On the possibility to use stratabound hydrothermal crusts as indicators for local or global changes in the environment

Stratabound manganese oxide deposits of hydrothermal origin from the Valu Fa back-arc spreading axis demonstrate distinct layer structure. The dense and porous layers are formed at two different regimes of hydrothermal sources activity. The mineralogical and chemical composition of the layers is different and has been studied by means of X-ray diffraction, X-ray fluorescence, and Mössbauer spectroscopy. Densitograms received from X-ray topography negatives reveal periodicity of the hydrothermal activity of the sources around the spreading axes. An intriguing result is that some of the periods are typical for the solar activity cycles. The porous and dense layers in the structure match with the known intervals of abnormally low activity and intervals of high activity of the Sun, respectively.