- Re-modelling and interpretation of regional magnetic data defines crustal-scaleshear zones and associated splays through the Mt Roberts project area
- Gold mineralisation at Mt Roberts is known to be shear-hosted
- Newly defined structural trends match well with known gold occurrences
- New targets defined from regional prospectivity analysis
The Company currently holds two mining leases at the Mt Roberts gold project (M36/279 and M36/341; see Figure 1 in the link below) through a farm-in agreement with Mount Roberts Mining Pty Ltd (MRM) (see Note 1 below). Alt has also recently reached an agreement with Montezuma Mining Ltd (MZM) to acquire the surrounding exploration licence application E36/843 (see Note 2 below), substantially increasing the Company's potential landholding in the area. The Company is required to finalise Native Title, Heritage and Access agreements to expedite the final grant of E36/843 and is currently negotiating with the native title Prescribed Body Corporate with this aim.
This expanded landholding enables the Company to take a whole system, district-scale approach to exploration.
Jubilee Mines NL flew a detailed, low-level aeromagnetic survey over the Mt Roberts-Leinster Downs area in 2000. Whilst Jubilee's focus was nickel sulphide, the survey highlighted major structural trends and lithological domains. With new modern processing techniques surpassing those previously available, Alt Resources contracted geophysical consultant David McInnes to re-examine and re-interpret the Jubilee Mines data.
Figure 2 (see the link below) displays a number of magnetic images produced by different data processing and filtering methods to enhance the level of structural and geological detail and complexity that can be determined from the dataset. In Figure 2a (see the link below), the standard magnetic intensity (reduced to pole) is shown. Figure 2b (see the link below) shows the same processing as Figure 2a (see the link below) but with a tilt filter to highlight structural trends. Figure 2c (see the link below) is a grey scale image that has been filtered to sharpen magnetic features and remove any regional (background) trends. Figure 2d (see the link below) shows the dataset filtered to remove remanence effects (variations in magnetic field orientations recorded in the rocks).
The new images in Figure 2 (see the link below) have highlighted greater detail in major and secondary structures on a project scale. Detailed structural interpretation and domain definition were undertaken by structural geology consultant Dr Michael Doublier. Dr Doublier's interpretation is shown in Figure 3 (see the link below), in which a series of major, parallel, deep crustal shear zones (red lines) are interpreted to transect the area, striking NNW. These major structural zones flank the Leinster Anticline and are parallel to the anticline fold axis.
The area is further affected by secondary shear zone splays (orange lines in Figure 3 in the link below) which appear to host the majority of known gold mineralisation throughout the project area (see Figure 4 in the link below). In the Leinster Downs and Mt Roberts area, these splays appear to form a strike slip duplex indicating significant displacement along the major, primary shear zones.
The new, detailed structural analysis has been combined with regional, historical gold exploration data, available from the Department of Mines and Petroleum. The resulting regional prospectivity analysis of the Mt Roberts gold district highlights a number of important target areas within Alt's tenure. Figure 4 (see the link below) shows regional gold-in-soil and rock chip analysis from the combined datasets of several historical explorers. Gold mineralisation is clearly focused along secondary shears within structural duplex zones, occurring between NNW striking major shear zones. A number of key target areas have been highlighted by Alt Resources on Figure 4 (see the link below), several of which have never been drill tested (as shown in Figure 5 in the link below). A very high-grade rock chip is also shown in Figure 4, collected by Sir Samuel Mines geologists in 2005 from the spoil adjacent to a historical prospector's pit.
Figure 5 (see the link below) shows the maximum Au in drill collars (including aircore, reverse circulation and diamond drillholes) throughout the area, with significant intercepts highlighted. At Mt Roberts itself, the majority of data shown in Figure 5 (see the link below) is the result of Alt's 2016 first pass drilling campaign, which intersected high grade gold beneath the historical workings and confirmed a 200m strike length for mineralisation. Some of the more significant intercepts included (see Note 3 below):
MRRC0003: 3m @ 28 g/t Au, including
1m @ 67.4 g/t Au
MRRC0006: 3m @ 1.95 g/t Au from 17m
MRCC0007: 1m @ 5.59 g/t Au from 29m
MRRC0008: 1m @ 20.3 g/t Au from 49m
MRRC0009: 1m @ 24.4 g/t Au from 64m, and
4m @ 7.96 g/t Au from 78m, including
2m @ 13.75 g/t Au from 82m
MRRC0014: 1m @ 3.57 g/t Au from 51m
MRRC0032: 7m @ 1.66 g/t Au from 35m
Regionally, significant intercepts from historical drilling shown in Figure 5 (see the link below) are the result of work by Agnew Gold Company, Consolidated Gold, Jubilee Mines, Arrow and Western Mining. The data are available from open file reports on the Department of Mines and Petroleum website. Those intercepts which fall within the area of new structural modelling are strongly associated with the secondary shear splays, lying between the major NNW striking structures. A small non-JORC compliant gold resource also exists at the Maria deposit, just west of the northern end of E36/843, comprising 82,000 tonnes @ 4.9 g/t Au, indicated and inferred (Wiluna Gold Mines, 1996; described in Rohde, 1997). Similar to mineralisation at Mt Roberts, Maria represents shear hosted gold in metasediments, occurring within the core of a regional north-plunging syncline (Mt White Syncline). Maria is located 7 km northwest of Mt Roberts.
On granting of E36/843, Alt Resources intends to follow up the new prospectivity analysis with field reconnaissance of target areas identified, rock chip sampling, geological mapping and air core drilling. Furthermore, the Company has approval in place to undertake resource and exploration drilling programs on the Mt Roberts mining leases. This work will commence in September 2017, with drilling planned over a 6 week period.
1. See ARS announcement, 30th August 2016: http://abnnewswire.net/lnk/7868340D
2. See ARS announcement, 30th June 2017: http://abnnewswire.net/lnk/VWKE8L2Y
3. See ARS announcement, 16th November 2016: http://abnnewswire.net/lnk/KQJ6UJ73
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About Alt Resources Ltd
Alt Resources Limited (ASX:ARS) is an Australian based mineral exploration company. The Company portfolio of assets include the Paupong IRG Au-Cu-Ag mineral system in the Lachlan Orogen NSW, the Myalla polymetallic Au-Cu-Zn deposit, the Mt Roberts gold project and the newly acquired Mt Ida South gold project incorporating the Bottle Creek gold mine.
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Alt Resources Ltd (ASX:ARS) Further High-Grade Historical Gold Intercepts at the Un-Mined Southwark Gold Deposit, Bottle Creek