The Detroit Project has potential for oxide and structure controlled primary gold deposits
The Detroit project has potential for intrusive-related gold deposits. It lies within the Detroit Mining District, 290km southwest of Salt Lake City, and contains numerous historical copper, gold and manganese mines. Alderan controls 27km2 of tenements at Detroit through a series of option agreements with companies such as Tamra Mining LLC and Freeport McMoRan plus several local claim owners.
Detroit lies within the east-west trending Tintic igneous belt which Alderan believes has geological similarities to the Bingham copper-gold-molybdenum mining district further north in Utah and the Battle Mountain and Carlin gold and copper mining districts in Nevada, both of which host world-ranked gold and copper mines. Mineralisation styles at Detroit include porphyry copper-gold plus distal disseminated and structurally controlled oxide and primary gold.
Past mining at Detroit dates back to the 1870s and historical reports indicate production of ~125,000oz gold and 25,000t manganese.
The district has been explored for copper and gold by numerous companies including major mining companies such as Anaconda Copper, Kennecott, Newmont, BHP and Freeport but no one company was able to build a contiguous land position to enable district-wide modern exploration. Exploration in the 1960s delineated the thin, low-grade Basin Porphyry chalcocite copper deposit on the eastern margin of the Basin Porphyry complex. The US Geological Survey (USGS) also explored the area, sampling extensive gold mineralised jasperoids.
Alderan exploration focused on Detroit from 2020-22 and included the following:
- Stream sediment, rock and grid soil sampling
- Magnetic and induced polarisation geophysical surveys plus
- Diamond drilling to test district magnetic and IP anomalies
- Diamond drilling focused on verifying gold mineralisation modelled from historical exploration at the historical Drum gold mine and Mizpah prospect
- Preliminary cyanide leach gold recovery test work
- 27 June 2022 – Alderan secures highly prospective area between Drum and Mizpah gold deposits and Detroit Project
- 25 May 2022 – High grade oxide gold mineralisation in all Drum drill holes
- 28 April 2022 – Alderan successfully completes maiden drilling at Drum
The Drum oxide gold deposit was mined from the adjacent East and West open pits between 1984-89 and produced 125,000 oz gold at a grade of approximately 1.2g/t Au. Prior to Alderan commencing work, it had received no exploration since mining ceased.
Alderan’s exploration since acquiring Drum at the end of September 2021 includes reviewing and modelling historical drill hole data, geological mapping, rock sampling and diamond drilling and preliminary cyanide leach gold recovery test work. This work has verified remnant gold mineralisation left behind when mining ceased, identified new mineralisation as the mineralised horizons are open down dip and along strike and also indicated high gold recoveries for oxide mineralisation.
Key findings from Alderan’s exploration include:
- Exploration potential exists for 42-60Koz Au grading 1.1-1.4g/t of residual mineralisation left when mining ceased. This estimate is constrained to the historical drill holes while the deposit is open down dip and along strike to the south
[It should be noted that this exploration potential quantity and grade is conceptual in nature, that there has been insufficient exploration to estimate a Mineral Resource and that it is uncertain if further exploration will result in the estimation of a Mineral Resource]
- There is potential for high grade structure related mineralisation as indicated by assays up to 38.8g/t Au over 1.5m sample intervals in historical drill hole intersections including:
- 7m @ 6.4g/t Au including 4.6m @ 18.1g/t Au (YC-58A)
- 9m @ 5.0g/t Au including 9.1m @ 10.8g/t Au (YC-113A)
- 2m @ 4.5g/t Au including 6.1m @ 10.3g/t Au (YC-174)
- 1m @ 4.3g/t Au including 18.3m @ 7.7g/t Au (YC-169)
- 1m @ 3.2g/t Au including 15.2m @ 6.4g/t Au (YC-242
- Historical drilling was shallow with an average drill hole depth of less than 50m with holes not testing for primary gold mineralisation below the oxide ore
- Alderan in-pit rock sampling returned assays of +0.5g/t Au for 34 of 75 samples with 20 of these assaying +1g/t Au. The highest-grade sample assayed 10.7g/t Au confirming the potential for high grads gold
- Alderan verification drill holes successfully intersected gold mineralisation grading +1g/t Au confirming the grade and thickness of residual mineralisation and the potential for down dip extensions:
- 9DD22-001: 3m @ 2.9g/t Au within 16.2m @ 1.0g/t Au below north end of East Pit;
- 9DD22-003: 5m @ 2.5g/t Au within 17.8m @ 1.7g/t Au below south end of East Pit;
- 9DD22-004: 1m @ 2.3g/t Au from surface at mined north end of West Pit;
- 9DD22-005: 2m @ 2.0g/t Au from surface at mined north end of West Pit;
- 9DD22-006: 1m @ 1.1g/t Au from surface at mined south end of West Pit;
- 9DD22-007: 9m @ 0.42g/t Au (waste dump) and 5.9m @ 1.2g/t Au 150m down dip of West Pit (hole did not reach target depth);
- The mineralisation at Drum dip at approximately 20o-30o to the southeast and remains open
- First pass cyanide leach gold recoveries for Drum reverse circulation drill hole samples averaged 95% for oxide mineralisation. Gold recoveries for mixed oxide-sulphide mineralisation averaged 78% and was low order for the sulphide zone
- 2 November 2022 – Alderan intersects thick gold zones in all Mizpah drill holes
- 30 September 2022 – Alderan intersects thick gold zones from surface at Mizpah
- 25 August 2022 – Alderan completes drilling at Mizpah oxide gold deposit
At Mizpah, 2km north of Drum, Alderan has reviewed and modelled the historical drill data and completed one diamond hole aimed at testing for down dip extensions 350m west of the north-western margin of the known deposit. This hole intersected 69m @ 0.18g/t Au from 87.5m downhole.
