THE INTRAPLATE VOLCANO-TECTONIC ACTIVITY IN NORTH-EASTERN AND SOUTH SECTORS OF THE PACIFIC LITHOSPHERIC PLATES WITH THE CONNECTION OF THE CHANGE OF ITS RELATIVE MOTION

The analysis of altimetric data in combination with bathymetry and gravimetry materials in the north-eastern and southern sectors of the Pacific Ocean, as well as detailed data on the underwater relief, the structure of the sedimentary cover, the composition and absolute age of basalts obtained within the area of domestic geological exploration for ferromanganese nodules (the Clarion-Clipperton zone) is carried out. Structural trends formed by local cone-shaped local structures of presumably volcanic nature, grouped along transform faults belonging to various stages of the kinematics of the Pacific Plate, have been traced in the structure of the oceanic lithosphere at various scale levels. The first trend corresponds to the extension of the fault system corresponding to the spreading system on the crest of the East Pacific rise before the restructuring of its planned geometry in the Paleocene-Eocene, the second coincides with their extension after the change in the relative movement of the Pacific Plate. The trends are characterized by planned disagreement, and an increase in the number of seamounts is observed in the areas of their intersection. Within the area of detailed studies, obvious signs of volcanic-tectonic activity were revealed: high dissection of the underwater relief, hills of different heights with steep slopes, whose volcanic nature is confirmed by differentiated basalts raised from their slopes, the absolute age of which indicates the multistage outpourings that occurred in an intraplate environment. The angular velocity of rotation of the spreading axis and the linear velocity of its advance with changes in the kinematics of the Pacific plate are estimated and possible reasons for changes in its relative motion are considered. An improved scheme of adaptation of the spreading zone to a change in the direction of relative plate movement is proposed, acc0ording to which an essential factor of intraplate volcanic-tectonic activity is the relaxation of stresses in the plate caused by external influence on it.

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New geophysical data from the northern Cordillera: preliminary interpretations and implications for the tectonics and deep geology

Canadian Journal of Earth Sciences ◽

10.1139/e94-081 ◽

1994 ◽

Vol 31 (6) ◽

pp. 891-904 ◽

Cited By ~ 20

Author(s):

C. Lowe ◽

R. B. Horner ◽

J. K. Mortensen ◽

S. T. Johnston ◽

C. F. Roots

Keyword(s):

Gravity Data ◽

Field Studies ◽

Geophysical Data ◽

Fault System ◽

Tectonic Activity ◽

Denali Fault ◽

The North ◽

The Pacific ◽

Proterozoic Basement ◽

Seismic Sections

In this paper we analyze recently acquired geophysical data from the northern Cordillera and their relation to the mapped geology. A prominent gravity high (> −45 mGal (1 Gal = 1 cm/s2)) coincides with a magnetic low and an aseismic region in west-central Yukon where the underlying geology is dominated by quartzo-feldspathic rocks having moderate densities. Extension (~15%), magmatic underplating, and accretion of the anomalous region onto oceanic crust are three possible explanations.Magnetic, gravity, and seismicity data all show significant differences in the physical state of the crust on either side of the Tintina Fault and, together with geological data indicating large offset, suggest it was once a major crustal-scale strike-slip fault. The new gravity data also delineate an arcuate zone of steep gradients (up to 1.4 mGal/km) in the miogeocline, which may correlate with a west-dipping Proterozoic basement ramp mapped on deep seismic sections farther to the north and a transition from thin (east) to thick sediment cover (west). Seismicity data show that current tectonic activity is concentrated along the Pacific – North America plate margin in southwestern Yukon and adjacent Alaska and, although there is a marked decrease in activity inland of this margin, notable concentrations occur along the Denali Fault System and in the eastern miogeocline. There is a distinct absence of earthquakes in parts of the Selwyn Basin and in the northern Yukon–Tanana Terrane. Limited field studies suggest activity is confined to the upper 10–15 km of the crust.

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Seafloor Topography Caused by Plate Bending Just Prior to Subduction, Observed at the Pacific Plate off the North-eastern Japan Arc

Journal of Geography (Chigaku Zasshi) ◽

10.5026/jgeography.126.cover02_01 ◽

2017 ◽

Vol 126 (2) ◽

pp. Cover02_01-Cover02_02

Keyword(s):

Pacific Plate ◽

Plate Bending ◽

Seafloor Topography ◽

The North ◽

The Pacific ◽

North Eastern ◽

Eastern Japan

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The geology of the north-eastern corner of Greenland - photogeological studies and 1993 field work

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v161.8240 ◽

1994 ◽

Vol 161 ◽

pp. 21-33

Author(s):

H.F Jepsen ◽

J.C Escher ◽

J.D Friderichsen ◽

A.K Higgins

Keyword(s):

