Economic Geology
Vol. 53, 1958, pp. 220~226
REVIEWS
The Diamonds of Siberia. By A. P. BOBRIEVICH and others. Pp.158; figs. 192, map 1. Gosudarstvennoe nauchnotekhnicheskoe izdatel'stvo literatury po geologii i okhrane nedr, Moscow 1957. Price, Roubles 14.85. (In Russian.)
This book is contributed by 14 authors and presents an account of preliminary studies, during the period of 1954-1956, of diamond deposits in the basin of Vilyuy, the left tributary of Lena River, in eastern Siberia. The diamond deposits occur in an area of 300,000 sq km in the central part of the Siberian platform. There are two subprovinces where the diamondbearing kimberlite pipes have been
discovered.
Both subprovinces are located on the border of the Tungusian syneclise where the stratigraphic sequence is represented almost exclusively by Ordovician carbonaceous formations and trap effusives. The southern subprovince is located in the basin of Malaya Botuobiya River (tributary of Vilyuy), and is associated with a local swell on the slope of Mesozoic subsidence. The largest kimberlite "pipe Mir," measuring 490 by 320 m, was discovered in this region within Ordovician dolomites, limestones, and marls.
The pipes are filled with brecciated kimberlite with inclusions of related ultrabasic rocks, eclogites, and Archean crystalline schists. The inclusions of limestone are not altered. Generally, kimberlite contains up to 50 percent of foreign material. Slickensides are developed on the surface of kimberlite fragments, especially near the contact with the country rock. The fractures served as channels for hydrothermal solutions that resulted in carbonatization of kimberlite.
The southern subprovince is located in the basin of Daaldyn River, on the northeastern horder of the syneclise. Here again, the vertical kimberlite pipes pierce horizontal carbonaceous deposits of Lower Paleozoic age, with trap intrusions forming dikes and sills.
The swarms of kimberlite pipes are structurally related to deep tectonic fractures; however, the area of predominant distribution of kimberlite pipes is located outside the region of maximum development of trap. In this subprovince, the diameters of pipes range from 40 to 600 m (pipe "Zarnitsa"). The age of kimberlite pipes is considered as post-Permian, and even as post-Triassic.
The kimberlites are composed of olivine, phlogopite, augite, ilmenite, perovskite, and apatite. The diamonds are associated with this suite of minerals. Pyrope, monoclinic pyroxene, spinel, chromite, kyanite, corundum, and rutile are present as fragments derived from xenoliths.
The secondary minerals are represented by serpentine. calcite, quartz, dolomite, chalcedony, and zeolites. The pyrope-rich xenoliths of eclogite represent a rock unknown within the Siberian Archean formations. The association of kimberlite with eclogites throughout the world demonstrates a close genetic relationship of these rocks.
A gradual transition between Archean hypersthene schists and eclogite has been recorded in xenoliths in kimberlite.
The most characteristic companions of diamond are pyrope and ilmenite.
Pyrope from kimberlites has a higher content of chromium and calcium than pyrope from other rocks.
Ilmenite, in turn, contains considerably more iron and magnesium oxide than the ordinary ilmenite. Chromium and vanadium are present in ilmenite taken from kimberlite, and are absent in ilmenite from trap.
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