Oracle Ridge Copper Project (100%)
Eagle Mountain Mining Limited (ASX:EM2), is a copper focused exploration and development Company with a key objective of becoming a low emission producer at its high-grade Oracle Ridge Copper Project in Arizona, USA, to supply the rapidly growing green energy market.
Underpinned by solid foundations, Eagle Mountain has the projects, resources and expertise to build a sustainable copper mining Company.
Project Highlights
A JORC Resource of 28.2Mt at 1.35% copper, 11.06g/t silver and 0.16g/t gold using a 0.8% copper cut-off grade for 380,000 tonnes of contained copper.
Ongoing drilling program with strong pipeline of quality drill targets aiming to increase Resources
Good credentials to potentially be a low emission mining operation
Existing underground mine with 18km of development and extensive local infrastructure
Tier 1 mining jurisdiction of Arizona, USA
The Company continues to deliver strong drill results outside the Mineral Resource Estimate
A highly regarded board and management team motivated to deliver stakeholder value
Well leveraged to the long term forecasted increasing demand for copper
Overview
Arizona is at the heart of America’s mining industry and home to some of the world’s largest copper discoveries now owned by major mining companies including BHP, Rio Tinto, Freeport McMoRan and Hudbay.
Eagle Mountain Mining's main focus is the Oracle Ridge Copper Project, a high grade, advanced stage underground copper/gold/silver project, a JORC Resource 28.2Mt at 1.35% Cu, 11.06g/t Ag and 0.16g/t Au for 380,000 tonnes (or 837,800,000 lb) contained copper, 10Moz contained silver and 142koz contained gold.
The Company continues drilling at Oracle Ridge, with results demonstrating significant high grade copper mineralisation outside the existing Resource.
Project Location
The Oracle Ridge Copper Mine is located less than a two-hour drive from Tucson, Arizona and only a half-hour from the mining town of San Manuel (Figure on right). The nearby San Manuel copper mine was the world’s largest underground copper mine by the 1980’s and produced over 700 million tons of ore from underground alone.
The Arizona mining sector is well supported by world-class infrastructure and a highly skilled workforce. A rail line from the town of San Manuel leads north about 50 kms to a copper smelter.
Regional Map showing the location of the Oracle Ridge Copper Project
Geology and Mineralisation
The deposit at Oracle Ridge is classified as a copper-dominated skarn, with lenses of material with elevated sulphide concentrations occurring within Carboniferous to Cambrian carbonate-rich sediments that have been intruded by late Cretaceous granodiorite sills and dykes. Grade tenor appears to be largely controlled by the proximity to the granodiorite contact and the composition of the sediments. Copper mineralisation has also been identified within the granodiorite, but it is largely limited to the contact zones.
The main copper minerals are bornite, chalcocite, and chalcopyrite, with very little copper occurring in oxide or silicate form. The deposit also contains elevated concentrations of silver and gold, which generally show close associations with copper and, in past operations, have reported to the concentrate. The mineralisation occurs in multiple forms, including fine disseminations, fracture and vein fill, and coarse blebs. The main gangue minerals are magnetite, pyroxene, serpentine, grossularite, dolomite, calcite, and quartz.
Cross-Section of Conceptual Skarn Mineralisation
Mineralisation at Oracle Ridge occurs within five main skarn zones, hosted by three limestone formations; Abrigo, Martin and Escabrosa. These same formations also host significant skarn deposits at other major porphyry mines in Arizona. Skarn alteration and copper mineralisation is believed to have formed during the Laramide, a geologic period when many major world class copper deposits such as Globe-Miami, Magma, Resolution, Ray and San Manuel-Kalamazoo were formed in Arizona and throughout the southwestern US.
Skarns are formed by an influx of hot solutions and a nearby intrusive was likely responsible for altering the mineral composition of the pre-existing limestone and prior to depositing copper, gold and silver minerals. The location of the intrusive at Oracle Ridge is not known and locating this system remains a key exploration objective for the Company. A conceptual section of Oracle Ridge is shown in the Figure below.
