Gold-bearing iron formations are widely distributed within extensive metasedimentary terranes of the Archean Slave Province, situated in the northwestern Canadian Precambrian Shield. Mineralized iron formations occur within thick turbidite sequences overprinted by a protracted history of deformation, metamorphism, and plutonism. Economically significant gold prospects are specifically sited at structural culminations characterized by polyphase folding. Based on garnet–biotite geothermometry on the stable prograde metamorphic assemblage of enveloping metapelites, peak metamorphic conditions are approximated to be 570 °C and 4 kbar (1 kbar = 100 MPa). Diagnostic prograde mineralogy reveals that two facies of silicate iron formation are represented at the five gold occurrences investigated: (1) amphibolitic iron formation (AIF), characterized by quartz + grunerite + hornblende + pyrrhotite ± garnet ± graphite + ilmenite, and (2) pelitic iron formation (PIF), consisting of quartz + biotite + garnet + ilmenite ± grunerite ± hornblende. Textures reveal that grunerite crystallization preceded hornblende and garnet. Within AIF, banded pyrrhotite is in textural equilibrium with prograde metamorphic minerals. Retrograde hornblende, garnet, zoisite, apatite, carbonate, ferroactinolite, and gold-bearing sulphide minerals replace the prograde mineral assemblages on the margins of quartz veins that intensify at AIF fold hinges.It is hypothesized that the iron-formation-hosted gold deposits of the Slave Province are a result of multistage processes. Gold concentrated at high background levels within pyrrhotite-bearing AIF was remobilized during fluid migration into brittle AIF fold hinges in subsequent metamorphic and deformational events. Metamorphic fluid, ponded in fractured AIF hinge domains, caused retrogressive replacement, quartz veining, and gold-bearing sulphide precipitation during waning temperature. Although the mineralized hinge zones commonly display evidence of late chloritization, this alteration did not further affect gold distribution. The gold precipitated with destabilization of thio complexes due to sulphidation prior to low-temperature hydrothermal activity.
Regional and Local Geology |
 Regionally, the Pickle Crow Property lies within the Uchi subprovince of the Canadian Shield, the same belt of 2.7-3.0 billion year old metavolcanic and metasedimentary rocks that host the deep, rich mines of the Red Lake area, including Goldcorp’s high grade Red Lake Mine. Gold deposits in the Uchi subprovince are known for their excellent continuity in the depth dimension. The Property area is located within the Pickle Lake greenstone belt of the Uchi subprovince, the term “greenstone” referring to the greenish hue of one of the principal rock types, chiefly metabasalts (metamorphosed mafic lavas), that comprise the belt. The Pickle Lake greenstone belt is an approximately 70 kilometre long by 25 kilometre wide area of supracrustal rocks and internal granitoid plutons surrounded by large granitoid batholiths. The supracrustal rocks have seen polyphase deformation and been metamorphosed to greenschist facies with amphibolite facies occurring in the thermal aureoles of younger plutonic bodies. Locally, on the Property itself, the principal rock types are metabasalts (greenstone) with intercalated metasediments, principally carbonate-magnetite banded iron formation, as well as quartz-feldspar porphyry and felsic to intermediate volcanic and volcaniclastic units. Needless to say the only true indicator will be the assay results, which have been sent to the lab, and a rush has been requested for the return of results. Another fact to remember in regards to Jiminex's current drilling program is they were working on finishing the hole they were drilling, after which the drill will be moved back to the area of hole #3, and more holes will be drilled in an attempt to gain insight into the size and amount of potential resource in this area of the property. This drilling program is scheduled for 16 holes and they were working on hole #5 at the time of their most recent news release dated May 4, 2011. With the amount of gold that has historically been discovered in this area it is not difficult to acknowledge the potential in this exploration effort by Jiminex. For those of you that find this company of interest, I suggest you do your due diligence. A good place to start would be the companies website at www.jiminex.com. For disclosure purposes I have not received any compensation of any kind for this post. I do own shares in JIM. |
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