Summary:
The Jadar deposit, discovered in 2004 in western Serbia, is a concentration of lithium and boron in a mineral new to science named jadarite, LiNaSiB3O7(OH). The deposit is located in a valley with flat-lying farmland covering a surface area of 3.0 km by 2.5km. Known lithium and borate mineralisation lies at depths from 100 m to 720 m below surface.
Jadarite mineralisation is present in three broad zones containing stratiform lenses of variable thickness. These units are hosted in a much thicker gently dipping sequence mainly composed of fine-grained sediments affected by syn and post depositional faulting.
The mineralization is hosted in a lacustrine sedimentary sequence of Miocene age dominated by calcareous claystones, siltstones, sandstones and clastic rocks (about 400 m to 500 m thick). The sequence dips to the north at between 0 and 25 degrees or more, but typically between 5 and 10 degrees, and it includes several thin tuff beds that provide valuable marker horizons for stratigraphic correlation. Miocene sediments lay unconformable on a basement of Cretaceous age.
The deposit includes three types of mineralization occurring as stratiform lenses of variable thickness, and hosted in gently dipping sequence of mainly fine-grained sediments that is dissected by faults:
- Jadarite LiNaSiB3O7(OH) mineralization, new to science and so far unique to this deposit; occurs within a stratiform sedimentary lacustrine sequence with sub-horizontal beds of jadarite as rounded grains, nodules, or concretions generally in the range 1 mm to 10 mm in a siltstone/mudstone matrix. Jadarite is mainly concentrated in three gently dipping tabular zones known as the Upper, Middle and Lower Jadarite Zones (UJZ, MJZ and LJZ).
- Sodium borates, mainly in the form of Ezcurrite - Na4B10O17·7H2O, but also as Kernite - Na2B4O7·4H2O, and Borax - Na2B4O7·10H2O, occurs as lenses that are interbedded with jadarite-bearing siltstones and mudstones, present mainly enclosed or adjacent to the LJZ with a more restricted areal distribution.
- Gypsum occurs as layers of gypsiferous sandstone mixed with carbonate and crosscut by fibrous selenite gypsum veinlets; it is concentrated in the upper part of the sequence in the transition from lacustrine to brackish conditions (sub economic).
The genesis of the jadarite and borate mineralisation is conceptual at this stage:
- Jadarite and borate beds are thought to have formed at or near the water–sediment interphase in the sediments from hydrothermal fluids entering the basin.
- The jadarite and borate mineralisation has similarities to other deep water borate environments (i.e. Furnace Creek Fm. in US).
Jadarite bearing sediments are affected by sedimentary processes during deposition, including dewatering, sliding, slumping and extensional/compressional fractures associated with these events. Mineralisation is affected by normal and reverse fractures post-lithification with limited remobilisation of jadarite and other borate minerals.
Significant mineralogical changes in the vertical are controlled by the geochemical evolution of the basin and mineralising events over time, and by the basin scale graben faulting that constrains the jadarite and NaBo mineralisation.
The Jadar deposit is sub-divided in three major zones known as the Upper, Middle and Lower Jadarite Zones (UJZ, MJZ and LJZ), of which the LJZ is the most laterally continuous and homogeneous in grade and thickness. As such, it is the basis for the economic study of the project at this stage and contributes to all reported Mineral Resources.
Jadarite mineralisation in the LJZ occurs as a lens shaped orebody with an average thickness of approx. 15 m (ranging in thickness from 2 m to 50 m). It occurs with economic concentrations from approximately 300 m to 720 m below surface in the studied area.