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Kirill Ivanov, Institute of Geology and Geochemistry RAS (Russian Federation)
Yuri Fedorov, Lukoil-Western Siberia (Russian Federation)
Yuri Erokhin, Institute of Geology and Geochemistry RAS (Russian Federation)
Olga Pogromskaya, Institute of Geology and Geochemistry RAS (Russian Federation)
Yuri Ronkin, Institute of Geology and Geochemistry RAS (Russian Federation)
Irina Plotnikova, Kazan State University (Russian Federation)
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New data have been obtained from 59 rare, rare-earth and other elements in crude oil from the West Siberian (Sredneobsky and Shaimsky regions) and the giant Romashkino deposit (Tatarstan Republic, Eastern part of East-European platform, South-Tatrian uplift). ICP-MS analyses made with high resolution mass-spectrometer ELEMENT 2. The principle geochemical anomalies in these samples include limitedly low content of most elements, except for the elements V, Ni, Cr, Ca, Sr, Na, Rb, Cs. For the West-Siberian oils marked a PGE (platinoid) presence in substantial quantities, especially of palladium.
While normalizing on contents in primitive mantle [Taylor, McLennan, 1985] in oils are established positive anomalies on U, Sr, Ti, Y, Zr, and negative anomalies on Sm, Hf, Th, Nb, Nd. The rare-earth elements in the West Siberian oils demonstrate a particular type of trend characterized by enrichment of the light lanthanides (La/Yb=16-19) and a sharply positive Eu anomaly. The crude oil samples of the Romashkino deposit, when similarly normalized against the primitive mantle distribution in oil of rare and scattered elements, manifest positive anomalies of Sr, Rb, Cs, Hf, Zr, Eu, U and negative anomalies of Ti, Th.
The content of PGE is about one order lower in the Romashkino crude oil than in the West-Siberian. Rare-earth elements in the Tatarian oil show approximately one type of trend with gradual enrichment of light lanthanoids with high La/Yb ratio up to 20 units and the presence of sharply positive Eu anomaly. Oils from the West Siberia and Tatarstan are of different geochemical types. The elemental distribution in the crude oil from all studied deposits does not match such of any known crystal rock. The experimental data presented should be taken into consideration during origin of oils is being discussed.
Oils have the geochemical features of ultramafic rocks and it might be one of the evidences of the abiotic deep origin of oils investigated. The distribution of elements, and particularly of the Group VIII platinum series, is characteristic of such in the mantle of the Earth. Furthermore, there has never been observed elevated abundances of palladium, europium, or the light lanthanides in any biological material. Nor is there known any biological process that might concentrate these elements. The ICP-MS method begins a new stage in oil inorganic geochemistry study.
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