- A review of recently acquired detailed geophysical data has highlighted compelling new Gold targets in under explored locations
- XRF elevated Arsenic results indicate a significant extension to known Gold anomalies
- Contiguous tenement position at Lammerlaw allows proven targeting methodologies to be extended along the full ~25km of prospective structural corridor
- Extension of Duration granted for Lammerlaw Prospecting Permit PP60544, securing the strategic landholding
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.
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.
Geophysical Data for NAE Otago Projects Re-Processed
Legacy electromagnetics and magnetics geophysical surveys’ data covering the NAE Otago permit areas have been reprocessed using the latest techniques by Fathom Geophysics Ltd. Advance image processing over NAE Otago Project used cutting edge algorithms, to produce automated interpretation of topography, magnetics and electromagnetic images.
Fathom’s structural detection algorithm produces images that highlight structural complexity and edge features (faults, contacts and other structures) to reduce subjectivity by the interpreter. When the products are combined with other exploration data sets such as geochemistry and mapping, target interpretation can be applied with limited cognitive bias. Results of this process have highlighted additional targets and improved structural understanding of the Lammerlaw area. (Refer Figure 1 and 2.)
Re-processed geophysics and geochemical trends confirm the likely continuation gold targets across the full length of the Lammerlaw permits. Targeted geochemical sampling will now be used to test concepts.
Figure 2: Examples of newly acquired geophysical images over the Lammerlaw/Mahinerangi area.
Anomalous Arsenic Zones Extended in Lammerlaw EP60807
Ongoing activity in Lammerlaw Exploration Permit EP60807 has highlighted kilometer scale geochemical trends hosting anomalous arsenic-gold plus antimony and tungsten mineralisation. Arsenic geochemistry best highlights geochemical trends due to its common relationship with gold occurrence. Within Lammerlaw Exploration Permit EP60807 arsenic in auger and rock samples highlight two sub-parallel, semi-continuous structures roughly 5-6km in length and a third smaller linking structure (Figure 3).
Outcrop exposure at Lammerlaw is sparse, with only competent psammitic schist outcropping on ridges and in creeks. Shear zones and pelitic schists which are more likely to host geochemical trends are recessive in the landscape and rarely outcrop.
Recent field work has utilised historic aerial photography to locate surface prospecting pits and shafts dug in the 1870-90’s. Old workings were often dug intermittently along lines, following indicators of gold mineralisation. Recently collected samples from old workings commonly record anomalous arsenic, antimony and tungsten geochemistry using pXRF. These results extended the strike of prospective geochemical trends by hundreds of meters in some locations. Soil auger sampling continues to be an effective way of testing geochemical trends at Lammerlaw. During May 2022, an additional 120 auger samples and 64 rock chip samples were collected to extend known mineralised trends.
Geochemical tends within Lammerlaw EP60807 can be divided into four main prospects, Antimony, Bucks, Fulton’s and Bella. Each prospect has a historic legacy of mining and exploration, historic records are summarised below:
The Antimony Mine was discovered in Stony Creek during the late 1870s, with intermittent mining occurring between 1880 and 1900. The lode strike WNW-ESE and dips 45o NE, with historic prospecting proving an 800m strike length. Two shafts were sunk in the bed of Stony Creek approximately 120m apart, from which mining of antimony rich ore took place. The structure hosing mineralisation is 1.2-1.5m wide with the stibnite-bearing material being typically 0.5m thickness within. In one location massive scheelite was extracted from the center of the lode (Marshall, 1918). Historic records note the lode was had poor gold content (Finlayson, 1908).
Modern prospecting of the Antimony Mine has been entirety by surface sampling. Early work highlighted a 1km long antimony and tungsten geochemical tend centered on the historic Antimony Mine. Limited gold focused exploration records a rock chip grade up to 9.57g/t Au and up to 22.6% Sb from mullock. Exploration completed by NAE has extended the length of the geochemical trend hosting the Antimony Mine to roughly 3.5km (Figure 2). Preliminary pXRF data for samples collected in May 2022 along newly defined geochemical trend, show anomalous geochemistry for arsenic, antimony and tungsten.
There is no historical documentation for Bucks Prospect, although it is commonly indicated on historic maps. The rough location of Bucks is coincident with an arsenic-gold geochemical trend defined by NAE auger sampling (Figure 2). This 1.9km geochemical trend is now well defined by auger and rock chip samples with peak values of 92ppb Au and 349ppm As in NAE auger samples. These results reflect the position of recently sampled quartz-arsenopyrite breccia in float samples. All gold assays for float and rock chip collected during May 2022 currently being processed.
