Composition, structure, and age of the pre-Jurassic basement rocks in the northeastern framing of the Krasnoleninsky anticlinal fold
The paper presents the results of the unique detailed studies (mineralogical and petrographical, petrological and geochemical (LAICP-MS method), isotopic geochronological, and palynological) of the pre-Jurassic basement rocks from the north-eastern margins of the Krasnoleninsky anticlinal fold. Medium-scale geological scheme of pre-Jurassic basement architecture was created for the north-eastern framing of the Krasnoleninsky anticlinal fold. Three structural and facies zones are identified within the area: one volcanogenic and two metamorphic; different composition, structure, and age of rocks are typical of them. They have their own geological history and represent separate blocks — terranes bounded by regional faults. Documented and examined in detail 5350 m of core taken in the course of dense drilling together with geochronological data on the volcanogenic rocks revealed the fundamental difference from the existing view on composition and architecture of the sequence. The acidic composition of volcanites is ascertained rather than previously considered basic one. Imbricated thrusts are well represented in the volcanogenic sequence, while previous investigations reported about the conformable continuous volcanite beds infilling the graben-type structure. It is found that volcanogenic sequence was formed involving the ancient sialic crust; but the rocks of metamorphic blocks do not belong to this sequence. Conformity of volcanites geochemical features with geodynamic settings of the continental transform margin is established, so the question of validity of the sequence attribution to intermediate pre-Jurassic basement sequence yet remains.
Key words: structural and facies zones; geodynamic settings; absolute age; Krasnoleninsky anticlinal fold.
For citation: Shadrina S.V. Composition, structure, and age of the pre-Jurassic basement rocks in the north-eastern framing of the Krasnoleninsky anticlinal fold. Geologiya nefti i gaza = Oil and gas geology. 2018;(4):27–33. DOI: 10.31087/0016-7894-2018-4-27-33.
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S.V. Shadrina Scopus
Surgutneftegaz, Tyumen, Russia;