Specific features of the formation and material composition of the Suntar volcano-tectonic structure basic rock intrusions (NW Yakutia)

Specific features of the structure were studied and comparative analysis was performed of the material composition of substratum and dyke intrusions of Vilyuy-Markhinsky and Charo-Sinsky dike belts, formed during the evolvement of the Suntar volcano-tectonic structure. These intrusions have a broad areal spread. Sub-bedded bodies of dolerites are registered on the greater part of Srednemarkhinsky and Malobotuobinsky diamondiferous regions, including Nakyn and Mirny kimberlite fields. The total thickness of these intrusions in Malobotuobinsky and Srednemarkhinsky regions changes along the sections of individual boreholes from 3050 m to 480 m. Bodies with thickness up to 500 m were revealed in Charo-Sinsky region. The scale of occurrence of basic composition intrusive magmatism is emphasized by extent of dyke swarms related with sub-bedded bodies as well. Thus, the length of Vil-yuy-Markhinsky dyke belt is 800 km, with 20 km width in the south-west (Malo-Botuobinsky region) to 150 km width in the northeast (Srednemarkinsky and Tyungsky regions). The number of dykes transversely to the strike changes accordingly from 4-5 to 3040. Charo-Sinsky dyke belt has a 500 km extent. Up to 20 dyke bodies are mapped transversely to the strike of this belt. Basing on the similarity of petrographic and petrochemical compositions of intrusions and the general scheme of formation, a conclusion about the uniformity of their mantle chamber was made. Differentiation of magmatic melt, which used to form sub-bedded and fissuring intrusives, also occurs in the lateral alteration of their petrographic composition. Tholeiitic gabbro-dolerites are most common for the internal parts of dyke belts. Their subalkaline differences, as well as monzonite-porphyries, quartz syenite-porphyries, trachydolerites and alkaline syenite-porphyries, are broadly developed in the peripheral parts. Tight spatial conjugation of kimberlite bodies and subalkaline basic rocks allows forecasting new areas, perspective on kimberlite magmatism occurrence. Discovery of a new Hompu-Maisky kimberlite field within Charo-Sinsky belt is an example of successful implementation of a similar forecast.

Keywords

Authors

References