Publication Date:
2020-08-24
Description:
Textural, geochronological, and geochemical data are presented here for cassiterite from the giant (149.7 million tonnes [Mt]) Mesoproterozoic Sullivan Pb-Zn-Ag deposit, which has been subjected to several tectonothermal events. These data provide constraints on the age and origin of the tin concentrations and new insights into related base metal mineralization. Sullivan is rare among sediment-hosted, stratiform Pb-Zn-Ag deposits in having high tin contents in ore (up to 2.5 wt %; avg 310 ppm Sn). Cassiterite occurs in all facies of this deformed and metamorphosed deposit, including (1) high-grade veins with arsenopyrite and pyrrhotite, (2) bedded Pb-Zn-Ag ores, (3) massive pyrrhotite, (4) footwall and hanging-wall tourmalinites, and (5) other altered wall rocks. New in situ U-Pb dates for Sullivan cassiterite obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are modeled by a multicomponent-based algorithm that yields three age peaks: 1475 ± 4 Ma (51% of the data), 1366 ± 10 Ma (25%), and 1074 ± 7 Ma (24%). These dates are attributed, respectively, to primary tin mineralization at ca. 1475 Ma, the East Kootenay orogeny at ca. 1370 to 1300 Ma, and the Grenvillian orogeny at ca. 1100 to 980 Ma. Based on the presence and local abundance of cassiterite in all ore and ore-related rocks at Sullivan, the U-Pb date of 1475 ± 4 Ma reported here represents the first direct age for ore mineralization in the deposit. Occurrence of texturally discordant rims on Sullivan cassiterite grains having U-Pb dates coeval with the East Kootenay and Grenvillian orogenies suggests that these young dates reflect dissolution-reprecipitation processes associated with channelized metamorphic fluid flow. LA-ICP-MS U-Pb dates obtained on low-U (
Print ISSN:
0361-0128
Electronic ISSN:
1554-0774
Topics:
Geosciences
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