Event type:
Lecture, Evening meeting
Organised by:
East Midlands Regional Group
Event status:
EVENT CLOSED
The Triassic succession in the post-Variscan Cheshire Basin includes the Sherwood Sandstone, Mercia Mudstone and Penarth groups. The Sherwood Sandstone comprises, in ascending order, the Chester, Wilmslow Sandstone and Helsby Sandstone formations and is host to widespread occurrences of barite mineralisation and more localised copper-dominated polymetallic ore deposits. The latter, which occur mainly in the Helsby Sandstone, were mined in the Alderley area c.20 km south of Manchester, and to a lesser extent at Bickerton, west Cheshire, and at Eardiston, Pim Hill, Yorton, Clive and other localities in north Shropshire.
Alderley and Clive, the main sites where the mineralisation can be studied in situ, are the subjects of this account. At Alderley polymetallic mineralization is present in the highest part of the Wilmslow Sandstone but is developed mainly in the Helsby Sandstone, in two units of fluvial origin and one of aeolian origin. At Clive it occurs in the topmost Helsby Sandstone, beneath the argillaceous Mercia Mudstone. The mineralization is epigenetic and has a complex paragenesis; primary polymetallic minerals have been largely altered to secondary species. Faults and host-rock character influenced ore body form and disposition. The fluvial host rocks include mudstone aquicludes that constrained fluid movement and resulted in irregular, discontinuous ore bodies. In contrast, the relatively homogeneous aeolian deposits hosted larger and more extensive ore bodies. The voids left by mining afford the opportunity to visualise, from an internal perspective, the influence of structure and host rock facies on intrastratal fluid migration.
Speaker
Dr Geoff Warrington, University of Leicester
Time
Refreshments at 6.30pm, talk starts at 7pm
*There is no access to the building after 7.15pm