中国科学院海洋研究所机构知识库

深部碳循环作为一种全球性的表层-深层物质交换过程，对全球气候、地球各圈层演化都有十分重要的控制作用。而碱性岩，尤其是大洋碱性OIB与全球碳循环之间存在十分紧密的成因联系，使得碱性OIB成为研究全球碳循环的理想材料。西太平洋拥有最古老的洋壳，最密集的海山分布以及大量的碱性OIB的出露，对研究碱性OIB的成因有着天然的优势。

本研究选择西太平洋，麦哲伦海山群中未有前人取过样的Kocebu海山碱性OIB为研究对象，采用岩相学、矿物学和地球化学手段进行研究。我们发现本区碱性OIB具有明显较高的原生CaO和P₂O₅含量，较低的SiO₂含量，高场强元素以及K元素存在负异常，广泛存在高钛辉石，说明本区碱性OIB可能来自于一个富含CO₂的地幔源区；相对较高的TiO₂和La/Yb比值，相对较低的MgO则说明本区碱性OIB可能来自于碳酸盐化的榴辉岩源区。

Global carbon cycle, as a global surface-deep exchange process, has an important controlling effect on the global climate and the evolution of the Earth's spheres, and there is a close relationship between alkaline OIBs and the global carbon cycle, making alkaline OIBs as an ideal material for studying the global carbon cycle.The Western Pacific has the oldest oceanic crust, the densest distribution of seamounts, and wide distribution of alkali basalts, which has a natural advantage for studying alkaline OIBs.

Therefore, in this study, we collected alkaline OIBs from Kocebu Seamount, where rock samples have not been collected yet. The chemical composition of bulk rock and mineralogical characteristics of these samples were studied. We found that alkaline OIBs of this area have higher CaO and P₂O₅, lower SiO₂ content, high field strength element (HFSE) negative anomaly, more distinctly K negative anomaly and the ubiquity of titanaugite, which indicate a carbonate rich mantle source. Based on the relatively high TiO₂ contents and La/Yb ratios, low MgO contents suggest that the volcanic rocks of this area could have been derived from a mantle source with carbonated eclogite.

第1章 引言... 1

1.1 研究背景及研究意义... 1

1.2 研究现状... 2

1.3 研究内容... 4

1.4 研究方法... 5

1.5 完成工作量... 6

第2章 区域概况... 7

2.1 区域构造综述... 7

2.2 沉积特征... 7

2.3 构造特征... 8

2.4 火山活动特征... 9

第3章　样品处理及分析方法... 11

3.1　样品的前处理方法... 11

3.2　样品的分析方法... 12

3.2.1　全岩主微量元素测试... 12

3.2.2　电子探针微区成分分析... 15

第4章　样品岩相学及矿物学分析结果... 17

4.1　岩相学... 17

4.2 矿物学... 20

4.2.1　磷灰石... 20

4.2.2　辉石... 22

4.2.3　长石... 25

第5章 样品元素组成分析结果... 29

5.1　主量元素... 29

5.2　微量元素... 30

第6章　讨论... 33

6.1　本区样品磷质来源... 33

6.1.1　高SiO₂组... 33

6.1.2　低SiO₂组... 34

6.2　本区玄武岩的成因... 35

6.2.1　后期蚀变影响... 35

6.2.2　岩浆特征及结晶分异影响... 37

6.2.3　岩浆源区... 41

结论... 43

参考文献... 45

附录... 53

致谢... 87

攻读学位期间发表的学术论文与研究成果... 89