Petrographic and Petrochemical Characteristics of Suevite Matrix, Western Part of the Kara Astrobleme (Russia)

Abstract

The Kara Astrobleme is a unique geological object located in the northwestern part of the Arctic zone of Russia. Impactites from the Kara crater are diamondiferous to various degrees. At present the Kara suevites are relatively poorly studied. Until now the petrographic features of the matrix have been described in general terms, and petrochemically the cementing mass of the suevites has not yet been studied. In 2015 suevite breccias of the southern part of the Kara Astrobleme were subdivided into three different types. It was later suggested that the suevites of the western part of the impact crater, located at the Put’yu and Sayakha rivers, could be type II suevites, but at the same time they had a number of distinctive features which might be associated with different formation conditions of these rocks. Hence it is relevant to study the matrix of the suevites of the mentioned areas to clarify their facies and formation features. The paper presents results of a comprehensive study with a detailed description of the suevite matrix at Put’yu and Sayakha rivers conducted for the first time for the suevites of the Kara Astrobleme. Through optical and microprobe studies we described petrographic and petrochemical features of the cementing mass of the suevites. We discovered that the matrix of the studied rocks was characterized by the similarity of the mineralogical composition, but differing in structural and content features. We found that all the studied rocks belonged to the aerodynamic ejection facies, within which they differed in the temperature conditions of formation which might be associated with the different initial position of the suevite material in the impact cloud. The research results clarify the type and facies of suevites in other areas of the impact structure that will allow defining facies variability and detail characteristics of suevite breccias of the Kara Astrobleme. The obtained data demonstrate genetic regularities of impactites and allow predict the diamond content of the Astrobleme as a whole.