THE PETROLOGY AND GEOCHEMISTRY OF ALTERED QUARTZ-DOLERITE IN THE CLOSEHOUSE MINE AREA

Abstract

Summary The nature of the altered quartz-dolerite dykes at Closehouse mine has been investigated using petrographic, rapid chemical, X-ray fluorescence, X-ray diffraction and emission spectrographic techniques. Normal dolerite is shown to have been converted into a clay-carbonate rock (White Whin) which is similar to other examples in the Northern Pennines where metasomatism has taken place. Ba, Rb, Zn, Pb, CO 2 , K 2 O and H 2 O are enriched in the White Whin adjacent to the vein while Sr, Zr, Cu, Ni, Cr, V, MgO, Na 2 O and iron are depleted. SiO 2 , Al 2 O 3 , TiO 2 and Mn remain constant. These changes were possibly effected by the mineralizing fluids responsible for the barite deposits within the altered dolerite at Closehouse.