Mineralogical controls on mine drainage of the abandoned Ervedosa tin mine in north-eastern Portugal

The Ervedosa Mine, in north-eastern Portugal, has Sn-bearing quartz veins containing cassiterite and sulphides that cut Silurian schists and a Sn-bearing muscovite granite. These veins were mined for Sn and As₂O₃ until 1969. Cassiterite, the main Sn ore, has alternate lighter and darker growth-zones. The darker zones are richer in Fe, Nb, Ta and Ti, but poorer in Sn than the adjoining lighter zones. Exsolution blebs of ferrocolumbite, manganocolumbite, Ti ixiolite, rutile, ilmenite and rare wolframite were found in the darker zones. Arsenopyrite is the most abundant sulphide and contains inclusions of pyrrhotite, bismuth, bismuthinite and matildite. Other sulphides are pyrite, sphalerite, chalcopyrite and stannite. Secondary solid phases consisting mainly of hydrate sulphate complexes of Al, Fe, Ca and Mg (aluminocopiapite, copiapite, halotrichite, pickeringite, gypsum and alunogen, meta-alunogen) occur at the surface of the Sn-bearing quartz veins and their wall rocks (granite and schist), while oxides, hydroxides, arsenates and residual mineral phases (albite, muscovite and quartz) occur in mining tailings. Toxic acid mine waters (acid mine drainage AMD), which have high conductivity and significant concentrations of As, SO₄ and metal (Cu, Zn, Pb, Fe, Mn, Cd, Ni and Co), occur in an area directly affected by the mine. Surface stream waters outside this area have low conductivity and a pH that is almost neutral. Metal and As concentrations are also lower. Stream waters within the impact area have an intermediate composition, falling between that of the AMD and the natural stream waters outside impact area. Waters associated directly with mineralised veins must not be used for human consumption or agriculture.     

Lithogeochemical exploration for polymetallic Sn-Cu-Ag-Au-Pb-Zn vein mineralization at north mammoth prospect, northeast victoria, australia

A follow-up surface lithogeochemical survey was implemented at North Mammoth Prospect, northeast Victoria, to investigate possible extensions to polymetallic vein mineralization outcropping as a 20-m-wide by 200-m-long gossanous zone in rugged, scree-covered terrain. The en-echelon pyritic veins contain subeconomic Sn, Cu, Pb, Zn, Ag and Au mineralization and occur within locally folded, fractured, brecciated and bleached metasediments adjacent to high-level, altered, quartz feldspar porphyry dykes. The dykes form part of the 3.5-km-long Mammoth Porphyry Complex. An orientation traverse across the mineralized zone and adjacent wall rocks over a 1300 m × 200 m area involved the collection of 27 rock chip samples (0.5–1.0 kg) that were analyzed for 20 major and trace elements by XRF and AAS methods. Acid soluble Sn and cxF were also determined. The results showed that the less mobile elements including Sn (total), Au, As (as the arsenate), Pb and Ba were most effective in outlining the mineralized zone. Major elements (K, Na, Fe, Ca, Mg), more mobile trace elements (Cu, Zn, Rb, Sr, cxF), acid soluble Sn and element ratios (K/Na, Fe/Mg, Rb/Sr, Zr/Y, Ti/Zr) were either difficult to interpret or failed to increase the anomaly size. The expanded lithogeochemical programme (130 samples from a 2.4-km² area) showed that weakly to strongly anomalous Sn, Pb and As values outline a zone of mineralized and bleached metasediments east of the porphyry complex. A 750 m × 250 m halo of anomalous Sn values includes North Mammoth Prospect as well as possible strike extensions to the mineralized veins. Contrasting dispersions for Au and Ba may indicate a multiphase intrusive/mineralization history for the porphyry complex. Pervasive fracturing infilled by iron oxides in the host rocks has probably facilitated lithogeochemical trace element dispersion in the weathered zone.     

