Thermodynamic study of the association and separation of copper and gold in the Shizishan ore field, Tongling, Anhui Province, China

The Shizishan ore field is the largest gold–copper ore field in the Tongling ore district of Anhui Province, China. Copper and gold deposits in the district are present as one-commodity deposits or as deposits with both commodities. Copper and gold mineralization are either cogenetic or are temporally and spatially distinct. We present the results of systematic geochemical analysis of fluid inclusions from typical Au–Cu deposits in the Shizishan ore field; these data are used to determine the solubility of Cu and Au in the ore-forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization. Our results indicate that copper in the ore-forming fluids was transported as CuCl₂⁻ and CuCl⁰ complexes and that the solubility of copper was controlled by variations in Cl⁻ concentration. In addition, the precipitation of copper was controlled by changes in temperature, pH, fO₂, and fO₂. In comparison, gold in the ore-forming fluids was transported as Au(HS)₂⁻ and Au₂S(HS)₂²⁻ complexes, and the solubility of gold was controlled by variations in total sulfur concentration; the precipitation of gold was controlled by temperature, pH, fO₂, and fO₂. These differences between the two elements meant that copper and gold in the ore-forming fluids responded in different ways to changes in physicochemical conditions. Copper precipitated under relatively acidic conditions at high temperatures, while gold precipitated under weakly alkaline conditions at relatively low temperatures; this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the Shizishan ore field.     

铜陵市大气降尘中Cd元素污染特征及其对土壤的影响

为了评价有色金属矿山城市大气降尘中重金属元素的污染状况、来源及其对土壤重金属累积的影响,分析测试了铜陵市大气降尘样品中Cd元素的含量.分析结果表明,降尘样品中Cd元素的平均含量为16.44/μg/g,明显高于安徽省江淮流域多目标调查中铜陵土壤Cd元素的平均含量;降尘中Cd元素含量较高的样品出现在矿山和冶炼厂附近.用富集...     

铜陵地区成岩成矿背景探讨

铜陵地区是长江中下游多金属成矿带重要矿集区之一,也是我国重要的有色金属基地之一,以盛产铜、金等矿产而闻名于世,尤其是铜矿资源十分丰富,享有中国古铜都之称.铜陵地区内的矿床类型主要为夕卡岩型、层控夕卡岩型,其次为规模小、位于一些矿床深部的斑岩型(铜官山、新桥等),成矿作用与晚中生代(120～140Ma)大规模的岩浆活动有关[1,2].矿床与侵入岩岩体在空间上密切相关,在时间上与岩体的侵入时间相接近.侵入岩体可划分为碱性系列及钙碱性系列,不是从碱性玄武岩浆直接分异演化而成的,而是底侵的碱性玄武质岩浆与下地壳闪长质岩浆混合、发生AFC过程的产物.构造环境为岩石圈伸展作用下的拉张环境.尽管铜陵地区研究程度很高,但在该区仍有找寻到新的隐伏矿床的可能,本文旨在通过总结前人对该区的研究,为铜陵地区下一步的勘探工作提供科学依据.     

安徽铜陵硫铁矿集中开采区矿山地质环境评价研究

安徽铜陵地区是我国典型的硫铁矿集中开采区。研究区内新桥硫铁矿等数座硫铁矿山的长期开采造成了生态环境的破坏,对铜陵地区硫铁矿集中开采区矿山进行地质环境评价可为矿山生态恢复提供依据。本文在资料分析和实际调查的基础上,选取了地质环境背景、矿业开发、矿山地质环境问题和地质灾害4种要素下20种评价指标,采用层次分析(analytic hierarchy process,AHP)法确定了各要素和指标的权重值。在此基础上运用模糊数学综合评判对研究区进行矿山地质环境评价,并采用ArcGIS的网格化插值评价法对比验证。结果表明:地质环境背景、矿业开发、矿山地质环境问题和地质灾害对矿山地质环境影响的权重值分别为0.10、0.14、0.37、0.39。模糊综合评价二级初判结果为:矿山地质环境问题对研究区矿山地质环境总体上影响较大,其中水土污染问题最为突出;一级初判结果为研究区内矿山地质环境总体较好。网格化插值评价将研究区矿山地质环境划分为严重区、较严重区和轻微区,面积占比分别为4.62%、32.04%、63.34%。模糊数学综合评价与网格化插值评价结果基本一致,AHP与模糊数学综合评判法对硫铁矿集中开采区的地质环境评价适用性较好。评价结果可为当地开展矿山地质环境保护和治理工作提供依据。     

