Abstract:

The Zhonggu ore field, as an important orecluster in the southern part of the Ningwu volcanic basin, hosts series of iron deposits which are represented by Gushan and Baixiangshan and usually occurred at the contact zone between the dioritic porphyry and sedimentary rocks. Our investigation shows that neither the dioritic porphyry nor the sedimentary rock is the source of iron ores, and that the source of most ironrich orebodies is the ore magmahydrothermal system in the deep chamber. Ore magma which was formed by liquid immiscibility is the main source of Gushan deposit, and the residual ironrich hydrothermal fluids which occurred as NaFeCl complex is the main source of Baixiangshan deposit. According to the quantitative estimation of iron ores and porphyry intrusion, the primary magma is probably the ferrobasalt, which formed in the environment of largescale thinning of lithosphere and upwelling of the asthenosphere and by the reaction between metamorphic oceanic crust (eclogite) and asthenosphere (peridotite), and AFC process occurred enroute.

Key words: Zhonggu, ore magmahydrothermal system, porphyry iron deposit, ferrobasalt