Spreading in the Northern Part of the Eurasian Lithospheric Plate from GPS Measurements and Its Possible Geodynamic Interpretation

Over the whole area of the Eurasian lithospheric plate considered in the paper —rom the Atlantic to the Pacific Ocean—the velocity vectors of the horizontal eastward displacements of GPS sites form a gentle, smooth, huge arc, convex towards the north. Three relatively narrow bow-shaped bands can be distinguished within the arc. The southernmost band, most provided with measurement data (bow-shaped band A in this paper) is discussed in detail in (Shevchenko et al., 2021). The direct, real results of the published geodetic measurements have shown that the length of this band increases by 5 to 10 mm annually. The arc is lengthening. In the cited paper, we considered and rejected five interpretations of this lengthening, which are based on the idea of external action of the above bow-shaped band on the rocks of the Earth’s crust/lithosphere. The most probable cause of the elongation seems to be the internal process of the increase in the volume of these rocks within the band due to the supply of the additional mineral material into these rocks by the deep fluids and its subsequent crystallization. In this paper, we present the results of similar geodetic measurements in other two bow-shaped bands, B and C. It turns out that bow-shaped band C located to the north of the other bands, is lengthening (and at a similar rate) as band A located to the south of the other bands. At the same time, bow-shaped band B, which has an intermediate position between bands A and C, is moving eastward without lengthening. Geodetic measurements in the axial part of the Mid-Atlantic Ridge in the Iceland island suggest that the general expansion of the Atlantic Ocean and the corresponding eastward motion of the Eurasian lithospheric plate are related to the injection of plastic magmatic wedges (of basic composition) in the axial, rift zone of the ridge. Against the background of this general eastward motiont of the lithospheric plate, its constituent parts (the bow-shaped bands A and C are markers of these parts) are moving in the same eastward direction with a velocity increasing from west to east. We attribute this increase in the velocity and the corresponding lengthening of the two bands to the above inflow of the additional mineral material and its subsequent crystallization.