In this section
@inbook{Wilkinson:2015,
author = {Wilkinson, JJ and Hitzman, MW},
booktitle = {Current Perspectives on Zinc Deposits},
editor = {Archibald and Piercey},
pages = {59--72},
publisher = {Irish Association for Economic Geology},
title = {The Irish Zn-Pb Orefield: The View from 2014},
url = {http://www.iaeg.org/},
year = {2015}
}
TY - CHAP
AB - The carbonate-hosted zinc-lead deposits of the Irish Orefield are stratigraphically and structurally controlled. Ore deposits are restricted to two stratigraphic units of Lower Carboniferous (Tournaisian and Visean) age: (1) the Waulsortian Limestone Formation in southern and central Ireland; and (2) the Navan Group of north central Ireland. The Waulsortian-hosted deposits occur largely in the complexly faulted hangingwalls of large (>150 m offset) normal faults within relay-ramp systems formed during transtensional fault movement. The giant Navan deposit occurs broadly within a complexly faulted, horst-related anticlinorium that was also subject to syndepositional, submarine mass wastage which removed a significant thickness (>300 m) of sedimentary cover above the mineralized zone. Ore-controlling faults in the Irish Orefield formed in response to extensional tectonism in the Tournaisian and early Visean but their location and orientation were probably controlled by pre-existing faults within the Lower Paleozoic basement.Fluid inclusion studies indicate that the presence of two fluids was critical for the formation of major deposits: (1) a moderate temperature (mostly 130 to 240°C but locally up to 280°C), low to moderate salinity (8-19 wt% NaCl equiv.), reduced and sulfur-poor, metal-bearing fluid (the “principal ore fluid”); and (2) a relatively low temperature (50-130°C), high salinity (>20 wt% NaCl equiv.), Br-enriched bittern brine. Sulfur, lead and strontium isotope data and fluid geochemistry indicate that fluid 1 originated as partially evaporated seawater that derived metals and sulfur from Lower Paleozoic (± Precambrian) basement during deep circulation. Fluid geochemistry suggests that fluid type 2 was reservoired within the Carboniferous sequence and never interacted with siliciclastic rocks. A connected permeability structure linking feeder faults with permeable sedimentary horizons was important for allowing the
AU - Wilkinson,JJ
AU - Hitzman,MW
EP - 72
PB - Irish Association for Economic Geology
PY - 2015///
SN - 978-09509894-5-7
SP - 59
TI - The Irish Zn-Pb Orefield: The View from 2014
T1 - Current Perspectives on Zinc Deposits
UR - http://www.iaeg.org/
ER -
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