Geochemical stream sediment survey in Winder Valley, Balochistan, Pakistan

A pilot scale geochemical survey of sediments from the Winder Stream (SW Pakistan) and its tributaries was carried out. The Winder Stream mainly receives sediment from the southern extensions of the Mor and Pab Ranges in the District of Lasbela (Balochistan). In these two mountain ranges, rocks from Jurassic to Cretaceous age are exposed. Rocks of the Ferozabad Group comprise of carbonates and siliciclastics of Lower–Middle Jurassic age and occupy the dominant part of the Mor Range. These strata host syngenetic and epigenetic Zn–Pb–Ba mineralizations of Stratiform Sediment-Hosted (SSH) and Mississippi Valley Type (MVT) deposits.Quantitative estimates of mobile and immobile elements were made from active stream sediments of the Winder stream and its tributaries. The samples were analyzed for Ag, Zn, Pb, Cu, Ni, Co, V, Mn, Fe and Ba using atomic absorption spectroscopy. The abundance of these elements is discussed in relation to local geological conditions such as bedrock, climate, weathering, mobility and pH of the dispersing waters. A number of Zn anomalies have been distinguished in the study area. Kharrari (Zn, 360 ppm), Sand (Zn, 340 ppm) and Draber (Zn, 210 ppm) are demarcated as new areas for Zn mineralization. The present study also indicates prospects of Ag, Cu and V in the rocks of the Mor Range.Relationships between various elements have been identified from scattergrams and reflect genetic associations. Whereby the positive correlation between Cu–Zn (0.55, n=18) and Cu–Pb (0.63) is related to possible sulphide mineralization.     

The genesis of metal zonation in the Weilasituo and Bairendaba Ag–Zn–Pb–Cu–(Sn–W) deposits in the shallow part of a porphyry Sn–W–Rb system,Inner Mongolia,China

The Weilasituo and Bairendaba Zn–Pb–Ag–Cu–(Sn–W) sulphide deposits are located in the southern part of Great Xing'an Range of Inner Mongolia in China. The deposits are located at shallow depths in the newly discovered Weilasituo porphyry hosting Sn–W–Rb mineralization. The mineralization at Weilasituo and Bairendaba consist of zoned massive sulphide veins within fractures cutting the Xilinhot Metamorphic Complex and quartz diorite. The Weilasituo deposit gradually zones from the Cu-rich Zn–Cu sulphide mineralization in the west to Zn-rich Zn–Cu sulphide mineralization in the east. The Bairendaba deposit has a Cu-bearing and Zn-rich core through a transitional zone devoid of copper to an outer zone of Zn–Pb–Ag mineralization. Three main veins contain more than 50 wt.% of the contained metal in the two deposits with their metal ratios displaying a systematic and gradual increase in Zn/Cu, Pb/Zn and Ag/Zn ratios from the western part of Weilasituo to the eastern part of Bairendaba.Three stages of vein-type mineralization are recognized. Early, sub-economic mineralization consists of a variable proportion of euhedral arsenopyrite, pyrite, quartz, and rare wolframite, scheelite, cassiterite, magnetite and cobaltite. This was succeeded by main stage mineralization with economic concentration of zoned Cu, Zn, Pb and Ag sulphide minerals along strike within the veins. The zones consist of the assemblages: (1) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–quartz–fluorite) at west Weilasituo; (2) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) at east Weilasituo; (3) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) in the centre of Bairendaba; (4) pyrrhotite–Fe-rich sphalerite–galena(–chalcopyrite–tetrahedrite–quartz–fluorite) in the transition zone of Bairendaba; and (5) pyrrhotite–Fe-rich sphalerite–galena–tetrahedrite(–chalcopyrite–falkmanite–argentite–pyrargyrite–quartz–fluorite) in the outer zone at Bairendaba. Post-main ore stage is devoid of sulphides and characterized overprinting of fluorite, sericite, chlorite, illite, kaolinite and calcite.Zircon SHRIMP U–Pb dating, Zircon LA–ICP–MS U–Pb dating, molybdenite Re–Os isochron dating, and muscovite Ar–Ar dating indicate the Beidashan granitic batholith was intruded at 140 ± 3 Ma (MSWD = 3.3), the porphyritic monzogranite from marginal facies of the Beidashan batholith was intruded at 139 ± 2 Ma (MSWD = 0.75), the mineralized quartz porphyry was intruded at 135 ± 2 Ma (MSWD = 0.91), the greisen mineralization occurred at 135 ± 11 Ma (MSWD = 7.2), and the post-main ore stage muscovite deposited at 129.5 ± 0.9 Ma. The new geochronology data show the porphyry Sn–W–Rb and vein-type sulphide mineralization are contemporaneous with granitic magmatism in the region.The metal zonation at the Weilasituo and Bairendaba deposits is a result of progressive metal deposition. This was during the evolution of a metal-bearing fluid along the strike of the veins and during the main stage of ore formation at the upper part of the deep-seated porphyry Sn–W–Rb system. This progressive zonation indicates that the deposits represent end-numbers formed from one ore-forming fluid, which moved from west to east from the porphyry. The metal zonation patterns of the major veins are consistent with metal-bearing fluid entering the system with the precipitation of chalcopyrite proximally and sphalerite, galena and Ag-bearing minerals more distally. We show that the mechanism of metal deposition is therefore controlled by thermodynamic conditions resulting in the progressive separation of sulphides from the metal-bearing fluid. The temperature gradient between the inflow zone and the outflow zone appears to be one of the key parameters controlling the formation of the metal zonation pattern. The sulphide precipitation sequence is consistent with a low fS₂ and low fO₂ state of the acidic metal-bearing fluid. The metal zonation pattern provides helpful clues from which it is possible to establish the nature of fluid migration and metal deposition models to locate a possible porphyry mineralization at depth in the Great Xing'an Range, which is consistent with the geology of the newly discovered porphyry Sn–W–Rb system.     

