Geology
The Buena Vista magnetite deposits are the product of late stage alteration of a localized intrusive local gabbro that resulted in intensely scapolitised lithologies and the deposition of magnetite.
The most well-known example of this type of magnetite mineralization is the Kiruna magnetite deposit in Sweden which has been in production since the early 1900’s.
The distribution and nature of the magnetite mineralization at Buena Vista is a function of ground preparation by faulting and fracturing forming a series of open fractures, breccia zones and networks of fine fractures.
As a consequence the magnetite mineralisation has been developed as disseminations within the altered gabbro through to massive pods and occasionally vein like intrusions.
These ground conditions produce variations in mineralization types from massive pods grading +60% magnetite to lighter disseminations grading 10-20% magnetite.
The mineralisation has been best developed within a number of discrete but proximal deposits (Section 5, West and East deposits) that outcrop and exhibit a strong magnetic signature.
The strike of the deposits is approximately east-west for the Section 5 and West deposits and south west-north east for the east deposit. The dip is generally towards the north.
Metasomatic magnetite deposits such as those at Buena Vista have important beneficiation advantages over the other main type of magnetite deposit which is a banded iron hosted magnetite, also sometimes known as a taconite.
Buena Vista has been extensively drilled with three main programmes having been carried out.
DRILLING EVALUATION
The initial programme was by Columbia Mines (US Steel) in the early 1960’s and was by BQ, NQ and HQ diamond drilling and holes were surveyed for dip using a Tropari instrument.
A total of around 112 holes for 18,215 metres was completed and all holes were geologically sampled and logged.
Around 5,000 samples across the magnetite mineralized zones were taken from the drill core and the magnetite content determined by Davis Tube. All testing was carried out at the Colorado school of Mines Research foundation.
In 2010 a confirmatory diamond drill programme of 8 holes comprising 1,415 metres was carried out by Richmond Mining Limited. This programme, which was HQ was designed to twin various 1960’s holes in order to test for vertical and lateral continuity as well as provide QA/QC information on the historic drilling.
All of the holes were geologically logged and then halved or quartered and samples assayed by American Assay Laboratories in Reno and SGS Laboratories in Perth.
In 2012 Nevada Iron Limited carried out a programme comprising 19 drill holes for 3,431 metres of HQ diamond drilling and 50 holes for 13,024 metres of 138 mm reverse circulation drilling.
This programme was designed to provide infill drilling for an expanded resource estimate, extend the boundaries of the known mineralized areas and provide additional core for definitive metallurgical beneficiation test work. All drill holes from this programme were geologically logged and the diamond holes surveyed down hole.
Samples from this programme were prepared by ALS Global Laboratories in Reno and analysed by ALS Laboratories in Perth.
