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K‐Ar Ages of Tin‐Polymetallic Mineralization in the Oruro Mining District, Central Bolivian Tin Belt
Author(s) -
Sugaki Asahiko,
Shimada Nobutaka,
Ueno Hirotomo,
Kano Shimpei
Publication year - 2003
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2003.tb00176.x
Subject(s) - hypogene , alunite , mineralization (soil science) , jarosite , geology , cassiterite , geochemistry , weathering , tin , sericite , mineralogy , hydrothermal circulation , pyrite , metallurgy , paleontology , materials science , sphalerite , soil science , soil water
. K‐Ar age determinations were carried out on vein‐ and rock‐forming minerals from five vein‐type tin‐polymetallic ore deposits of the Oruro mining district in the central part of the Bolivian tin belt. The sericite from vein selvedges and an altered host rock provides good estimates of the ages of hypogene mineralization, and supergene alunite and jarosite provide ages for erosional and weathering episodes. It is concluded that hypogene mineralization in the Oruro mining district took place during the early to middle Miocene: 15.8±0.8 Ma at San José, 20.1±l.l Ma at Morococala, 20.5±1.0 Ma at Avicaya, and 19.6±1.0 Ma at Llallagua. Fine grained supergene alunite (δ 34 S = ‐10.1 960) and jarosite yield K‐Ar ages of 6.7±0.7 Ma at Avicaya and 3.9±0.7 Ma at Bolivar, respectively, suggesting that erosion and chemical weathering were active at those times.