The petrology and mineralogy of the pegmatite complex at Bismuth,Torrington, N.S.W.

The pegmatite complex of epi‐Permian age at Bismuth near Torrington, N.S.W., consists of an elongated intrusion of a granitoid quartz‐topaz rock (silexite) together with a series of pegmatites of varying composition. The principal pegmatite consists of orthoclase, biotite, quartz and beryl with concentric zoning passing outwards into fine‐grained biotite‐beryl rock containing a number of ore minerals: arsenides of Co, Fe and Ni, wolframite, bismuth, bismuthinite, molybdenite, joseite, cassiterite, rutile, uraninite and monazite. Small pegmatite veins issuing from this main body contain, in addition to the silicate minerals, high temperature tetrahedrite, chalcopyrite and sphalerite. A second group is characterised by quartz, orthoclase and beryl with occasional patches of tourmaline.

Emplacement at no great depth is indicated by breccia veins and stock‐works filled with pegmatite.

The origin of a silica hydromagma is considered in terms of existing experimental work and in terms of field occurrence. Structural evidence suggests that the quartzose intrusion preceded the injection of the pegmatite fluids, both being derived from the parent Mole biotite granite.     

甘肃省夏河县甘加贡玛—阿姨山地区水系沉积物地球化学特征

夏河县地区位于中秦岭断褶带西段,观音大庄—力士山断裂带南侧、夏河—合作断裂带中部,属夏河—合作成矿带。通过开展1 ∶ ５万水系沉积物测量工作,并对异常进行查证解释,从区域地质背景和矿区地质特征入手,重点分析了甘加贡玛—阿姨山地区的水系沉积物金异常,表面该区水系沉积物异常分布与构造展布方向一致,金异常对地层的选择性明显;通过对水系沉积物测量中Au、Ag、Cu、Pb、Zn、As 、Sb、Hg、Cr、Ni、Sn、W、Mo、Bi等14种元素分析结果进行R型聚类分析和相关性分析,得出区内可选用Au、Cu、Pb、Zn 4种元素作为主成矿元素进行成矿预测。     

老挝普老地区多金属矿地球化学异常特征及找矿前景

普老地区Pb、Zn、Sn多金属异常区位于老挝北部长山成矿带,1∶5万水系沉积物地球化学测量发现了以Pb、Sn为主,伴生Zn、Ag、W、Sb、Bi、As、Hg、Cu、Au等元素异常。1∶1万土壤地球化学测量圈定了3个综合异常带,Pb、Zn、Sn等元素具有异常强度高、规模大、浓集中心明显的特点,经异常检查发现铅锌、锡多金属矿化点13处。研究和分析异常区元素的地球化学分布和异常特征,认为该区多金属异常为矿致异常,具有寻找热液型铅锌、锡及多金属矿的潜力。     

