The 250km2 Wallbrook tenement package is considered highly prospective for the discovery of significant gold mineralisation.View ASX Announcements
The Wallbrook tenement package covers 250km2 and is an amalgamation of tenements acquired from Newmont and Saracen Minerals in 2018.
In November 2018, Nexus completed a Tenement Sale and Purchase Agreement to acquire from Newmont the surrounding 190km2 tenement package adjacent to Nexus’ existing 60km2 Wallbrook Gold Project. Nexus acquired from Newmont the surrounding three tenements covering 190km2 for a total consideration of $13,100 and a 2% net smelter royalty on all mineral product extracted and recovered from the tenements. ( pdf ASX release 29 November 2018 – Nexus Completes Wallbrook Tenement Acquisition from Newmont (355 KB) ).
Nexus had previously acquired the central Wallbrook exploration tenements from Saracen, in January 2018 for consideration of 1,490,000 Nexus shares. (ASX release 23 January 2018 - Nexus Wallbrook Gold Project Update).
Regional and Local Geology
The region is dominated by metamorphosed volcaniclastic sediments, andesite, basalt and other sedimentary and variously metamorphosed rock units. These rock units have been intruded by numerous small, variably mineralised, porphyritic intrusions. The majority of these intrusions identified to date are under cover or very weathered. Their composition varies from syenite to quartz monzonite to tonalite. These intrusions are discordant with respect to the lithological layering and major regional structures, suggesting emplacement late in the tectonic evolution of the greenstone belt, indicating mineralisation associated with the intruded porphyries may be relatively “local” to the position of the intruded porphyry.
Gold mineralisation has been identified and mined historically in a belt stretching from the Porphyry mining district to the Wallbrook area 8km to the southeast. Over 350,000 ounces of gold have been produced from multiple operations from 1921 to 2012. This same region today contains a current JORC 2012 mineral resource inventory of 31Mt @ 1.5g/t for 1.5M ounces gold (all Saracen Resources, see their 2017 Annual Report). None of these historically mined ounces nor the current mineral resource inventory are contained on Nexus tenements.
Nexus Exploration Activities
The Wallbrook Gold Project is considered underexplored and highly prospective for the discovery of significant gold mineralisation. Drilling recently completed by Nexus in the March 2019 quarter (see ASX releases 26/4/2019) and drilling completed by Nexus in 2018 (see ASX releases 16/10/2018 and 6/9/2018) has demonstrated this prospectivity. Within the Carosue Dam district 5 million ounces of gold resources are hosted in a similar geological setting to that underlying the Nexus tenement holding (see Saracen Annual Report 2018 – Mineral Resources and Ore Reserve Statement).
The Crusader resource model has been prepared after the completion of a 40 hole (4,626m) reverse circulation drilling program by Nexus. The resource model also includes 45 reverse circulation holes (4,951m) and 1 diamond drill hole (159m) drilled by previous operators (see ASX release 8/7/2019).
The Crusader prospect lithologies are dominated by volcaniclastic sediments, intermediate (andesitic) volcanics, intrusive felsic porphyries and granite/quartz monzonites. The dominant feature in the area is the Wallbrook Quartz Monzonite, which outcrops 3km to the south of Crusader. North of the monzonite are relatively smaller granitic intrusions and related narrow porphyry dykes/sills. These granitoid/porphyry dykes and apophyses trend in a north-westerly or northly direction parallel to the regional trend.
The mineralisation is closely associated with a quartz-goethite supergene stockwork in the oxide regolith profile. The stockwork intensity correlates closely with higher gold grades. In the fresh rock, high-grade mineralisation is constrained to a series of steeply dipping structures defined by quartz sulphide veining within a potassic altered volcaniclastic host rock. Future drill programs will test for depth extensions to the mineralisation intersected in this program, as well as testing for strike extent of the mineralised corridor that continues >5km to the north of the drilling completed to date.
