ThomasEdwardLane.pdf

The sphalsrlte deposit at Newfoundland Zinc nines near narlieln
~srbour, western ~evfoundlend is situated in the upper part of the Lmer
ocdovician St. George Group, a cmpiex ot dolostones, limestones and
breccias in ths middle of a Lawer Paleozoic shallav-water, carbonate
~latfona sequence. It is a zino-dominated Mlssiasippi Valley Type [HVTl
depposit, a svhtype of WYTs that is characteristic of the Appalachians.
phis study shows that zinc qeralization acsurred during one phase of e
cmplex history of repaated dolwitiretion and fracturing of the host
carbonates along northeast-trending lineaments. This history is
Interpreted through an integrated analy6iS ef the sedhentolqic,
stratigraphic and structural framwork, petrqrsphy, cathodolminercence
and gwshemirtry.
me upper St. George Group carbonates were deposited along the
edge of the tropical Iapetus Ocean during Early to early Middle Or&-
vician tine when the paesive emtinema1 wrgin began to experience the
initial effects of plate convergence. Shallow subtidal muddy carbonates
(-toehe Porntion) shailuued upwards into restricted-water, rhythmi-
cally interbedded pcloidal grainstones and mudstones (Peloidal or Costa
Bay Member) and peritidal laminites and bur--mttled mudstones
(guathuna Formation). Defamation and fragmentation of the platform
and marine regression during early Xiddle Ordovician the resulted in
the regional St. Oeoma Unmnfomity and the formation of rak-matrix
breccias from subsurface karst. The mine stratigraphy records a minimum