In order to explore the mineral resources buried in sea mud,it is necessary to use seabed resistivity measuring equipment,which works closer to the sediments than ordinary ship-based geophysical measuring equipment. B...In order to explore the mineral resources buried in sea mud,it is necessary to use seabed resistivity measuring equipment,which works closer to the sediments than ordinary ship-based geophysical measuring equipment. Because of the harsh environment of seafloor,high pressure and highly conductive seawater,marine magnetotelluric method developed slowly. The sea floor environment is similar to the environment of logging, According to the design of dual lateral logging equipment,a new equipment for seafloor electrical resistivity measurement is designed. Four 3D FEM models that contain resistivity abnormal targets are built to test the ability of this equipment to locate different shape of shallow buried resistivity abnormal targets in sea mud. The authors propose the method to correct the response curve while the bottom surface of this equipment is suspended or not parallel to the seafloor. The resistivity of targets can be calculated accurately.展开更多
The Jiamusi and Songnen blocks converged in the easternmost segment of the Central Asian Orogenic Belt as a result of the subduction and subsequent closure of the Mudanjiang oceanic plate during the Permian-Jurassic.T...The Jiamusi and Songnen blocks converged in the easternmost segment of the Central Asian Orogenic Belt as a result of the subduction and subsequent closure of the Mudanjiang oceanic plate during the Permian-Jurassic.The Mudanjiang suture zone was later directly affected by subductions of the Paleo-Pacific plate and Pacific plate and is therefore an ideal place to study the subduction polarity and later transformation of a paleo-suture zone.Using three-dimensional inversion of magnetotelluric data collected along a 160-km-long profile across the Mudanjiang suture zone,we established a resistivity model of the suture zone and adjacent area.Our results reveal the subduction polarity and subduction trace of the Mudanjiang oceanic plate and provide geoelectrical evidence for reactivation of the Mudanjiang suture zone induced by the(Paleo-)Pacific plate subduction.The suture zone shows a complex conductive structure.The west-dipping crustal-scale conductor beneath the Songnen-Jiamusi collision zone represents the fossil subduction zone and indicates the westward subduction polarity of the Mudanjiang oceanic plate.Furthermore,the Mudanjiang fault identified by surface geology does not fully represent the deep structure of the Mudanjiang suture zone.The definition of the suture zone should be extended to the whole conductive region with a lateral extent of~70 km.Solid conductive minerals beneath the arc in front of the subduction zone were exhumated up from deep to the upper crust.The“chimney”-shaped conductor connected with the mantle represents the intrusive pathways of mantle-derived materials,suggesting that the Mudanjiang suture zone was reactivated by subductions of the Paleo-Pacific plate and Pacific plate,leading to remelting of the cooled and crystallized materials in the pathways.Therefore,subduction of the(Paleo-)Pacific plate destroyed the lithospheric structure of the paleo collision zone in the eastern segment of the Central Asian orogenic belt,and the large-scale crustal conductor beneath the suture zone reflects reactivation of the paleo-suture zone.展开更多
文摘In order to explore the mineral resources buried in sea mud,it is necessary to use seabed resistivity measuring equipment,which works closer to the sediments than ordinary ship-based geophysical measuring equipment. Because of the harsh environment of seafloor,high pressure and highly conductive seawater,marine magnetotelluric method developed slowly. The sea floor environment is similar to the environment of logging, According to the design of dual lateral logging equipment,a new equipment for seafloor electrical resistivity measurement is designed. Four 3D FEM models that contain resistivity abnormal targets are built to test the ability of this equipment to locate different shape of shallow buried resistivity abnormal targets in sea mud. The authors propose the method to correct the response curve while the bottom surface of this equipment is suspended or not parallel to the seafloor. The resistivity of targets can be calculated accurately.
基金supported by the National Natural Science Foundation of China(Grant Nos.42230303,41504076,41874125)the China Geological Survey Project(Grant No.DD20190010)the Fundamental Research Funds for the Central Universities(Grant No.JLUXKJC2021ZZ11).
文摘The Jiamusi and Songnen blocks converged in the easternmost segment of the Central Asian Orogenic Belt as a result of the subduction and subsequent closure of the Mudanjiang oceanic plate during the Permian-Jurassic.The Mudanjiang suture zone was later directly affected by subductions of the Paleo-Pacific plate and Pacific plate and is therefore an ideal place to study the subduction polarity and later transformation of a paleo-suture zone.Using three-dimensional inversion of magnetotelluric data collected along a 160-km-long profile across the Mudanjiang suture zone,we established a resistivity model of the suture zone and adjacent area.Our results reveal the subduction polarity and subduction trace of the Mudanjiang oceanic plate and provide geoelectrical evidence for reactivation of the Mudanjiang suture zone induced by the(Paleo-)Pacific plate subduction.The suture zone shows a complex conductive structure.The west-dipping crustal-scale conductor beneath the Songnen-Jiamusi collision zone represents the fossil subduction zone and indicates the westward subduction polarity of the Mudanjiang oceanic plate.Furthermore,the Mudanjiang fault identified by surface geology does not fully represent the deep structure of the Mudanjiang suture zone.The definition of the suture zone should be extended to the whole conductive region with a lateral extent of~70 km.Solid conductive minerals beneath the arc in front of the subduction zone were exhumated up from deep to the upper crust.The“chimney”-shaped conductor connected with the mantle represents the intrusive pathways of mantle-derived materials,suggesting that the Mudanjiang suture zone was reactivated by subductions of the Paleo-Pacific plate and Pacific plate,leading to remelting of the cooled and crystallized materials in the pathways.Therefore,subduction of the(Paleo-)Pacific plate destroyed the lithospheric structure of the paleo collision zone in the eastern segment of the Central Asian orogenic belt,and the large-scale crustal conductor beneath the suture zone reflects reactivation of the paleo-suture zone.
