Characteristics And Genesis Of The Washan And Jishan Porphyry Iron Deposits In The Ningwu District

The Ningwu region is one of the major porphyry iron deposit clusters in the Middle-Lower Yangtze Fe-Cu-S-Au metallogenic belt. Over 30 iron ore deposits have been found in the region. A comprehensive study has been carried out on the characteristics of metallogenic background, deposit geology, ore-forming fluid and ore geochemistry of the Washan and Jishan typical porphyry iron deposits, with a focus on the genesisi of the deposits.The following are major achievements obtained in this thesis.1 The ore-controlling factors, ore body shape, ore mineral assemblage,ore texture and structure and ore types of the Washan and Jishan iron deposits have been preliminary found out through the geological investigation and microscopic observation. This supports identification of mineralization and alteration types and leads to division of mineralization stages.2 The ore-forming temperature of the Washan and Jishan iron ore deposits have been determined to be 200 ~ 300℃through the fluid inclusion, indicating that the deposits belong to a middle- to high-temperature hydrothermal ore deposits.3 The ore geochemical data provide new evidence for close temporal, spatial and original relationship between the iron ore deposits and the surrounding gabbro diorite porphyrite. It is inferred that the gabbro diorite porphyrite is the mother rock supplying iron material for the formation of the iron ore deposits.4 The genesis and ore-forming mechanism of the Washan and Jishan iron ore deposits have been preliminary ascertained, leading to establishment of a new model for the formation of the deposits.