Estimation of lead and zinc emissions from mineral exploitation based on characteristics of lead/zinc deposits in China

Nonferrous mining activities are some of the largest sources of heavy metals emissions into the environment and China is one of the largest producers and consumers of lead and zinc in the world.The cumulative productions and emissions of lead and zinc from mining-related activities in China were estimated.Up to 2007,the cumulative productions of lead and zinc in China were estimated to be about 6.69 and 12.59 Mt,respectively;and about 1.62 Mt lead and 3.32 Mt zinc emitted into the ambient environment during the mining,processing and smelting activities,representing 24.39% and 26.36% cumulative production,respectively.Among these three types of mining-related activities,mineral processing contributes the most to the total emission of 50.67% lead and 45.51% zinc.

Order of sphalerite and galena precipitation: A case study from lead-zinc deposits in southwest China

Most of the lead and zinc deposits in Southwest China, are characterized by mineral zoning, which is especially true for the Huize and Zhaotong deposits. The mineral assemblage zoning is consistent for both horizontal and vertical zoning, from the base(center) of the ore body to the top(outermost), the mineral zones are as follows. I-1: coarse-grained pyrite and a little puce sphalerite;I-2: brown sphalerite, galena, and ferro-dolomite;I-3: galena, sandy beige and pale yellow sphalerite, and calcite;and I-4: fine-grained pyrite, dolomite, and calcite. Among them, sphalerite is the landmark mineral of different zoning. From I-1 to I-3, the color of sphalerite changes from dark to light, its crystalline size changes from coarse to fine, and its structure changes from disseminated to veinlet. This mineral zoning is seen not only on a microscopic scale, but is also clear on a mesoscopic and macroscopic scale. It is caused by the order of the sphalerite and galena precipitation. We studied the metallic minerals and fluid inclusions using a thermodynamic phase diagram method, such as lgfO2–lgfS2, pH–lgfO2, pH–lg[Pb^2+] and pH–lg[HS^-], discussed the constraints on the order of the sphalerite and galena precipitation in the migration and precipitation process of lead and zinc under different pH values, oxygen fugacity, sulfur fugacity, and ionic activity. We also explain the formation mechanism and propose that the main controlling factor of the order of the sphalerite and galena precipitation is sulfur fugacity.

Lead Isotope Studies of Massive Surphur-Iron-Gold Deposits in the Tongling Area, Anhui Province

Pb isotope ratios and their variation have been measured and explained on ores of massive S-Fe-Au depos-its hosted in the Middle-Upper Carboniferous, on feldspars from diorite bodies closely related tomineralization and on whole rocks from ore-hosting strata (carbonate rocks) in the Tongling area, Anhui Prov-ince. Through a comparison of Pb isotope features of these geological bodies, it has been suggested that oresubstances of the deposits were derived from ore-hosting strata. In the meanwhile, the measurement of ore Pbisotopes of different mineralization types of the same deposit indicates that different mineralization types havedistinct Pb isotope characteristics, showing the potentiality of the Pb isotopic method used in mineral explora-tion.

Qinling-Type Lead-Zinc Deposits

Qinling-type Pb-Zn deposits are located in the Qinling fold belt, occurring in the fine-clastic and carbonate rocks of the Devonian marine facies. They are reformed sedimentary deposits originating from hydrothermal waters, and may be subdivided into 2 subtypes: hydrothermal sedimentary deposits (Changba subtype) and reformed hydrothermal sedimentary deposits (Bijiashan-Qiandongshan subtype). In comparison with some of the famous Palaeozoic Pb-Zn deposits in the world, the Qinling-type Pb-Zn deposits constitute an independent type, which possesses some characteristics of both hydrothermal sedimentary deposits (Meggen type) and reformed hydrothermal deposits (Mississippi Valley type).

Chemical composition of oscillatory zoned garnets from the largescale Mengya'a Pb–Zn skarn deposit: implications for fluid physicochemical conditions and formation

The Mengya’a Lead–zinc deposit is a large skarn deposit in the north of the eastern segment of Gangdese metallogenic belt.The garnet is the main altered mineral in the Mengya’a area.The color of the garnet varies from chartreuse to dark yellow brown and to russet.The brown garnet(Grt1)is related to pyrrhotite and chalcopyrite,and the green garnet(Grt2)is associated with lead–zinc mineralization.LA-ICP-MS is the induced coupled plasma mass spectrometry.This paper has used this technique to investigate Grt1 and Grt2.Grt1 develops core–rim textures with strong oscillation zone occurring in rim,whereas Grt2lacks core–rim textures and featured by oscillation zone.LA–ICP–MS analysis shows that garnets of Mengya’a are rich in CaO(29.90–37.52%)and FeO(21.17–33.35%),but low in Al_(2)O_(3)(0.05–4.85%).The calculated end members belong to grandite(grossular–andradite)garnets andradite.The negative Al(IV)versus Fe^(3+),positive Al(IV)versus total Al stoichiometric number,the positive Al(IV)versus Fe^(3+),and the negative Al(IV)versus total REE,all indicate that the substitution of REEs in garnets is controlled by YAG.All Garnets are depleted in large lithophile elements(e.g.,Rb=0.00–4.01 ppm,Sr=0.03–8.56 ppm).The total REE in Grt1 core is high(ΣREE=233–625 ppm),with HREE enriched pattern(LREE/HREE=0.33–1.69)and weak negative Eu anomalies(δEu=0.21–0.47).In contrast,the total REEs in the Grt1 rim and Grt2 are low(ΣREE=12.4–354 ppm;ΣREE=21.0–65.3 ppm),with LREE enriched pattern(LREE/HREE=0.54–34.4;LREE/HREE=11.4–682)and positive Eu anomalies(δEu=0.35–27.2;δEu=1.02–30.7).After data compilation of garnet chemicals,we found that the early fluid responsible for the core of Grt1 was a relatively closed and chloride-depleted fluid system.It was close-to-neutral,with a low water–rock ratio.The core of garnet was formed by fluid diffusion in metasomatic processes.The fluid was changed into a relatively open system with reduced,chloride-rich,and weakacid fluid.It was fluid infiltration and metasomatism that resulted in the formation of Grt1 rim and Grt2.