浙江省常山县八面山矿区萤石及钨、锡多金属成矿地质特征

八面山萤石、钨锡多金属矿床赋存于中、上寒武统碳酸盐岩地层内,沿燕山期侵入的岩前二长花岗岩体环状分布。成矿具有多阶段、多类型特征,主要有矽卡岩型萤石、锡多金属矿床、蚀变花岗岩型锡矿床(或矿化体)、高温热液石英脉型钨锡多金属矿床、中低温热液交代(伴充填)萤石矿床等。其中以似层状、透镜状和陡倾斜脉状产出的萤石矿床规模最大,是近几年浙江省新发现的萤石矿床类型,对今后本区域进一步开展勘查找矿具有重要指导意义。     

辽宁新甸金矿床成因

元古宇辽河群盖县组是一套黏土、半黏土质陆源碎屑沉积夹中-酸性火山岩或火山碎屑岩沉积建造,在地质历史发展过程中发生了变形变质作用,导致岩石中的硅质成分分异而形成硅化石英脉,同时,岩石中的成矿物质也发生了初步的迁移和富集.燕山期的花岗岩浆活动交代重熔了变质岩系,变质岩系中大量的成矿物质被活化、迁移至岩浆期后热液中,在成矿热液演化为偏酸性-还原性条件下,金等成矿元素发生了沉淀作用.稳定同位素、稀土元素特征表明金矿床的成矿物质来源于盖县组变质岩系,成矿热液为岩浆期后热液.伴随岩浆活动产生的一系列剪切构造既为成矿热液运移提供了通道,也为矿质沉淀提供了有利空间.新甸金矿床属于岩浆期后热液型矿床.     

华南海相火山喷流沉积矿床成因研究简评——兼述徐克勤教授在该领域的重大贡献

在华南地区,发育着大量层状和层控铜、铅、锌、铁、金、银、锡、硫等矿产资源,20世纪70年代以前,一般都认为这些矿床是热液或矽卡岩成因。徐克勤教授在70年代中期提出了断裂拗陷带构造背景条件下的火山喷流沉积一热液叠加成因机制,并在嗣后长久的岁月中,带领南京大学师生进行了大量的研究工作,取得了丰富的研究成果。这一成因认识,已经在国内科研人员中获得广泛的认同,并被大量地质找矿实践所支持。     

热水沉积过程混沌序列弱信号的提取

运用地层垒积序列的概念和Logistic混沌序列叠加过程分解模型, 对岩比参数序列中的弱信号进行提取, 进一步研究热水沉积作用强度演化的定量特征, 为对热水沉积盆地古地理环境进行三维动态模拟奠定了基础.      

The nature and origin of brecdation and mineralization at the White Crystal ore deposit,Ardlethan tin mine,New South Wales

The White Crystal ore zone consists of an ovoid mass of fine grained quartz‐tourmaline topaz rock containing disseminated cassiterite together with prominent vughs of quartz and/or tourmaline, cassiterite, and sulphides. Toward the margins of the ore zone the decreasing intensity of alteration illustrates formation via a process of brecciation, infill, and alteration. The rectangular slab‐like fragments are commonly aligned and their plunge indicates a dip towards a common epicentre. The tourmalinized ore zone is surrounded by successive zones of sericitization and argillization. The brecciation is of large scale tensional origin which is suggestive of collapse. Beneath the ore zone mineralization/alteration continues at subeconomic grades and limited data suggests an intrusive hydrothermal style of brecciation. The entire system is a form of breccia pipe and has yielded some 1.5 Mt of ore at around 0.64% Sn.     

Detecting the flow relationships between deep and shallow aquifers in an exploited groundwater system,using long‐term monitoring data and quantitative hydrogeology: the Acque Albule basin case (Rome,Italy)

Five years of hydrogeological monitoring and field activities performed in the complex hydrogeological system of the Acque Albule basin (AAB) were conducted to define the hydrogeological setting, the relationship between deep and shallow aquifers and a conceptual groundwater flow model of this exploited area using conventional quantitative techniques. The basin, which is located close to Rome (Italy) on the west side of the Apennine chain and just north of the Colli Albani volcano, subsided after development of a north–south fault system (about 115 000 y bp). The AAB experiences intense hydrothermal activity, which has produced a large travertine deposit (80‐m thick). The travertine deposit constitutes a fractured aquifer that is the final destination of more than 5 m³ s^‐1 of water and is strongly dewatered by quarry activities. The complex hydrogeology of this basin was investigated, revealing two main hydraulically connected aquifers, one thermalised and partly confined into the limestone bedrock and one unconfined in the travertine. The two aquifers are separated by a non‐continuous clayey aquiclude. The hydrogeological survey and geological characterisation contributed to the development of the groundwater flow conceptual model. Analysis and comparison of the monitored levels highlighted the pattern of flow between the deep and shallow parts of the flow system. Copyright © 2012 John Wiley & Sons, Ltd.     

