Thursday, December 7, 2017 - 18:30 to 20:00
Pillo Hotel, Ashbourne, Co. Meath
The earliest record of mining in the Silvermines district dates from 1289, when copper was mined at Gortnadiha. Mining resumed in the 17th Century at numerous localities on the footwall side the Silvermines Fault, and continued intermittently until 1874. Mining again restarted in 1949 at Shallee (Pb) and Knockanroe (oxide Zn) until the late 1950’s.
In the late 1950’s a world-class deposit of barite was discovered, and opencast mining began in 1963 by Magnet Cove Barite (Ireland) Ltd. Soon after the Lower and Upper G orebodies grading 11% combined Pb+Zn were also discovered. These, along with the B and K Zone orebodies were worked underground from June 1968 to October 1982 by Mogul of Ireland Ltd. The Magcobar mine closed in September 1992.
Silvermines contains a range of geological features that have been well described in the literature and have been intensively studied using various laboratory techniques ranging from fluid inclusion, isotopic and petrological examinations.
The talk will initially examine in detail what we do know about the mineralization at Silvermines focussing on the geology of the deposits. The second part of the talk will summarize the laboratory studies that have been completed over the decades by various workers and will endeavour to draw these aspects together into a summary of the current best understanding of these intriguing Zn-Pb deposits.
As ideas on Irish Zn-Pb deposits have swung from exhalative to epigenetic to syn-diagenetic, Silvermines has been used to support all of these models. More recently detailed isotopic results and tectono-stratigraphic dating have confirmed the exhalative – syndiagenetic models proposed in the 1970’s and debunk late replacive models of the 1990’s.
The term “Irish-type” Zn-Pb deposits was originally used for Silvermines in the mid 1970’s and the evidence presented should help to define what this term really means.