Chemical evidence for,and implications of,a primary FeS phase in the Ankarvattnet Zn-Cu-Pb massive sulphide deposit,central Swedish Caledonides

The origin of the pyrrhotite in the Ankarvattnet massive sulphide deposit is discussed, based on chemical relations between the different mineralization types. A metamorphic genesis is rejected and a premetamorphic origin is alternatively suggested, which is in agreement with similar ideas for the origin of the pyrrhotite in other deposits. The pyrrhotite is thought to have formed in the stringer zone to a massive pyritic layer with similar formation mechanisms as for volcanogenic massive sulphide deposits. The recognition of a stringer zone mineralogy provides better possibilities to understand the physico-chemical character of the ore forming environment.     

河北红石砬铂矿床铂、钯地球化学异常特征

红石砬铂矿地球化学异常组分简单,仅发育Ｐｔ和Ｐｄ的强异常,部分伴生Ａｕ异常,不伴生Ｃｒ、Ｃｏ、Ｃｕ、Ｎｉ、Ｖ、Ａｓ、Ｓｂ、Ａｇ、Ｐｂ等元素异常。岩石、土壤、水系沉积物中Ｐｔ、Ｐｄ的分布和异常模式与铂族矿化特征、矿体剥蚀程度及其表生地球化学行为等有关。矿体出露地表时,Ｐｔ、Ｐｄ呈强异常分布,异常的ｗ（Ｐｔ）／ｗ（Ｐｄ）比值与矿石中ｗ（Ｐｔ）／ｗ（Ｐｄ）比率基本一致;隐伏矿体上方,Ｐｄ有明显的浓集,ｗ（Ｐｔ）／ｗ（Ｐｄ）比值小于地表矿体。表生环境中,Ｐｔ、Ｐｄ可以呈矿物碎屑、可溶态等多种形式迁移,在疏松沉积物中形成异常。因此,以Ｐｔ、Ｐｄ作为直接指示元素,进行地球化学勘查,可以发现这种类型的铂族矿床。     

The Wilga base-precious metals deposit, Benambra, Victoria, Australia

Wilga is one of several Au-bearing volcanogenic massive sulphide deposits localized within Silurian felsic volcanics of the Lachlan Fold Belt of NE Victoria. Exploration has delineated a resource of 3.7 Mt averaging 3.4% Cu, 5.5% Zn, 0.4% Pb, 31 g/t Ag and 0.5 g/t Au within a lensoid-shaped sulphide body which strikes NE, dips NW and occurs at a depth of 50–160 m below surface. This body has maximum dimensions of 470 m strike, 350 m down-dip and 37 m true width delineated by 59 surface diamond drill holes and an exploration adit with 40 underground diamond drill holes. There are two main types of mineralization: Stratiform massive sulphides , (mainly pyrite, low-Fe sphalerite, variable chalcopyrite and minor galena with very minor silica/dolomite gangue) and Stratiform chloritic sulphides (mainly chalcopyrite, with subordinate pyrite and sphalerite, in a gangue of chlorite and minor dolomite). The deposit is layered with at least 6 distinct stratigraphic horizons/cycles of mineralization each characterized by a Cu-rich base and Pb-(Zn)-Au-As-rich top. Facies variations are locally rapid. Economically the deposit consists of 3 sub-lenses of roughly equal tonnage: a Cu-rich central lens of Chloritic Sulphides (av. 5.9% Cu, 3.6% Zn, 0.3% Pb, 32 g/t Ag and 0.2 g/t Au) between upper and lower lenses of Zn-rich Massive Sulphides (av. 1.8% Cu, 6.7% Zn, 0.5% Pb, 31 g/t Ag and 0.7 g/t Au). Gold mineralization, locally up to 7 g/t over 6 m, shows a strong spatial association with Pb, (Zn) and As in pyritic massive sulphides.     

The mineralogy and chemical composition of the Woodlawn massive sulphide orebody

The main Woodlawn ore lens is a polymetallic, massive sulphide deposit’ with pyrite the major constituent, variable sphalerite, galena and chalcopyrite, and minor arsenopyrite, tetrahedrite‐tennantite, pyrrhotite and electrum. The silicate gangue minerals are chlorite, quartz, talc and sericitic mica. Other mineralization in the vicinity consists of footwall copper ore in chlorite schist and several smaller massive sulphide lenses. The predominant country rocks are felsic volcanics and shales, with abundant quartz, chlorite and mica, and talc in mineralized zones.

