Hydrogeochemical Characteristics and Genesis of Luohe Iron Deposit

As one well-explored region of Luzong Mesozoic volcanic basin, the groundwater revealed in Luohe iron deposit can be divided into two types, namely, unconfined and confined groundwater. The unconfined groundwater is alkalescent HCO₃^--Ca⁺·Mg²⁺ water, while the confined groundwater is the SO₄^2--Ca²⁺ brackish warm water due to the fact that their hydrochemical compositions are almost not affected by external changes because of the water blocking properties of regional structure and volcanic tuff. Ion proportionality coefficients and correlation analyses illustrate that major hydrochemical reactions in confined groundwater are sulfate mineral solution and cation exchange. PHREEQC inverse simulation shows that the cause of SO₄^2--Ca²⁺ confined groundwater is the numerous anhydrite, quartz and hydromica solution in site, at the same time, some calcite and chlorite precipitate as the secondary minerals. Meanwhile, Ca²⁺that was dissolved from anhydrite absorbs and exchanges with Na⁺ in clay mineral, and few pyrites have redox reaction. The analysis verifies the hydrogeological condition of relative closed, limited recharge and static reserves of deep groundwater in Luohe iron deposit.