Field Work ◽

Tectonic Activity ◽

Mobile Belt ◽

North East ◽

The North ◽

Upper Proterozoic ◽

North Eastern ◽

Field Season ◽

Upper Boundary ◽

Middle Proterozoic

Late Archaean and Early Proterozoic crust-forming events in North-East and eastern North Greenland were succeeded by Middle Proterozoic sedimentation and volcanic activity; Late Proterozoic through Tertiary sedimentation was interrupted by several periods of tectonic activity, including the Caledonian orogeny in East Greenland and the Mesozoic deformation of the Wandel Hav mobile belt. Photogeological studies helped pinpoint areas of special interest which were investigated during the short 1993 field season. Insights gained during field work include: the nature of the crystalline basement terrain in the Caledonian fold belt, redefinition of the upper boundary of the Upper Proterozoic Rivieradal sandstones, revision of Caledonian nappe terminology, and the northern extension of the Caledonian Storstrømmen shear zone.

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The Influence of Geodynamic Evolution on the Formation of the Cenozoic Sedimentary Cover of the North-Eastern Part of the Sakhalin Shelf

10.3997/2214-4609.202050035 ◽

2020 ◽

Author(s):

A.Y. Makarova

Keyword(s):

Sedimentary Cover ◽

Geodynamic Evolution ◽

The North ◽

Sakhalin Shelf ◽

North Eastern ◽

North Eastern Part

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On the Distribution of Phytoplankton in the North-eastern Part of the Pacific (Tôhoku Region) in Autumn. (Oct.-Nov., 1951)

Journal of Engineering Physics and Thermophysics ◽

10.5928/kaiyou1942.9.109 ◽

1953 ◽

Vol 9 (2) ◽

pp. 109-114

Author(s):

H. Kon

Keyword(s):

The North ◽

The Pacific ◽

North Eastern ◽

North Eastern Part

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Structural Characteristics and Mechanism of the Horsetail Structure in China Offshore Basins: Case Studies from Liaodong Bay Area, Bohai Bay Basin and Weixinan Area, Beibuwan Basin

10.5194/egusphere-egu2020-4581 ◽

2020 ◽

Author(s):

Jie Zhang ◽

Zhiping Wu ◽

Yanjun Cheng

Keyword(s):

Structural Characteristics ◽

Strike Slip ◽

Pacific Plate ◽

Strike Slip Fault ◽

Bohai Bay ◽

Liaodong Bay ◽

Clockwise Rotation ◽

Bay Area ◽

The North ◽

The Pacific

<p>The horsetail structure, also named brush structure, generally refers to a sets of secondary faults converged to the primary fault on the plane. Based on 2-D and 3-D seismic data, the structural characteristics, evolution and mechanism of the horsetail structure of Liaodong Bay area in Bohai Bay Basin and Weixinan area in Beibuwan Basin are analyzed. In the Liaodong Bay area, the primary fault of the horsetail structure is the NNE-striking branch fault of Tan-Lu strike-slip fault zone. The NE-striking secondary extensional faults converged to the primary strike-slip fault. Fault activity analysis shows that both the primary and secondary faults intensively activated during the third Member of the Shahejie Formation (42~38 Ma). In the Weixinan area, the NE-striking Weixinan fault is the primary fault of the horsetail structure, which is an extensional fault. A large amount of EW-striking secondary extensional faults converged to the primary NE-striking Weixinan fault. Fault activity analysis shows that NE-striking primary fault intensively activated during the second Member of the Liushagang Formation (48.6~40.4 Ma), whereas the EW-striking secondary faults intensively activated during the Weizhou Formation (33.9~23 Ma). The different structure and evolution of the horsetail structure in the Liaodong Bay area and Weixinan area are mainly resulted from the regional tectonic settings. About 42 Ma, the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the right-lateral strike-slip movement of NNE-striking Tan-Lu fault and the formation of NE-striking extensional faults along the bend of the strike-slip fault, therefore, the horsetail structure of Liaodong Bay area formed. However, the formation of the horsetail structure of Weixinan area is related to the clockwise rotation of extension stress in the South China Sea (SCS): 1) During Paleocene to M. Eocene (65~37.8 Ma), the retreat of Pacific plate subduction zone resulted in the formation of NW-SE extensional stress field in the north margin of the SCS, NE-striking primary fault of horsetail structure formed; 2) During L. Eocene to E. Oligocene (37.8~28.4 Ma), the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the clockwise rotation of extension direction from NW-SE to N-S in the north margin of the SCS, a large amount of EW-striking secondary faults of horsetail structure formed, and the horsetail structure was totally formed in the Weixinan area until this stage.</p>

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