DESCRIPTIVE MODEL OF EPITHERMAL Mn

MODEL 25g

By Dan L. Mosier

DESCRIPTION Manganese mineralization in epithermal veins filling faults and fractures in subaerial volcanic rocks.

GEOLOGICAL ENVIRONMENT

Rock Types Flows, tuffs, breccias, and agglomerates of rhyolitic, dacitic, andesitic or basaltic composition.

Age Range Tertiary.

Depositional Environment Volcanic centers.

Tectonic Setting(s) Through-going fracture systems.

Associated Deposit Types Epithermal gold-silver.

DEPOSIT DESCRIPTION

Mineralogy Rhodochrosite, manganocalcite, calcite, quartz, chalcedony, barite, zeolites.

Texture/Structure Veins, bunches, stringers, nodular masses, disseminations.

Alteration Kaolinitization.

Ore Controls Through-going faults and fractures; brecciated volcanic rocks.

Weathering Oxidization zone contains abundant manganese oxides, psilomelane, pyrolusite, braunite, wad, manganite, cryptomelane, hollandite, coronadite, and Fe oxides.

Geochemical Signature Mn, Fe, P(Pb, Ag, Au, Cu). At Talamantes W is important.

EXAMPLES

Talamantes, MXCO (Rocha and Wilson, 1948)

Gloryana, USNM (Farnham, 1961)

Sardegna, ITLY (Burckhardt and Falini, 1956)