Giant Swarms of Precambrian Mafic Dikes and Potential
Diamond Resources of Ancient Platforms

M. Z. Glukhovsky

Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia

e-mail: marat@ilran.ru

Received September 12, 2005

Abstract—By the examples of the Siberian Platform and Canadian Shield, it is shown that spatial juxtaposition
of Phanerozoic diamond-bearing kimberlite fields with giant swarms of Precambrian mafic dikes is caused by
both systematic and incidental events. The first of these include (1) origination of mantle plumes and associated
lenses of high-temperature mantle melting in the subequatorial “hot belt” of the early Earth, (2) formation of
magma chambers that generated mafic dikes in these asthenospheric lenses, (3) shear stress, and (4) ultrahigh-
pressure metamorphism of igneous and country rocks. As a result, the association of diamond-bearing high-
density mafic and ultramafic rocks was formed under favorable thermal and fluidal conditions. These processes
occurred first in the embryonic (multiplate) Neoarchean tectonic setting at a depth of 40–60 km (present-day
elevation marks) and then at a deeper (100–150 km) level during the transition to the Proterozoic true plate tec-
tonics. These processes left behind giant swarms of Precambrian mafic dikes, as well as structurally and genet-
ically related deep-seated morphological and density anomalies. The relatively high position of two lithospheric
units of diamond-bearing rocks, each underlain by a thick layer of the cold mantle, prevented these units from
thermal and mechanical erosion during subsequent plate-tectonic stages characterized by deeper location of
asthenospheric layers. The occurrence of clusters of Phanerozoic diatremes in ancient giant swarms of mafic
dikes, as well as the enrichment of pipes in xenogenic diamond-bearing material derived from different levels
of the tectonically delaminated lithosphere, may be attributed to incidental events that controlled the fertility of
a relatively small number of kimberlite pipes.

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