Projects Jervois | Jervois |
|
|
|
|
Jervois Range copper-silver-base metals project 280km east north east of Alice Springs, Northern Territory, covering an aggregate area of 117km. The Jervois Project comprises two exploration licences, 16 mineral claims and 14 mineral leases, plus three authorised holdings and covers a total area of 117km2. A complete tenement schedule is included in the annual report. The project is located some 280km east north east of Alice Springs, Northern Territory, centred at 136°15’E: 22°40’S. Geologically the polymetallic copper-lead-zinc-silver +/- gold deposit is situated within a northerly striking J shaped stratigraphy of Proterozoic metasediments. The mineralisation was initially discovered in the Jervois Range area in 1929 leading to sporadic, shallow open cut mining of near surface secondary copper oxide and copper carbonate until 1961, following which there was intermittent exploration by several companies. In 1980 Plenty River Mining Company constructed a 125,000 tpa plant to exploit high grade silver lead zinc ore at the Green Parrot deposit. Following the mining of approximately 40,000 tonnes mining was suspended in 1983 due to a sharp metal price fall. The main exposed deposits that have been delineated from past work are from the north:
Regional SettingThe Jervois Range prospect lies within the Arunta Orogenic Domain, comprising two basement units of Middle Proterozoic age referred to as the Jervois and Bonya Blocks. The basement rocks are overlain by the Georgina Basin sediments of Upper Proterozoic to Devonian age. Basement rocks are part of the Arunta Orogenic Domain and consist of crystalline metamorphic and igneous rocks of amphibolite to granulite facies. The prospective lithologies within the tenement are considered to be contained within the Bonya Schist, Division 2 of the Arunta Orogenic Domain. This unit is made up of quartzo-feldspathic muscovite and sericite schists, ranging from pelitic to psammopelitic in composition, with local occurrences of cordierite, sillimanite, garnet and andalusite. The mine sequence, in addition to these lithologies, also contains chlorite schist, garnet ± magnetite quartzite, calc-silicates, epidote rich units and impure marbles. The topography of the tenement is dominated by the Jervois Range, composed of Georgina sediments to the west, and the “J Range”, comprising Bonya Schist, and including the mine sequence. Three periods of deformation are recognised in the Jervois area, with refolded folding of the mine sequence resulting in the “J’ shape of the Bonya Schist outcrop in the tenement area. Exploration to date has delineated three main zones of copper-lead-zinc-silver ± gold mineralisation in potentially economic concentrations. Local GeologyFour main suites may be noted within the Bonya Schist. These suites can be broadly subdivided as Suite 1 to Suite 4. The sequence, from oldest to youngest is as follows: Suite 4: Fe-Mg Silicates Intrusive rocks including mafic granitoids are also contained within the area, although their presence is at variance with the strike of the ‘suite rocks’. Suite 4: Fe-Mg-Silicates The oldest of the suites range from the basal quartz-magnetite-biotite-chlorite schist unit, which crops out to the south of the tenement, to the overlying quartz-chlorite schist at the top of the suite. The magnetite schist is clearly defined on aeromagnetic images as a dominant anomaly, which traces a ‘J’ structure and is used to map the stratigraphy. Suite 3: Mine Sequence This steeply dipping sequence consists of two major and two minor units, varying along strike. The two major units consist of a knotted schist and a quartz sericite schist, which defines the eastern extent of the Green Parrot pit. The two minor units are a garnet-chlorite-magnetite rock, containing gossanous zones with traces of lead and zinc, and a lode horizon consisting of variations of quartz muscovite biotite schist, particularly well developed in the Green Parrot pit. Suite 2: Mg-Silicate suite This consists dominantly of a cordierite-muscovite schist and is considered to be volcanic in origin. It is observed predominantly within the ‘J’ structure. Suite 1: Gneissic Suite This consists predominantly of felsic gneisses and is considered to be the youngest unit in the region. It has been inferred to be rhyolitic in origin. Previous Exploration Following the discovery of the Jervois mineralisation in the 1920s, some small-scale mining of the oxides took place and concentrates were transported to Mt Isa for treatment. 1961 - 1965 New Consolidated GoldfieldsFrom 1961 - 1965, New Consolidated Goldfields (Australasia) Pty Ltd undertook the first modern exploration program. This involved regional and detailed prospect mapping, geochemistry, magnetic and Turam surveys. Diamond drill holes totalling 1,901 metres were drilled in this period (DDH Series). The program was terminated because it had failed to find ore reserves of the required tonnage and grade. Ore reserves for Reward, Green Parrot and Bellbird were estimated to total 2.4 million tonnes at 2% copper to a depth of 95 metres (Catley, 1965, Wilson and Ward, 1962). 