Polyphase nature of Grib pipe formation and its manifestation in paleomagnetic rock properties and sieve diamond characteristics

Paleomagnetic pipe rock properties and sieve diamond characteristics are discussed. To determine paleomagnetic characteristics, 59 samples (41 kimberlites and 18 xenotuff breccias) were taken from pipe rocks in 2019- 2020. Based on analysis results and the obtained data comparison, reasons of magnetic anomaly epicenter shift are validated and polyphase nature of Grib pipe formation is proved. The results suggest complex pipe structure with abnormally magnetized kimberlites. They could be the main anomaly, a focus of early prospecting, which resulted in the pipe discovery. Their location, mostly in the central and eastern pipe combined with primarily east-trending residual magnetization, can account for the eastward anomaly shift and partly beyond the pipe contour. Polyphase pipe nature is also confirmed by various sieve characteristics of diamonds from the orebody.