New Findings of Diamonds and Diamond Indicator Minerals in the Middle Timan and Prospects of the Search for Their Original Sources

Abstract

In the poorly studied southeastern part of the Chetlas uplift, ring structures typical for magmatic pipe-type bodies (diatremes) have been established. The main part of the ring structures is located in the areas of the distribution of the Upper Devonian sediments. This fact indicates the lower age threshold of the formation of the objects forming them as Late Devonian, i.e., similar to the age of kimberlites of the Arkhangelsk diamond-bearing province. To assess the prospects of one of the most numerous groups of the ring structures, heavy-mineral concentrate sampling of the modern stream sediments was conducted. While studying the heavy-mineral concentrates, chromium-bearing pyrope—a kimberlite indicator mineral—was revealed, and the first diamond grain was found. About 20% of pyropes are characterized by a high preservation of relict endogenous surfaces. The diamond has the appearance of a flattened aggregate with the distinct octahedron faces modified by surfaces of joint growth with other mineral grains. Findings of diamonds and signs of the formation of the diamond indicator minerals in the stream sediments of the studied area make it possible to detect their nearby original sources.