CHEMISTRY AND MINERALOGY OF SOME LOWER AND MIDDLE CHALKS FROM GIVENDALE, EAST YORKSHIRE

the Givendale area of Yorkshire was determined; acetic acid residues were mechanically, chemically and mineralogically analysed. All nine chalk samples proved to be exception-ally pure calcium carbonate (96 _+ 1 '5~o), with only small amounts of MgO (1-03 _+ 0"53~o), A1202 (0.33_+0'28~o) and Fe202 (0'20 _+ 0'14~oo). Insoluble residues ranged from 1.07 to 4'46~o. Clay formed 56--88~o of the insoluble residue. The non-clay fraction consisted of flint, quartz, collophane, limonite, feldspar, tourmaline and zircon. The clay fractions were dominated by montmorillonite (50~o) with secondary illite (30~o), apatite (3~o), and quartz (8-30~oo). Kaolinite was detected by X-ray diffraction in the Lower Chalk. As part of a geochemical study of groundwater in Lower and Middle Chalk (Pitman, 1977a, b), data was required on the chemical and mineralogical properties of the chalk underlying an experimental catchement at Givendale, East Yorkshire. The most comprehensive work on the insoluble residues from chalk to date has been that of Weir & Catt (1965) who examined the mineralogy of the clay, silt and sand sized fractions from Upper Chalk, identifying montmorillonite, mica, quartz and apatite as being the dominant minerals, and analysed the chemistry of the clay fraction. Youn