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515746 
Journal Article 
Direct dating of hydrothermal W mineralization: U-Pb age for hubnerite (MnWO4), Sweet Home Mine, Colorado 
Romer, RL; Luders, V 
2006 
Yes 
Geochimica et Cosmochimica Acta
ISSN: 0016-7037 
70 
18 
4725-4733 
English 
We have investigated the potential of hubnerite for U-Pb dating. Hubnerite forms typically at medium to low-temperatures in a wide range of pneumatolytic-hydrothermal mineral deposits, particularly porphyry molybdenum and Sn-specialized granites. Hubnerite from the Sweet Home Mine (Alma, Colorado) formed in a Pb-rich, U-poor environment, developed relatively radiogenic Pb isotopic compositions. The low Pb-common contents in hubnerite (0.075 to 0.155 ppm) demonstrate that Pb is efficiently excluded from the crystal lattice. In contrast, U may substitute for Mn. The U-Pb data of hubnerite scatter. Most of the scatter originates from samples with Pb-206/Ph-204 values below 50, where Pb-blank contributes up to 30% to Pb-total. Using the least radiogenic galena Pb, samples with Pb-206/Pb-204 values above 70 have overlapping Pb-206(*)/U-238 and Pb-207(*)/U-235 values and yield a Pb-206/U-238 age of 25.7 +/- 0.3 Ma (2 sigma). Late stage apatite from the Sweet Home Mine yields a Pb-206/(204) Pb-U-238/Pb-204 isochron corresponding to an age of 24.8 +/- 0.5 Ma (2 sigma). A comparison of the U-Pb hubnerite ages with literature Ar-40/Ar-39 ages on earlier sericite and the U-Pb age on later apatite suggests that (i) hubnerite yields accurate U-Pb ages and (ii) the evolution of the Sweet Home mineralization from greisen-type mineralization to medium-temperature hydrothermal vein mineralization took place in a few hundred thousand years at most. Aqueous low-N-2-bearing and aqueous inclusions in the dated hubnerite have homogenization temperatures between 325 and 356 degrees C and moderate salinity (up to 6.7 wt% NaCl equiv.). Thus, hubnerite represents one of the rare examples of a mineral that can be dated accurately and carries petrological information. (c) 2006 Elsevier Inc. All rights reserved. 
fluid inclusion; infrared microthermometry; botryoidal hematite; alpha-recoil; disequilibrium; systematics; germany; sr; geochronology; schwarzwald