Geothermal regime and geodynamics of the North Pacific Ocean |
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| Authors: | E V Verzhbitskii M V Kononov V D Kotelkin |
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| Institution: | (1) Institute of Oceanology, Russian Academy of Sciences, Moscow, 117997, Russia;(2) Faculty of Mechanics and Mathematics, Moscow State University, Moscow, 119899, Russia |
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| Abstract: | The distribution of heat flow in the North Pacific Ocean has been examined, and a map of geothermal and geomagnetic fields for the Bering Sea as it is known today has been made. Reliable data are lacking regarding the time of origin for features of oceanic and continental genesis in the Bering Sea, which is an obstacle to the study of geodynamic processes in the North Pacific. Heat flow data were used to yield numerical estimates for the age of seafloor features in the Bering Sea: the Kamchatka Basin (21 Ma), Shirshov Ridge (95 Ma for the northern part and 33 Ma for the southern), the Aleutian Basin (70 Ma), Vitus Rise (44 Ma), Bowers Ridge (30 Ma), and Bowers Basin (40 Ma). These age estimates are corroborated by combined geological, geophysical, and plate kinematic data. A thermochemical model of global mantle convection has been developed in order to perform a numerical simulation of the thermal process involved in the generation of extended regional features in the North Pacific (the Emperor Fracture Zone, Chinook Trough, etc.). The modeling suggests a plume-tectonic origin for these features, yielding the optimal model for the tectonic evolution of the North Pacific. An integrated geological and geothermal analysis leads to the conclusion that the northern and southern parts of the Shirshov Ridge are different, not only in geologic age, but also in tectonic structure. The northern part is of imbricated-thrust terrane origin, while the southern part is of ensimatic island-arc origin, similar to that of Bowers Ridge. The seafloor of the Aleutian Basin is an outlier of the Upper Cretaceous Kula plate where, in the Vitus Rise area, backarc spreading processes originated during Eocene time. The terminating phase of activity in the Bering Sea began about 21 Ma by spreading in the older seafloor of the Kamchatka Basin. We developed plate-tectonic reconstructions of evolution for the North Pacific for the times 21, 33, 40, and 70 Ma in the hotspot system based on age estimates for the seafloor features derived from heat flow data and modeling of the thermal generation of regional faults, as well as on an analysis of geomagnetic, tectonic, and geological data. |
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