Page 298 - Introduction to Mineral Exploration

12

Cliffe Hill Quarry,

Leicestershire –

Development of

Aggregate Reserves

Michael K.G. Whateley and William L. Barrett

12.1 INTRODUCTION land and marine sources, an aggregates supply
−1
shortfall of between 15 and 30 Mt yr p.a. is
The annual production and use of construction predicted for the next decade for southeastern
aggregates in the UK, including both sand England. The deficiency in indigenous aggre-
and gravel and hard rock, amounts to approx- gates will have to be satisfied by increasing
imately 220 Mt. The materials are used for imports into the region from elsewhere in the
road building, construction, civil engineering, UK and also from overseas. Leicestershire is
concrete, house building, chemicals, and other well placed as a supplier and has suitable qual-
specialized applications. Within such a wide ity rock resources to benefit from this demand.
market rocks with particular properties are bet- In the mid 1970s it became apparent that the
ter suited to certain applications than others. profitable microdiorite (markfieldite) quarry of
The physical properties of the rocks are defined Cliffe Hill in Leicestershire (Fig. 12.1) belong-
in terms of their response to different tests, ing to Tarmac Roadstone Ltd, East Midlands
most of which are covered by the relevant Brit- was running short of recoverable reserves.
ish Standards. Some international, American Significant resources remained at the site, but
and local (but not British Standards) tests are these were sterilized beneath the processing
also used. plant (Fig. 12.2).
Tarmac Quarry Products Ltd (Tarmac) is one The markfieldites of the Charnwood Forest
of the leading aggregate, ready mixed concrete, area occur as a number of relatively small
and waste disposal companies in the UK; it also igneous bodies intruded 550 Ma ago into late
operates in Europe and Scandinavia, as well as Proterozoic pyroclastics and metasediments.
the Middle and Far East. In 1999 it became Markfieldite differs from other microdiorites
a subsidiary of Anglo American plc. Tarmac in having a granophyric groundmass and it has
operates about 100 active quarries and sandpits a general uniformity and strength which puts
in the UK, spread from Ullapool in northwest it amongst the best and most consistent gen-
Scotland to the south coast of England. eral purpose construction aggregate materials
The biggest market for aggregates in the UK in the UK. An impressive durability means
is the southeast of England where ironically that the markfieldite can also be used for all
there is no hard rock and demands have histor- classes of railway track ballast, as well as road
ically been met from sand and gravel sources stone.
(both land based and marine dredged) and by Charnwood Forest contains major faults,
supplies railed in from elsewhere in England. e.g. the Thringstone Fault, which brings Car-
Notwithstanding the expected efforts to ex- boniferous rocks against the Proterozoic
pand local sand and gravel output from both sequence to the west of Stud Farm (Fig. 12.1).