| Abstract:The silicon geochemistry is a key to hydrothermalism and also a strong link between various hydrothermal deposits, connecting them into a giant integrated ore-forming system. In this paper a new model for hydrothermal processes is put forward, which can be formularized as HACONS(mantle ichor)A→R E(HCONS)→E+SiO2, where H stands for hydIogen, halogens(chlorine, fluorine, bromine and iodine)and heat, A fm alkalis(sodium, potassium, lithillln, rubidium and cesium, C for carbon, O for oxygen, N for nitrogen, S for sulfur, selenium and tellurium, R tor pathway rocks in the upper mantle and the earth crust through which hydrothermal solutions pass, E for ore-forming elements and Si for silica in various forms such as quartz, opal, chlcedony, chert, sinter, silicification and siliceous sediments. The mantle ichor trends to ascend from the depth towards the surface, leaching ore-forming elements from pathway rocks through alkaline metasomatism(the introduction of alkalis into altered rocks), transporting the released componemts in the form of complex anions, precipitating them at shallower places, and thus resulting in the concentration or/and mineralization. The characteristic paragenetic associations are invariably ore minerals plus free silica. |
