Geochemical Characteristics And Metallization Of The Zhaojikou Pb-Zn Deposits And Xuncun Au Deposits In Dongzhi District, Anhui Province

The Zhaojikou large-sized deposit and Xucun deposit are discovered currently in southern Anhui province. Based on the latest exploration results and previously published data on the Zhaojikou deposit, the author carried on field investigation and indoor studies. The fluid inclusion petrography, microthermometric, ions and gass compositions of the fluid inclusions, metal sulphides electron microprobe anasys, metal sulphides trace element, metal sulphides REE element, Pb isotope of metal sulphides and Rb-Sr dating of fluid inclusion of sphalerite were carried out. The geochemical characteristics and the material sources of the Zhaojikou Pb-Zn deposit and Xucun Au deposit are discussed. The main results are as follows:1. Electron microprobe on metal sulphides of Zhaojikou deposit shows ore-forming matters were main from magmatic hydrothermal. The normalized REE patterns display LREE enrichments. The samples of the metal sulphides of the ores, magmatic rocks and sedimentary stratum from the ore district have similar characteristics of slightly positive Ce anomalies, which impliy lead-zinc mineralization was concerned with magmatic activity. The trace elements of the metal sulphides shows lead-zinc were mainly from magmatic hydrothermal. Lead isotope compositions of ore minerals shows that Pb isotope compositions are consistent with those of the magmatic rocks, and have concentrated within the shallow earth crustal source region. The ore deposits belong to low temperature hydrotheramal ones and formed in a ralative shallow and open environment.2. Study of the fluid inclusions in quartz of the Xucun deposit indicates that ore fluids have low-medium temperature, low density, low salinity, and they formed in a low pressure and shallow environment. Compositions of the fluid inclusions shows that the hydrochemical type of the ore-forming fluids from the Zhaojikou Pb-Zn deposit is CaSO4-NaCl-H2O type, and that of the Xucun Au deposit is CaSO4-NaCl-KCl-H2O type. Both the two deposits were concerned with magmatic activity, the ore-forming fluids in the metallogenic stages were high fo2. The fs2 values of the Zhaojikou Pb-Zn deposit was positively related to the ore-forming temperatures and negative related to mol. FeS(%) content of sphalerite. The pH is neutral to weak alkaline.3. The Rb-Sr isochron age of the fluid inclusions from sphalerite is 128±1Ma, which corresponding with the diorite porphyry that the ores occurred in. The 87Sr/86Sr ratios of the fluid inclusion from sphalerite indicate that the metamorphic wall-rock and the magmatic rocks are the main sources of the Zhaojikou Pb-Zn deposit mineralization.4. Geochemical meaturement should that attach importantly to the area of geochemical anomaly delineated, screening, and discriminate, pay attention to the development of early Paleozoic slip (push) of body basal formation development zone, strengthen the fault structural belt, tectonic fracture zone, fold superposition of multiphase composite belt, small dike contact zone and the discovery and study of hydrothermal alteration zone, at the same time, can’t ignore the discovery of large-scale intrusive body and its contact zone near the higy-temperature in W-Mo mineralization.