构造-岩浆作用对热液活动的控制机理:马努斯海盆为例

Influence of tectonic-magmatism on hydrothermal activity: a case study of the Manus Basin

综述了马努斯海盆热液区构造特征、基底差异,结合马努斯海盆热液区热液活动与构造-岩浆特征,探讨了二者的耦合关系,以及构造-岩浆作用对热液活动的影响和控制。马努斯海盆位于西南太平洋俾斯麦海的东北部,是世界上扩张速度最快的海盆之一。马努斯海盆西部(马努斯扩张中心,Manus SpreadingCenter,MSC)主要由海盆扩张成熟期产生的大洋中脊玄武岩组成,属于成熟弧后扩张中心,发育Vienna Woods热液区;海盆东部(东南裂谷, Southeast Rift, SER)则是一个拉张裂谷,处于扩张的早期阶段,属于不成熟弧后扩张中心,发育PACMANUS、DESMOS、SuSuKnolls三大热液区。MSC与大洋中脊的热液活动相似,而SER因受到火山、俯冲作用影响更为显著,其热液流体具有岩浆流体和俯冲流体的特征。与Vienna Woods热液压相比, PACMANUS、DESMOS以及SuSu Knolls三个热液区的水深相对较浅(1 150～1 740 m),是地球内部热物质由内向外迁移的结果,其下部岩浆作用强烈。此外,岩浆脱气作用和数值模拟结果表明,PACMANUS热液系统中具有岩浆流体的输入。与ViennaWoods热液区相比, PACMANUS、DESMOS、SuSu Knolls热液区的热液活动强度及流体组成主要受控于岩浆作用。

We reviews the regional geological setting,tectonics,and magmatism of the Manus Basin in this study.Based on the hydrothermal and tectonic data of the Manus Basin hydrothermal field,the relation between tectonic-magmatism and hydrothermal activity is discussed,especially,in terms of the impact of tectonic-magmatism on hydrothermal activity.The Manus Basin is a rapidly spreading back-arc basin,which is located in the northeastern Bismarck Sea of the southwestern Pacific Ocean.The Manus spreading center(MSC),lies in the western Manus Basin and is a mature back-arc spreading center with the development of the Vienna Woods hydrothermal field.Basalts in the MSC are similar to those of mid-ocean ridge basalts(MORB).The southeast rift(SER)is an immature spreading center during its early stages of spreading.Located in the eastern Manus Basin,it gives rise to the PACMANUS,DESMO,and SuSu Knolls hydrothermal fields.The MSC is similar to the mid-ocean ridge,while the SER’s hydrothermal fluid is more influenced by volcanism and subduction,resulting in a magmatic and subduction-type fluid.Comparing to Vienna Woods,PACMANUS,DESMOS,and SuSu Knolls are relatively shallow(1150–740 m),and the underlying magmatism is more intense.Additionally,the numerical simulation and the magmatic degassing effect yielded a magmatic fluid in the hydrothermal system of the SER.In contrast with the MSC,we observe that the hydrothermal activity intensity and fluid composition of the SER are mainly controlled by magmatism.