The Penco Module deposits have been defined as “regolith-hosted REE deposits” or “ion-adsorption deposits” (IAD). These are traditionally formed by tropical or subtropical weathering and decomposition of intrusive rocks with a primary enrichment in either mid/heavy REEs (peralkaline igneous rocks) or light REEs (peraluminous igneous rocks or carbonatites), where REEs are readily liberated by ionic solutions and are hence ion exchangeable (Wang et al., 2015; Dostal, 2017; Borst et al., 2020). Exchangeable REEs are associated with kaolinite and halloysite, the dominant clay minerals in IADs due to their role in adsorbing and fractionating REEs (Wu et al., 1990; Bau, 1991; Jeong, 2000; Bao and Zhao 2008; Williams-Jones et al., 2012; Sanematsu and Watanabe, 2016; Li et al., 2019; Yang, 2019; Borst et al., 2020 and references within).

The regolith profiles in the Project were developed through subtropical weathering of a peraluminous garnet-bearing granitoid, hence richer in LREEs. The regolith ranges between 25 to 48 m in thickness and is more developed in the garnet-rich granitoid than the other granitoids. The primary REE source is hosted in monazite-allanite and lesser xenotime, garnet and ilmenite. A secondary paragenesis formed by a late propylitic hydrothermal alteration (chlorite, sericite, epidoteallanite, locally biotite) replaced monazite with allanite and torite, and was relevant for the subsequent REE fractioning (Dold, 2015).

The exchangeable ........

The Penco Module covers a surface area of approximately 600 ha. However, the property directly involved has a surface area of approximately 250 ha.

Mining Methods
As the aforementioned technical studies for the Preliminary Economic Assessment of the Project were developed, the following outcomes were obtained based on the available information:

• The final sequence obtained, following the plans indicated in the previous point, corresponds to Victoria Sur - Victoria Norte - Luna - Maite - Alexandra.
• A sequential exploitation of the sectors is carried out. Once mining has been completed in one sector, then begins in another.
• Regarding the final pit shells selected by sector.
• Overall pit angles per rock type were used in the pit optimization analysis. No final pit and mining phase designs were generated during this stage of the Project.
• The mining Project consists of 5 pits: Victoria Norte, Victoria Sur, Alexandra, Maite, and Luna. In addition, there are Waste Disposal Facilities called Jupiter and Neptuno plus three temporary topsoil deposits or stockpiles.
• Three types of materials are obtained from mining the deposits: mineralized material, waste, and topsoil, which are destined for processing plants, disposal areas and temporary stockpiles respectively. Mineralized material will be sent to the processing plant, the waste and filtered tailings (mineralized material that have already been processed) will be sent to ........

Overview
The rare earth carbonate production process was designed based on the results obtained in the tests developed by the Universities of Concepcion and Toronto, in addition to the Chapi batch tests.

The Project considers an average production of 1,275 t/a (dry basis) of carbonate of earth rare, where the raw material is an ionic clay mineral containing various lanthanides whose feed to the process is at a rate of 240 wet t per hour.

The mineral in a first stage is selected wet to a defined granulometry <1mm. This mineral under 1 mm is leached with an acidic ammonium sulfate solution (pH =3.0 – 4.0) through a countercurrent process. The leaching solution is not selective, in addition to extracting rare earths, it leaches a series of polluting elements.

This solution enriched with rare earths and pollutants is subsequently treated to precipitate, by chemical reaction, the pollutants, mainly aluminum and iron, by means of an acidic solution of am ........