An important textural feature of the massive ore is the fine compositional banding. Bands, which vary in thickness from a few tens of micrometres to several millimetres, are produced by variations in the sulphide content. Post‐depositional metomorphism and minor fracturing have only slightly modified this banding.

Apart from the major element constituents—Pb, Zn, Fe, Cu and S—the ore is characterized by significant (100–1000 ppm) values for Ag, As, Cd, Mn, Sb and Sn, and lower (1–100 ppm) values of Au, Bi, Co, Ga, Hg, Mo, Ni, Tl. In and Ge. Variations in the base‐metal sulphide content, the gangue mineralogy, and trace elements, are used to separate the orebody into hanging‐wall and footwall zones. The hanging‐wall zone shows a more variable trace element content, with higher Tl, Sn, Ni, Mn, Ge and Sb, but lower Ag, Cd, and Mo, than the footwall zone.

In general style of mineralization, mineralogy, and chemistry, the Woodlawn deposit resembles other volcanogenic massive sulphide deposits in eastern Australia, in New Brunswick in Canada, and the Kuroko deposits of Japan.     

Mineralization and regional alteration at the Mons Cupri stratiform Cu–Zn–Pb deposit, Pilbara Craton, Western Australia

The Mons Cupri Cu–Zn–Pb deposit is hosted by conglomerate of the ca. 2,965 Ma Cistern Formation, which forms part of the Bookingarra Group in the Central Pilbara tectonic zone of the Pilbara Craton. The deposit has two distinct mineralized zones: a 5- to 10-m-thick, stratiform, Zn–Pb-rich semi-massive sulphide lens, which overlies a funnel-shaped Cu-rich stringer zone. The deposit is located 5–20 m stratigraphically below the contact of the Cistern Formation with the overlying Rushall Slate. A high-Mg basalt (the Comstock Member) is located near the base of the Rushall Slate. Regional alteration mapping indicates that feldspar-destructive alteration facies are restricted to the vicinity of the deposit, with intense chloritic alteration restricted to the stringer zone and a narrow cross-cutting zone that can be traced for 700 m to the east, in the footwall of the deposit. Feldspar-destructive zones are well developed in the Comstock Member, indicating that mineralization occurred after deposition of the Rushall Slate. The Mons Cupri stratiform semi-massive sulphide lens is hosted by a conglomerate, and textural evidence indicates that this lens formed by replacement. These observations, combined with Pb isotope data, suggest that the Mons Cupri deposit formed epigenetically, at least 30 Ma after deposition of its host rock.Editorial Handling: B. Gemmell     

Volcanogenic and tectonic features of the Rakkejaur sulfide deposit,Skellefte district,Sweden

The Rakkejaur volcanogenic massive sulfide deposit is conformably situated in a transition zone between Proterozoic pyroclastic and overlying clastic sedimentary rocks. Ore and host rocks are isoclinally folded and slightly overturned. Two distinct types of mineralization occur: Cu-bearing stringers and disseminations, and Zn-rich stratiform banded massive sulfides. Precipitation of stratiform ore was concurrent with late volcanism and continued during the early stages of clastic sedimentation. Pyroclastic debris containing fragments of the underlying stringer-mineralized metavolcanic rocks were deposited in the lower parts of the massive sulfides. Banding of the stratiform massive ore is evidenced by alternating concentrations of pyrite and sphalerite and by interlayered sedimentary strata. Slumping and synsedimentary fragmentation of the massive sulfides took place locally. Epigenetic stringer mineralization was emplaced in two separate conduits located in the footwall metavolcanic rocks. Both mineralized vents are in contact with and beneath the same cap of massive sulfides.Zn, Pb, Ag, and Sb grades are elevated in the banded ore and tend to increase with stratigraphic and lateral distance from the zones of stringer mineralization. Gold occurs in association with arsenic or in amalgam, and each assemblage displays different distribution patterns. Most of the gold is contained in the stratiform ore where distal areas generally show higher Au/As ratios. The Au-As assemblage, however, occurs within one of the conduit zones and in close proximity to the other conduit within the massive sulfides. The ore-forming processes resulted in metasomatic alteration of the footwall rocks, mainly by introduction of Mg and Fe and depletion of Na.     

