Placer diamond potential of the siberian craton: possible sources and ages

Abstract

Many diamond placers in the Siberian craton are heterogeneous consisting of several components that differ in origin and ages of the source. The diamonds are either kimberlite hosted or are exotic varieties which occur mostly in the northeastern craton periphery and come from primary deposits of unknown types and ages. The two groups of diamond placers in the area represent two evolution trends: those found in Mid dle Paleozoic kimberlites originated in the Famennian and the exotic diamond groups became involved in sedimentation in the Carnian. The trends have been associated with successive weathering of older diamond hosts and redeposition of the minerals into younger sediments. Having joined since the Late Triassic, the two trends eventually produced a polygenetic and multistage mixture of diamond groups in placers.

Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

“…Wide distribution of the highchromium pyropes (to 14 wt.% Cr 2 O 3 ) in the kimberlites in this field and other northern parts of the Siberian platform, and pressure estimates of the xenoliths at w5.1 GPa (Brey and Kohler, 1990) or 6.2 GPa (McGregor, 1974), as well as the abundance of diamond placers in the northern Prianabarie (Sobolev, 1974;Afanasiev et al, 2011), suggest that the mantle keel in the northern part of Siberian platform was similar in thickness to that in the central part of the Yakutian kimberlite province. This is supported by geophysical mantle profiles (Koulakov and Bushenkova, 2010;Pavlenkova, 2011;Kuskov et al, 2014).…”

“…The exceptions are some Devonian kimberlites in Starorechenskoe, Toluopskoe and Ukukite fields and late Jurassic kimberlites like the Obnazhennaya pipe common in Kuoyka (Taylor et al, 2003) and some northern kimberlite fields (Moralev and Glukhovsky, 2000;Zaitsev and Smelov, 2010). Mesozoic kimberlites in Siberia are of low diamond grade but numerous diamond placers in the northern part of Siberian craton (Afanasiev et al, 2011) suggest undiscovered sources. Diamond inclusions from placers in Cir Anabar are essentially eclogitic (Sobolev et al, 1998;Shatsky et al, 2015) while in the central part of the Siberian craton (Logvinova et al, 2005) both peridotitic and eclogitic inclusions are common.…”

Attrition in the kimberlite system

“…re-sedimentation). Attrition of kimberlite indicator minerals during transport within glacial and fluvial systems is of interest to diamond exploration because of its capacity to inform on distances to the source kimberlite pipe (McCandless 1990; Afanas’ev et al 2008; Afanasiev et al 2011; Afanasiev and Pokhilenko 2013). Several experimental studies have established the relative attrition susceptibility of different kimberlite indicator minerals (e.g., garnet, ilmenite, pyroxene) by using experimental duration as a proxy for transport distance.…”