Fulton’s Prospect is a group of quartz vein occurrences in an area worked extensively for alluvial gold and tungsten (other names include Neighborhood, Golden Crown and Reeferk). Fulton’s Creek located below prospect area was noted as remarkably rich in coarse alluvial gold. Extensive areas were hydrosluiced, feed by an extensive network of water races. Only a small amount of prospecting was on quartz lodes directly, discontinuous veins up to 3ft thick are recorded (Marshall, 1918). Remnant prospecting pit and adits commonly follow individual quartz veins and indicate a E-W strike of mineralisation.
Prior to NAE work in the Fulton’s area, there was no significant modern exploration sampling in the area. The recent westward extension of the auger sampling completed in 2021 to cover Fulton’s Prospect has proven a large gold-arsenic geochemical tend. These results indicate Fulton’s Prospect is part of a 3.4km geochemical tend with probable parallel trend in places (Figure 2). Peak values of 300ppm As and 50ppb Au are recorded in previous NAE auger samples. Recent sampling of quartz vein float and from prospecting pits has recorded strongly anomalous arsenic and tungsten values. Further sampling work is required at Fulton’s to extend test the geochemical trend further west.
The Bella Lode was discovered in the 1890’s and worked intermittently until 1900. The Lode runs E-W and dips steeply N, with a maximum thickness of 6ft and averaged 15g/t Au. Underground working followed the vein for 400ft where it pinched and swelled between 0.6-1.8m wide. At 15m in depth, the vein reportedly pinched out leaving only sheared host rock. In addition to lack of ore for processing, Bella required chemical treatment to recover gold, indicating it was very fine or locked in sulfides. The Lode also contained some scheelite (Marshall, 1918).
Modern prospecting has included sporadic soil and rock sampling. Previous soil sampling proved ineffective owing to the lack of dispersion of mineralisation in wall rock. Historic samples collected from the Bella Lode gave peak Au assay of 17.3g/t.
Recent activity by NAE has used historic aerial photography to extend the strike length of the Bella geochemical trend to roughly 2km (Figure 2). Samples from prospecting pits and shafts provide anomalous As and W values when analysis with pXRF. Float samples of mineralised quartz vein were also located along strike from the Bella Mine.
Other Areas of Interest
As understanding of the Lammerlaw Project develops, it has become clear that there are overlapping chemistries of individual geochemical trends, as well as potentially narrow footprint size of anomalies. To ensure no potential targets have been overlooked within the existing soils grid, samples not previously sent for gold assay have now been submitted. This includes 109 samples from between the Fulton’s and Bucks prospects.
Field work completed in May 2022 has highlighted the potential that geochemical trends may have semi-continuous strike across the Lammerlaw Project area. It now seems likely that Fulton’s and Bella sit along the same structure. Further surface sampling will used to highlight this potential in in the area immediately north of Bella Prospect. In this area, a westward continuation of the Antimony Mine geochemical trend is projected and loosely defined by isolated sample points.
Extension of Duration for Lammerlaw PP60544 Granted
NAE has been successful in application for an EoD for Lammerlaw Prospecting Permit PP60544. Importantly, this allows continued exploration along strike from the Lammerlaw Exploration Permit EP60807 where ongoing surface exploration continues to expand geochemical tends.
The extended permitting period for Lammerlaw Prospecting Permit PP60544 secures an extensive ground as holding part of the Company’s 100% owned Otago Project. The granting of EoD for Lammerlaw Prospecting Permit PP60544 maintains NAE’s Otago permitted ground, with the combination of the two contiguous Lammerlaw Permits provides ~25km of prospective structural corridor to test further.
The initial Lammerlaw Prospecting Permit PP60544 was granted on 26 November 2019. Surface exploration in the subsequent two years highlighted the northeastern portion of the original Permit as the most prospective for structurally controlled orogenic gold mineralisation, and at completion of the initial two years of tenure, became Lammerlaw Exploration Permit EP60807. Contemporaneously, an EoD application for the original Lammerlaw Prospecting Permit PP60544 was sort. The balance of the original Lammerlaw Prospecting Permit area has been relinquished due to its lower perspectivity.
The targeting strategy for Lammerlaw uses contrasting high and low electromagnetics response as lineaments, potential indicators of favorable structural and lithological contacts for gold mineralisation. Results returned for surface sampling Lammerlaw Prospecting Permit PP60544 have successfully proven this concept. Coincident arsenic and gold geochemical trends follow contacts between high and low electromagnetic response. Re-processed geophysics now allows accurate delineation of these prospective lineaments.