闽东北地区金银矿床的水系沉积物地球化学特征

闽东北地区位于政和—大埔断裂带东侧。在晚侏罗世—早白垩世,该地区经历了十分强烈的火山活动,形成了分布广泛、厚度巨大的陆相火山沉积岩系,其下伏基底地层中的迪口组与福建省金矿或矿化关系极为密切,是福建省重要的含金矿源层,有较好的成矿条件。水系沉积物异常重现性试验及元素的表生迁移研究表明,不同采样批次、不同季节、不同年份在相同采样介质和采样点获得的主要成矿元素异常重现性较好。与全国水系沉积物元素平均含量相比,Au、Ag、Pb、Zn异常较明显。水系沉积物元素异常统计揭示,Au、Ag、As、Sb的成矿能力评价最高。这种元素异常组合表明,与火山岩有关的金矿是本区最有利的成矿矿种,并在闽东北地区经钻探验证,取得了良好的找矿效果。     

Pathfinder applications of arsenic, antimony and bismuth in geochemical exploration

The potential applications of As, Sb and Bi as pathfinder elements in geochemical exploration have been researched using a new, rapid technique for the simultaneous determination of the three elements. Following a warm hydrochloric acid sample leach, the volatile hydrides of the elements are generated and flushed into an inductively-coupled plasma linked to an emission spectrometer. The technique offers a combination of good analytical precision and detection limits of 100 ppb for each of the elements.The principal sulphide ore minerals commonly contain traces of As, Sb and Bi, and concentrations of more than 1% of any one of these have been found in some sulphide specimens. During sub-aerial oxidation of sulphides, any As, Sb and Bi present is released and forms dispersion patterns in the surficial environment. Geochemical surveys of localities in the United Kingdom have demonstrated that anomalous dispersion trains of these elements can be detected in the sediments of streams draining the mineralized localities. In a geochemical mapping programme covering 16,000 km² of central Nepal, over 3500 stream sediment samples were analyzed for As, Sb and Bi, and many known occurrences of Cu, Pb and Zn mineralization are reflected by As, Sb and Bi anomalies. However, bedrock lithology appears to be an important factor influencing Sb and Bi dispersion patterns.In the areas studied, some or all of the elements As, Sb and Bi produce stream sediment anomalies that compare favourably in terms of contrast and extent with the heavy metal expressions, even though none of the three elements have been reported as important constituents of the mineralization with which they occur.     

西藏尼雄地区水系沉积物地球化学特征及异常分布规律

西藏尼雄地区位于拉达克—冈底斯拉萨—腾冲陆块,区内已发现尼雄特大型富磁铁矿、日阿中型铜多金属矿等矿床.文章以1：5万水系沉积物地球化学调查为基础,总结水系沉积物地球化学特征及分布规律.研究发现区内成矿作用与亲铜元素和铁族元素有关,二叠系昂杰组、拉噶组是区内金矿的有利地层,敌布错组是寻找银、锌、铅、镉矿产的最佳地层,所圈化探异常与已有矿（化）点区域套合较好.     

青海拉脊山东段水系沉积物地球化学异常特征

青海拉脊山东段水系沉积物地球化学测量,发现金源、喇嘛庙、七里寺峡Au、As、Ag、Bi、Sb、Hg等元素的水系沉积物组合异常.Au、Ag、As相对高浓度带发育形态、分布范围、异常浓集中心吻合,与区内已知尼旦沟金矿床地球化学异常特征可以类比,发现有金、铜矿体和金矿化,显示铜金成矿的有望远景地段.     

The Ashele Deposit: A Recently Discovered Volcanogenic Massive Sulfide Cu-Zn Deposit in Xinjiang, China

