Abstract
The variety of morphology and properties of natural diamonds reflects variations in the conditions of their formation in different mantle environments. This study presents new data on the distribution of impurity centers in diamond type Ib-IaA from xenolith of bimineral eclogite from the Udachnaya kimberlite pipe. The high content of non-aggregated nitrogen C defects in the studied diamonds indicates their formation shortly before the stage of transportation to the surface by the kimberlite melt. The observed sectorial heterogeneity of the distribution of C- and A-defects indicates that aggregation of nitrogen in the octahedral sectors occurs faster than in the cuboid sectors.
Highlights
Diverse physical and chemical properties of natural diamonds are believed to reflect the variations in the conditions of their formation in contrasting media
One of the dominant modern viewpoints on the origin of mantle eclogites is the formation in the process of subduction of the oceanic crust under ancient cratons [6,7,8]
Diamonds from mantle eclogites exhibit a diversity of morphological and color characteristics: octahedral crystals, macles, cuboids, and coated diamonds have been found in xenoliths of eclogites [9,10,11,12,13,14]
Summary
Diverse physical and chemical properties of natural diamonds are believed to reflect the variations in the conditions of their formation in contrasting media. It was established that in the lithospheric upper mantle the host to most diamonds are ultrabasic (peridotitic—P-type) and basic (eclogitic—E-type) rocks, which are often found as xenoliths in kimberlites [1]. Despite the majority of mineral inclusions in diamonds belong to peridotitic paragenesis [2,3] the most common diamondiferous xenoliths in kimberlites are eclogites [4]. Such diamondiferous xenoliths give unique opportunity for reconstruction of diamond-forming processes and allow identifying specific characteristics of diamonds in chemically different substrates. Eclogitic diamonds worldwide have wide variations of carbon isotope composition [15,16,17]
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