陕西石泉-旬阳金矿带整装勘查区饶峰幅等7个图幅区1:50 000水系沉积物测量原始数据集

首次汇集了陕西石泉-旬阳金矿带整装勘查区内7个图幅1：50 000水系沉积物测量18种元素（Au、Cu、Zn、As、Sb、Hg、Bi、Ti、V、Ag、Sn、Pb、W、Mo、Ni、Co、Cr、Cd）的测试数据,共包含数据点13 169个,数据180 944个,第一次建立了该勘查区的地球化学数据库。在此基础上,编制了233张各类地球化学系列图件,并建立了空间数据库。通过本数据集在区内共圈定各类单元素异常2 083处,其中金元素异常304处;圈定金找矿靶区10处,金成矿远景区12处;经过后期矿产综合检查,整装勘查区内共发现金矿产（点）53处,其中,中型规模金矿床8处,小型规模金矿床18处,金元素异常与金矿床（点）对应程度较好,矿致异常达189处,显示1：50 000水系沉积物测量是勘查区内较好的找矿手段之一。     

二郎坪群海相火山岩中块状硫化物矿床地质特征及其找矿方向

以阴沟矿床为例,通过岩相学、岩石学、地球化学研究,指出该类矿床指示矿物(岩石)为重晶石、硅质岩、黄铁矿、黄铜矿、方铅矿、闪锌矿等,指示元素为Cu、Pb、Zn、Ag、Au、As、Sb、Mo、Ba等;并分析这些矿物和元素垂直分带,水平分带规律;确定了找矿标志,为重晶石脉或帽和黄铁矿化带.然后分析了二郎坪群海相火山岩形成海底火山喷流块状硫化物矿床的地质环境和条件,并指出在该区进一步扩大找矿的远景和方向.     

Environmental geochemistry of the derelict Webbs Consols mine,New South Wales,Australia

Small-scale mining and mineral processing at the Webbs Consols polymetallic PbZnAg deposit in northern New South Wales, Australia has caused a significant environmental impact on streams, soils and vegetation. Unconfined waste rock dumps and tailings dams are the source of the problems. The partly oxidised sulphidic mine wastes contain abundant sulphides (arsenopyrite, sphalerite, galena) and oxidation products (scorodite, anglesite, smectite, Fe-oxyhydroxides), and possess extreme As and Pb (wt% levels) and elevated Ag, Cd, Cu, Sb and Zn values. Contemporary sulphide oxidation, hardpan formation, crystallisation of mineral efflorescences and acid mine drainage generation occur within the waste repositories. Acid seepages (pH 1.9–6.0) from waste dumps, tailings dams and mine workings display extreme As, Pb and Zn and elevated Cd, Cu and Sb contents. Drainage from the area is by the strongly contaminated Webbs Consols Creek and although this stream joins and is diluted by the much larger Severn River, contamination of water and stream sediments in the latter is evident for 1–5 km, and 12 km respectively, downstream of the mine site. The pronounced contamination of local and regional soils and sediments, despite the relatively small scale of the former operation, is due to the high metal tenor of abandoned waste material and the scarcity of neutralising minerals. Any rehabilitation plan of the site should include the relocation of waste materials to higher ground and capping, with only partial neutralisation of the waste to pH 4–5 in order to limit potential dissolution of scorodite and mobilisation of As into seepages and stream waters.     

Evolution of mineralizing fluids of cassiterite–wolframite and fluorite deposits from Mueilha tin mine area, Eastern Desert of Egypt, evidence from fluid inclusion

Sn–W deposit of the Mueilha mine is one of many other Sn–W deposits in the Eastern desert of Egypt that associated with albite granite. Two forms of Sn–W mineralizations are known at the Mueilha Sn-mine area, namely fissure filling quartz veins and greisen. Cassiterite and/or wolframite, sheelite, and beryl are the main ore minerals in the greisen and quartz veins. Subordinate chalcopyrite and supergene malachite and limonite are also observed in the mineralized veins. To constrain the P–T conditions of the Sn–W mineralizations, fluid inclusions trapped in quartz and cassiterite, have been investigated. The following primary fluid inclusion types are observed: CO₂-rich, two-phase (L?+?V) aqueous, and immiscible three-phase (H₂O–CO₂) inclusions. Low temperature and low salinity secondary inclusions were also detected in the studied samples. Microthermometric results revealed that Sn–W deposition seem to have taken place due to immiscibility at temperature between 260°C and 340°C, and estimated pressure between 1.2 to 2.2 kb. Microthermometric results of fluid inclusions in fluorite from fluorite veins illustrated that fluorite seems to be deposited due to mixing of two fluids at minimum temperature 140°C and 180°C, and estimated minimum pressure at 800 bars.     

