TECTONO-MINEROGENIC CYCLES AND MINEROGENETIC EVOLUTION THROUGH GEOLOGICAL HISTORY IN THE QINLING OROGENIC BELT

It has been disputed for a long time whether tectonic and minerogenic cycles did ever exist through geological history.On the basis of the theory and method of the minerogenic series of ore deposits,the authors advanced and discussed a concept of "tetono-minerogenic cycle".Cyclicity of tectono-minerogenic activities in the Qinling orogenic belt is systematically discussed in this paper,and six tectono-minerogenic cycles are drawn:(1) from the Latest Archean to the initial Proterozoic;(2) the Early Proterozoic;(3) Middle Proterozoic and the Late Proterozoic;(4) the Early Paleozoic;(5) the Late Paleozoic and (6) Mesozoic to Cenozoic.Minerogenic evolution is duscussed by a summarization of the characteristics of each of the six minerogenic cycles.The mineralization in the Qinling orogenic belt was either long and continuous or intermittent and cyclic.Many of the ore deposits are formed in two major peak mineralization periods,one is from the Middle Proterozoic to the Early Paleozoic,characterized by mantle-derived magmatic intrusions and marine volcanism;the other is from the Mesozoic to the Cenozoic,during which the intermediate and acid magmatic intrusions and continental volcanism are mainly derived from the crust or with a mantle-crust source.The 24 minerogenic series of ore deposits in this orogenic belt are considered to have formed in three major types of tectono-minerogenic processes,ie splitting,convergence,and a relatively stable stage.The mineralization associated with volcanism and splitting would have experienced a vibration between the north and south Qinling orogenic belt through out the geological history.