PROSPECTING FOR TRIASSIC DIAMOND DEPOSITS, UNUSUAL IN RUSSIA, IN THE NORTHERN OLENEK RISE (REPUBLIC OF SAKHA (YAKUTIA)
Work schedule: 2013-2015
Major work results for the project:
- Compilation of 1:100 000 diamond potential prospective map for the northern Olenek rise;
- Validation of Triassic primary kimberlite-type diamond deposit potential discovery; these deposits could be sources of “northern” diamond (Ebelyakh type) high-grade placers;
- Localization of the Kilimyarskoye diamondiferous kimberlite field and the Verkhnenikabytsky group of kimberlite bodies within it;
- Crater parts of two kimberlite pipes were revealed within the group;
- High-grade diamond placer (Ebelyakh type) of the Nikabyt river valley and a diamond placer in Rhaetian Upper Triasssic offshore deposits (Bulunkanskaya series) are associated with the Verkhnenikabytsky group;
- Verkhnenikabytsky group primary diamond inferred resources were estimated and approved: 78 M ct (potential), Nikabyt river placer: 1,190,000 m3 sands and 797,300 ct diamonds (inferred), 2,604,000 m3 sands and 940,640 ct diamonds (undiscovered);
- Identified kimberlite pipe vents revealing and their diamond potential (inferred resources) estimation is recommended.
In terms of the Siberian platform regional tectonics, the Kilimyarskoye diamondiferous kimberlite field is located in the northern Olenek arched uplift within the Lena-Anabar trough conjunction zone (Fig. 1).
In compilation of 1:200 000 northern Olenek rise diamond potential prospective map, geological-structural and geophysical criteria indicating potentially diamondiferous fields and orebody groups within within them were defined. As a result of criteria complexing, the Kilimyarskoye potentially diamondiferous kimberlite field was localized and 4 sites of potential kimberlite body groups localization (Fig. 2) were identified. Within the Verkhnenikabytsky site, local magnetic anomalies were proved by drilling revealing kimberlite pipe vents.
Parameters of two revealed pipes were used to quantify primary diamond inferred resources. Pipe areas were determined by geophysical data, estimation scope was set by the project specifications, diamond grades were estimated based on the expected truncation and diamonds discharged to Nikabyt river placer.
Alluvial diamond inferred resources were estimated based on sampling data using reduction factors.