Abstract: The Ashele Cu-Zn deposit is a recently discovered volcanogenic massive sulfide deposit in Xinjiang, Northwestern China. It is the largest Cu-Zn deposit in this type of deposits in China, which were formed in the early period of later Palaeozoic Era. This deposit is hosted within a suit of bimodal submarine volcanic rocks of the Ashele Formation of Lower-Middle Devonian System formed in an environment of paleocontinental margin rift setting. Lensoid orebodies occur between spilitic rocks developed at footwall and quartz-keratophyric tuff at hanging wall. Zonation of metal elements in the Ashele mine is one of typical volcanic-related exhalative Cu-Zn sulfide deposits in the world. Black ores enriched in Pb, Zn and Ag occurs on the top of the No. 1 orebody in the Ashele deposit, yellow ores enriched in Cu in the middle part, and the chalcopyritization stringer below the massive sulfide ores. Zonation of ore-structure in the No. 1 orebody is also apparent and corresponds to the zoning of elements, i. e. lamellar and/or banded sulfide-sulfate ores on the top, massive sulfide ores in the middle, and stockwork veinlets associated with altered breccia pipe on the bottom. Four epochs of mineralization in the Ashele deposit has been recognized. The first period of syngenetic-exhalative deposition of sulfides is the main epoch of mineralization, and the ores deposited subsequently subjected to thermo-metamorphism at the second epoch, superimposed by hydrothermal mineralization at the third epoch, and weathered or oxidized at the fourth epoch.
More than 100 categories of minerals have been recognized in the Ashele mine, but only pyrite, chalcopyrite, sphalerite, tetrahedrite, galena, barite, quartz, chlorite, sericite, and calcite are dominant, making up various types of ores, and alteration pipes or horizons. Studies of ore petrology suggest that the massive ores were volcanogenic and deposited by exhalative process.     

陕西秦岭巴山地区化探异常查证找矿实例分析

在陕西秦岭巴山地区9万km²内,通过1:20万区域化探扫面,发现了一批多元素综合异常,并根据地质构造背景分析划分出五个异常带(区)。其中新发现的北秦岭Au、Ag、Pb、Zn异常带,规模大、元素组合复杂且含量高,为一重要的金、多金属成矿带。1986年开始,在该区大力开展区域化探异常查证工作。通过1:5万水系沉积物测量,圈定了以金元素为主的化探异常。在主体异常部位系统地开展了1:1万土壤测量和槽探工程,于当年就在周至县马鞍桥发现了金矿体。随后又根据化探异常特征,布置了钻探和坑探工程验证。经进一步检查和详查,确认马鞍桥金矿为一大型金矿床。     

A magnetite-rich Cyprus-type VMS deposit in Ortaklar: A unique VMS style in the Tethyan metallogenic belt,Gaziantep, Turkey

The Ortaklar VMS deposit is hosted in the Koçali Complex consisting of basalts and deep sea pelagic sediments, which formed by rifting and continental break-up of the southern Neotethyan in Late Triassic. The basalts are of NMORB-type without notable crustal contamination. From the surface to depth, the Ortaklar deposit consists of a gossan zone, a thick massive ore zone and a poorly developed stockwork zone. Primary mineralisation is characterised by distinctive facies including sulphide breccias (proximal), graded beds (distal), stockworks and chimney fragments. Ore mineral abundances decrease in the order of pyrite, magnetite, chalcopyrite, and sphalerite. Two distinct phases of mineralisation, massive magnetite and massive sulphide, are present in the Ortaklar deposit. Textural evidence (e.g., magnetite replacing sulphides) and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages. The transition from sulphide to magnetite mineralisation is interpreted to relate to variation in H₂S content of ore fluids. The 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in Fe and H₂S. The 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in Fe but poor in H₂S, replacing the pre-existing sulphide ore.The alteration patterns, mineral paragenesis, lithological features (massive ore-stockwork ore-gossan) of the Ortaklar deposit together with its trace elements, Cu-Pb-Zn-Au-Ag and REE signatures are all consistent with a Cyprus-type VMS system. The δ³⁴S values in pyrite and chalcopyrite samples range from 2.6 to 5.7‰, indicating that the hydrothermal fluids were associated with sub-seafloor igneous activity, typical of Cyprus-type VMS deposits. However, magnetite formed later than sulphide minerals in the Ortaklar deposit, contrasting with typical Cyprus-type VMS deposits where magnetite generally occurs in lower sections. Consequently, although the Ortaklar deposit generally conforms to Cyprus-type deposits, it is distinguished from them by its late stage and high magnetite concentration. Thus, the Ortaklar deposit is thought to be an exceptional and perhaps unique Cyprus-type VMS deposit.     

