Geodynamic Evolution of the Western Part of the Russian Arctic and Its Diamond Potential

The study of the geodynamic evolution of the Baltic Shield showed that the melts of diamondiferous kimberlites and related rocks were formed due to the pulling of “heavy” ferruginous sediments of the Early Proterozoic into subduction zones beneath the Archean cratons. Later, during the Neoproterozoic and Paleozoic stages of rifting, melts conserved in the lower crust and subcrustal lithosphere were able to penetrate into the near-surface zones of the crust and form magmatic complexes of alkaline–ultramafic and kimberlite magmatism. The authors showed that diamondiferous kimberlite and lamproite explosion pipes, as well as related carbonatite and alkaline–ultramafic intrusions, are mainly located above the subduction zones of the Svecofennian (Karelian) plates, which functioned about 2.0–1.8 Ga ago. At the same time, alkaline ultramafic intrusions and (sodium) carbonatites are located closest to the front of the subduction zone of Proterozoic plates (from 100 to 200–300 km). Then (at a distance of 200 to 400 km), there is a zone of location of calcite carbonatites and melilitites, and sometimes nondiamondiferous kimberlites. Diamondiferous kimberlite and lamproite diatremes are located farther than other similar formations approximately 300 to 600–650 km from its front. Such a regular spatial arrangement of magmatic complexes of a single series unambiguously indicates a change in depth of their origin. The farther from the surface boundary of the paleosubduction zone the magmatic bodies are located, the deeper the facies representing them.

Ratio of structural impurity distribution in diamond crystals and kimberlite pipe diamond potentiak (case study of Arkhangelsk region and Yakutia)

IR spectroscopy was used to compare diamonds from 12 pipes, Arkhangelsk region. Based on positive correlation between average N and H values in diamonds from various deposits, it was found that crystals from low-grade diamond pipes are relatively enriched in hydrogen compared with diamonds from Lomonosov and Grib deposits. In terms of structural impurity distribution, Arkhangelsk deposit diamonds differ from Yakutian diamonds; it could be due to various composition of compared diamonds’ source matter and thermodynamic conditions of their growth. It is shown that hydrogen is a negative factor of diamond potential in both Yakutian and Arkhangelsk diamonds. This can partly be explained by impuri-ty blocking effect on diamond crystal growth.

Diamond study features in forecasting and prospecting (Siberian platform)

Based on the completed research and data summary on diamonds specific features (an example from the Siberian platform), conclusions were made that indications exist at all levels of their location: from kimberlite-related provinces, subprovinces, fields, diatremes to ore shoots. Population of diamond varieties in kimberlite rocks forms parasteric, rather than paragenetic, associations related to their coexistence in kimberlites. Morphological criteria of kimberlite diamond potential were defined depending on rounded diamonds content in them. Significant differences in kimberlites diamond potential were not revealed to the explored depth of diatremes. A conclusion about the absence of horizontal concentric zonality in the change of diamond typomorphic features was made.

Diamond study features in forecasting and prospecting (Siberian platform)

Based on the completed research and data summary on diamonds specific features (an example from the Siberian platform), conclusions were made that indications exist at all levels of their location: from kimberlite-related provinces, subprovinces, fields, diatremes to ore shoots. Population of diamond varieties in kimberlite rocks forms parasteric, rather than paragenetic, associations related to their coexistence in kimberlites. Morphological criteria of kimberlite diamond potential were defined depending on rounded diamonds content in them. Significant differences in kimberlites diamond potential were not revealed to the explored depth of diatremes. A conclusion about the absence of horizontal concentric zonality in the change of diamond typomorphic features was made.

Prospects for diamond potential of the Charo-Sinskaya fault zone

New data on the geological structure of the CharoSinskaya zone of deep faults located on the southern side of the Vilyui syneclise are presented. Based on the processing of the seismic survey results, the deep structure of the territory has been analyzed, and graben-like structures similar to those found near the known kimberlite fi lds of Yakutia have been identifi d. Taking into account the results on the mineralogy of the indicator minerals of kimberlite, a new kimberlite field location is predicted.

Typomorphic properties of kimberlite indicator minerals and their use in forecasting diamond deposits on the Siberian Platform

The results of mantle nodule investigations in kimberlite diatremes of the main Siberian Platform diamondiferous regions were analyzed. Morphology and chemistry of garnets, chrome-diopsides, clinopyroxenes, olivines, picro-ilmenites, chromites, chrome-spinellids and diamonds were investigated in detail. Generally, the quantity of diamond association minerals is proportional to diamond potential of a certain kimberlite variety for each type of kimberlite rocks composing pipes.

Hydrotermal mineralization hosted by Cambrian sedimentary rocks asevidence of kimberlite-hosting structure, Syuldyukarskoye field, Yakutia

The paper describes diamondiferous kimberlite area within a new Yakutian Syuldyukarskoye fi ld and presents detailed mapping results of ore-hosting shear evidence, veinlet bleaching of redbeds, outcrops of metagrained pyrite, pyrite-calcite and calcite veinlets hosted by Cambrian terrigenous-carbonate rocks where kimberlites occur. Kimberlite localization is shown at fault junction as well as kimberlite long axis combination with west-northwest orehosting shear. These tectonic structures combine with veinlet bleaching halos, those of pyrite-calcite and calcite veinlets, and calcite druses characterized by red photoluminescence and phosphorescence. Red, blue and partially white photoluminescence is caused by manganese concentration in calcites (> 0,1%). Hydrothermal calcite nature is supported by C and O isotope composition variations, which reflect the input of medium temperature formational and meteoric waters, carbon of sedimentary carbonate rocks and deep hydrocarbons. Anomalous Ba, Cr, Ni and La content is recognized in hydrothermal calcites from near-kimberlite environment. Kimberlite position in the southeastern part of endogenous mineralization halos and greater diamond potential of the western kimberlite body, which is larger compared to the eastern one, allow forecasting of new productive bodies.

Editorial for Special Issue “Minerals of Kimberlites: An Insight into Petrogenesis and the Diamond Potential of Deep Mantle Magmas”

Kimberlites are igneous rocks that represent the deepest magmas originated from the mantle (>150 km) and typically occur within cratons [...]