Dateline is confident a substantial rare earths system is present within its Colosseum project, where work has historically focused on its gold endowment.

Technical studies found that multiple fenite dyke outcrops over a 1.6km strike suggests the presence of a large underlying alkaline carbonatite, a type of rock that is known to host some of the world’s largest rare earth element deposits.

Dateline Resources’ (ASX:DTR) REE expert Tony Mariano expressed surprise at the amount of fenites and the extent to which they could be traced.

“The existence of the fenitised rocks in conjunction with the mantle derived trachyte dykes, set only a few miles from the richest carbonatite orebody in the world, makes the search for an underlying rare earth bearing carbonatite that is similar to the one at the Mountain Pass mine very compelling,” he added.

Mountain Pass is the only operating REE mine in the US and has the highest grade (7%) REE content of any carbonatite in the world.

Highlighting just how valuable a REE endowed carbonatite could be for the company, Mountain Pass has a mine life of about 35 years while its owner MP Materials is sitting on a market capitalisation of about US$6bn.

Further support for Dateline’s belief in Colosseum’s REE potential came from the studies noting that 86% of the fenite samples assayed had returned anomalous REE values while all samples had anomalous strontium and barium, which are indicator elements for a carbonatitic system.

“The highest Total Rare Earth Element (TREE) reading of 0.391% (3,910 ppm) from a fenite sample is significant because these anomalous levels of REE in the fenites (indicator rocks) shows that there are abundant REE in the system that generated these rocks,” Mariano explained.

He added that both strontium and barium are highly anomalous in rocks at Mountain Pass.

Colosseum project

Colosseum has historically been focused on gold mining with the company defining a remaining JORC 2012 resource of 20.9Mt at 1.2 grams per tonne (g/t) gold, or 813,000oz of contained gold, despite sitting along strike from Mountain Pass.

This state of affairs lasted until Dateline identified radiometric anomalies which highlighted its potential to host REEs.

A subsequent site visit by Mariano and his father Dr Anthony Mariano – who are leading experts in REEs – in February 2022 resulted in the collection of samples that were confirmed by laboratory analysis as being fenites and other mantle derived rocks that are associated with alkalic-carbonatitic activity.

These rocks are used as a vector in the search for REE bearing carbonatite bodies.

Dr Mariano noted in late April that the “occurrence of multiple outcrops of these lithologies at a distance of almost a mile apart within the Colosseum claims suggest the possibility of a large underlying alkaline carbonatite occurrence”.

His comments prompted the company to undertake a more thorough and extensive program to determine if additional evidence of an underlying carbonatite at the Colosseum could be found.

“This is obviously an important time to be searching for critical metals. The Colosseum project is located in what is arguably amongst the best geological addresses to find another major REE discovery,” Dateline managing director Stephen Baghdadi said.

“Should the current promise of the geological findings be fulfilled, the proximity to the Mountain Pass REE mine may provide an opportunity to fast track the commercialisation of any potential discovery.

“We are fortunate to have experts of the calibre and experience of Messrs Mariano assisting us in our analysis of the potential of REEs at Colosseum.

“Their intimate knowledge of the Mountain Pass – Colosseum corridor has enabled us to identify in a few months what would normally take years to find.”

Next steps

Dateline plans to review ground gravity data combined with airborne gravity gradiometer data (supplied by the United States Geological Survey) alongside geochemical and geophysical results to better rank and prioritise targets for drill testing.

It has also retained the services of the former Mountain Pass geophysicists to help interpret the gravity data while a report by structural geologist Dr Russel Mason will be incorporated into its planning and drill targeting.




This article was developed in collaboration with Dateline Resources, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.