Laser ablation of stream-sediment pebble coatings for simultaneous multi-element analysis in geochemical exploration

Laser ablation of the Fe and Mn oxide coatings on stream sediments has been tested as a means of rapidly introducing this highly sorptive geochemical exploration medium into an inductively coupled plasma emission spectrometer (ICP) for simultaneous multielement analysis.Training data were obtained by selectively leaching coatings on about ten 1-cm diameter pebbles from 50 sites in the Allen drainage system, Southwest England. The Pb, Zn, Fe and Mn concentrations of the resulting leachates were determined by atomic absorption spectrophotometry. This procedure is relatively rapid and economical, but the leachate is suitable only for the determination of a restricted range of elements (mainly heavy metals). The laser-microprobe testing data were obtained by vaporizing approximately 1 μg of coating from one pebble from each sample site with a laser pulse, producing a crater in the coating 150–200 μm in diameter and 30–50 μm deep. The ablation was effected within a cell which the laser beam penetrates via a quartz window and the vaporized material quickly condenses into an aerosol which is carried in a flow of argon passing through the cell to the ICP, for simultaneous determination of up to 36 elements.Training and testing data for the elements determined were normalized by ratioing to Fe or Mn following a preliminary statistical inspection of the data to ascertain predominant correlations. In the Allen drainage basin, where a narrow and impersistent galena vein with subordinate sphalerite occupies a north-south-trending fracture, Pb determinations on coatings correlate well with the Fe content of coatings, while Zn correlates with Mn. The Pb/Fe dispersion patterns produced by the training and testing procedures are essentially similar, as are the Zn/Mn patterns from each of the procedures, demonstrating the potential of the novel laser microprobe technique.Anomalous Pb/Fe and Zn/Mn ratios in pebble coatings occur in the vicinity of the mineralized fracture. These compare favourably in terms of anomaly contrast and length of dispersion trains (especially their extension beyond major confluences) with the Pb and Zn anomalies detected by the more conventional analysis of the minus 200 μm fraction of the stream sediment. The low levels of potential pathfinder elements associated with mineralization do not lend themselves readily to determination in leachates derived from pebble coatings. Laser microprobe data, however, revealed a low-order but punctual As/Fe anomaly in a tributary, where this cuts the mineralized vein.     

青海北祁连冷龙岭地区水系沉积物元素地球化学特征及异常圈定

青海冷龙岭地区位于北祁连成矿段的东段,是形成与海相火山岩有关的块状硫化物矿床及岩浆热液型矿床的有利地区,具有良好的找矿潜力。在1∶5万水系沉积物测量成果的基础上,对青海冷龙岭地区Au、Cu、Pb、Zn等17种元素的地球化学特征进行了初步分析,发现本区Ag、Pb、Zn、W、Sn、Bi、Mo、Ba、Cd等元素丰度明显高于青海省及祁连地区水系沉积物的平均丰度值;元素分布特征显示下奥陶统阴沟群除Hg、La、Ce相对贫化外,各元素都呈现不同程度的浓集,加里东期侵入岩中Ag、Cu、Pb、Zn、W、Au、Sn、Bi等元素富集程度较高,海西期正长岩内Ba、La、Ce等元素富集程度较为显著;R型聚类分析和因子分析显示区内的主要成矿元素组合为Cu Pb Ag Mo Ba La Ce,Au具有独立成矿的潜力。结合元素地球化学参数及富集离散特征,认为本区Au、Ag、Cu、Pb、Zn、Mo、La、Ce等元素具有一定的找矿潜力。本次工作共圈定8个综合异常。根据研究区成矿地质背景、异常特征及查证成果,与该区域内浪力克铜矿床和青分岭金矿床的地质地球化学特征对比研究后,优选出干沙河和三道路圈—倒阳河2个成矿远景区。     

The environmental impact of Aguilar mine on the heavy metal concentrations of the Yacoraite River,Jujuy Province,NW Argentina

