Kiowarrah

Introduction..

 The Kiowarrah Tin Mines (EL 6745) are located 35km north of Yass in central NSW (Figure 1).  Access to the project area is through Gunning Rd via Rye Park, or along Dalton Rd via Dalton. Both are secondary roads that connect to the Hume Highway at Gunning.  The occurrence of tin mineralisation in the Dalton district was first reported in 1932 when alluvial and reef tin deposits. At Kiowarrah, two distinct levels of gravels containing tin were recognized.  The younger gravels carried good tin throughout the lower portion of the deposit, although poor overall values over the full depth.  The alluvial deposits was worked until 1938 for small quantities of tin by Clare, Cooper and Smith until V. Medway extracted 18 tonnes of tin concentrates from the period 1938-1948.  Mining of the deposit continued sporadically by the Kiowarrah Alluvial Tin Mining Syndicate using steam driven gravel pumps to sluice the area until 1955.  The most recent work in the Kiowarrah field was conducted by The Shell Company of Australia Limited from 1979-1983.  Several programs of exploration mapping, sampling and drilling occurred as the region was considered prospective for a low-grade, large tonnage tin-tungsten deposit.  

Regional Geology

 The Kiowarrah exploration license lies within the Lachlan Fold Belt and located predominantly within Ordovician sediments which include greywacke, shale’s, slate and rare calcareous units. Silurian Duro Volcanics outcrop in the south-west corner of the tenement.   The Lachlan Fold Belt is widely intruded by Silurian and Devonian granites of the Bowning Orogeny, and although no granite is known to outcrop within the license area, high level intrusions beneath the Ordovician and Silurian cover are thought to be the source for mineralisation in the Rye Park – Kiowarrah area.  This has given rise to local pyrometamorphism of the interbedded limey lenses with mineralisation of W, Bi and Cu, hosted within epidote-garnet-talc-magnetite skarns.  

Project Geology

Ordovician Metasediments

 Ordovician sediments within the exploration license consist of highly-folded quartz-rich sandstone, siltstone, shale and dark carbonaceous slate.  Sediments located in the east of the license area are dominantly unaltered quartzite sandstones and siltstones with minor pelitic slaty horizons. Thick, barren, milky white quartz veins are common in this region, and no mineralisation has been documented. Structural information recognizes a single phase of deformation as the sediments are tightly folded about a sub-vertical, northerly striking axial plane cleavage.  In contrast, sediments in the west of the license area are comprised of siliceous black slates, ferruginous quartzite sandstones, and cherty siliceous rocks, interpreted as strongly silicified shale’s.  Two periods of deformation have been identified within sediments in the west, as silicified black slate outcrops across prominent ridges display folding of both bedding and the strong axial plane cleavage.   Two distinct outcrops of silicified shale’s exhibit notable alteration. A prominent, northerly striking ridge lies 750m to the west of Opton Creek Mine and displays higher metamorphic grade siliceous schist and crenulated slates. The second is a 400m long ridge of silicified dark crenulated slate located 1.5km south of the High Rock homestead.   The origin of this relatively localized second phase of deformation has not yet been ascertained. Initially the intrusion of a high level granitic pluton was proposed as a source for the development of the cassiterite bearing quartz veins, and the crenulation and silicification within sediments.  The lack of outcropping granites and effects of proximal alteration from a contact aureole suggest that the source of fluids is located at depth or has come from a distant source in the region.  Thus the hypothesis is still plausible.

Silurian Volcanics

 Silurian volcanics occur as coarse grained volcano-clastics composed of phenocrysts of 2mm-5mm quartz crystals and 1mm-2mm K-feldspar with minor plagioclase, within an altered chlorite and sericite groundmass.  A relatively strong, sub-vertical axial plane cleavage is pervasively developed throughout the volcanic in the license area.  Mapping has identified a coarse-grained crystal tuff as the lowermost Silurian unit that was selected as the stratigraphic base of the sequence due to its prominent outcrop and expression of a distinct, abrupt change in the sedimentation history.  The tuff lies stratigraphically above a black carbonaceous shale that is considered Silurian in age, although it was included within the Ordovician sequence due to the similar nature it shares with shale’s found in the underlying sediments.   The Ordovician-Silurian contact strikes north-south within on a regional scale, however, locally within the Kiowarrah license, the contact is highly irregular and strikes approximately east-west. Detailed mapping of the contact area shows that both the Silurian and Ordovician sequences dip sub-vertically and the irregular contact is due to transgressive-regressive volcanic-metasediment sequence which possibly indicates an early eruptive centre. 

