Under Explored Orogenic Gold System
Golden Hill comprises one fully permitted concession totaling 4,468 hectares within the Bolivian Pre-Cambrian shield. Mineralization is of greenstone hosted orogenic gold type, with over four kilometres of gold-bearing quartz veins associated with a regional structure mapped on the property. An additional six kilometers of structure to be explored. Limited drilling has been completed on the property, consisting of only 8 holes totaling 1,620 meters to a maximum depth of 154 meters. Three high-priority drill ready gold mineralized targets have been identified at the La Escarcha, Gaby and Brownfields along with additional targets that warrant further exploration.
Golden Hill Property is located in the underexplored, pre-cambrian Bolivian Shied, Bolivia. Golden Hill is located on a crustal scale structure which hosts at least six other significant gold occurrences and deposits, at the juxtaposition of several different lithologies, including meta-volcanics with abundant iron-rich ferromagnesian minerals. From a regional perspective and comparison with other greenstone belts worldwide, Golden Hill is an attractive project.
Pro-Mining Community and Fully Permitted
The local community is pro-mining and in favor of project development. The community is currently providing support workers to assist with Mantaro's field work. The property is fully permitted for both drilling and mining with no community agreement needed to advance the project.
Easy Access with Established Camp
Golden Hill is located 15 kilometers directly to the east of the Historic mining town of San Ramon — 140 km Northeast of Santa Cruz, Bolivia’s second largest city, for a travel time of approximately 3.5 hours via paved highway. The area is typical of sub Amazonian terrain with year round operating capability. Access throughout much of the concession is good. The property includes an operational 50 t/d gravity circuit processing plant and a well maintained fully functional exploration/mining camp, which includes an office, canteen, mechanical workshop and dormitories with capacity for around 20 workers.
Permitted to Mine and Drill
Prior to the option agreement with Mantaro, one of the main quartz veins at La Escarcha was being mined at a rate of up to 25 tonnes per day to a depth of 60 meters. The mined material was processed at site and gold recovered using a combination of simple gravity circuits. The mine permit at Golden Hill allows for production to be increased subject to the Company completing its own economic studies on the project and to sufficiently fund any upgrades. MGH have reported that gold grades increase downwards from surface to the -60 m level which is currently under limited development.
Limited Drill Testing
To date four major gold mineralized zones have been identified across over 4 km strike length by surface oxide mining, historical trench sampling and mapping. La Escarcha, Gabby, Garrapittilia and Brownfields. Drilling on the property is limited to the immediate La Escarcha Pit area, with 1620 m completed historically between eight diamond drill holes. Highlight intercepts included 13.5 meters at 7.1 g/t Au and 2.6 meters at 17 g/t Au. Over three and a half kilometres of the gold mineralized system remain to be drill tested.
Mineralization at Golden Hill is of Greenstone Hosted Orogenic type. Gold is contained within one to five meter wide sub-vertically dipping quartz shear zones, typically found along faults at the contacts between mafic volcanic and metasedimentary units of pre-cambrian age. These deposit types have the potential for kilometres of strike extension and kilometre + depth potential. The vein system has been traced for over 4 km on the property, located in the hanging wall of a regional controlling fault to the west. This style of mineralization can be observed across the region and notably 2 km to the north of the property at the Puquio Norte gold mine which produced over 350 koz Au between 1997 and 2003.
The Bolivian Pre-Cambrian shield is larger than the Abitibi greenstone belt in Canada, yet the Bolivian shield has produced <10 Moz Au compared to 170+ Moz Au in the Abitibi from over 100 mines since 1901. Similarly, the gold endowment of the West African shield, the greenstone belts of NE South America (Venezuela, Guyana, Suriname and Brazil) and the Yilgarn province of Western Australia much greater than equivalent areas of the Bolivian shield as the Bolivian shield remains largely under-explored.
As with other greenstone belts and mineralized provinces worldwide, mineralization in the Bolivian shield is hosted along major crustal structures which juxtapose different lithologies against each. Regional-scale structures serve to focus mineralizing fluids, whilst rocks of different competency, provide a regime for both ductile and brittle deformation and thus creation of space for deposition of quartz, pyrite and gold. Mafic volcanics are especially favourable hosts due to the high iron content which reacts with sulphur in mineralizing fluids to form pyrite — causing gold to precipitate from the mineralizing fluids.
The Golden Hill concession is centered on a broadly north-south trending regional structure that hosts the La Escarcha underground mine and Gabby, the Garrapatillia and Brownfields workings and gold-bearing vein occurrences in its western hanging wall. The same structure hosts numerous saprolite gold and hard rock gold deposits to the north and south of the Golden Hill concession over a strike length of at least 25 kilometres — underpinning the significant control the structure exerts on gold mineralization.
A northwest-trending splay of this structure hosts areas of alluvial and saprolitic/hard rock workings within the Golden Hill concession and immediately to the north. At least six strike kilometers of these structures are known within the concession — in addition to the four kilometers between La Escarcha and Brownfield which have been mapped in detail. Known mineralization and surface anomalism is open along strike on all structures.
Mineralization between La Escarcha and Brownfields is characterized by a series of broadly parallel, north-south trending, very steeply dipping quartz veins that are between 1 to 5 meters wide. Mineralization is hosted in mafic metavolcanics, at the contact of metavolcanics and metasediments, and within metasediments.
Veins are well exposed in underground workings at La Escarcha where they comprise multiphase white quartz and slivers of wall rock (see Figure …) which are fracture oxidized. Veins are up to 5 meters wide and contain significant visible gold.
Mine staff have reported that gold grades increase downwards from surface to the -60 m level which is currently under limited development. Most gold appears to be free hosted in fractures within quartz and pyrite.
Planned Work Program
La Escarcha, Gaby and Brownfield are drill ready targets. Ahead of drilling, Mantaro is planning to channel sample all underground levels at la Escarcha, in addition to the 200 kilogram bulk sample that has already been taken for bench-scale metallurgical testing at SGS Lakefield. This initial program will assist Mantaro in fine tuning drill targeting. Mantaro also has the option of continuing development and exploration from the existing underground workings.
A concession-wide mapping and rock-chip grab sampling program is planned for early September in order to focus regional soil and trench sampling programs. Alluvial and saprolite workings are much more extensive than known hard-rock targets and underground workings, which suggests that gold mineralization along regional structures is more extensive than currently known. Defining the source of this alluvial and saprolitic gold will be an important focus of Mantaro’s field work.