AK&M 23 January 2025 16:10
The Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences (GEOHI RAS), together with scientists from Lomonosov Moscow State University, the Institute of Oceanology of the Russian Academy of Sciences and the Geological Institute of the Russian Academy of Sciences, conducted a comprehensive geochemical study of rocks 600-500 million years old from Eastern Siberia. The results of the analysis showed that at that time — at the turn of the Proterozoic and Paleozoic — there was a dry desert climate, and clastic deposits accumulated as a result of the destruction of ancient mountains due to sudden changes in air temperature.
The authors found out that about 600-500 million years ago, sands accumulated in the depressions of the relief of the Siberian paleomaterial, represented by ancient plains, river valleys, intermountain and foothill depressions, which eventually turned into sandstones and siltstones of the Silimkun formation. The source for their formation was other, more ancient rocks composing the continental rocks of that time.
“During the Silimkun period, sands, products of the destruction of rocky uplands, were transported mainly by wind and to a lesser extent by rivers in the south of the Siberian Paleomaterial. Due to the temperature difference, the grains of minerals in the rocks either shrank or expanded, and gradually the mountain range was broken up by a network of cracks, from which the products of its destruction were removed by wind and water,” said Ruslan Gabdullin, one of the authors of the study, senior researcher at the Laboratory of Geochemistry of Sedimentary Rocks of GEOKHI RAS, Doctor of Geological and Mineralogical Sciences.
By studying the composition of the petrified sands, scientists were able to find out what the mountains were made of, through which the ancient rivers flowed. For the first time, a comprehensive geochemical study was carried out for these deposits using high-precision and modern equipment from the GEOHI RAS, which included determining the content of elements using a series of different methods.
“A detailed study of the chemical composition of the studied clastic rocks allows geologists and geochemists to accurately determine the parent rocks, as a result of the destruction of which the studied sediments of the Silimkun formation were formed,” commented Ruslan Gabdullin.
Scientists have established that the sandstones of the Silimkun formation were formed as a result of the destruction of granitoids of the Kalar massif, presumably granite porphyry and fine-grained porphyritic biotite granites. It was these rocks that formed the ancient mountains and hills in eastern Siberia.
The climatic conditions of the late Precambrian — Early Cambrian time are of interest not only from the point of view of understanding the climate of the past, but also from the perspective of forecasting natural resources — the possible generation of certain groups of minerals. In particular, the vast metal reserves of the Udokan copper deposit are associated with the Proterozoic-Early Paleozoic sedimentary formations in this region.
The study was carried out with the financial support of the Russian Ministry of Education and Science.
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