M.V. Rodkin, S.A. Punanova
Trace element composition of natural objects: correlation dependences
Key words: correlation analysis; mud volcanic waters; carbonic acid waters; hydrocarbon reservoirs; trace element composition; polygeny; Earth’s crust; biota.
For citation: Rodkin M.V., Punanova S.A. Trace element composition of natural objects: correlation dependences. Geologiya nefti i gaza. 2022;(4):99–107. DOI: 10.31087/0016-7894-2022-4-99-107. In Russ.
Funding: The work is conducted within the research plan of ITPZ RAS and ITPG RAS (research issue FMME-2022-0004, State Recording No. 122022800270-0), as well as within the framework of the State Assignment on the subject: “Scientific and methodological basis for exploration and prospecting of oil and gas accumulations confined to mega-reservoirs of sedimentary cover.” Research, development, and engineering work State Recording No. 122022800253-3 in ROSRID.
The authors discuss correlations of trace element composition of natural objects and average modelled composition of different types of biota (marine and terrestrial) with different levels of the Earth’s crust (Upper, Middle, and Lower). Content of trace elements in carbonic acid waters and mud volcanic fluids from the Greater Caucasus region, in natural thermal springs, water bodies, and pore solutions from the Uzon volcano caldera (Kamchatka), as well as in oils of mega-reservoirs from major petroleum basins of Russia and oil manifestations of Kamchatka are analysed. In the vast majority of analyzed oil samples from the Volga-Ural (Romashkinsky field) and West Siberian (Shaimsky field group) petroleum basins, maximum correlation of oil trace element composition with composition of the Lower crust is observed. Trace element composition of oils and oil manifestations in the Uzon volcano caldera (Kamchatka) has closer correlation with composition of the Upper crust. Maximum correlation with composition of the Middle continental crust is identified for carbonic acid and mud volcanic waters from Greater Caucasus. The observed patterns are interpreted as a consequence of close association of the mentioned fluid systems with ascending flow of newly mobilised water — product of dehydration. Under conditions of tectonic activity and higher deep temperatures, dehydration reactions proceed at lesser depths, and ascending fluid flows bear the trace element mark of lesser depths. Contribution of terrestrial organisms predominates in Greater Caucasus mega-anticline, and marine organisms — in mud volcanic fluids of Azerbaijan, Georgia, and Taman Peninsula. The revealed differences confirm the polygeny of trace element sources in naphtides and hydrotherms, which are associated with a living matter and ascending flows of deep fluids, and is indicative of the efficiency of the used option of correlation analysis for studies of trace element composition of natural objects.