| 摘要: |
| 板块俯冲和板内岩浆作用都是导致地表和地球内部物质大规模循环的重要地质过程。但是，两个地质过程的岩浆成因机制，以及成因上的内在联系都存在很大争议。西太平洋是全球沟-弧-盆体系最发育的地区，也是全球板内火山作用（海山和洋底高原）分布最集中的场所。为阐明西太平洋海盆的上地幔软流圈性质、岛弧岩浆形成的控制机制、以及板块内部火山作用（碱性火山岩）的成因机制，在中国科学院战略性先导科技专项（A类）“热带西太平洋海洋系统物质能量交换及其影响”项目的资助下，本文对西太平洋马里亚纳-雅浦俯冲系统、汤加-科玛迪克俯冲带及其俯冲前缘海盆的成因机制、南中国海扩张期海盆玄武岩和板内火山作用、西太平洋海盆上地幔的Dupal异常分布和成因机制等展开了系统的岩石学和地球化学研究，并取得了新的科学认识和成果。主要认识包括：（1）雅浦岛弧主要由变质岩-角闪岩组成，其形成于3—6Kbar温压条件下，代表岛弧下部来自帕里西维拉海盆的变质基底；（2）加洛林洋脊主要由玄武岩组成，其不是一个岛弧，而可能是一个地幔柱形成的洋底高原；（3）汤加-科玛迪克岛弧岩浆组成体现了西南太平洋俯冲板片俯冲速率的直接影响；（4）厘定了汤加-科玛迪克俯冲前缘板块的年龄（103.7Ma），并认识到其代表古太平洋扩张中心并消耗了Ontong Java超级地幔柱的组分；（5）首次在南海发现了碳酸盐化的硅酸岩岩浆向碱性玄武岩转化的现象，提出了板内碱性玄武岩成因的新链条；（6）西太平洋海盆的地幔广泛存在Dupal异常，该异常从西太平洋岛弧俯冲带一直延伸至南海海盆，其中南海海盆的Dupal异常主要受到大陆裂解和海南地幔柱作用的双重影响。通过以上认识，进一步揭示了西太平洋沟-弧-盆体系和板内岩浆体系作用机制，以及俯冲板片物质与板内火山活动之间的成因关联，这对于深刻理解板块构造导致的地球内外物质循环规律有一定的推动作用。 |
| 关键词: 玄武岩 板块俯冲 俯冲带 板内火山 地幔 西太平洋 |
| DOI：10.11693/hyhz20170900227 |
| 分类号:P736.1 |
| 基金项目:中国科学院战略性先导科技专项（A类），Y3A3130301号；国家自然科学基金项目，41376065，41522602号。 |
|
| PROCEEDINGS OF SUBDUCTION SYSTEM AND INTRA-OCEANIC VOLCANISM OF THE WESTERN PACIFIC |
|
ZHANG Guo-Liang1,2, WANG Shuai1, ZHANG Ji1, LUO Qing1, LI Tie-Gang2,3
|
|
1.Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2.Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;3.The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
|
| Abstract: |
| Plate subduction and intra-plate volcanism are geological processes that cause exchange of materials between the Earth's interior and surface. However, the origin of volcanism and relationships between the two geological processes are highly debated. The Western Pacific features the most abundant subduction zones, back-arc basins, and intraplate volcanism in the world. Funded by the project of “Western Pacific Ocean System: Structure, Dynamics and Consequences”, we studied the Mariana-Yap subduction system, Tanga-Kermadec subduction system and the genesis of its subducting plate, ridge magmatism intraplate volcanism of the South China Sea basin, and the origin and distribution of the Dupal anomaly in the Western Pacific basins. We following conclusion are made. 1. The Yap arc is dominated by metamorphic rocks (amphibolite) and was formed under pressure of 3—6 Kbar, which represent the metamorphic basement of the Parece Vela basin. 2. The Caroline Rise is mainly composed of basalt and likely represent an oceanic plateau formed by a mantle plume. 3. The volcanic rock compositions of the Tonga-Kermadec arc reflect the influence of subducting rate of the southwestern Pacific plate. 4. The Osbourn trough that formed the subducting plate of the Tonga-Kermadec arc was age-dated, which represents a section of spreading ridge of the ancient Pacific and consumed components of the Ontong Java superplume. 5. Carbonated silicate melts were discovered in the South China Sea basin and can form alkali basalts through reactions with the lithospheric mantle. 6. Most of the Western Pacific basins has the Dupal anomaly in the mantle. The above-mentioned results would shed light on the mechanism of subduction system and intraplate volcanism of the Western Pacific, which is important for understanding the global plate tectonics that causes the exchange of Earth's interior and surface. |
| Key words: basalt plate subduction subduction zone intraplate volcanism mantle western Pacific |