Exploration
Since acquiring the project in November 2019, the Company has continued to build on the geological knowledge of the mine and region. This work has included reinterpretation of existing data, structural reviews, multispectral studies, and geophysical surveys.
Mineralisation accessible from underground development
Infrastructure
The project has substantial infrastructure at the mine including approximately 18 kilometres of underground development, access roads, tailings storage facility (closed), underground ventilation, electrical and water services and surface infrastructure including offices and maintenance buildings. The existing infrastructure will reduce capital costs and the time required to re-start potential production, which will be assessed in any future mining study.
The existing infrastructure and approved permits will reduce capital costs and the time required to re-start potential production, which will be assessed in any future mining study.
Existing underground mine at Oracle Ridge includes accessible underground workings providing rapid restart potential
Existing underground mine at Oracle Ridge includes accessible underground workings providing rapid restart potential
Principal Geologist Brian Paull holding core from WT-21-06 (from 371.6m) which assayed 34.4% Cu, 367g/t Ag and 26.2g/t Au
Oracle Ridge Extension “OREX”
Based on encouraging results from an initial field mapping program at OREX in 2020, a detailed mapping project was completed in early 2021, confirming extensive occurrences of outcropping skarn hosted copper-silver-gold mineralisation along the lower contact of the Leatherwood intrusive and the skarn horizon.
Multiple grab samples were collected with many returning high-grade mineralisation (see below left figure which shows the location of the lower Leatherwood – sediments contact and some of the high-grade rock chip samples along this zone). The limestone formations and resulting skarn are very similar to those encountered at the Oracle Ridge mine.
The results of this latest field work indicates that OREX is an outstanding target to define additional skarn-hosted copper mineralisation at Oracle Ridge. Alteration and mineralisation at OREX and at the Oracle Ridge mine displaymany similarities. At the mine, orebodies occur at or near the upper Leatherwood-sediments contact while mineralisation at OREX has been identified at the lower Leatherwood-sediments contact.
The lower contact of the Leatherwood intrusive at OREX can be traced at surface for over four kilometres and displays discontinuous skarn alteration and mineralisation over its entire length. Based on Eagle Mountain’s recent mapping and review of historical drilling information (ASX announcement 12 October 2020), the Company believes that the prospective contact exists at depth below the Leatherwood for approximately three kilometres in an east-west direction (second figure below).
Drilling undertaken by Eagle Mountain Mining outside the existing Resource and the location of the outcropping Lower Leatherwood Sediments contact which showed extensive outcropping mineralisation
Schematic cross section of the Oracle Ridge mine and OREX prospect. The orebodies at the Oracle Ridge mine are located at the upper contact of the Leatherwood intrusives. Recent results and re-interpretation of historical information have confirmed the prospectivity of the lower Leatherwood intrusive at the OREX prospect.
JORC Resources
Mineral Resource Estimate (MRE) for Oracle Ridge increased substantially in November 2023, to 28.2Mt at 1.35% copper, 11.06g/t silver and 0.16g/t gold using a 0.8% copper cut-off grade for 380,000 tonnes of contained copper. A summary of the Resource is presented in Table 1 below.
Table 1 – Summary of Updated MRE Resource Categories (1% copper cut-off grade)*
Resource Category
Tonnes
[Mt]
Cu
[%]
Ag
[g/t]
Au
[g/t]
Contained Cu [t]
Contained Ag [Oz]
Contained Au [Oz]
Measured
3.1
1.4
13.93
0.18
43,000 t or 94,800,000 lb
1.4 MOz
18 kOz
Indicated
12.2
1.36
11.96
0.18
166,000 t or 366,000,000 lb
4.7 MOz
71 kOz
Subtotal M+I
15.3
1.37
12.35
0.18
209,000 t or 460,800,000 lb
6.1 MOz
89 kOz
Inferred
13.0
1.32
9.53
0.13
171,000 t or 377,000,000 lb
4.0 MOz
53 kOz
Total
28.2
1.35
11.06
0.16
380,000 t or 837,800,000 lb
10.0 MOz
142 kOz
* Differences may occur in totals due to rounding
Figure 1 - Summary of Oracle Ridge resource growth.
