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Nowe doniesienia z wnętrza Ziemi

Grabarczyk Anna, Wiszniewska Janina, Ruszkowski Michał

Przegląd Geologiczny

2019

Vol. 67, nr 10

812--816

A new research has been done on the high pressure minerals from the Earth’s Mantle Transition and Lower Zone. The Earth’s Mantle extends from the “Moho” (Mohoroviè) discontinuity down to a depth of 2,900 km and constitutes 83% of the Earth’s volume and 67% of its mass.The mantle is further divided into two seismic regions: the upper and thelower mantle separated by a seismic zone of discontinuity at a depth of 670 km, which is also the maximum depth to which subducted lithospheric plates can reach. The additional discontinuity zone, i.e. a depth of 410 km together with a zone of 670 km, corresponds to the transformation site of the silicate mineral structure, which also affects the speed of propagation of seismic waves. Mantle peridotite samples indicate that olivine is the main component of the uppermost part of the upper mantle, up to adepth of 410 km. At greater depths, down to 660 km, in the so-called Transition, transformation of olivine into its high-pressure poly-morphs (wadsleyite and ringwoodite) showing a spinel structure, is observed. Experimental research data on natural bridgmanite((Mg, Fe)SiO3), which exhibits a perovskite structure and is the main mineral of the lower mantle and the most common mineral in the Earth, have been presented. The problem of nitrogen and water amounts in the Earth’s lower mantle and a content of new iron polymorphs in the Earth’s core have also been discussed.