scholarly journals Lake Superior-type iron-formation

1995 ◽  
Author(s):  
G A Gross
Keyword(s):  
Lake Superior ◽  
Iron Formation ◽  
Superior Type

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

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

1995 ◽  
Vol 90 (1) ◽  
pp. 118-134 ◽  
Author(s):  
Gema Ribeiro Olivo ◽  
Michel Gauthier ◽  
Marc Bardoux ◽  
Euripedes Leao de Sa ◽  
Jose Teotonio F. Fonseca ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Lake Superior ◽  
Iron Formation ◽  
Structural Controls ◽  
Iron Mine ◽  
Superior Type

Palladium minerals from the Cauê iron mine, Itabira District, Minas Gerais, Brazil

1995 ◽  
Vol 59 (396) ◽  
pp. 455-463 ◽  
Author(s):  
Gema Ribeiro Olivo ◽  
Michel Gauthier
Keyword(s):  
Copper Oxide ◽  
Lake Superior ◽  
Minas Gerais ◽  
Iron Formation ◽  
Chloride Complexes ◽  
Mylonitic Foliation ◽  
The Core ◽  
Physico Chemical ◽  
Iron Mine ◽  
Chemical Conditions

AbstractPalladium-bearing minerals from the Cauê iron mine, Itabira District, Minas Gerais, Brazil, are found in gold-rich jacutinga, a hydrothermally-altered Lake Superior-type carbonate-bearing oxide facies iron-formation. Palladium occurs as: native palladium with trace contents of Au, Fe and Cu; palladseite ((Pd,Cu,Hg)17Se15), which was found in the core of a grain of palladium; palladium–copper oxide ((Pd,Cu)O); and arsenopalladinite (Pd8(As,Sb)3), with inclusions of palladium–copper oxide. The palladium and palladium–copper oxide grains are coated with films of gold and commonly do not exceed 100 µm in width. These palladium minerals occur in hematite bands and in boudinaged bands of quartz and white phyllosilicate parallel to the S1 mylonitic foliation. Palladium-copper oxide also occurs as inclusions in gold grains which are strongly to weakly stretched parallel to S1.Palladium mineralization is interpreted as synchronous with intense D1 shearing and contemporaneous with the peak of thermal metamorphism. At high oxygen fugacities and high temperatures (up to 600°C), Pd may have been transported as chloride complexes and deposited following changes in pH caused by mineralizing fluids reacting with jacutinga. Deposition may also have been prompted by the formation of insoluble selenide and arsenide–antimonide minerals and by the dilution of C1 concentrations in the mineralizing fluid. Textural studies, and the zonation observed in palladium and other hydrothermal minerals, suggest that oscillations in the physico-chemical conditions of hydrothermal fluids occurred during the mineralizing event.

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.

Sign in / Sign up

Export Citation Format

Share Document