Table 2 – Summary of Updated October 2022 MRE Resource Categories at 0.8% Cu cut-off
Resource Category
Tonnes
[Mt]
Cu
[%]
Ag
[g/t]
Au
[g/t]
Contained Cu [t]
Contained Ag [Oz]
Contained Au [Oz]
Measured
2.8
1.40
14.67
0.19
39,000
1,324,000
17,000
Indicated
13.2
1.28
12.91
0.19
170,000
5,496,000
80,000
Subtotal M+I
16.0
1.30
13.22
0.19
209,000
6,820,000
97,000
Inferred
10.3
1.15
12.43
0.14
118,000
4,114,000
46,000
Total M+I+I
26.3
1.24
12.91
0.17
327,000
10,933,000
143,000
* Differences may occur in totals due to rounding
Significantly greater tonnages occur at lower copper cut-off grades, or higher grades are estimated with higher cut-offs, providing optionality for future mining and processing studies (refer to Table 2 and Figure 1 below).
Aim & Strategy
Eagle Mountain Mining has a key objective of becoming a low emission producer at its high-grade Oracle Ridge Copper Project in Arizona.
To support this aim, the Company is focused on expanding the Resource base through a three tiered strategy:
Eagle Mountain’s growth strategy
Targeting the Low Emission Production of Copper
Oracle Ridge has a significant gravity advantage compared to other underground operations, which has the potential to be beneficial in many aspects of production.
The figure below shows some of the technologies that will be considered as part of potential future studies, to assist the Company become a low emission copper producer.
Diagram showing the potential for a low emission copper project at Oracle Ridge.
History
The below table shows a chronological history of the Oracle Ridge Copper Project:
Property Owner
Time Period
Events
Phelps Dodge Copper Co.
1873-1937
- Mining in district begins
- 20 t/day copper smelter constructed
- Exploration and Development
Daily Arizona Copper Co, Control Mines
1937 – 1968
- 90 t/day flotation plant constructed
- Operations occur sporadically
Continental Copper Inc, Union Mines Inc
1968 – 1988
- Large scale analysis of mineralisation
- Reported US$19 million expenditure on exploration and development
Santa Catalina Mining Corp
1988 – 2004
- 750 short ton (st)/day mill constructed 1991
- 1000 st/day mill expansion completed 1993
- Roughly 1 million st of ore processed 1991-1995
- 2000 st/day feasibility study 1994
- Operation closed 1996 and mill removed
Marble Mountain Ventures LLC
2004 – 2010
- Real estate developers – no mining or exploration
Oracle Mining Corp
2010 – 2014
- Gold Hawk, renamed Oracle Mining Corp, purchased 100% in the Oracle Ridge property from Marble Mountain Ventures
- 115,850 metre validation drill program 2010-2012
- Air Quality Permit received 2012
- MOU with Pima County on land exchange
- NI43-101 2014
- Secured note granted to Vincere
Receiver of Oracle Ridge Mining LLC (ORM) –
Vincere Resource Holdings LLC
2014 – November 2019
- Vincere’s secured note puts ORM in receivership
- Oracle Ridge Mine assets held on care and maintenance at cost of approx. US$400,000 per annum
Wedgetail Operations LLC
November 2019 – Current
- A subsidiary of Eagle Mountain acquired an 80% interest in Oracle Ridge out of receivership;
- Eagle Mountain (via Silver Mountain Mining Operations) becomes the Operator
Wedgetail Operations LLC
April 2021
- Wedgetail Operations LLS move to 100% ownership