东太平洋海隆13°N和赤道附近表层沉积物中的元素赋存状态

为了解海底热液活动对沉积物元素赋存状态的影响,对东太平洋海隆(EPR)13°N和赤道附近表层沉积物样品17A-EPR-TVG1、17A-EPR-TVG5做了全样及顺序提取分析,探讨了Al、Ca、Fe、Mn、Ti、Ba、Zn、Cu、Sr、V、Mo、U及稀土元素赋存状态。XRD结果显示,17A-EPR-TVG1沉积物的主要矿物形态为黄铁矿,17A-EPR-TVG5沉积物样品主要矿物为方解石。受热液影响明显的17A-EPR-TVG1沉积物中,除Ca、Sr外,其余元素主要赋存于铁锰氧化物与残留相中。正常深海沉积物17A-EPR-TVG5中,除Al、Ba、Ti外,其余元素主要赋存于碳酸盐相及铁锰氧化物相中。稀土元素的顺序提取结果显示,17A-EPR-TVG1沉积物4个相态稀土元素北美页岩配分曲线中均有Eu正异常,17A-EPR-TVG5沉积物4个相态稀土元素北美页岩配分曲线中均出现Ce负异常,分别指示了二者形成过程中热液与海水的加入。     

Petrogenesis and Solidification Depth of the Jurassic Daebo and Cretaceous Bulguksa Granitic Rocks in South Korea

We investigated the Jurassic Daebo and Cretaceous Bulguksa granitic rocks in South Korea. The former are distributed mainly in the Gyeonggi and Yeongnam massifs and the latter are present in the Gyeongsan basin and Ogcheon belt. The Daebo granitic rocks generally are of ilmenite series and I to S type. These rocks are associated with Au–Ag hydrothermal deposits, whereas the Bulguksa granitic rocks are of magnetite series and I type, and are associated with Pb–Zn, Cu and Mo–W hydrothermal deposits, as well as Au–Ag hydrothermal deposits. The Daebo granitic rocks show adakitic signatures in their chemical compositions. They are considered to have been derived from partial melting of the thick lower continental crust. Conversely, the Bulguksa granitic rocks in the Gyeongsan basin are non‐adakitic and are considered to have been derived from partial melting of a mantle wedge. Magmas of the Daebo granitic rocks formed at relatively shallow levels, but solidified at deep levels compared with those of the Bulguksa granitic rocks. The Bulguksa granitic rocks in the central to western Ogcheon belt are considered to have been formed by fractionation of magmas derived from partial melting of continental crust. The total Al contents of biotite and hornblende in the granitic rocks increased, with the Bulguksa granitic rocks in the Gyeongsan basin < the Bulguksa granitic rocks in the Ogcheon belt and Gyeonggi and Yeongnam massifs and the Daebo granitic rocks in the Ogcheon belt < the Daebo granitic rocks in the Gyeonggi and Yeongnam massifs. This order corresponds to an increase in solidification depth.     

Interpretation of Mineral Zoning in Submarine Hydrothermal Ore Deposits in Terms of Coupled Fluid Flow‐Precipitation Kinetics Model

Major minerals (sulfates, sulfides, quartz) are distributed in different parts of submarine hydrothermal ore deposits. For instance, the abundance of barite increases stratigraphically upwards in the massive orebodies of the Kuroko deposits (black and yellow ores), while quartz is abundant in the lower parts (siliceous ore). The different distribution of barite and quartz in the Kuroko deposits can not be accounted for by thermochemical equilibrium calculations based on the precipitation due to mixing of ascending hydrothermal solutions with ambient cold seawater. In the present study, a coupled fluid flow‐precipitation kinetics model was used to calculate the amounts of quartz, barite, and anhydrite precipitated from a hydrothermal solution mixed with seawater, assuming reasonable values for temperature, precipitation rate, fluid flow velocity, mineral surface area/fluid mass ratio (A/M), and initial concentrations of hydrothermal solution and seawater before mixing occurred. The results indicate that barite precipitates more efficiently than quartz from discharging fluids with relatively higher flow velocity, lower temperatures and under the condition of lower A/M ratios on the seafloor (black ore), whereas quartz precipitates more effectively from solutions with lower flow velocity, higher temperatures and higher A/M ratios beneath the seafloor (siliceous ore) and in the orebody (barite ore, ferruginous chert ore). Anhydrite precipitates in shallow sub‐seafloor environments with lower precipitation rates and higher A/M ratios than barite and higher precipitation rates and lower A/M ratios than quartz. These results explain the observed occurrences of barite, anhydrite, and quartz in the Kuroko deposits. Namely, barite is abundant in black ore and barite ore which formed above the seafloor, anhydrite formed in high‐permeability tuff breccias, and quartz formed in low permeability dacite intrusive bodies in the sub‐seafloor environment.