Giant swarms of Precambrian mafic dikes and potential diamond resources of ancient platforms |
| |
| Authors: | M Z Glukhovsky |
| |
| Institution: | (1) Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia |
| |
| 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 tectonics. These processes left behind
giant swarms of Precambrian mafic dikes, as well as structurally and genetically 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. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
