Color and morphologie of plasers diamond is index genesis of bedrock source
|Location||International Geological Congress,oslo 2008|
|Author||Rodin, R.S.; Gess, L.V|
|Holding Date||10 September 2008|
The world diamond commercial production manufactures from kimberlites and lamproites. The search of fundamental diamond sources is conducted by placers, therefore it would be expedient to know in search process by found crystals how is the fundamental source is represented. Let is examine two most important characteristics, applied to geological objects study, in our case, diamonds- morphology and color. In lamproites sandy tuffs of the Argyll field fragments of irregular shape prevail among diamonds, twins and aggregate growths are to a lesser degree, and the majority of crystals are strongly resorbed dodecahedrons (monograph of Jakes and others,1998).Among them brown varieties (up to 80%) prevail, colorless and yellow are less than 20%.
On the basis of diamond study in the north-east of Siberian Platform. I.F.Gorina (1973) came to the conclusion: the following diamond varieties are typical for the given region: ochtahedrons, ballases, carbonado, completely-strained dodecahedrons, deformed cuboids. Listed crystals are tinted in yellow, green, brown colors. Such crystals are not faced in no one from kimberlite pipes of the diamondiferous province of the Sakha Republic (Yakutiya).But, if in rocks of Argyll pipe, along with clastogene quartz rare fission-fragments of lamproite magma are discovered, then in the Ebelyakh field, that situated on Middle Cambrian dolomite of Anabara Formation, in numerous karst depressions only tuffisites in the form of terrigenous rocks with fragmental quartz are revealed.
Diamondiferous tuffisites are discovered for the first time in Eastern Pri-Anabar, in Ebelyakh diamondiferous region (Yepifanov, Rodin, 1990). Later they were revealed in Ural (Ribalchenko and others, 1997) and in western Tunguska syneclise (Rodin, Yepifanov, 2001). Tuffisites peculiarity is that they practically not distinguishable from usual volcanogenic-sedimentary rocks in field conditions.
Such diamondiferous formations are discovered in Tichany region of Tunguska syneclise, in Tugana zircon-ilmenite placers (200 diamonds are extracted from 3 tons of technological sample); in Vishera region, Ural (dodecahedrons — "Ural diamonds" prevails among diamonds). Secondary jointing is frequently visible in quartz grains in enclosing rocks of Vishera region in the form of planars, with series of subparallel rectilinear fractures, tracers are also distributed here, they testify that given rocks underwent hyperbaric transformations.
There are two main conclusions: kimberlite crystals in most cases are colorless, diamonds of lamproites are tinted in different colors and table-cut octahedrons prevail among kimberlite diamonds, lamproites crystals are represented by rhombododecahedrons.