The Yacoraite River and its tributaries run down the eastern slope of the Aguilar Range. It is one of the tributaries of the Rio Grande, located in Quebrada de Humahuaca, a UNESCO World Heritage site. The Aguilar underground mine (Pb–Ag–Zn) is located in the upper reaches of the Yacoraite River drainage basin. The aim of this work is to characterize the presence of heavy metals in water and sediments of the Yacoraite River and to identify their sources. The analysis shows the seasonal variation of heavy metals concentration in water and their relation with the World Health Organization (WHO) limits established for human consumption. The Yacoraite basin is naturally anomalous in some metals and some elements, such as As which is controlled by the chemical composition of regional lithology. During the wet season, Al, Co, Mo and Pb concentrations in water samples are higher than during the dry season; in addition, these metals are also higher than WHO limit values. High enrichment factors for Ba, Mo, Pb, Zn and Cd were found in Casa Grande stream, indicating the direct influence of the mining activities. Cd, Pb and Zn are present in the Aguilar ore minerals, such as sphalerite and galena. Sediments collected during the dry season show a drastic increase in the concentration of As, Pb, Ba, Zn, Cd and Mn. The Müller geo-accumulation index in Casa Grande indicates that it is a highly polluted stream. The concentrations of As, Pb, Ba, Zn, Cd are also high in Yacoraite River: Security Quality Guidelines indicates toxicity. A decrease in enrichment factors and geo-accumulation indices observed in sediments indicates the occurrence of precipitation/adsorption processes in the river to restore the equilibrium composition. Strict environmental controls in Aguilar Mine are necessary to avoid the uncontrolled input of toxic metals in Casa Grande stream and Yacoraite River.     

Compositions of magmatic hydrothermal fluids determined by LA-ICP-MS of fluid inclusions from the porphyry copper–molybdenum deposit at Butte, MT

We analyzed 85 fluid inclusions from seven samples from the porphyry Cu–Mo deposit in Butte, MT, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Butte deposit formed at unusually great depth relative to most porphyry deposits, and fluid inclusions in deep veins trapped a low-salinity, CO₂-bearing, magmatically derived, supercritical fluid as a single aqueous phase. This fluid is interpreted to be the parent fluid that cooled, decompressed, unmixed, and reacted with wall rock to form the gigantic porphyry Cu deposit at Butte. Few previous analyses of such fluids exist.Low-salinity, aqueous fluids from the earliest veins at Butte are trapped in deep veins with biotite-rich alteration envelopes (EDM veins). These veins, and the Butte quartz monzonite surrounding them, host much of the Butte porphyry Cu mineralization. Twenty fluid inclusions in one EDM quartz vein are dominated by Na, K, Fe (from 0.1 to 1 wt.%) and contain up to 1.3 wt.% Cu. These inclusions contain only small amounts (tens of ppm) of Pb, Zn, and Mn, and typically contain Li, B, Ca, As, Mo, Ag, Sn, Sb, Ba, and W in less than detectable quantities. The abundance of Cu in early fluids indicates that a low-salinity, Cu-rich, aqueous ore fluid can be directly produced by aqueous fluid separation from a granitic magma. Similar inclusions (eight) in an early deep quartz–molybdenite vein with a K-feldspar selvage have similar compositions but contain significantly less Cu than most inclusions in the biotite-altered vein. Analyzed inclusions in both veins contain less than detectable concentrations of Mo even though one is molybdenite-bearing.Low-salinity, CO₂-bearing aqueous fluids are also trapped in pyrite–quartz veins with sericitic selvages. These veins cut both of the above vein types and contain inclusions that were trapped at lower pressure and temperature. Thirty-nine inclusions in two such veins have compositions similar to early fluids, but are enriched by up to a factor of 10 in Mn, Pb, and Zn relative to early fluids, and are slightly depleted in Fe. Many of these inclusions contain as much or more Cu than early fluids, although little chalcopyrite is found in or around pyrite–quartz veins.Eighteen halite-bearing inclusions from three veins from both chalcopyrite-bearing and barren veins with both K-silicate and sericitic selvages were analyzed as well. Halite-saturated inclusions are dominated by Na, K, Fe, and in some inclusions Ca. Whereas these inclusions are significantly enriched in Ca, Mn, Fe, Zn, and Pb, fluids in all three veins contain significantly less Cu than early, high temperature, low-salinity inclusions.Analyses of all inclusion types show that whereas bulk-salinity of the hydrothermal fluid must be largely controlled by the magma, fluid–rock interactions have a significant role in controlling fluid compositions and metal ratios. Cu concentrations range over an order of magnitude, more than any other element, in all four samples containing low-salinity inclusions. We infer that variations are the result of fluid trapping after different amounts of fluid–rock reaction and chalcopyrite precipitation. Enrichment, relative to early fluids, of Mn, Pb, and Zn in fluids related to sericitic alteration is also likely the result of fluid–rock reaction, whereby these elements are released from biotite and feldspars as they alter to sericite. In halite-bearing inclusions, concentrations of Sr, Ca, Pb, and Ba are elevated in inclusions from the pyrite–quartz vein with sericitic alteration relative to halite-bearing inclusions from unaltered and potassically altered samples. Such enrichment is likely caused by the breakdown of plagioclase and K-feldspar in the alteration envelope, releasing Sr, Ca, Pb, and Ba.     

