| |
 | |
|
|
|  The Moran Lake IOCG Model The presence of IOCG (Olympic Dam) type mineralization on the Moran Lake has been confirmed by the Phase 1 sampling of Shell Canada Resources drill cores from the 1970's. The Moran Lake property is host to significant uranium resources defined by Shell Canada, and was identified by Crosshair personnel as having the potential to host IOCG type mineralization. To validate this theory, Crosshair sampled selected portions from 23 of 58 available archived drill cores to test for IOCG type alteration and mineralization. The results show widespread and locally strongly enriched copper and silver values as well as anomalous gold values. Over 1/3 of the approximately 600 samples collected assayed > 200 ppm copper of which 44 samples returned copper values between 1000 to 6310 ppm Cu (0.1% to 0.63% Cu) over individual sample widths ranging from 0.55 to 1.12 metres. These results take on more significance given that Shell drilled the exploration holes to test surface uranium mineralization, and were not aware of the adjacent gravity anomaly or the significance of the hematite rich breccias observed in several drill holes. The IOCG Model IOCG type deposits are typically large, iron rich systems that carry variable amounts of copper, silver and gold and locally significant amounts of uranium. The largest known deposit of this type is the mid- Proterozoic Olympic Dam deposit in South Australia, which has a total resource of 3.8 billion tonnes with an average grade of 1.1% copper, 339 ppm uranium, 3.0 g/t silver and 0.50 g/t gold. Olympic Dam is the world's largest uranium deposit and one of the world's largest copper deposits.
Even with its immense size, Olympic Dam is very complex, with alteration and mineralization largely structurally controlled and highly variable. In fact, published data show that of nine holes drilled within 1 kilometre of the core of the deposit in 1975 and 1976, four were barren and were shown by later drilling to lie less than 400 metres from ore (Figure 1). The center of the Olympic Dam deposit is actually barren, and directly underlies the core of a corresponding gravity anomaly with most of the ore located in irregular bodies of hematite breccia flanking the core, but locally extending outwards along narrow structures for several kilometres (Figure 2). The matrix of the ore breccias are hematite rich with fragments of intensely altered host rock, locally the texture of the breccia is described as a "streamed texture" related to fluid flow. The breccia bodies also pinch and swell over short distances and vary greatly in strength of mineralization. The ore is rarely massive, mainly occurring as disseminated to locally vein type mineralization within hematite rich breccias. The dominant copper bearing sulphide is chalcopyrite.
Applications to Moran Lake The Moran Lake area is underlain by a mid-Proterozoic sequence of volcanic, sedimentary and igneous intrusive rocks, part of the Central Mineral Belt, which is of similar age to the Olympic Dam region. Both Olympic Dam and the Moran Lake area lie near the margins of a continental craton in areas of high heat flow (lots of igneous and volcanic activity and containing a high background uranium content), a setting critical to the formation of uranium rich IOCG deposits like Olympic Dam. The presence of chalcopyrite bearing, hematite rich breccias, locally with "streamed textures" has been known at Moran Lake for over 25 years (see web site for photo of mineralized breccia, Figure 4), but were not recognized as important IOCG type characteristics until recently. They closely resemble portions of the Olympic Dam breccia complex. Drilling carried out by Shell in the 1970's intersected several intervals of hematite rich breccias, locally copper bearing, which lie on the flanks of a significant gravity anomaly. Shell was not aware of the gravity anomaly as it was not defined until an airborne survey covered the region in 2003, nearly 25 years after the Shell drilling programs. The position of the Shell drilling in relation to the gravity anomaly suggests that the mineralization observed in the Shell holes lies along a structure emanating outwards from the core of the gravity anomaly and thus would constitute part of the lower grade portion of the system (Figure 3). This relationship between structure and the gravity anomaly is present at Olympic Dam where narrow breccia bodies are focused along structures emanating from the core of the complex. Using Olympic Dam as a model, it would appear that the most prospective area based on all previous work would lie to the east, south and west of the gravity anomaly in the intervening 3 kilometre distance between the C and B zones and flanking (but not within) the core of the gravity anomaly. The presence of poly-metallic mineralization (uranium, copper, silver and gold) at Moran Lake was hinted at by Shell, and has now been verified by the results of the Phase 1 sampling program.
| | ||||||
)
)
)
)