Characteristics And Origin Of The Taochong Fe Deposit In Fanchang, Anhui Province

The Fanchang area is an important segment of the Middle-lower Yangtze River Cu-Fe mineralization belt. In the area occur a great number of the Fe-Cu-Au skarn deposits, of which the Taochong iron deposit is one of the largest deposits. Due to its large scale, high grade and remarkable geologic feature, the Taochong iron deposit is a representative skarn-type one in this area. A geological, petrological, Mineralo- graphical and mineralogical, especially REE geochemical study has been carried out on the Taochong skarn and associated deposit, with a focus on the analysis of their origin.The following are major achievement obtained in this thesis.1. Closely associated with skarns, the ore bodies of the Taochong deposit are stratoid in shape and occur mainly between the Huanglong and Qixia Formations. The skarns consist mainly of andradite, with a little hedenbergite, quartz and calcite, while ores are mainly composed of magnetite, specularite, calcite and quartz, with some skarn minerals.2. The formation process of the deposit can be divided into four stages, including skarn, specularite -magnetite, quartz-sulfide, and carbonate stages. The skarns and associated ores are spatially distributed as zones, including①marbleized limestone of the Qixia Formation;②dense and massive ore;③radial ore;④hedenbergite skarn;⑤hedenbergite and andradite skarn;⑥andradite skarn;⑦dolomitic marble of the Huanglong Formation.3. The REE analyses of the skarns and ores support the formation of the skarns under the condition of high temperature and oxidation, but the ores under the condition of high temperature, low pressure and strong oxidation.4. The normalized REE patterns of the skarns, strata rocks, and granites indicate an origin of the skarns by magmatic crystallization and no contributions of the granites and some ones of the strata rocks to the formation of the skarns.5. The Taochong iron deposit could be formed by the precipitation of ore-forming material after mixing of ore-bearing magmatic water with meteoric water.