Late Mesozoic high-K calc-alkaline magmatism in Southeast China: the Tongling example

ABSTRACT

We report new zircon U–Pb ages, Hf isotopic and geochemical results for the Tongling granitic plutons of Southeast China. SHRIMP U–Pb ages for the Miaojia quartz monzodiorite porphyrite,the Tianebaodan and Tongguanshan quartz monzodiorites, the Xinqiaotou granodiorite porphyry, and the Shatanjiao and Nanhongchong granodiorite are 143 ± 2, 141 ± 1 and 142 ± 1, 147 ± 1, and 145 ± 1 and 139 ± 1 Ma, respectively. Combined with previous geochronological data, our results indicate that the porphyritic rocks are older than rocks of the same type lacking porphyritic texture. Geochemically, these high-K calc-alkaline intrusive rocks are characterized by arc-like trace element distribution patterns, with significant enrichment in LILE and LREE but depletion in HFSE. Lu–Hf isotopic compositions of zircons from the high-K calc-alkaline (HKCA) rocks have ε_Hf(t) values of magmatic 139–147 Ma zircons from ?8.1 to ?25.6, with two-stage model ages (t_DM2) of 1.71–2.67 Ga, whereas ε_Hf(t) values of inherited 582–844 Ma zircons range from 5.4 to ?9.5, with t_DM2 of 1.39–2.22 Ma, younger than t_DM2 values of igneous zircon, indicating that newly formed mantle material was added to the continental crust of the Yangtze Block. Moreover, ε_Hf(t) values of inherited zircon cores older than 1000 Ma are from ?7.8 to ?26, similar to magmatic zircons, and the t_DM2 values are all greater than 3.0 Ga (3.16–3.75 Ga), reflecting partial melting of ancient sialic material. We conclude that the plutonic melts were derived from both the enriched mantle and the ancient crust. The HKCA Tongling intrusions coincide temporally with the J₃–K₁ magmatic event that was widespread in Southeast China. This igneous activity may have accompanied sinistral slip along the Tan-Lu fault due to oblique subduction of the Palaeo-Pacific plate.     

铜陵矿集区舒家店矿区正长花岗岩的年代学和地球化学特征及其指示意义

舒家店岩体位于长江中下游成矿带中部的铜陵断隆区,与繁昌断凹区(盆地)临近,主要的岩浆岩岩石类型有辉石闪长岩、石英闪长斑岩和花岗闪长岩等。正长花岗岩为舒家店岩体深部新发现的岩石类型,其矿物组合与岩体内其他类型岩石明显不同,其形成的背景存在争议。本文通过对岩体中正长花岗岩的锆石LA-ICP MS精确定年、Hf同位素和地球化学组成分析,研究舒家店岩体正长花岗岩的年代学、岩浆源区等问题。研究显示舒家店岩体为"异源同体"的复式岩体,岩体中的正长花岗岩的侵入时间为126.5±1.6Ma~129.8±2.4Ma,明显晚于早期的辉石闪长岩和石英闪长斑岩(138.2±4.6Ma~143.7±1.7Ma),也明显晚于舒家店斑岩型铜矿床的形成时代。全岩元素地球化学和锆石Hf同位素组成指示舒家店岩体中正长花岗岩为叠加到早期辉石闪长岩及石英闪长斑岩之上的后期岩浆活动的产物,可能与繁昌盆地内花岗岩有相同的源区,为新元古代新生地壳(类似新元古花岗岩)部分熔融的产物,其岩浆源区处于高温低压的环境,相较于辉石闪长岩和石英闪长斑岩起源更浅,指示长江中下游成矿带在145~123Ma地壳处于不断减薄的过程。     

