Michigan · Marquette County
Past Producer

Winthrop Mine

Marquette County, Michigan, United States
Iron
⌖ Show on mapUSGS source ↗
Commodities
PrimaryIron
Commodity typeM
Deposit
Deposit typeBedded, Chemical Sediment
Model241: Superior Fe (BC name is Lake Superior & Rapitan types iron-formation)
Deposit sizeS
WorkingsUnderground
Orebody formSTRATABOUND
Materials
Ore mineralsHematite, Magnetite, Goethite
GangueQuartz
Geology
Host rockIron Formation · Negaunee Iron-Formation
StructureWestward plunging synclinorium open at western end; regional trends are eas
AlterationSome magnetite formed by replacement of ferrous iron minerals during diagenesis and most iron silicate probably formed by metamorphism of an early silicate mineral.
Economic & production
Development statusPast Producer
Production yearsSHIPPED ORE EVERY YEAR 1869-1889 AS BRAASTAD-WINTHROP.
First production1869
Last production1903
Discovery year1844
Identification
Deposit ID10082789
MRDS IDW062139
Alternate namesBraastad-Winthrop
RegionNA
Data scoreB
Coordinates46.45306, -87.69169
References
JAMES, H. L., 1955, ZONES REG. METAMORPHISM. IN N. MICHIGAN.: GEOLOGICAL SOCIETY OF AMERICAN BULLETIN, V. 66, P. 1455-1488.THE LAKE SUPERIOR IRON ASSOC., 1938, LAKE SUPERIOR IRON ORES.LAKE SUPERIOR IRON ORE ASSOCIATION, 1952, LAKE SUPERIOR IRON ORES: CLEVELAND, OHIO, 2D ED., 334 P.GRATON-SALES VOL. A. I. M. E., THE MARQUETTE DISTRICT: ORE DEPOSITS OF THE U. S., 1933-1967, P. 508-517.LAURA, D.K., 1981, THE EARLY PROTEROZOIC PRE-IRON FORMATION, MENOMINEE GROUP SILICICLASTIC SEDIMENTS OF THE SOUTHERN LAKE SUPERIOR REGION; EVIDENCE FOR SEDIMENTATION IN PLATFORM AND BASINAL SETTINGS: JOURNAL OF SEDIMENTARY PETROLOGY, V. 51, NO. 2, P. 397-414.SIMS, P.K., 1990, GEOLOGIC MAP OF THE PRECAMBRIAN ROCKS OF IRON MOUNTAIN AND ESCANABA 1 DEGREE X 2 DEGREES QUADRANGLES, NORTHEASTERN WISCONSIN AND NORTHWESTERN MICHIGAN: U.S. GEOLOGICAL SURVEY MISCELLANEOUS INVESTIGATION SERIES, I-2056.BOYUM, B.H. AND REED, R.C., 1988, MARQUETTE MINERAL DISTRICT OF MICHIGAN, MINING HISTORY AND GEOLOGY, IN SCHULZ, K.J., 34TH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY FIELD TRIP GUIDEBOOKS, V. 34, PART 2, P. B-1-B-15.BOYUM, B.H., 1988, THE ORIGIN AND EXTENT OF THE HARD AND SOFT IRON ORES OF THE MARQUETTE RANGE, MICHIGAN, IN KISVARSANYI, GEZA, AND GRANT, S.K., NORTH AMERICAN CONFERENCE ON TECTONIC CONTROL OF ORE DEPOSITS AND THE VERTICAL AND HORIZONTAL EXTENT OF ORE SYSTEMS, PROCEEDINGS VOLUME: UNIVERSITY OF MISSOURI, ROLLA, P. 301-311.MOST ALL OF THIS DISTRICT HAS BEEN MAPPED AT 7 1/2 MINUTE QUADRANGLE SIZE. TOO MANY GEOLOGISTS HAVE BEEN INVOLVED TO MENTION INDIVIDUALLY. GAIR, J.E., 1975, BEDROCK GEOLOGY AND ORE DEPOSITS OF THE PALMER QUADRANGLE, MARQUETTE COUNTY, MICHIGAN: U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 769, 159 P.LAKE SUPERIOR IRON ORE ASSOCIATION, 1952, LAKE SUPERIOR IRON ORES: CLEVELAND, OHIO, 2D ED., 75-92 P.