Detecting kimberlite pipes at Ekati with airborne gravity gradiometry

Abstract

From late April to the end of July 2000, a 39,000 line km airborne gravity gradient survey was completed over the EkatiÔ mine property in the NWT, Canada. This was the world?s first airborne gravity gradient survey for the purpose of detecting kimberlite pipes. Preliminary data processing was done on site at the EkatiÔ diamond mine. Subsequent drilling of gravity anomalies in the year 2000 has resulted in the discovery of two new kimberlite pipes. More anomalies will be drilled in 2001. The AGG data shows that more than half of the known kimberlite pipes have associated gravity anomalies. Some pipes with a diameter as small as 100 m or less can be detected in the AGG data. The AGG data has a 300 m resolution with an average RMS noise of 7.6 Eotvos in the derived vertical gradient. Laser profilometer data and differential GPS data were also acquired in the survey to construct a detailed digital elevation model for terrain correction. Besides detecting kimberlite pipes, the AGG data is also useful for mapping details of geological structures. This is complementary to the magnetic data acquired simultaneously with the AGG data.