Geological and Geochemical Characteristics of the Huangshilao Stratabound Gold Deposit in the Tongguanshan Orefield,Tongling, East‐Central China

The Huangshilao gold deposit (>13.5 t Au) is comprised of stratabound pyrite‐dominant massive sulfide ores, and is distinguished from the skarn Cu, Au, and Cu–Au deposits that are dominant in the Tongguanshan orefield, Tongling, east‐central China. The stratabound orebodies are situated along flexural slip faults along the unconformity between the Upper Devonian Wutong and the Upper Carboniferous Huanglong Formations. The ores, dominated by crystallized pyrite, colloform pyrite, and pyrrhotite, are systematically sampled from the underground stopes along strike drifts. The δ³⁴S values of ore sulfides yield a wide variation from ?11.3 to 11.4‰, but mostly within 4–8‰, corresponding to the δ³⁴S range (3.4–8.7‰) of the Yanshanian Tongguanshan and Tianshan quartz diorite intrusions in the Tongguanshan orefield, suggesting a magmatic dominated sulfur source. Few obvious negative δ³⁴S values are induced by an involvement of sedimentation‐related biogenic sulfur. The wide δ³⁴S variation denotes an incongruent physical and chemical interaction of the two sources. Combined analysis of gold contents and sulfur isotopes of the sulfides show that the magmatic hydrothermal solution provides primary metals despite a small quantity that may have been contributed by the sedimentary pyrites. The hydrothermal alteration, thermal metamorphism, trace element concentration in pyrites, and existing aeromagnetic data jointly suggest that the hydrothermal fluid migrated vertically from an intrusion below, along the flexural slip faults, but not laterally from the nearby outcrop of Tianshan stock.     

安徽铜陵地区成矿控制因素的探讨

铜陵地区是长江中下游铁铜硫金成矿带的重要成矿区。区内矿床众多，类型复杂，成因多样。为了查明本区的控矿因素，本文运用宏、微观相结合，地质观察研究与同位素、稀土元素等地球化学以及流体包裹体分析相结合的方法，区域地质背景、地层岩性、岩浆岩、构造及成矿流体性质等与成矿的关系，认为不同成因、不同类型的矿床所受的控制因素具有明显差异。     

铜陵舒家店斑岩铜矿成矿年代学研究及其成矿意义

舒家店铜矿床是长江中下游成矿带中新发现的斑岩型铜矿床,位于铜陵断隆区与繁昌断凹区(盆地)的过渡部位,矿床成矿时代确定对该矿床成因研究及区域成矿规律的认识具有重要意义.在详细野外地质工作的基础上,选择与黄铜矿密切共生的辉钼矿和热液蚀变矿物黑云母为对象,分别利用Re-Os和40Ar-39 Ar阶段加热同位素定年方法,得到舒家店铜矿床辉钼矿Re-Os模式年龄和黑云母40 Ar-39 Ar坪年龄分别为140.6±2.0Ma和142.8±1.1Ma,分别代表了舒家店铜矿床的矿化年龄和钾硅酸盐化蚀变年龄.并通过与铜陵断隆区和繁昌断凹区成岩作用和成矿时代的对比,表明舒家店铜矿床属于铜陵断隆区中生代岩浆热液活动的产物.     

层次分析法在矿床大比例尺定位预测中的应用--以铜陵凤凰山铜矿为例

通过铜陵凤凰山铜矿成矿规律研究,利用找矿分析成果和多元找矿信息,运用层次分析法,开展隐伏矿床大比例尺定位预测研究,建立了矿床定位预测模型,并对预测单元进行了成矿有利度计算和评价。已知矿体和工程验证结果表明,该方法可较好地用于大比例尺定位预测分析和成矿预测单元的分级评价。