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Rift Environment and Project Criteria
Prime Meridian's focus is projects within the Midcontinent Rift System (MRS), a dynamic, deep seated structural environment that hosts a number of significant mineral deposits (eg the Eagle deposit announced by Rio Tinto in 2002 as hosting 5.2 million tonnes grading 3.67% nickel, 3.06% copper plus cobalt, PGE and gold). Prime Meridian's projects must have the potential to host large mineral deposits to be included in its drill programs.
Rift environments around the world are host to many large mineral deposits due to the following characteristics:
Conceptual Diagram of Rift Environment |
- tapping of the Earth's mantle, the source of many metals;
- development of structural conduits for metal transport, and
- development of structural traps where metals are deposited.
As a result of this favourable and dynamic structural environment the rift is amenable to the formation of several types of mineral deposits including magmatic nickel-copper, iron-oxide-copper-gold and volcanogenic massive sulphide deposits, all of which occur in close association with the MRS.
Projects
Beginning in 2000, Prime Meridian acquired the following Projects, now totaling approximately 20,600 hectares (51,000 acres), in the Upper Peninsula of Michigan and Minnesota. All are associated with Midcontinent Rift System (MRS) terranes. In the company's 2007 drill testing and geophysical survey campaigns, 4000 close spaced line kilometres of combined aeromagnetics/EM were flown over three Project areas, and drilling was conducted at individual targets on six Projects by 13 core holes. In addition, two individual targets were eliminated without drilling by ground geophysical surveys and geologic mapping. The status of the Projects as of end-2007 is summarized below:
ACTIVE PROJECTS
| Michigan |
Hectares |
Current Exploration Stage |
Target Type |
| Baraga Basin |
4,165 |
4 drill ready targets |
Copper-Nickel |
| Turner |
890 |
1 drill ready target |
Copper-Nickel |
| Wilson Creek |
3,860 |
4 drill ready targets
4 others drilled 2007 |
Iron Oxide-Copper-Gold |
| Minnesota |
Hectares |
Current Exploration Stage |
Target Type |
| Winterfire |
550 |
Airborne geophysics flown 2007;
6 drill ready targets |
Copper-Nickel |
| Water Hen |
290 |
Geophysics required |
Copper-Nickel |
Infrastructure
Prime Meridian's projects are in a region accessible by road and rail. Power and deepwater Great Lakes ports are readily available. Michigan and Minnesota are both states with long histories of mining, and both have recently modernized their mining regulations. Under Michigan's new sulfide mining regulations, Rio Tinto has, as of January 2008, received all permits to begin construction and mining at its Eagle nickel-copper deposit. A number of large copper-nickel projects in the Duluth igneous complex of the Midcontinent Rift System in Minnesota are currently finishing feasibility studies, and two have submitted applications for mining permits.
Regional Geology
Prime Meridian's nickel-copper exploration program is focused along the margins of the 1,100 Ma Keweenawan Midcontinent Rift System (MRS). Rifting and related igneous activity occurred during a 32 million year period from 1109 to 1087 Ma when the rise of a new mantle plume produced crustal fracturing and extension and large volumes of basaltic magma were emplaced as lava flows and related mafic intrusions.
The location of the MRS can be seen in the following diagrams
Midcontinent Rift |
Gravity Map of Central USA Showing Rift |
The following diagram shows a schematic cross section of the MRS through the Upper Peninsula of Michigan to Northeastern Minnesota, across the Lake Superior basin |
Project Exploration Targets
Prime Meridian's work programs are designed to identify prospective areas within the MRS, acquire the mineral tenure, and advance the Projects to the drilling stage. This is done by mapping and sampling outcrops, combined with airborne and ground geophysical surveys, a combination that has successfully developed drill targets for the company since it began work here in 2000.
The magmatic nickel-copper projects' drill targets are based on an exploration model where metals and rock are ejected from deep in the earth along structures formed by the MRS. A key element is to determine where these deep sourced rocks, peridotite and olivine gabbro, occur and which ones have economically viable nickel-copper mineralization.
The best example of this deposit model in the immediate area is Rio Tinto's Eagle deposit. Other well known examples of this deposit model include Voisey's Bay in Labrador, Canada. Prime Meridian's planned program will drill test Copper-Nickel targets on the following Projects using this exploration model:
- Bararga Basin;
- Winterfire
- Water Hen
- Turner.
The largest and most advanced of the IOCG (Iron oxide copper gold) projects is the Wilson Creek Project where fieldwork located ore grade mineralization in boulders. The Salobo and Igarape Bahia deposits, located in the Carajas Mineral Province, Brazil and the Cloncurry District in Australia are the best known IOCG examples comparable to the Wilson Creek project geology and geochemistry. IOCG deposits occur in a number of tectonic environments but intracratonic rifts, such as the MRS, host the majority of IOCG deposits.
Prime Meridian's 2007 drill program tested three individual targets at the Wilson Creek Project using the IOCG model, and encountered widespread IOCG-style alteration of host rocks and short intervals of copper mineralization (see Press Release, January 9, 2008).
Drilling in 2007 |
In addition to the magmatic copper-nickel and IOCG deposit models Prime Meridian, on an opportunistic basis, continues to evaluate properties within the MRS environment for other deposit models.
Prime Meridian's exploration team has many years of developed expertise and insight into the potential of the area. Our intent is to grow into a mining company through the continued advancement of projects to drill testing leading to economic discovery.
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