We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the C...We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the Caroline Ridge and Yap Trench.Rocks were collected from both landward and seaward trench slopes and exhibited geochemical characteristics similar to backarc basin basalt(BABB)and mid-ocean ridge basalt(MORB),including high Fe content,tholeiitic affinity,high TiO_(2) value at a given FeO_(T)/MgO ratio,Ti/V ratio between 20 and50,low Ba/Nb ratio and Th/Nb ratio,and trace element patterns commonly displayed by BABB and MORB,which are distinct from arc lava.These rocks seem to have been generated during mantle upwelling and decompression melting at a spreading center.However,compared with typical forearc lava produced by seafloor spreading in the Mariana forearc region,such as the early Eocene forearc basalts and late Neogene forearc lava in the southernmost Mariana Trench,the Yap Trench lava is derived from a more fertile mantle and feature a more minor subduction component;thus,they cannot be the products of forearc mantle decompression melting.We suggest that the landward slope lava represents backarc basin crust that was overthrust onto the forearc lithosphere during the collision of the Caroline Ridge with the Yap Trench(20–25 Ma),which played a key role in the evolution of the Yap subduction system.Moreover,the seaward slope lava represents the subduction plate crust that accreted onto the deep trench during the collision.This collision event resulted in the cessation of Yap Arc magmatism;thus,the Yap Trench volcanic rocks(<25 Ma)previously suggested to be arc magma products may actually represent the nascent island arc lava with a lower subduction component than in the mature Mariana Arc lava.展开更多
基金The National Key R&D Program of China under contract No.2017YFC1405502the Scientific Research Fund of the Second Institute of Oceanography,Ministry of Natural Resources under contract Nos QNYC1901 and JG2002+1 种基金the National Natural Science Foundation of China under contract No.41976072the“13th Five-Year Plan”for Resources and Environment Projects of the China Ocean Mineral R&D Association(COMRA)under contract No.DY135-G2-1-01。
文摘We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the Caroline Ridge and Yap Trench.Rocks were collected from both landward and seaward trench slopes and exhibited geochemical characteristics similar to backarc basin basalt(BABB)and mid-ocean ridge basalt(MORB),including high Fe content,tholeiitic affinity,high TiO_(2) value at a given FeO_(T)/MgO ratio,Ti/V ratio between 20 and50,low Ba/Nb ratio and Th/Nb ratio,and trace element patterns commonly displayed by BABB and MORB,which are distinct from arc lava.These rocks seem to have been generated during mantle upwelling and decompression melting at a spreading center.However,compared with typical forearc lava produced by seafloor spreading in the Mariana forearc region,such as the early Eocene forearc basalts and late Neogene forearc lava in the southernmost Mariana Trench,the Yap Trench lava is derived from a more fertile mantle and feature a more minor subduction component;thus,they cannot be the products of forearc mantle decompression melting.We suggest that the landward slope lava represents backarc basin crust that was overthrust onto the forearc lithosphere during the collision of the Caroline Ridge with the Yap Trench(20–25 Ma),which played a key role in the evolution of the Yap subduction system.Moreover,the seaward slope lava represents the subduction plate crust that accreted onto the deep trench during the collision.This collision event resulted in the cessation of Yap Arc magmatism;thus,the Yap Trench volcanic rocks(<25 Ma)previously suggested to be arc magma products may actually represent the nascent island arc lava with a lower subduction component than in the mature Mariana Arc lava.