The Geology and Geochemistry of Porphyrite Iron Deposits in the Nanjing-Wuhu Area,Southeast China
For the iron deposits occurring in andesitic volcanic rocks of the Lower Yangtze Area,the genetic mod- el for porphyrite iron deposits was proposed by Chinese geologists more than ten years ago on the basis of their detailed studies in the Nanjing-Wuhu Basin.It comprises a set of deposits of different genetic types ranging from late magmatic segregation,ore-magma injection,pneumato-hydatogenetic replacing and hydrothermal filling as well as sedimentary origin.The deposits are closely connected with the gabbro-diorite porphyrite subvolcanic intrusive bodies both in space and in genesis.Mineralization and wall-rock alteration are consistent with the history of the magmatic evolution.Geochemical studies on trace elements and S,O,Sr isotopes have proved that the porphyrite iron deposits are of magmatic origin. The proposed model may be applied to iron ores associated with andesitic volcanites,for example,in Chile,Mexico,Pakistan,Turkey,etc.