Geology of the Kamo Mine area

Abstract

Summary Detailed reVISIOn of geologic maps, sections, and columns of Kamo Mine area are based primarily upon the interpretation of fieldwork and drilling, both before and after the complete flooding of New Kamo Mine in November 1955. The Kamo Coal Measures (Kaiatan-Runangan), Ruatangata Sandstone (Runangan), Whangarei Limestone (Landon), and Waitakian sandstones are referred to the Te Kuiti Gronp. The Onerahi Formation of Ferrar has been re-defined as comprising a chaotic assemblage of upper Cretaceous and Eocene argillaceous rocks, and much rarer Waitakian sandstones, that now overlies the Te Kuiti Group and probably the Parahaki dacites of about Taranaki age. This formation is considered to have been emplaced locally by gravity slumping, shortly after Kaikoura faulting. Its source was probably an overthrust, nappe, piercement, or diapiric structure to the west. Kerikeri basaltic volcanism followed the formation of a terrace at about 220 ft A.S.L. (Milazzian). Tectonic strikes show a consistent difference of 15° to 20° from those observed at Waihi. The coal is relatively high in ash, mostly as calcite veinlets, except in those areas of the mine where the limestone cover is thin, or missing. Some coal remains, but it can only be worked if a safe and economic method is developed for mining below flooded workings. The flooding followed pillaring below cavernous limestone, and eventually a rate of inflow was established of about 10 g.p.m. for each foot of hypothetical drawdown below the level of the mine portal. This water was connected to an apparently limitless source of confined groundwater, that was also connected to the local source of carbon-dioxide impregnated “soda-water”.