Orosur Mining Inc – Operational Update
CORPORATE
Orosur Mining Inc – Operational Update
• Minera Monte Aquila reviewing its position in relation to Anzá.
• Mapping and sampling at El Pantano enhances prospectivity.
• Regional sampling results from Ariquemes provide vectors for next
phase.
London, May 4th 2023. Orosur Mining Inc. (“Orosur” or the “ Company”)
(TSXV/AIM:OMI), announces an update on the progress of exploration activities
across its project portfolio.
Anzá - Colombia
The Anzá Project (“Project”) is an advanced stage exploration project in the mid-Cauca
belt of northern Colombia that plays host to most of that country’s major gold deposits.
Anzá comprises a number of contiguous granted exploration titles and applications
totalling roughly 200km2.
Since late 2018, Anzá has been the subject of an Exploration Agreement with Venture
Option ( “Exploration Agreement ”) with Colombian company Minera Monte Águila
(“MMA”). MMA is itself a 50/50 joint venture (“JV”) between Newmont Corporation
(“Newmont”) (NYSE:NEM, TSX:NEM) and Agnico Eagle Mines Limited (“Agnico”)
(TSX:AEM), and is the Colombian vehicle by which these two companies jointly
exercise their rights and obligations with respect to the Exploration Agreement over
the Project.
The first phase of the Exploration Agreement was completed in September 2022, with
MMA spending in excess of US$10m on the Project and in so doing earning an equity
interest of 51%. MMA subsequently informed the Company of its intention to progress
to Pha se 2. This included the payment to the Company of a US$2m option fee
(received in February 2023) and formation of a new mining company required to
crystallise the various ownership stakes.
As at December 31, 2022, MMA had already incurred some US$3.65 million in excess
Qualifying Expenditures for Phase 1. This excess may be carried forward and credited
towards MMA’s investment obligation of US$4 million for the first year of Phase 2.
MMA has advised the Company that it has reduced exploration expenditures on the
Project and effectively placed it in care and maintenance. The Company expects that
MMA will continue to focus on protecting the asset and maintaining positive
relationships with local community groups while it explores opti ons regarding its
involvement in the Project.
The Company will keep shareholders informed as MMA reaches a decision regarding
their involvement in the Project . The Company has great faith in the prospectivity of
the Anzá Project and stands ready and able to reassume operatorship of Anzá if that
is deemed a viable option.
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El Pantano - Argentina
The El Pantano Project is an early -stage gold exploration project in Santa Cruz
province, southern Argentina.
The El Pantano Project covers nine contiguous licences total ling over 600km2 in the
prolific Deseado Massif region, roughly 45km from Anglo Gold’s Cerro Vangua rdia
mining camp.
The El Pantano Project is subject to an Exploration & Joint Venture agreement
(“Agreement”) with private Argentinean company DESEADO DORADO S.A.S and its
shareholders (“Deseado”), the details of which were announced on February 15 th
2022.
As announced on March 2 nd, 2023, low level reconnaissance field work has been
ongoing at El Pantano for the current field season since late 2022 and will continue
until roughly mid-May 2023 before ceasing for the winter recess.
These work programs are focussed on geological mapping, soil and rock chip
sampling, and ground magnetic surveys. As a largely untouched, grass-roots project,
these programs were designed to collect the necessary underlying base data to
confirm the prospectivity of the project, develop the exploration model and to begin
the process of defining targets for the next phase of work after the winter recess.
Thus far, the results of these programs have exceeded the Company’s expectations
and El Pantano has the potential to develop into a large scale gold exploration project.
As noted in March 2023, Company geologists and a specialist structural geology
consultant were invited to visit Newmont’s Cerro Negro gold project, as it was felt by
various visitors that El Pantano bore many similarities to Cerro Negro, both in geology
and geographic scale. This visit provided substantial guidance to the Company’s
exploration team to allow more efficient targeting over El Pantano’s large area.
Most of the gold/silver depo sits of the Deseado Massif region are of the low -
sulphidation epithermal style. In particular, there is a close correlation to major crustal
scale fractures related to the breakup of the Pangea supercontinent and opening of
the Atlantic Ocean in the mid to upper Jurassic. This is often manifested locally as
major SE -NW rift systems with pervasive silicification and veining, over tens of
kilometres, precisely the features that are present at El Pantano and which attracted
the Company to the project.
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Fig 1. Low Sulphidation Schematic – Poster by Williams Mata Rimac
From an exploration perspective, a key feature is the mechanism by which gold is
precipitated from solution to form low-sulphidation gold deposits, which is by boiling.
Hot, gold -bearing fluid rising from depth , boils as the binding pressure of the
surrounding host rocks falls below a cert ain point, occasionally producing large, and
very high-grade gold deposits, as seen at Cerro Negro, that are constrained to a
particular vertical level of the epithermal system (the boiling zone).
The quartz vein systems will then invariably continue upward to the surface, but have
often been stripped of gold, thus producing minimal s urface gold geochemical
anomalism.
