From left to right, Matti Kinnunen (GTK), Jouko Jylänki (Otanmäki Mine) and Janne Hokka (GTK) testing a differential GPS to mark the exact drilling points at the Otanmäki tailings site. Photo: Teemu Karlsson (GTK)
In August 2022, GTK visited the Finnish case site, Otanmäki, located in the municipality of Kajaani, in central Finland. Otanmäki is a closed vanadium, titanium and iron mine last active between 1952-1985. The visit was hosted by FutuRaM partner, Otanmäki Mine Oy, owner of the Otanmäki ilmenite tailings project.
Otanmäki is a pioneer in pursuing commercial extraction of tailings waste in Finland. The field investigations started in 2017, including 140 sampled auger drill holes and 21 hand-dug shallow pits, resource modelling, moreover, lab- and pilot-scale beneficiation tests at GTK Mintec. The prefeasibility study of the project is in the final phase, aiming to start the ilmenite production by 2025. The current interim tailings resource is 9.8 Mt at 7.9 % TiO2 which is bridged to UNFC E2;F2;G2.
The objective of GTK’s field visit was to plan further investigations at the Otanmäki site as part of the FutuRaM project. The investigations will include, for example, a test of different drill sampling methods to determine the sample representativenesses and the optimal sampling method for accurate resource estimation. Furthermore, around 45 additional close-spaced points will be drilled to determine the sensitivity to local variability, and to choose the optimal drill-hole spacing (sample strategy). The drillings will be conducted by GTK in spring 2023.
After the field trip, a GTK drone team was sent to Otanmäki for drone photogrammetry. Based on three flights with a flight height of 120 m, a detailed (1.6 cm/px) orthoimage was created. The main purpose of the 3D surface model will be to help planning the drilling points. However, it can also be utilised in e.g. defining the amount of tailings material and hydrogeological conditions.
A surface 3D model of the 145 ha Otanmäki tailings area was created based on drone photogrammetry performed by GTK in autumn 2022. Image: GTK.
The Otanmäki case will serve as an example for future projects on UNFC classification of secondary raw materials. The test work is to enhance sampling and modelling methods, and to provide assessment of best practices for wider application in other tailing sites. These FutuRaM project activities will also contribute in ensuring the start of the production of titanium mineral ilmenite. Titanium is one of the raw materials classified as critical and of especial importance for the EU economy.
Writers: Teemu Karlsson, Janne Hokka, Jouko Jylänki.