scholarly journals Les gites d or palladiferes des mines de Caue et de Conceicao dans les formations de fer du type lac Superieur du district d Itabira Craton Sao Francisco Bresil structure mineralogie geochronologie et metallogenie = (Palladium-bearing gold deposits of the caue and conceicao mines hosted by lake superior-type iron-formations of the Itabira district Sao Francisco craton Brazil structure mineralogy geochronology and metallogeny)

1994 ◽  
Author(s):  
Gema Ribeiro. Olivo
Keyword(s):  
Lake Superior ◽  
Gold Deposits ◽  
Iron Formations ◽  
Superior Type

HURONIAN STRATIGRAPHY OF THE McGREGOR BAY AREA, ONTARIO: RELEVANCE TO THE PALEOGEOGRAPHY OF THE LAKE SUPERIOR REGION

1966 ◽  
Vol 3 (2) ◽  
pp. 203-210 ◽  
Author(s):  
Grant M. Young
Keyword(s):  
United States ◽  
Lake Superior ◽  
Lake Huron ◽  
North Central ◽  
North Shore ◽  
Bay Area ◽  
The North ◽  
Central United States ◽  
Iron Formations

Mapping in the McGregor Bay area of Ontario has shown the presence of a sequence of formations which closely resembles that of the original Huronian of the Bruce Mines–Blind River area. Iron-rich siltstones and argillites above the Lorrain formation are correlated with the lower part of the Animikie iron-formations of the Port Arthur region of Lake Superior and the north central United States. The oldest Proterozoic rocks of the region south of Lake Superior are considered to be correlatives of the Cobalt group of the north shore of Lake Huron.

Concentration of gold during retrograde metamorphism of Archean banded iron formations, Slave Province, Canada

1993 ◽  
Vol 30 (8) ◽  
pp. 1566-1581 ◽  
Author(s):  
R. Craig Ford ◽  
Norman A. Duke
Keyword(s):  
Hydrothermal Activity ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
High Background ◽  
Multistage Processes ◽  
Slave Province ◽  
Sulphide Precipitation ◽  
Iron Formations ◽  
Gold Bearing

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.

Age of volcanic rocks and syndepositional iron formations, Marquette Range Supergroup: implications for the tectonic setting of Paleoproterozoic iron formations of the Lake Superior region

2002 ◽  
Vol 39 (6) ◽  
pp. 999-1012 ◽  
Author(s):  
D A Schneider ◽  
M E Bickford ◽  
W F Cannon ◽  
K J Schulz ◽  
M A Hamilton
Keyword(s):  
Lake Superior ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Age Determination ◽  
Iron Formation ◽  
Continental Rifting ◽  
The South ◽  
Zircon Age ◽  
Iron Formations ◽  
Northern Michigan

A rhyolite in the Hemlock Formation, a mostly bimodal submarine volcanic deposit that is laterally correlative with the Negaunee Iron-formation, yields a sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon age of 1874 ± 9 Ma, but also contains inherited Archean zircons as old as 3.8 Ga. This precise age determination for the classic Paleoproterozoic stratigraphic sequence of northern Michigan, the Marquette Range Supergroup (MRS), necessitates modification of previous depositional and tectonic models. Our new data indicate that the Menominee Group, previously ascribed to continental rifting during early, pre-collision phases of the Penokean orogenic cycle, is coeval with arc-related volcanic rocks now preserved as accreted terranes immediately to the south and is more aptly interpreted as a foredeep deposit. We interpret these to be second-order basins created by oblique subduction of the continental margin rather than basins formed on a rifting margin. Along with a recently reported age for the Gunflint Formation in Ontario of 1878 ± 2 Ma, our data suggest that an extensive foredeep in the western Lake Superior region was the locus of iron-formation deposition during arc accretion from the south. Further, we interpret the lower MRS (Chocolay Group), a glaciogenic and shallow-marine succession that lies atop Archean basement, to be equivalent to the upper part of the Huronian Supergroup of Ontario and to represent the original continental rifting and passive-margin phase of the Penokean cycle. The upper MRS (Baraga Group) represents deeper marine basins, dominated by turbidites and lesser volcanic rocks, resulting from increased subsidence and continued collision. A stitching pluton, which cuts correlatives of the Hemlock Formation in a thrust sheet, yielded a U–Pb zircon age of 1833 ± 6 Ma, consistent with other post-tectonic plutons in Wisconsin and northern Michigan, indicating that Penokean convergence lasted no longer than ~40 million years.

Palladium-bearing gold deposit hosted by Proterozoic lake superior-type iron-formation at the Caue iron mine, Itabira District, southern Sao Francisco Craton, Brazil; geologic and structural controls; reply

1995 ◽  
Vol 90 (8) ◽  
pp. 2372-2374
Author(s):  
Gema Ribeiro Olivo ◽  
Michel Gauthier ◽  
Marc Bardoux ◽  
Euripides Leao de Sa ◽  
Jose Teotonio F. Fonseca ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Lake Superior ◽  
Iron Formation ◽  
Structural Controls ◽  
Iron Mine ◽  
Superior Type
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