In December 2019, NAE was granted a 265 km2 Prospecting Permit (PP60544) covering the prospective Lammerlaw area in Otago, New Zealand. The Lammerlaw Prospecting Permit was granted to NAE after winning a competitive Newly Available Acreage process when the area became available in early 2019.
The Lammerlaw Prospecting Permit adjoins NAE’s Otago Pioneer Quartz Exploration Permit 60502 to the southeast.
The Permit contains the historically mined Bella Lode where gold was mined in the late 1800’s with an average grade of 15 g/tonne Au over 0.6-1.8m thickness, before the mine closed in 1901. The Permit also contains a historically mined antimony lode and scheelite (tungsten) workings with minor occurrences of copper, silver and mercury.
New Zealand’s largest alluvial gold deposit, Gabriels Gully (>0.5 Moz produced), is located approximately 3km directly to the south of the Permit the source of the gold remains unidentified.
Macraes Style Shear Hosted Gold Exploration Targets
The regional geology is dominated by the Otago Schist belt, a high-grade metamorphic schist, which has a long history of both hard rock and alluvial gold mining. The Otago Schist is divided into structural blocks or zones of increasing metamorphic grade known as; Sub-Greenschist Facies, Lower Greenschist Facies, Upper Greenschist Facies and Amphibolite Facies. Gold mineralisation at the >10Moz Au Macraes deposits, hosted in the Hyde Macraes Shear Zone (“HMSZ”), occurs entirely within the Lower Greenschist Facies zone in the northeast of the Otago Schist belt.
MacKenzie and Craw (2016) identified the potential for Macraes style shear zone hosted gold deposits to occur in the southern part of the Otago Schist belt within the Lower Greenschist Facies zone, inside the Permit area. These southern shear zone gold exploration targets have been identified as being a ‘mirror image’ of the geology present in the northern margin of the Otago Schist belt (approximately 60km to the northeast) containing the Hyde Macraes Shear Zone (“HMSZ”) which hosts the Macraes gold mine (>10 Moz).
Gold mineralisation such as that found along the HSMZ on the northeastern side of the Otago Schist belt may therefore also be present on the southwestern side of the Otago Schist belt within the Permit as illustrated in the schematic cross section below.
Geological Cross section – Otago Schist Belt & Southern Shear Zone Gold Exploration Targets
Comparison with Macraes Gold Deposit
The Macraes gold deposit, including the Frasers Open Pit and Underground mine, is the largest gold mine in New Zealand and has produced more than 4 million ounces of gold since opening in 1990. It has a current mineral resource of over 6 Moz making the deposit >10 Moz in total. The Macraes mine is developed in a regionally continuous shear zone known as the Hyde Macraes Shear Zone (“HMSZ”). The HMSZ is up to 150m thick and dips at approximately 20° to the northeast.
The mineralised HMSZ and associated cross faults correlate with conductivity highs (resistivity lows) from an airborne geophysical survey flown for Glass Earth NZ Ltd in 2007. Conductivity/resistivity lineaments may therefore be used as a tool to help identify the occurrence of potentially mineralised shear zones in the ‘mirror image’ geological setting within Lower Greenschist Facies target zone in the southern part of the Otago Schist belt within NAE’s Lammerlaw and OPQ Permits.
Priority Gold Exploration Targets Identified by Geophysical Data Review
In March 2020, NAE commissioned Anthony Coote (APSAR Ltd) to examine regional geophysical and other data over the Lammerlaw and OPQ Permits. Priority targets for follow up exploration were identified based on contacts between contrasting metamorphic rocktypes comprising carbonaceous pelitic schists overlying psammitic mafic schists which preferentially host mineralised shearing and veining in other deposits in Otago. These areas are identified by sharp boundaries between high and low response on airborne EM surveys as shown below.
Conductivity Lineaments over the Hyde Macraes Shear Zone
Conductivity/resistivity lineaments may therefore be used as a tool to help identify the occurrence of potentially mineralised shear zones in the ‘mirror image’ geological setting within Lower Greenschist Facies target zone in the southern part of the Otago Schist belt within the Permit.
Conductivity/Resistivity Lineaments as an Exploration Tool
Conductivity (or resistivity) lineaments within the Lower Greenschist zone can therefore be used to target Macraes Style shear hosted gold exploration targets zone in the southern part of the Otago Schist belt within the Permit.
More specifically, MacKenzie & Craw (2016) propose that the boundary of a lens shaped block in the south of the Otago schist belt as defined by conductivity features may be analogous to the contact between Upper and Lower Greenschist Facies schist where the Macraes Footwall Fault and gold mines are located and the Tuapeka Fault Zone near the southern boundary of the Permit may be analogous to the Waihemo Fault System to the north of the Hyde Macraes Shear Zone. The main part of the lens shaped block lies within NAE’s Permits and remains untested.
Target Areas on Airborne Resistivity
The culmination of the geological setting being analogous to the Hyde Macraes Shear Zone, the presence of conductivity/resistivity lineaments similar to the Hyde Macraes Shear Zone to target exploration, the close proximity of New Zealand’s largest alluvial gold deposit (Gabriels Gully), and historic mines being located on the Permit make it particularly prospective for gold exploration.
June 2020 Exploration Program
In June 2020, NAE’s NZ based technical team completed the first phase of ground exploration targeting Macraes style shear hosted gold targets on the Lammerlaw Permit. Further ground exploration targeting Macraes style shear hosted gold targets on the OPQ Permit was also completed at the same time.
Work completed in June 2020 included soil and rock chip sampling and geological mapping completed over 7 of 21 planned soil lines identified by the APSAR geophysical data review. The 7 soil lines completed were located withing the OPQ Permit and within the lower-lying south eastern end of the Lammerlaw permit around the Bella Lode. Poor weather and early snow cover prevented sampling at the other 14 soil lines on the Lammerlaw Permit. In total:
- 217 soil samples were collected for analysis by pXRF and fire assay for Au
- 52 rock chip samples were collected for analysis by pXRF and fire assay for Au
- Structural measurements & lithological descriptions collected at 61 outcrop locations
Results from the June 2020 program included 7 anomalous results (12-33ppb Au and 10-100ppm As) indicating potential for shear hosted gold mineralization along metamorphic boundaries in both Lammerlaw & OPQ Permits.
Four of the anomalous gold and arsenic results are located near the historic Bella Lode mine in the Lammerlaw Permit and extend a soil anomaly in this area previously defined by Macraes Mining Company to >1.5km strike length, extending up to 600m from the metamorphic boundary.