1969 - 1973 PetrocarbApart from some small scale mining of the oxidised zone by Mr K Johansson, no further exploration was undertaken until Petrocarb Mineral Exploration (SA) Pty Ltd acquired certain key leases in 1969-70. During 1971 and 1972 intensive diamond drilling and lesser percussion drilling took place to test the known mineralised horizons. About 110 holes were drilled including some 55 diamond core holes (JR, JA and JG Series) and 22 percussion holes (MP Series) on the Reward, Marshall and Green Parrot prospects. A smaller number of diamond and percussion holes were drilled at Green Parrot Scheelite (PE2- 7, PE 1-4), Crystallisation Plant Scheelite (WP 1-4), Pioneer A (PAl), Pioneer B Scheelite (PBl-4), Cox's West (PEl), Mineral Lease 613H (Rockface PFl-5) and at Jericho. Costeaning of scheelite prospects also took place in 1972. In late 1970, McPhar Geophysics carried out a detailed dipole-dipole IP survey of the Reward -Green Parrot mineralised zone and the Bellbird zone together with orientation VHEM and vertical flux gate magnetometer surveys. Copper ore reserves for Reward, Marshall and Bellbird defined by the Petrocarb drilling were calculated at 2,295,600 tonnes at 2.5% copper and about 50 g/t silver (Ypma, 1983) to a maximum depth of 130 metres. In addition, a further 300,000 tonnes at 9% lead, 3% zinc, 1.5 % copper and 170g/t silver were estimated for Green Parrot (Holmes, 1972). 1973 - 1974 Petrocarb Joint VentureA joint venture agreement between Petrocarb Exploration NL, Wilstone Pty Ltd and Union Corporation (Australia) Pty Ltd was negotiated in late 1973 whereby Union would undertake exploration in the Jervois area. The program which was implemented in 1974, involved colour air photography, geological mapping at 1: 10,000 and 1: 1,000 scale, soil and rock chip geochemistry on selected targets, a review of previous geophysical work and test surveys using a variety of methods by Scintrex, and the drilling of seven diamond core holes totalling 1,723 metres. A reserve of 2,085,000 tonnes at 3% copper, 55 g/t silver over an average intercept width of 4.7 metres was estimated for Marshall and Reward. This was short of the objective and Goldner recommended drilling to 600 metres vertically (Goldner et aI, 1974). Union Corporation, about this time, was contemplating with drawing from Australia and the Joint Venture terminated without this recommendation being implemented. 1980 - 1983 Plenty River MiningThe Jervois area remained inactive between 1975 and 1980 when Plenty River Mining Company NT Limited negotiated a tribute agreement with Petrocarb whereby Plenty River would be assigned the leases in return for payment of a royalty on production. In 1980 the PR Series of about 50 percussion holes (PR 1 - 57) were drilled in the Marshall - Green Parrot area for ore definition and open pit planning and grade control. Other drilling in 1981-83 included 17 percussion holes (R 1 - 17) and four diamond core holes (RWD 1 - 4) at Reward in 1983; 14 percussion holes about 500 metres north of Reward yielded narrow low grade copper intersections; 24 percussion holes at HM (Sykes) Lode intersecting narrow low grade copper intercepts; and 11 percussion holes at Killeen Prospect, at the southern end of the "J" east of Bellbird intersected zinc mineralisation with minor copper. Costeaning was undertaken at Cox's, Killeen and HM Lode. A treatment plant designed to treat Green Parrot lead-zinc-copper-silver ore at a rate of 125,000 tonnes per annum was completed in early 1982 together with township and services at a cost of $A15 million. Open pit mining at Green Parrot using company equipment commenced in 1982, and the plant was successfully commissioned in April 1982. It was then placed on care and maintenance in June 1982 after having produced about 500 tonnes of concentrate. The company became public by the issue of shares through a prospectus dated 28th March 1983. In this prospectus, Terence Willsteed and Associates produced ore reserve estimates based on previous drilling plus 50 shallow percussion holes (PR Series) drilled in July, August 1980 for greater ore definition (Willsteed, 1983). The plant was again commissioned in August 1983 and operated on Green Parrot oxidised ore for five months, treating 25,000 tonnes. Due to a sharp decline in metal prices the plant was placed on care and maintenance in December 1983 and has not operated since. About 2,000 tonnes of concentrate were sold at a grade of 50.4% Pb, 5.4% Zn, 0.6% Cu, 680 g/t Ag and 0.1 % Bi. About 40,000 tonnes of ore were mined from the Green Parrot pit (300 metres long by 25 metres deep). 1983 - 1984 Plenty River Mining -Anaconda Joint VentureWith the objective of discovering a large stratiform base metals orebody of the Broken Hill type, Anaconda Australia Inc. negotiated a joint venture with Plenty River Mining in September 1983. The Anaconda program primarily centred on the flying of an Input electromagnetic survey in October 1983 with follow up reconnaissance geology and geochemistry of 26 moderate to low order EM anomalies. At the same time the Jervois Range 1: 100,000 sheet magnetic data flown by the NT Department of Mines and Energy in 1981 was interpreted. The ground follow up of EM anomalies did not reveal any lode horizon rocks and the geochemical results were discouraging (Marjoribanks, 1983 and Dunnet et aI 1984). Anaconda withdrew from the joint venture in May 1984, about the time the parent was contemplating the ultimate shut down of activities in Australia. Following the withdrawal by Anaconda, Plenty River continued exploration with the principal activities being:
A major review by Yates, Ypma and Dickson summarised the work done to that time (Yates et aI, 1989). Regional DrillingSome diamond drilling was completed in the period 1984-1987 including four holes (X84 -1, 2, 3, 5) to test airborne magnetic anomalies in the Bellbird and Green Parrot South areas. No significant mineralisation was intersected and the targeting of further magnetic anomalies was abandoned. In 1986, accent was on testing geochemical anomalies due to high zinc in biotite. Four core holes were drilled at Pioneer, north of the Marshall-Reward resource (X86 1-4) yielding narrow copper intercepts, one at Anaconda, south east of the “J” line of lode (X86-5). and four holes at Killeen, east of Bellbird (X86-6 to 9). One of the Killeen holes showed intersections of 16% Zn over 0.9 metres and 15.1% Zn over 1.15 metres in calc-silicate rocks. Four core holes were drilled in 1987, three at Van Gils Prospect on the Outer J line of mineralisation (X87-1 to 3) and one (X87-4) at Killeen. Results at Van Gils were not encouraging, while at Killeen, zinc values in the range of 2% to 3.65% were intersected over 4.35 metres with one 0.15 metre interval at 12.5% Zn in calc-silicates. A further three diamond drill holes were later completed at Killeen in 1987 (X87-5 to 7) all of which yielded zinc/lead intersections. 1991 - 1996 Plenty River Mining - Normandy Poseidon Joint Venture Plenty River Mining reached an agreement with Normandy Poseidon in October 1991, whereby Poseidon Exploration Limited would extend their exploration of the ELs 6993, and 6994 to Include the ERLs 67-70. Exploration activities included a combined airborne magnetometer and EM survey. About 1,894 line kilometres were flown in 1991 for the assessment of Normandy Poseidon’s EL 6994 with about 418 line kilometres passing over Plenty River Mining’s ERLs 67-70. A new grid based on AMG was established and a fixed loop EM Survey (Sirotem MK III) was undertaken over the “J” structure. Three diamond holes (JD1, lA, 2, 3) were drilled east of the Marshall zone to test an EM anomaly coincident with the Sykes zone of mineralisation and its northern extension. One diamond drill hole was also drilled at the Bellbird zone on the south east limb of the “J” structure. 1997 - 1999 Britannia ExplorationIn 1997 Britannia Gold NL carried out a drillhole survey and RC drilling program following acquisition of the tenements from Tyson Resources NL who held an option to purchase from Plenty River Mining Company. The RC drilling program was carried out to fill in some gaps in earlier drilling by previous workers, and establishing resource figures for the copper oxide zone extending from surface to approximately 30 metres. A total of 1,618 metres (26 holes) were drilled to depths between 42 and 102 metres (Alcock, 1999). MIM Exploration from August 1999In early 1999, Britannia Gold NL offered the exploration lease and mine leases as part of a Joint Venture package to MIM Exploration Pty Ltd. MIM Exploration entered the Joint Venture agreement as manager and operator in August 1999. MIM Exploration completed an Airborne geophysical survey, petrological studies, and physical properties studies in the period from 5th August 1999 to 2nd October 1999. MIM Exploration carried out extensive geophysical surveying and percussion and diamond drilling. A summary of this work is given below: IP Survey In November and December of 2000 an IP and resistivity survey was undertaken on EL 9518 ‘Jervois’. The survey was designed to map, in greater detail, the lode horizon at the Marshall and Reward prospects ie. in-filling data previously acquired in 1999 (reported previously) and also to extend existing coverage both north and south of the Bellbird prospect. Acquisition and Processing A total of 34.4 line kms of acquisition was carried out on 13 lines bringing the total coverage for the tenement, including the April 1999 coverage, to 70.4 line km on 31 lines. MIM Exploration’s generic electrical and electromagnetic acquisition system ‘MIMDAS’ was used to acquire the data coupled with a Zonge GGT10 7.5 kV A transmitter. Drilling Thirty-four drill holes were completed. Almost all the drilling was focussed on testing the Marshall-Reward and Bellbird zones at depth. Several holes also tested MIMDAS IP anomalies to the north of Reward, to the north and south of Bellbird, and in the Rockface area to the east of Bellbird. Metallurgical Test Work Metallurgical test work was conducted on samples from drillhole J25 and J27 in order to gain a preliminary indication of the