Formation stages and ore matter sources of the Devdoraki copper deposit,Kazbek volcanic center,the Greater Caucasus

Comprehensive petrological–mineralogical, geochronological, and isotope-geochemical studies have been carried out at the Devdoraki copper deposit situated in the Kazbek neovolcanic center, the frontier territory between Georgia and Russia. The formation history of this deposit has been deciphered on the basis of K–Ar isotopic geochronological data, and the multistage evolution of ore–magmatic system has been established. The subeconomic disseminated and less abundant stringer pyrite mineralization formed at the first stage in the Early Cretaceous back to 130–120 Ma at the retrograde stage of regional metamorphism. The second productive stage was related to intense Quaternary volcanism of the Kazbek center. The late stringer base-metal mineralization formed about 400 ka ago in connection with the activity of minor volcanoes in the eastern part of deposit. In its western part adjoining the Kazbek volcanic cone, ore formation apparently continued over the entire period of recent magmatic activity from 400 to 100 ka ago. It is quite probable that this process is currently proceeding at deep levels of the Devdoraki deposit. Pb–Pb isotope-geochemical data show that Jurassic metasedimentary rocks that host sulfide mineralization could have been a main source of matter for early pyrite. At the second stage of base-metal mineralization formation, the source of ore matter was earlier metamorphic pyrite combined with hydrothermal solutions related to Quaternary endogenic activity within the Kazbek volcanic center. Gangue mineral matter (quartz, carbonates) was supplied simultaneously from the postmagmatic hydrothermal solution and host shale.     

Soil and stream sediment geochemical dispersion over the Bell Springs deposit, Hog Ranch Mine, Washoe County, Nevada

The Bell Springs deposit is a bulk-tonnage, low-grade gold deposit, formed in a hot-spring environment, that is hosted by middle Miocene weakly peralkaline, high-silica rhyolite ash flows and rheomorphic tuffs. Ore grade mineralization over about 460 × 460 m was controlled by northeast- and northwest-trending structures. Sixty-nine soil samples collected along a traverse across the Bell Springs deposit, screened into six mesh size fractions, +10, −10+35, −35+80, −80+120, −120+200, and −200, were treated by low-detection-limit acid digestion/organic extraction procedures, and analyzed by ICP or graphite furnace techniques for Au, Ag, As, Bi, Cd, Cu, Ga, Hg, Mo, Pb, Sb, Se, Te, Tl, and Zn. Twenty-five stream-sediment samples were collected from a drainage crossing mineralization and from a nearby tributary. Sediment size fractions of −200 mesh and −10+200 mesh were analyzed by the same procedures used for soils. In addition, analyses of bulk leachable gold via cyanide leach method (BLEG) was done on bulk −10 mesh sediments.Anomalous Au, Ag, As, Sb, and Mo in all soil size fractions revealed the underlying ore. Areas with anomalous Sb and As were about three times larger than areas with anomalous Au and Ag. Analyses of fine-fractions of stream sediments provided the best-defined Au anomalies in drainages. A multi-element factor calculated by multiplying Au, As, Sb, and Mo reinforced anomalous Au in drainages and correlated well with Bell Springs mineralization.     

A catchment basin approach to the analysis of reconnaissance geochemical-geological data from Albay Province,Philippines

A systematic approach for identifying mineral exploration target areas from reconnaissance stream sediment data without sufficient a-priori control information has been demonstrated in a portion of western Albay Province in the southern Bicol Peninsula of the Philippines. The approach involved devising a rapid method of catchment basin mapping using a geographic information system (GIS) so that the areal influence of the catchment basins may be incorporated in the geochemical data analysis. Areal proportions of mapped rock units occurring in the sample catchment basins and observed Mn and Fe contents in stream sediments are used as independent variables in multiple regression analysis to predict element contents in stream sediments related to lithologic and chemical controls. The predicted element contents are filtered-out from the original data to leave residuals in which the effects of other factors (e.g., mineralization) may be seen. A simple correction for the effects of downstream dilution is applied; this allows for the different sizes of the sample catchment basins so that positive geochemical residuals are enhanced. The inter-relationship of the different positive residuals in ‘highly enriched’ samples are investigated through principal components analysis to determine and quantify an ‘anomalous geochemical signature’. Lastly, the ‘anomalous geochemical signature’ is integrated with ‘proximity’ to faults/fractures to determine favourable target areas. For the test region, the lithologic controls explain between 80% and 100% of the variability in most of the elements studied. Chemical controls account for generally less than 5% of the variability in the data. Most of the dilution-corrected residuals reveal high relative enrichment in certain areas underlain by andesite and/or diorite. An anomalous Cu-Mg-Fe-Zn geochemical signature is disclosed by the principal components analysis of the dilution-corrected residuals in ‘highly enriched’ samples. Most sample catchment basins defined by this ‘anomalous geochemical signature’ pertain to areas underlain by andesitic rocks. Integration of the ‘anomalous geochemical signature’ and ‘proximity’ to faults/fractures reveals that some of these anomalous sample catchment basins are favourable target areas. These areas are interpreted to contain andesite-hosted stockwork or stringer zones that once formed part of a complete stratigraphic sequence of a volcanogenic massive sulphide occurrence. The results demonstrate the usefulness and ability of the procedures followed to extract significant anomalies from the reconnaissance geochemical data without the benefit of sufficient a-priori control data to aid in anomaly recognition. Similar procedures could also be applied elsewhere.     