The information in this report that relates to Exploration Results, Mineral Resources or Ore Reserves is based on, and fairly represents, information and supporting documentation, prepared, compiled or reviewed by Mr Andy Tudor, who is a Member of the Australasian Institute of Mining and Metallurgy and the Australian Institute of Geoscientists. Mr Tudor is the Managing Director and full-time employee of Nexus Minerals Limited. Mr Tudor has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity for which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the “Australian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves”. Mr Tudor consents to the inclusion in the report of the matters based on his information in the form and context in which it appears. The results are available to be viewed on the Company website www.nexus-minerals.com. The Company confirms that the form and context in which the Competent Person’s findings are presented have not been materially modified from the original announcements.
The information in this report that relates to the Crusader Mineral Resource Estimate is based upon information compiled by Mr Adam James, a Competent Person who is a member of The Australian Institute of Mining and Metallurgy and the Australian Institute of Geoscientists. Mr James is a full-time employee of Nexus Minerals Limited. Mr James has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity being undertaken to qualify as a Competent Person as defined in the 2012 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Mr James consents to the inclusion in the report of matters based on his information in the form and context in which it appears.
No Ore Reserves have currently been defined on the Pinnacles or Wallbrook tenements. There has been insufficient exploration and technical studies to estimate an Ore Reserve and it is uncertain if further exploration and/or technical studies will result in the estimation of an Ore Reserve. The potential for the development of a mining operation and sale of ore from the Pinnacles or Wallbrook tenements has yet to be established.
Crusader – Templar Prospects Gravity Survey
The prospects cover approximately 3km of a total >5km strike length of prospective geology defined to date. The detailed gravity data clearly defines a north-west lower density corridor extending through the Crusader and Templar prospects (Fig. 6), that appears to be rotating to a more northerly strike direction at the most northern end of the prospect.
Gravity readings were taken 25m apart on 100m line spacings over the Crusader prospect, and even more detailed readings 25m apart on 25m line spacings over the Templar prospect.
All known significant mineralisation in the area is located within this lower density corridor, which is consistent with focus of structure and fluid flow along the margins of intrusive bodies and indeed a large-scale pre-mineral crustal weakness which the intrusives have exploited.
Crusader – Templar Prospects Ground Magnetic Survey
Geological exposure is limited across the Crusader-Templar area due to transported sheetwash cover, so detailed ground magnetic data has been acquired to assist with mapping lithological continuity and identify structural discontinuities. Magnetic readings were taken using a highly sensitive fast-sampling magnetometer with continuous station recording along survey lines orientated east-west and spaced 25m apart.
The quality of the ground magnetic data is excellent and is proving to be an important aid in understanding the setting of mineralisation and assisting with ongoing drill targeting. The more intense magnetic character (seen highlighted in red on Fig. 7) is considered to be, at least in part, due to hydrothermal alteration of the host rocks.
The combination of mapped geology and surface geochemistry results, with the interpretation of 3D modelling of the gravity and ground magnetics results, will allow for drill targets to be generated.
Based on the positive high-resolution ground magnetic results received to date, the decision was made to extend the survey north of Templar prospect. The survey commenced during the quarter and will cover ~500 line km’s. Magnetic readings will be taken using a highly sensitive fast-sampling magnetometer with continuous station recording along survey lines orientated east west and spaced 50m apart. The survey will extend coverage northwards through The Gap prospect.
Geological mapping of the tenement package will focus on exploring for host rock alteration where surface outcrop is evident. Surface geochemistry data will be assessed and areas of limited or no coverage will be sampled in the search for high level gold anomalism.
The use of gravity surveys and high-resolution ground magnetic surveys have proven to be effective tools used to map the location of non-outcropping porphyritic intrusives and dyke stocks, above larger intrusive bodies. Induced Polarization (IP) / Resistivity surveys may also be utilized as they are also an effective exploration tool, with IP resistivity highs associated with possible intrusive bodies or siliceous alteration and chargeability highs with disseminated sulphides often associated with mineralisation. This work, in conjunction with factors determined as part of the Company’s R&D framework, will culminate in the drill testing of priority targets identified.