Major and trace element anomalies in stream sediments of the Teign Valley Orefield

A detailed geochemical and sedimentological study of twenty-two bulk stream sediments in the Teign Valley of southwest Devon shows the influence of lithology, mineralization and contamination on such cumulative samples. K, Cu and Ni in stream sediments emerge as potential indicators of lithology. Ba and S values, as well as barytes concentrations, demonstrate the contribution of Ba, Zn and Pb mineral lodes, whilst Fe, S and heavy-mineral percentages emphasize that of Fe lodes and contamination. As, Pb and Zn anomalies are observed within Fe-oxide crusts giving evidence of Fe in the role of scavenger. High Mn values are attributed to precipitations of the metal derived largely from impregnations of the Culm.     

Spatial variability of soils and stream sediments and the remediation effects in a Portuguese uranium mine area

The old Senhora das Fontes uranium mine, located in central Portugal, was closed down in 1971. The treatment of ores from this mine and other mines by heap-leach ended in 1982. Seven dumps partially covered by vegetation were left in the area. Soil and stream sediment samples were collected in December 2009. The remediation was carried out from May 2010 to January 2011. Stream sediment samples were collected again in October 2013. Before the remediation, soils from inside the mine influence area have higher Al, As, Co, Cr, Cu, Fe, Ni, Sr, Th, U and Zn concentrations than soils from outside this area, due to radionuclides, metals and metalloid released from the mine dumps. The principal component analysis (PCA) shows a distinction between soils from inside and outside the mine influence area. The U(VI), As(V) and metals from soils can be adsorbed to Fe-oxyhydroxides and the humic acid can increase the U uptake. Soils must not be used for public or private green and residential areas, because they are contaminated in U, As, Co, Cd and Ni. Before the remediation, downstream sediments have higher Al, As, Cu, Mn, Ni, Pb, U and Zn than upstream sediments, due to erosion and percolation of water through the mine dumps. The PCA shows a distinction between downstream and upstream sediments. The U(VI), Th and As(V) can be adsorbed to Fe-oxyhydroxides. The stream sediments are contaminated in As, Mn, Th and U. Downstream sediments are the most contaminated in U and As. After the remediation, upstream and downstream sediments have generally higher Al, Fe, As, Cr, Ni, Th, U and Zn concentrations than before the remediation, attributed to the relocation of dumps. Radionuclides, metals and metalloids were transported by surface water. Consequently downstream sediments have higher Al, As, Cu, Mn, Ni, Th, U and Zn concentrations than upstream sediments. The U(VI), Th and As(V) can be adsorbed to Fe-oxyhydroxides. Stream sediments became more contaminated in U, Th and As than before the remediation, but more intensively downstream.     

Contamination of surface waters by mining wastes in the Milluni Valley (Cordillera Real,Bolivia): Mineralogical and hydrological influences

