1975/01/01 by R. J. FLORAN, R. J. Floran, J. J. PAPIKE +1 · 2 citations
Earth and Planetary Sciences · #Geological and Geochemical Analysis #Geological formations and processes #Geological Modeling and Analysis
paper · doi:10.1130/0016-7606(1975)86<1169:potlro>2.0.co;2
Research Article| September 01, 1975 Petrology of the Low-Grade Rocks of the Gunflint Iron-Formation, Ontario-Minnesota R. J. FLORAN; R. J. FLORAN 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 117942Present address: Manned Spacecraft Center, TN6, Houston, Texas 77058 Search for other works by this author on: GSW Google Scholar J. J. PAPIKE J. J. PAPIKE 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794 Search for other works by this author on: GSW Google Scholar Author and Article Information R. J. FLORAN 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 117942Present address: Manned Spacecraft Center, TN6, Houston, Texas 77058 J. J. PAPIKE 1Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1975) 86 (9): 1169–1190. https://doi.org/10.1130/0016-7606(1975)86<1169:POTLRO>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R. J. FLORAN, J. J. PAPIKE; Petrology of the Low-Grade Rocks of the Gunflint Iron-Formation, Ontario-Minnesota. GSA Bulletin 1975;; 86 (9): 1169–1190. doi: https://doi.org/10.1130/0016-7606(1975)86<1169:POTLRO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The relatively unmetamorphosed middle Precambrian Gunflint Iron-Formation of Ontario has undergone considerable post-depositional recrystallization and locally intense replacement. Although these tend to obscure primary textural-mineralogical relations, textural elements similar to those of limestone can be identified and their mineralogy defined. Two fundamentally different kinds of iron formation are recognized: (1) cherty iron formation, which consists of granules, ooliths, and interstitial cements; and (2) banded or slaty iron formation, which is composed of matrices (fine-grained internally structureless laminae). Cherty iron formation corresponds broadly to the thick-bedded taconite and algal chert facies of Goodwin; slaty iron formation encompasses the thin-banded chert-carbonate and tuffaceous shale facies.Greenalite associated with cherty quartz and minor minnesotaite are dominant mineral constituents of granules; stilpnomelane and hematite are less common. Recrystallized calcite, ankerite, and siderite occur locally as cements and as replacement minerals. The most common cement is quartz. Iron silicate and siderite matrices are major constituents of slaty iron formation, which also contains considerable amounts of secondary calcite and ankerite. Stilpnomelane and chamosite are locally abundant in slaty rocks as apparent pseudomorphs after shards.Microprobe analyses of greenalite reveal little compositional variation; stilpnomelane from slaty iron formation is extremely heterogeneous. Both siderite and ankerite exhibit considerable substitution of Fe by Mg (and Mn locally) whereas calcite is almost pure CaCO3.Comparison of the greenalite, minnesotaite, and stilpnomelane crystal structures reveals many similarities. The crystal chemistry of magnesium and nickel analogues (serpentine, talc, and garnierite) has been used to predict structural details of the iron silicate minerals. These are consistent with textural and compositional data supporting a primary origin for the iron silicates. Quartz, recrystallized carbonate cements, microcrystalline siderite, hematite, and possibly magnetite are also considered primary phases. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.