Following the Cerro Negro visit, Orosur’s geologists recognised that much of the
modern-day surface across El Pantano sits at a high level in the epithermal system,
above any boiling zone, and therefore gold anomalism in soil geochemistry is likely
not an effective indicator of mineralising potential. Instead, greater attention should be
paid to the higher-level path finder elements, in part icular mercury (Hg) and Arsenic
(As), as well as textural variations in quartz veins and surrounding silicification that
provide guidance as to the level within the system.
Exploration programs were modified on this basis with positive results achieved.
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Ground magnetic surveys have been ongoing for several months using in house crews
and equipment. Magnetic surveys have proven a fast and effective method for
defining the primary structural corridors in the prospect area and this work will continue
for several more weeks. Some preliminary interpretations have been undertaken, in
advance of more detailed work once the survey is complete, and demonstrate that the
project is dominated by a very large, NW -SW rift system, exactly as predicted by the
local mineral system model.
Fig 2. Ground magnetic surveys with Au, Hg and As anomalism
Fig 3. Structural features with Au, Hg and As anomalism, and vein swarms
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Mapping and ground magnetic surveys have identified a major NW -SE structural
corridor over 20km long and 5km wide, with large areas of silicification, alteration and
geochemical anomalism over large areas. Gold anomalism in soils is evident in the
NW end of the main structure, suggesting th is area is somewhat lower in the
epithermal system, while the SE end shows significant Hg and As anomalism,
suggesting a higher level.
A large section of the central part of the main structure covering more than 10km is
not suited to soil geochemistry du e to being covered by river sediments and recent ly
transported cretaceous cover. Magnetic data however shows the main structure
continues uninterrupted under this thin cover.
Mapping to the north of the main structure has so far identified over 70 quartz veins
over an area in excess of 20km2, with textures indicative of cooler temperatures, fully
consistent with the model of a very large low-sulphidation epithermal system. Mapping
of this vein field continues with more being identified on a daily basis.
Future Work
As noted, mapping, sampling and magnetic surveying will continue until roughly mid -
May 2023 before the winter closure, with final assay results and magnetic survey data
then due in June.
Upon receipt of all data, a detailed process of compilation and interpretation will be
undertaken to better understand the mineral system and to plan work programs for
after the winter recess in September 2023.
The required environmental permit process for drilling will also commence in May 2023
such that drilling will then be able to be undertaken later in 2023 should appropriate
targets be identified.
Ariquemes - Brazil
The Ariquemes Project is a large-scale Tin (and associated metals) exploration project
in Rondonia State, Brazil, entirely within the world class Ariquemes Tin Field. The
project comprises a large number of granted licences and applications that in total
cover more th an 3,000km 2, representing the largest land holding in this key mining
district.
Ariquemes is a JV with Canadian listed Meridian Mining UK (TSXV: MNO) , whereby
Orosur has the right to earn a 75% stake in the project by investing US$4m in
exploration over a four-year period in two stages.
While the Ariquemes district is a major Tin producing region, most production is
sourced from local cooperatives or artisanal producers and as such little or no modern
exploration has ever been undertaken across the wider district.
The Company was therefore required to start exploration work at the regional scale,
collecting wide spaced stream sediment samples across the entire 3,000km 2 area as
the first pass to identify key areas for follow up.
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To avoid issues with access to farming land, samples were taken using the 10km x
5km road network across much of the area. During the campaign, over 400 samples
were taken, and then assayed for a wide variety of elements, including Tin, Niobium,
Titanium and a suite of rare earths.
Fig 4. Tin in streams
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Fig 5. Niobium in streams
Fig 5, Rare earths in streams
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Results from the reconnaissance program (Figs 4,5 and 6) demonstrate widespread
Tin, Niobium and rare earth anomali es across the wider area, with most Tin interest
focussed on the southern portion and a lease package to the far east of the area.
In general, Tin and Niobium are often found and exploited together given they derive
from the same source rocks, however the above data demonstrates a transition from
Tin dominance in the southern areas to Niobium dominance in the north – a fact that
was anecdotally know by local miners. The two metals are roughly similar in pricing
structure and as such the Company will examine commercial opportunities in both.
Rare earths on the other hand are not always correlated and there are several areas
of interest in the centre of the exploration that will be examined further.
Future Plans
Stream sediment sampling is largely a qualitive method due to the inherent uncertainty
in how minerals are concentrated in drainage systems. However, it is an efficient
method to cover large areas quickly.
Areas of substantial metal anomalism that have been subsequently identified, will now
be followed up by more direct, quantitative exploration methods in the coming months.
These will include detailed mapping, soil and rock chip sampling and auger drilling of
metal bearing drainages.
For efficiency, this work will be done by the Company’s exploration teams during the
winter recess in Argentina.
Orosur CEO Brad George commented:
“We respect MMA’s decision to reassess Anzá and fully understand the complex
dynamics and priorities of companies of that size, especially in light of recent mergers.
Orosur however see s a tremendous potential at Anzá and would welcome the
opportunity to get back into the driver ’s seat if that option is viable . In the meantime,
our other projects are growing in stature and positioning us well as a diversified
explorer.”