DESCRIPTIVE MODEL OF REPLACEMENT Mn

MODEL 19b

By Dan L. Mosier

DESCRIPTION Manganese oxide minerals occur in epigenetic veins or cavity fillings in limestone, dolomite, or marble, which may be associated with intrusive complexes.

GEOLOGICAL ENVIRONMENT

Rock Types Limestone, dolomite, marble, and associated sedimentary rocks; granite and granodiorite plutons.

Age Range Mainly Paleozoic to Tertiary, but may be any age.

Depositional Environment Miogeosynclinal sequences intruded by small plutons.

Tectonic Setting(s) Orogenic belts, late orogenic magmatism.

Associated Deposit Types Polymetallic vein, polymetallic replacement, skarn Cu, skarn Zn, porphyry copper.

DEPOSIT DESCRIPTION

Mineralogy Rhodochrosite ± rhodonite + calcite + quartz ± barite ± fluorite ± jasper ± manganocalcite ± pyrite ± chalcopyrite ± galena ± sphalerite.

Texture/Structure Tabular veins, irregular open space fillings, lenticular pods, pipes, chimneys.

Ore Controls Fracture permeability in carbonate rocks. May be near intrusive contact.

Weathering Mn oxide minerals: psilomelane, pyrolusite, and wad form in the weathered zone and make up the richest parts of most deposits. Limonite and kaolinite.

Geochemical Signature Mn, Fe, P, Cu, Ag, Au, Pb, Zn.

EXAMPLES

Lake Valley, USNM (Farnham, 1961)

Philipsburg, USMT (Prinz, 1963)

Lammereck, ASTR (Lechner and Plochinger, 1956)