likely recoveries obtainable from a conventional treatment plant. The composite sample from J25 covered the interval from 570m to 574.04m while J27 was sampled between 263 to 274m. From a metallurgical point of view, the ore is free milling and concentrates up well. For both samples, at a grind size of 80% passing 106 microns, the rougher cons graded around 20% copper at 75-80% copper recovery, and would clean up well. The remaining copper minerals would probably require a regrind to around 80% passing 65 microns to obtain to saleable copper concentrates. It appears that the Jervois ores tested should behave in a similar manner to Mount Isa ores, and achieve a +28% copper concentrate at better than 90% recovery. Exploration PotentialFollowing the termination of the joint venture between MIM and Britannia, a complete review of all the data was made with a view to upgrading the resource and suggesting recommendations for further work. The MIMEX Annual Report of 2 October 2002, concluded that drilling carried out at Marshall-Reward has shown potential for reasonable thicknesses of high-grade copper mineralisation at depth, however that it may be depth limited and not continuous over the length of the Marshall-Reward zone. In other words, the higher grade mineralisation may well be confined, as is normally the case, to “shoots” of, as yet, indeterminate dimensions – depending on economics, and structural geometry. The report further noted that drilling at Bellbird has intersected high-grade copper mineralisation over 7m true width in the central part of the prospect and lower-grade wider mineralisation in the south. It also states that EM data suggests that high-grade sulphides do not continue more than about 100m to 150m north of drillhole J33. In fact, there is insufficient detailed drilling to determine the structural geometry and northerly extent of the mineralisation and a plunging shoot (or shoots) cannot be discounted, indeed it is very common structure for most metalliferous deposits. From the above MIMEX comments, a more detailed evaluation of the shallower sections of the above three deposits, say to 250m vertical depth, plus the relatively neglected Green Parrot and Green Parrot – east lodes would seem to be a reasonable starting point for attempting to develop a more modest 5-7 million tonnes of “Measured Reserve” category which might be potentially achievable by in-fill drilling – especially at the shallower depths – within higher grade shoots and in poorly-tested contiguous zones along strike, where justified. Within the Marshall-Reward lode system there appears to be several north plunging higher grade zones assaying above 2% copper. Drilling density is currently insufficient to define resources in these zones. Both the northern and southern shoots show a broad southerly extension down to about 180m depth which could be interpreted as downward influence of higher level supergene alteration but this is very speculative conclusion without the benefit of supporting data. Infill drilling aimed establishing the ore potential of these shoots is the top priority for the Company at the Jervois Project. The relatively small number of “grade” drill holes intercepts at the Bellbird Lode (9 holes over 500m strike length) suggest that there may be an approximately 160 metres deep shoot plunging flatly at about 20 degrees north. The centre of the shoot more or less coincides with the extent of the DHEM conductive layer which probably had a northward constraint due to lack of available drill holes prior to the drilling and subsequent surveying of the two last drill holes – J37 and J38, which were drilled to test the original DHEM model. Detailed modelling of the latest DHEM survey is yet to be undertaken. Nevertheless, it is interesting to note that MIMEX consider the depth extent of the lode to be probably less than 300m which lends support to the flatly – plunging shoot concept. There is virtually no testing to 250 metres depth at Bellbird, within the confines of this possible shoot north of hole J33 although MIMEX delineated a target some 300m north – and fitting within the current shoot interpretation – which was unsuccessfully drilled by abandoned holes J6 and J7. Very shallow Britannia drill holes BR97-148 and BR-149 intersected 4m @ 1.67%Cu, 160m above the MIMEX target. Within the Green Parrot lodes system, south of the Marshall prospect, the Green Parrot East lode has the potential as a smaller but high grade accessory to the Marshall-Reward and Bellbird prospects. As previously noted, the western Green Parrot lode was subjected to a short-lived and unsuccessful mining operation by Plenty River Mining Co. MIMEX apparently consider the Green Parrot to be too restricted in size, and hence tonnage. However there does not appear to be much recognition by either MIM or Plenty River of the Green Parrot East lode which certainly deserves further investigation in view of a strong IP response and the several drill hole intersections with significant, albeit variable, Cu-Ag-Pb-Zn assays. |
Copyright © 2010 Reward Minerals Ltd.
Designed by Will
