Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Gold/Mining/Energy : Winspear Resources -- Ignore unavailable to you. Want to Upgrade?

To: russet who wrote (26786)	1/30/2002 12:20:26 PM
From: russet	Read Replies (1) \| Respond to of 26850

Interesting theory,.. http://www.poplarresources.com/s/RelatedArticles.asp?ReportID=31266 Tue Jan 1, 2002 Kimberlite Strip Model ("KSM") -------------------------------------------------------------------------------- KIMBERLITE STRIP MODEL ("KSM") The Kimberlite Strip Model ("KSM") is a proprietary methodology developed by Dr. Malcolm Light. The methodology consists of a suite of sophisticated geological and geophysical tools that allows for the identification and delineation of zones of interest where economically diamondiferous kimberlite pipes are most likely to occur within larger cratonic environments. These "zones" are also referred to as "corridors" or "strips". The use of the KSM technique substantially reduces the size of areas to be explored as it helps eliminate areas containing kimberlite pipes that are most likely to be barren or sub-economic. A brief description of the method is outlined below: SUBDUCTION-BASED MODEL The KSM is a subduction-based model, which predicts areas that are most likely to host diamondiferous kimberlites. It relies on three main principles: That the carbon from which diamonds are formed is organic crustal carbon supplied to the mantle by subduction of the oceanic lithosphere and accumulated along specific zones beneath the continental crust. These zones of carbon concentration occur at a depth where temperature and pressure combine to form diamonds. That kimberlites sampling the diamond rich carbon concentration zone utilize the large-scale crustal stress fracture systems related to the subduction processes as conduits for their rising to the surface. That the location of these large-scale crustal fracture systems (known as gem fractures) can be accurately calculated and predicated. By drastically narrowing the areas, which a search for diamondiferous kimberlites must cover, the Model provides both a powerful competitive advantage and a significant cost savings to companies exploring for diamonds. CRUSTAL CARBON ORIGIN FOR DIAMONDS Diamonds are not derived directly from kimberlites, but from mantle xenoliths collected in the carbon concentration zone and carried to the surface by the rising kimberlite magmas. Two types of diamonds have been identified, based on the types of mantle xenoliths they are associated with - eclogites and peridotites. It was originally thought that these xenoliths (and the diamonds they contain) were formed in the mantle, however recent geochemical and isotopic evidence points strongly to their origin as subducted crustal material. Isotopic evidence from the oldest known rocks in Greenland and South Africa indicates that organic life, capable of extracting CO2 from the atmosphere and depositing it as crustal organic carbon, was probably well established by 3.8 Ga. Thus, as source of crustal carbon existed from the earliest Archean, which is also the approximate age of formation of most diamonds. Isotope data shows that the carbon in diamonds is isotopically heavy. This is consistent with an isotopic fractionation event where isotopically light crustal carbon is heated during subduction, driving off the light carbon isotopes as CO2. Some diamonds are also enriched in iodine, which is present in high concentrations in oceanic crust but not in the upper mantle. As well, oxygen isotope data from eclogite xenoliths suggest that they are originally derived from basaltic rocks, which have been in contact with seawater. Finally, the mineralogy of periodite diamond inclusions and periodite xenoliths (Cr-rich, low Ca garnets with Mg-rich olivine and enstatite) is compatible with metamorphism of subducted oceanic crust consisting of spinel harzburgite cumulates or serpentinites. In summary, a growing body of evidence suggests that diamonds are derived from crustal carbon that is carried into the diamond stability field of the upper mantle during subduction of oceanic lithosphere. A further premise of the Kimberlite Strip Model is that this subducted crustal carbon will accumulate along specific areas within the subduction zone. Although the subducting plate is primarily experienced tensional stress, at about 200km depth it begins to encounter denser mantle material and is thrown locally into compression. This results in the shearing off of the carbonaceous sediments against the overriding plate along a zone parallel to the trend of the subduction zone. This zone of carbonaceous sediments