| Summary: | The Early-Silurian Woodstock Fe-Mn Deposits are a series of six, northeasttrending,
low grade manganiferous-iron deposits in western New Brunswick that
collectively represent the largest Mn resource in North America (194,000,000
tonnes; 13% Fe and 9% Mn). Recent expansion of Route 95 has allowed a more
detailed local stratigraphy, mineralogy, and geochemistry of the Fe-Mn deposits
within the context of the regional stratigraphy to ascertain the genesis of these
deposits. Geological mapping during the field seasons of 2008 and 2009 has
revealed six Lithofacies Associations (O, I, II, III, IV, V) within the area, that,
generally, are lying conformably on top of each other. However complications due
to folding and interbedding have resulting in juxtaposition of the lithofacies
associations so they are not always in stratigraphic order. These lithofacies
associations are composed of a turbidite-rich section of blue grey calcareous
sandstone (O) overlain by black pyritic mudstone (I), associated mineralized and
nonmineralized green (II) and red siltstone (III), and laminated to massive grey
green calcareous sandstone (IV and V).
Na/Mg ratios, chondrite-normalized REE patterns, and mineralogical
evidence of rapid changes in ocean redox conditions suggest the Fe-Mn mineralized
lithofacies were formed in the offshore zone of a continental shelf on a stable
cratonic margin. Al-Fe-Mn ternary and SiO2/Al2O3 binary plots developed from
archived drill core data indicate the Fe-Mn mineralization was initially derived from
hydrogenous-detrital sources without any indication of a hydrothermal input as a
source of Fe and Mn.
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