Minter Project, Central Lachlan Fold Belt, NSW
At the Minter Project near Lake Cargelligo, Cullen is targeting stockwork and vein-type tungsten mineralization related to the granitic cupolas (domes).
Broad zones of low-grade tungsten mineralisation in stockworks of quartz-carbonate-pyrite veinlets in hornfelsed sediments are known from 1980s drilling (best intersection 27m @ 0.16 % WO3, PDH2). The target at Doyenwae is higher-grade stockwork and vein type tungsten mineralisation within or adjacent to the underlying granitic cupolas (domes). This model is based on magnetic interpretation and analogies to vein/stockwork tungsten deposits elsewhere, such as in China and Europe.
Exploration drilling and soil sampling by Cullen to date indicates an extensive zone of tungsten-anomalous stockwork veining is considered to be related to underlying granitic cupola(s) as the potential source of the tungsten mineralisation.
In June 2012, Cullen completed a combined RC percussion-diamond drilling programme totalling 536.8 metres in three holes to test selected geological/geochemical targets at the Doyenwae and Orr Trig prospects. Holes were designed to test beneath zones of anomalous tungsten + tin geochemistry outlined by earlier soil sampling and shallow percussion/aircore/RAB drilling.
At the Doyenwae Prospect, RC percussion hole MRC005 averaged 447ppm tungsten over the full 111 metre length of the hole with localised two-metre zones of quartz-scheelite veining assaying up to 0.35% tungsten. Diamond drill hole CMDD001, drilled to 258.0 metres at the Doyenwae prospect, intersected significant quartz + sulphide veining throughout much of the hole. Examination of the core with an ultraviolet lamp detected widespread scheelite mineralisation occurring both within quartz veins and as disseminations/aggregates in silica-altered sandstone units; particularly in the interval from 130 metres to the end of the hole. The true width of potential mineralisation in both MRC005 and CMDD001 is uncertain as preliminary observations of vein orientations in the CMDD001 drill core indicate that the holes may be drilling at a low angle to some of the mineralised quartz veins.
At the Orr Trig Prospect, diamond core hole CMDD002; drilled to 267.8 metres, intersected scattered zones of narrow quartz veining and localised silicification over much of the hole with scheelite being observed as disseminations in sandstone and within quartz veins in the interval between 100m and 250m. Although it would appear that hole CMDD002 has been drilled in an appropriate direction with respect to the orientation of the quartz veins, the amount of observable scheelite mineralisation is less than that noted in CMDD001.
Encouraging final assays have been received from selective sampling of diamond core hole CMD001, drilled at the Doyenwae Prospect to test beneath anomalous tungsten delineated in prior shallow percussion/aircore drilling. CMD001 intersected multiple scheelite-bearing quartz veins in host sandstone and siltstones over the 258m drilled (see Cullen’s Quarterly Report announcement of 31 July 2012). In addition, disseminated to blebby scheelite occurs in silicified coarse sandstone units adjacent to the mineralised veins.
Initial sampling focussed on core with visible scheelite and returned numerous 0.5 to 4.1 m intervals assaying >0.1% tungsten. Higher grade zones included:
- 1m @ 0.55% W (0.70% WO3) from 131.5m;
- 1.5m @ 0.33% W (0.41% WO3) from 166.4m;
- 4.05m @ 0.46% W (0.58% WO3) from 185.1m ,including 1.2m @ 1.22% W (1.53% WO3) from 187.9m;
- 1.4m @ 1.08% W (1.36% WO3) from 232.7m and
- 0.45m @ 1.05% W (1.32% WO3) from 243.0m.
These results are the best to date at Doyenwae, compared to previous shallower RC drilling intersections by Aberfoyle (1980s) and Cullen. Geological logging and structural measurements indicate that CMD001 may have tested only a part of the potential width of the mineralised vein zone, as the hole appears to have been drilled sub-parallel to the vein trend.
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