The key conclusions following completion of this phase of exploration are:
- The historically outlined Mizpah oxide gold deposit has exploration potential for 3.0-4.0Mt at a grade of 0.4-0.8g/t gold (40,000-100,000 ounces). This estimate is constrained to the historical drillholes while the deposit is open down dip and along strike to the north and south.
It should be noted that this exploration potential quantity and grade is conceptual in nature, that there has been insufficient exploration to estimate a Mineral Resource and that it is uncertain if further exploration will result in the estimation of a Mineral Resource.
- There are high grade oxide gold intersections including:
- 6m @ 2.3g/t Au (MZ-104)
- 7m @ 1.9g/t Au (MZ-49)
- 2m @ 1.7g/t Au (MZ-93)
- 8m @ 1.4g/t Au (MZ-87-048)
- 8m @ 1.14g/t Au (MZ-87-052) – last assay 9.1g/t Au
- The mineralised system could be signficantly larger than modelling of historical drill holes indicates. Alderan’s holes DD20M-006 (83m @ 0.41g/t Au) and 3DD22-001, located 150m and 350m to the west respectively, are not included in the model.
- The deposit remains open at depth with 40 historical holes ending in +0.5g/t Au and 20 ending in +1g/t Au. The highest grade last assay in a hole is 9.1g/t Au.
- Average historical hole depth was only 28m and there are indications that a second mineralised horizon exists at depth.
- Gold mineralisation not only occurs in the Chisholm Formation and Tatow unit, the mined horizons at Drum, but also in the Howell Limestone which separates the Chisholm and Tatow.
- Mizpah mineralisation occurs from surface, dips gently and is un-mined hence if a mineable deposit was discovered, it would likely have a low stripping ratio.
Alderan’s next steps at Drum and Mizpah are to delineate the extent of the oxide gold mineralisation and explore for high grade primary mineralisation below the oxide. ‘Sighter’ metallurgical testwork will also be carried out.
Alderan district scale exploration at Detroit prior to entering the option over Drum gold mine included historical data compilation, tenement consolidation, geological mapping, stream, rock and soil sampling, ground magnetic and induced polarisation geophysical surveys plus diamond drilling to prioritise prospects.
Prior to tenement consolidation, the Company drilled seven diamond holes focussed in and around the Mizpah gold-silver prospect on Tamra joint venture ground. All holes intersected gold mineralisation with the best grades in hole DDM20-006 which intersected 7m grading 1.98g/t gold within a broad 83m intercept grading 0.41g/t gold. Historical exploration in the mid-1980s for a near-surface oxide gold deposit at Mizpah included 197 holes drilled to an average depth of less than 30m. Forty of the holes ended in highly anomalous mineralisation grading more than 0.5g/t gold and of these, twenty holes ended in +1g/t gold.
Alderan’s exploration has highlighted Detroit’s potential to host skarn, intrusive and structure related copper and gold mineralisation within and on the margins of the Basin Porphyry complex. Bulk leach extraction gold (BLEG) stream sediment samples draining the Basin Porphyry, Copperhead and Mizpah prospects are highly anomalous in copper and gold and supported by rock samples. Of 197 rock samples collected by Alderan, 17 graded >0.5% copper and 28 graded >1 g/t gold with maximum assays 3.2% copper and 9.1 g/t gold. Results support historical rock sample analyses including jasperoid samples collected by the US Geological Survey which graded up to 100g/t Au.
Following the stream and rock sampling, Alderan completed ground magnetic and induced polarisation (IP) geophysical surveys over the highest priority area. The ground magnetics identified anomalies likely to be caused by intrusives, associated skarns and structures and the IP highlighted chargeable zones which were interpreted to be caused by sulphide mineralisation potentially containing copper and gold.
The Basin Complex has a classic porphyry geophysical signature over 500m east-west by 300m north-south. The central Basin Main magnetic anomaly is surrounded by a low magnetic arc followed by an outer rim of variable magnetics. The IP chargeability anomaly covers and wraps around the magnetic anomaly and also highlights targets such as Mizpah, Copperhead, Southern and Northern Extension peripheral to the intrusive complex.
During the last quarter of 2021, Alderan completed a 1,707m drilling programme consisting of six diamond holes to test coincident geophysical and geochemical anomalies for porphyry copper and distal disseminated gold mineralisation. The objectives of the drilling were to intersect economic grades of copper and/or gold mineralisation, identify the cause of the anomalies and prioritise prospects for further exploration.
Exploration also commenced on the historical Drum oxide gold mine, located 2km south of Mizpah, following the execution of an option agreement with North Exploration LLC. Drum produced ~125,000 oz of gold between 1984-89 from an oxide heap leach operation and had received no exploration since ceasing production.
Assays for samples from the 2021 drilling programme were locally anomalous in copper and gold however the grades and intersection thicknesses were not sufficiently encouraging to warrant further drilling on the targets tested. Alderan is now focused on the Drum and Mizpah gold prospects which have potential for both near surface high grade oxide and primary structure controlled gold mineralisation.