yb)_(N)值(1.89~3.92),指示源区可能存在石榴子石。结合前人研究获得的西菲律宾海盆板内火山岩数据,我们发现乌尔达内塔高原碱性玄武岩具有与本哈姆隆起拉斑玄武岩相似的Sr-Nd-Hf同位素组成,但具有明显低的^(206)Pb/^(204)Pb同位素组成;西菲律宾海盆内碱性洋岛玄武岩与拉斑洋岛玄武岩的Sr-Nd-Hf同位素组成范围几乎相同,但铅同位素组成存在明显差异,碱性洋岛玄武岩的铅同位素比值范围更大。西菲律宾盆地形成环境复杂,板内火山岩形成时可能受到盆地扩张作用和地幔柱的影响,我们利用同位素数据模拟了地幔柱与扩张中心相互作用对板内碱性玄武岩的影响,模拟结果表明碱性火山岩的低^(206)Pb/^(204)Pb值不能通过与地幔柱有关的富集组分和与海盆扩张作用有关的亏损组分混合实现,表明乌尔达内塔高原碱性火山岩具有一个相对独立的地幔源区,形成时已远离扩张中心,不受扩张作用影响。另一方面,乌尔达内塔高原碱性玄武岩形成时晚于拉斑玄武岩1~2Ma,并且部分熔融程度更低,乌尔达内塔高原拉斑玄武岩和碱性玄武岩可能分别对应岩浆活动的主要阶段和晚期阶段。因此,我们认为乌尔达内塔高原与本�
Since the Eocene,the West Philippine Sea Plate has undergone complex geological evolution,accompanied by a large amount of magmatism during the basin formation process,forming a large number of intraplate volcanic rocks.The intraplate volcanic rocks mainly occur in the ocean floor plateau,and the interrelationships between these intraplate volcanic rocks have always been a focus of research attention.Among them,the Benham Rise and the Urdaneta Plateau are good entry points for studying the interrelationships between volcanic rocks within the ocean floor plateaus in the West Philippine Basin due to their unique tectonic positions.This study conducted electron probe mineral analysis on 10 volcanic rock samples obtained from the Urdaneta Plateau,including major,trace,and isotopic analyses of the whole rock.The analysis results indicate that all the volcanic rocks in the Urdaneta Plateau we obtained are alkaline basalts,and their mantle normalized trace element patterns exhibit typical oceanic island basalt characteristics;They have high(Sm/Yb)_(N) values(1.89~3.92),indicating the possible presence of garnet in the source area.Based on the volcanic rock data obtained from previous studies on the seafloor of the West Philippine Basin,we found that the Sr-Nd-Hf isotope composition range of alkaline island basalts and tholeiitic island basalts in the West Philippine Basin is almost the same,but there is a significant difference in lead isotope composition,with a larger range of lead isotope ratios for alkaline island basalts.These alkaline basalts from the Urdaneta Plateau have Sr-Nd-Hf isotopic compositions similar to those of the Benham Rise tholeiitic basalts,but have significantly lower ^(206)Pb/^(204)Pb isotopic compositions.The formation environment of the West Philippine Basin is complex,and the formation of intraplate volcanic rocks may be influenced by basin expansion and mantle plumes.We simulated the impact of the interaction between mantle plumes and expansion centers on intraplate alkaline basalts based on
作者
陈馨
张国良
CHEN Xin;ZHANG Guoliang(Center of Deep Sea Research,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China)
出处
《热带海洋学报》
CAS
CSCD
北大核心
2024年第4期42-56,共15页
Journal of Tropical Oceanography
基金
国家重点研发计划项目(2022YFF0801000)
国家自然科学基金项目(91858206、41876040)。
