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Marathon Co., Wisconsin, USA

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Location is approximate, estimate based on other nearby localities.
 
Latitude & Longitude (WGS84): 44° North , 89° West (est.)
Margin of Error:~11km


Marathon County displays some of the best outcrops of Precambrian rock in the state. Many of the rock occurrences are of interest to the mineral enthusiast.

The oldest rocks are gneisses and amphibolites, likely of Archean age, that have experienced amphibolite facies metamorphism. Overlying these, probably unconformably, are a complex sequence of Lower Proterozoic meta-volcanic and meta-sedimentary rocks that have undergone greenschist facies metamorphism. These appear to be the remnants of an island arc sequence caught between colliding continents during the 1.80 -1.85 billion year old Penokean Orogeny. These have been intruded by pre- and syn- and post-tectonic plutons, largely granitic in composition.

Notable post-tectonic and possibly anorogenic intrusions include the 1.4 billion year old Wolf River Batholith and the various plutons of the Wausau Complex. The Wausau Complex (including the Nine Mile Pluton and Stettin Pluton) is relatively well exposed, and consists of granites, syenites and nepheline syenites. These host complex pegmatites. Weathering has reduced many outcrops to “grus” which is produced in many quarries as crushed stone known as “rotten granite”. Unweathered granite is also produced for building stone and includes the red granite which is Wisconsin’s official state rock. A variety of minerals can be found in these plutonic rocks, including smoky quartz, zircon, anorthoclase (showing excellent moonstone schiller), phenakite and REE minerals. Xenoliths of quartzite occur in these plutons, the largest holding up Rib Mountain, where is can be readily examined in a state park, and represents the second highest elevation in the state..

Wide shear zones where the rocks have been cataclastically deformed cross-cut the Precambrian rocks. Examples are beautifully exposed in the Eau Claire Dells County Park along a scenic river gorge.

Several massive sulfide deposits and mineralized quartz veins are known, but so far (2013) no production has occurred. These potentially host gold, silver, zinc and lead.

Scattered outliers of Cambrian sandstone occur, and are worked for flagstone. Also several episodes of glacial drift coated the area. Interesting samples of glacially-transported rocks and minerals can be found by the dedicated collector.

Mineral List

Mineral list contains entries from the region specified including sub-localities

Actinolite

Aegirine

Agrellite

Albite

'Albite-Anorthite Series'

Allanite-(Ce)

'Allanite Group'

Almandine

Amphibole Supergroup

Anatase

Andradite

Anhydrite

Ankerite

Annite

'Anorthoclase'

'Apatite'

Arfvedsonite

Arsenopyrite

Augite

Baddeleyite

Baryte

'Bastnäsite'

'Bastnäsite Group'

Bavenite

Bertrandite

Beryl

var: Aquamarine

'Biotite'

Boulangerite

Brookite

Calaverite

Calcite

Cancrinite

Cassiterite

Catapleiite

Chalcopyrite

Cheralite

'Cheralite-(Ce)'

Chevkinite-(Ce)

'Chlorite Group'

Columbite-(Fe)

'Columbite-(Fe)-Columbite-(Mn) Series'

Columbite-(Mn)

'Columbite-Tantalite'

Cookeite

Cordierite

Cryolite

Diopside

Elbaite

Epidote

Euclase

Eudialyte

'Eudialyte Group'

'var: Eucolite'

Euxenite-(Y)

Fayalite

'Feldspar Group'

'var: Perthite'

Ferberite

'Fergusonite'

Ferro-hornblende

Florencite-(Ce)

Fluorapatite

Fluorite

Galena

'Garnet'

Goethite

Gold

Gorceixite

Grayite

Grossular

Gypsum

Hastingsite

Hedenbergite

Hematite

Hisingerite

'Hornblende'

Hübnerite

Ilmenite

Ixiolite

Jamesonite

Kaolinite

Kentbrooksite

'K Feldspar'

'var: Adularia'

Låvenite

Lepidocrocite

Leucoxene

Liandratite

'Limonite'

Magnetite

Malachite

'Manganese Oxides'

'var: Manganese Dendrites'

'Manganoan Calcite'

'Mica Group'

Microcline

var: Amazonite

Microlite Group

Miserite

Molybdenite

'Monazite'

Monazite-(Ce)

Monazite-(La)

Monazite-(Nd)

'Moonstone'

Muscovite

Natrolite

Nepheline

'Olivine'

Opal

var: Opal-AN

Orthoclase

'Parisite'

'Percivalite'

Perrierite-(Ce)

Phenakite

Plumbogummite

Polycrase-(Y)

Prosopite

Pseudobrookite

'Psilomelane'

Pyrite

'Pyrochlore'

Pyrochlore Group (TL)

var: Bariopyrochlore (of Hogarth 1977)

var: Ceriopyrochlore (of Hogarth 1977) (FRL)

var: Plumbopyrochlore (of Skorobogatova et al.)

'Pyroxene Group'

Pyrrhotite

Quartz

var: Smoky Quartz

'Rhabdophane'

Rhabdophane-(Ce)

Rhabdophane-(La)

Rhabdophane-(Nd)

Riebeckite

'Riebeckite Root Name'

'var: Crocidolite'

Romanèchite

Rutile

var: Ilmenorutile

var: Strüverite

Samarskite-(Y)

Sanidine

Schorl

'Serpentine Subgroup'

Siderite

Siderophyllite

Sodalite

Sphalerite

Staurolite

'Stibiconite'

Stilpnomelane

'Synchysite'

'Synchysite Group'

Talc

Tantalite-(Fe)

Tantalite-(Mn)

'Tapiolite'

Tapiolite-(Fe)

Thalénite-(Y)

Thorite

'Thorogummite'

Titanite

Topaz

'Tourmaline'

Uranophane

'Uranpyrochlore (of Hogarth 1977)'

'Uvite'

Wöhlerite

Wollastonite

Xenotime-(Y)

'Zinnwaldite'

Zircon


120 valid minerals. 1 (TL) - type locality of valid minerals. 1 (FRL) - first recorded locality of unapproved mineral/variety/etc.

Localities in this Region

USA
USA

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

LaBerge, G. & P. Myers (1983) Precambrian geology of Marathon County, Wisconsin: Wisconsin Geological and Natural History Survey: Information Circular 46, 88 p. with 2 maps.

Falster, A. (1986), Minerals of the Stettin Pluton, Marathon County, Wisconsin: Rocks and Minerals: 61 (2): 74-78.

Falster, A. (1987), Minerals of the pegmatite bodies in the Wausau Pluton, Marathon County, Wisconsin: Rocks and Minerals: 62 (3): 188-193.

Simmons, W., Webber, K & Buchholz, T. (2000) Pegmatites and pegmatite minerals of the Wausau Complex, Marathon County, Wisconsin: Memorie della Societa di Scienze Naturali e del Museo Civico di Storia di Milano: XXX: 13-28.

Falster, A. U., Simmons, W. B., Webber, K. & Buchholz, T. (1999), The Wausau Syenite complex, Marathon County, Wisconsin: origin, geochemistry and mineralogy of a mid-Proterozoic anorogenic intrusive complex and its pegmatites: The Canadian Mineralogist : 37 (3): 835-836.

External Links

Wisconsin Mineral index - Wisconsin Geological and Natural History Survey http://wgnhs.uwex.edu/wisconsin-geology/minerals-wisconsin/

Mineral and/or Locality  
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