This study is one of very few dealing with mining waste contamination in high altitude, tropical-latitude areas exploited during the last century. Geochemical, mineralogical and hydrological characterizations of potentially harmful elements (PHEs) in surface waters and sediments were performed in the Milluni Valley (main reservoir of water supply of La Paz, Bolivia, 4000 m a.s.l.), throughout different seasons during 2002–2004 to identify contamination sources and sinks, and contamination control parameters. PHE concentrations greatly exceeded the World Health Organization water guidelines for human consumption. The very acidic conditions, which resulted from the oxidation of sulfide minerals in mining waste, favoured the enrichment of dissolved PHEs (Cd > Zn ? As ? Cu ∼ Ni > Pb > Sn) in surface waters downstream from the mine. Stream and lake sediments, mining waste and bedrock showed the highest PHE content in the mining area. With the exception of Fe, the PHEs were derived from specific minerals (Fe, pyrite; Zn, Cd, sphalerite, As, Fe, arsenopyrite, Cu, Fe, chalcopyrite, Pb, galena, Sn, cassiterite), but the mining was responsible for PHEs availability. Most of the PHEs were extremely mobile (As > Fe > Pb > Cd > Zn ∼ Cu > Sn) in the mining wastes and the sediments downstream from the mine. pH and oxyhydroxides mainly explained the contrasted availability of Zn (mostly in labile fractions) and As (associated with Fe-oxyhydroxides). Unexpectedly, Pb, Zn, As, and Fe were significantly attenuated by organic matter in acidic lake sediments.     

Geological and anthropogenic influences on sediment metal composition in the upper Paracatu River Basin, Brazil

This work reports a geochemical study of sediments from the upper Paracatu River Basin. The objective is to define the influences of Au, Zn, and Pb mineral deposits and mining activities on the sediment metal sources, distribution, and accretion. The samples were analyzed using ICP/OES, AAS, and XRD techniques and were treated with principal components analysis and the geo-accumulation index. The main geochemical processes that control the sediment composition are pyrite oxidation, muscovite weathering, carbonate dissolution, and the erosion of oxisols enriched with Zn and Pb. The upper Rico Stream has high Al, Fe, Cu, Cr, Co, and Mn concentrations due erosion of oxisols and pyrite oxidation and muscovite alteration present in the parental rock. The artisanal alluvial gold mining increased the primary rock-minerals?? weathering and Hg sediment concentration. The lower Escuro River and Santa Catarina Stream are enriched with Zn and Pb due the erosion of metal-rich soils formed over galena, sphalerite, calamine, and willemite mineral deposits located upstream. Elements such as Ca, Mg, and Ba have low concentrations throughout the sampled area due the high solubility of these metals-bearing minerals. The dispersion of metals is limited by the basin geomorphology and their affinity to silt-clayey minerals and Fe and Mn oxides and hydroxides in circumneutral pH waters.     

Magmatic-to-hydrothermal crystallization in the W–Sn mineralized Mole Granite (NSW, Australia): Part I: Crystallization of zircon and REE-phosphates over three million years—a geochemical and U–Pb geochronological study

Zircon, monazite and xenotime crystallized over a temperature interval of several hundred degrees at the magmatic to hydrothermal transition of the Sn and W mineralized Mole Granite. Magmatic zircon and monazite, thought to have crystallized from hydrous silicate melt, were dated by conventional U–Pb techniques at an age of 247.6 ± 0.4 and 247.7 ± 0.5 Ma, respectively. Xenotime occurring in hydrothermal quartz is found to be significantly younger at 246.2 ± 0.5 Ma and is interpreted to represent hydrothermal growth. From associated fluid inclusions it is concluded that it precipitated from a hydrothermal brine ≤ 600 °C, which is below the accepted closure temperature for U–Pb in this mineral. These data are compatible with a two-stage crystallization process: precipitation of zircon and monazite as magmatic liquidus phases in deep crustal magma followed by complete crystallization and intimately associated Sn–W mineralization after intrusion of the shallow, sill-like body of the Mole Granite. Later hydrothermal formation of monazite in a biotite–fluorite–topaz reaction rim around a mineralized vein was dated at 244.4 ± 1.4 Ma, which distinctly postdates the Mole Granite and is possibly related to a younger hidden intrusion and its hydrothermal fluid system.

Obtaining precise age data for magmatic and hydrothermal minerals of the Mole Granite is hampered by uncertainties introduced by different corrections required for multiple highly radiogenic minerals crystallising from evolved hydrous granites, including ²³⁰Th disequilibrium due to Th/U fractionation during monazite and possibly xenotime crystallization, variable Th/U ratios of the fluids from which xenotime was precipitating, elevated contents of common lead, and post-crystallization lead loss in zircon, enhanced by the fluid-saturated environment. The data imply that monazite can also survive as a liquidus phase in protracted magmatic systems over periods of 10⁶ years. The outlined model is in agreement with prominent chemical core-rim variation of the zircon.