The first 40Ar/39Ar age data for trap intrusions of the western part of the Siberian Platform

Abstract

Based on geological and age data it is known [1, 2,etc.] that basite (trap) magmatism at the Siberian Platform was manifested during the wide time intervalfrom the Proterozoic to the Mezozoic. It has beenestablished that the maximum volumes of lava extrusions, tuffogenic formations, and subvolcanic intrusions formed during the short time interval at theboundary between the Permian and Triassic periods[3–5, etc.]. The maximum number of age datings,based on K–Ar and other modern methods was madefor the northern part of the Siberian Platform, wherelarge manifestations of trap magmatism of differentfacies and associated industrial copper–nickel sulfideore deposits are located [6, etc.]. It should be notedthat idea of the shorttime interval of intrusion of trapsinto the deposits of the platform cover and extrusion oflavas on the Earth’s surface has not been confirmedrecently by new age dating. In particular, the majorityof U–Pb age data from different zircon groups of theintrusions from the Norilsk region fall into the intervalof 230–270 Ma. In the same place, the less distributedgroups of zircons form two more ancient age clustersof ~300 and ~340 Ma [7].In the western part of the Siberian Platform, occupying an extensive area between the rivers of Nizhnyaya Tunguska and Podkamennaya Tunguska, thetrap magmatism and the age sequence of its formationhave been studied insufficiently. Structurally, this areacorresponds to the Tunguska syneclise, made up ofterrigenious–carbonate deposits of the platform coverand manifestations of the trap magmatism of differentfacies (Fig. 1).V.S. Sobolev [8] was the first to take into accountthe wide development of intrusive traps in the basin ofthe Nizhnyaya Tunguska River. Further, intrusivemagmatism of this extended territory has been studiedduring geological prospecting and thematic works.Findings of ore “boulders” and fragments of ore bodies of the Norilsk type, as well as recent geologicalprospecting works in this area, have raised interest inthe age sequence of the development of oremagmaticsystems associated with magnesian traps of the MiddleYenisei Province [9].The most complete information on wide development of trap intrusions in the thick sedimentary cover(4.2 km) of the Siberian Platform was obtained as aresult of geologicalprospecting works for oil and gas.