concentration corresponds to the diamond stability field and results in a high concentration of diamonds that can be sampled by vertically rising kimberlites. STRUCTURAL CONTROL OF KIMBERLITE EMPLACEMENT Large-scale tectonic forces generated by the subducting slab of oceanic lithosphere can be propagated into the overlying continental crust to produce major fracture systems. One of the most important of these to the Kimberlite Strip Model is a trench-parallel vertical fracture system that develops above the subducting plate at approximately 200km. This is the point where the subducting plate is locally placed under compressive stress - the vertical component of this compressive stress will result in the development of a vertical fault system known in the Model as the Gem Fracture. The Gem Fracture is located parallel to the subducting oceanic lithosphere trench and above the carbon concentration zone. The rising kimberlites utilize this gem fracture as the conduit by which they rise to the surface after sampling the diamond rich carbon concentration zone. The other important fracture system to the Model is the system of trench-normal fractures/faults known as transform faults. These develop within the oceanic crust and are subducted along with the descending slab. These faults can also propagate through the overlying continental crust, as has been demonstrated in Africa. The intersection of trench-parallel and trench-normal fault systems forms a zone of weakness within the crust which appears to have a strong control on the location of deeply-sourced intrusive bodies such as carbonatites, alnoites and kimberlites. It is thought that the intersection of these deep structures may also control the formation of mantle intrusives at depth. The areas of particular interest with regards to the intrusion of diamondiferous kimberlites are the intersection points of the transform faults and the gem fracture. A schematic outlining the description above is shown in Figure 1. Figure 1 APPLICATION OF THE STRIP MODEL The strength of the Kimberlite Strip Model is its ability to predict both the location of accumulation of crustal carbon beneath a continental craton, and the intersections of trench-normal and trench-parallel fractures, which control the emplacement of kimberlites. Applying the Model to real world situations requires that several parameters be accurately determined, including the location of the former subduction zone (specifically the location of the trench), the dip of the former subducting slab, and the geothermal gradient. These calculations comprise the proprietary portion of the Kimberlite Strip Model. They have been developed through theoretical principals and refined and calibrated using known diamondiferous kimberlite provinces in southern Africa. Applying the Strip Model to the other areas which host known diamondiferous kimberlites such as Russia and the Northwest Territories of Canada has shown an excellent correspondence between the predicted prospective areas and the actual kimberlite pipes. Although in these areas the location of these pipes was not used to calibrate the Model, the fact that the pipe locations were known prior to the application of the Model prevents these examples from being true tests of the Model. Critical evidence of the Model's validity comes from Scandinavia, where the Strip Model was applied and demonstrated prior to the announcement by Ashton Minerals of the discovery of 14 diamondiferous kimberlites in Finland. Although Ashton did not announce the location of the pipes, the location was subsequently determined. The almost exact coincidence of the kimberlite strip with these diamondiferous pipes is a convincing demonstration that the Kimberlite Strip Model is a powerful tool to aid in the search for diamondiferous kimberlite pipes. The KSM method has been used both in Quebec, Ontario (Victor Pipe) and in Scandinavia. In Quebec four new areas have been identified. Poplar Resources is now planning to systematically explore these four "kimberlite strips". http://www.poplarresources.com/i/pdf/KSM.pdf

To: russet who wrote (26786)	6/25/2002 10:03:43 AM
From: E. Charters	Read Replies (1) \| Respond to of 26850

Does this mean there are diamonds in the north? You could short circuit all that inclusion stuff by just studying the nickel temperature (proton probe) versus the chrome pressure(% of each) for any bunch of garnets (do not have to be pyrope), whether E or P type ,in groups or 100 or more per K-rock, and graphing the maximum P for each T. This curve is proportional to the geotherm (the radiation per metre in Watts of the crust.) Griffin and Ryan. EC<:-}