Previous exploration

Initial exploration conducted by Australian-Cities Service Inc., involved stream sediment sampling that originally outlined several base metal anomalies located within Ordovician metasediments.  The anomalies were tested by soil sampling and a ground magnetic surveys and their significance was downgraded due to the presence of black shale’s and pyritic slate bands. 

The Shell Company of Australia PTY. LTD. acquired the Kiowarrah license area with a view to delineating a large, low-grade, tin-tungsten resource. Styles of mineralisation considered to be possible targets in the area included stratabound stock-work vein systems and sheeted vein systems hosted within Ordovician metasediments. Rock chip sampling and costeaning of areas of highest quartz veining and alteration was conducted in conjunction with a detailed ground magnetic survey, aimed at delineating the most intense veining and produce structural and geological information on the veins.  

Conclusions from the costeaning program highlighted the preference of quartz vein to trend approximately east-west, parallel to the Opton magnetic linear, and dip steeply to the north.  The information on mineralisation was then used to outline a bedrock drilling program aimed at defining higher grade zones of mineralisation. A total of 387 holes were drilled for a total of 2,375m with collar locations spaced at 20m intervals along lines 100m apart. Two samples were taken in each 6m hole, with one sample collected at the weathered surface, and the second over the bedrock interval to end of hole depth. 

Three areas of ferruginisation and quartz veining within Ordovician sandstones and shale’s were identified from the drilling campaign and all were found to trend east-west, coincident with the Opton magnetic linear and striking quartz veins.  As a consequence of the bedrock drilling program, nine diamond drill-holes (PDH KM 1-9) were completed in December, 1981 for a total of 957m aimed at further definition of deeper targets. All holes were depressed at -60º and were targeted at tin-arsenic bedrock anomalies defined by the bedrock drilling program.  Samples were collected over 2m intervals.  Tin mineralisation was found to be encouraging and are displayed in Table 1.  The significant intercepts encountered within PDH KM7 (19m- true width- @ 0.165% Sn) identified from percussion drilling were tested at depth for possible extension of mineralisation by a deep diamond drill-hole, DDH KT1, drilled to a depth of 312.95m. DDH KT1 passed through a sequence of inter-bedded siltstones, sandstones and shale’s with only minor, erratic quartz veining rarely exceed more than 5% of rock volume.  Best intercepts are displayed in Table 2.

A further 13 drill-holes for a total of 1226m were completed in 1982 to fully evaluate the potential for an open pit style operation based on stockwork tin mineralisation. Drilling was collared at -60º and drilled to depths of between 81m – 106m. Sampling was conducted over two metre intervals and XRF assayed for Sn and As.  12 drill-holes intersected inter-bedded siltstones, sandstones and shale’s and one hole, PDH KM21 intersected graphitic and pyritic shale’s.  Only two holes, PDH KM13 and PDH KM20 intersected significant tin mineralisation (Table 3). Tin mineralisation was noted to occur in thick quartz veins up to 1m that are generally constricted to sandstone lithologies. Arsenopyrite and pyrite are generally more abundant than cassiterite within quartz veins and there is a good correlation between Sn and As. 

Table 1. Significant assay results from percussion drilling program conducted by The Shell Company of Australia at its Kiowarrah prospect, December 1981.  

Wolf Minerals at Kiowarrah

The Kiowarrah Tin Mines and alluvial workings were inspected by Wolf during the start of 2008 with rock chip samples collected from cassiterite-bearing quartz veins that were sent to ALS in Orange for analysis.  Results were below detection limit.  Ground truthing was conducted across the tenement to correctly identify the collar locations of the previous drilling programs conducted by Shell Australia.  No collars from drill-holes were positively identified.   The significant assay results from within costeaning and drilling programs has highlighted the potential for a large-tonnage, low grade tin deposit at the Kiowarrah Tin Mines.  The next phase of exploration will involve the creation of an infill RC drilling program aimed at further delineation of tin mineralisation and interpretation of its relationship with the Opton magnetic linear, the ferruginous envelope and associated arsenic mineralisation. The aim of the drilling is to extend the knowledge of the current interpretation of the geology and mineralisation and to produce a tin-tungsten resource.