Karstic sediments, residual and alluvial ore deposits of the Peak District of Derbyshire.
2009-05-13T11:15:19Z (GMT) by
Detailed sedimentological studies of both surface and underground karstic sediments from the Peak District have been undertaken. Mineralogical examination shows that the allochthonous fraction of the sediments have been derived mainly from the Namurian strata which surround, and once overlay, the area. The remainder of the allochthonous fraction has been derived from the Triassic sediments to the south of the area and from superficial loess deposits, many of which were introduced into the area during the Devensian Glaciation. Many of the deposits contain an autochthonous fraction consisting variably of chert, authigenic quartz, limestone and dolomite, fluorite, baryte, calcite and galena clasts released from the host rocks by phreatic solution and having suffered only limited transport. Scanning electron microscope (S. E. M.) studies of quartz grain surface textures show that many of the alloehthonous sediments have been transported under-fluvio-glacial conditions. A number of sedimentary accumulations in isolated cavities consist of reworked loessic silt which has been carried underground via joints by the mechanism of translatory flow. Palaeomagnetic studies of sediments in the Matlock area show that they consistently have a reversed remanent magnetism which may indicate that these fluvio-glacial sediments have an age in excess of 690,000 years b. p. The "ore" fraction of some of the deposits studied may form important sources of fluorspar when other, larger and more easily worked, deposits have been worked out, if the dressing problems can be overcome.