云南北衙地区钨矿化特征与找矿方向

云南北衙矿床是中国21世纪初新发现的超大型矽卡岩-斑岩型金多金属矿床之一,除已经勘查评价的Au、Fe、Cu、Pb、Zn等元素外,还伴生有一定量的W元素等有益组分。文章对北衙金多金属矿床万硐山矿段及外围马头湾和南大坪矿区中的钨矿化开展系统的岩石学和矿物学研究,初步查明了万硐山矿段和其外围矿床中的钨矿化特征。研究发现,这些矿区(段)的含钨矿物主要为白钨矿,在万硐山矿段和马头湾矿区还有少量的黑钨矿产出;钨矿化主要产于岩体与围岩地层接触部位的矽卡岩或其退化蚀变岩中,白钨矿多充填在石榴子石等矿物的晶体间隙,个别被石榴子石包裹(南大坪矿区);万硐山矿段和马头湾矿区中的白钨矿具有较高的w(Mo)。这些特征表明,北衙地区的钨矿化作用与典型矽卡岩型白钨矿矿床基本一致。万硐山矿段中白钨矿交代黑钨矿的过程与磁铁矿的结晶过程密切相关,暗示钨矿化与铁、金矿化作用是同一成矿作用的产物。北衙地区的区域土壤W元素地球化学异常具有良好的浓度分级,且部分异常中心与已知的矿床/点明显对应,说明北衙地区具有良好的钨矿找矿潜力,白钨矿和黑钨矿均可以作为找矿标志性矿物,而Mo元素地球化学异常则可以作为间接找矿标志。     

Tourmaline in the central Swedish ore district

More than 40 recently discovered tourmaline occurrences have been investigated in the Mid-Proterozoic Bergslagen ore district of central Sweden. Some are spatially associated with ores, others with zones of leaching, remobilization and migmatization. Among the tourmaline-bearing ore deposits are the Dammberg ZnPb-Fe sulphide deposit, the Sala Pb-Zn-Ag deposit, the Dalkarlsberg, Pershyttan and Håksberg Fe oxide deposits, the Leja Cu deposit, and the Zinkgruvan Zn-Pb-Ag deposit. Tourmaline has been recorded a) as tourmalinites and tourmaline-bearing chemical sediments; b) in tourmaline-bearing skarns; c) in tourmaline-quartz veins; d) as disseminations along the foliation in schists; e) in tourmaline pegmatites; f) in tourmalinized haloes in metavolcanites along tourmaline pegmatites; and g) in late joints. Tourmalinites, tourmaline-bearing chemical sediments and tourmaline-bearing skarns are spatially associated with sulphide and oxide mineralizations. The dravite components in these tourmalines are proportional to the size of Zn-Pb sulphide mineralizations. Tourmalines from quartz veins close to and within ore deposits contain high Zr and Cr contents. With increasing distance away from these deposits, the Zr and Cr contents fall significantly. Tourmalines from pegmatites have inherited a number of trace element enrichments through partial melting and assimilation of volcaniclastic sediments into granitic melts. Despite magmatic homogenization, Zn contents in these tourmalines reflect the proximity of Zn-Pb-sulphide deposits, decreasing away from them. Tourmalines from late joints with Zn contents above the 100 ppm level are also indicative for the proximity of Zn-Pb sulphide mineralizations. Thus, some trace elements in these tourmalines may represent suitable exploration tools.     

粤北盆地流体系统及其矿化特征

盆地构造演化流体系统矿化作用是当代矿床学研究的新课题。盆地演化过程 ,压实流体系统温度场、动力场和地球化学场可以通过地质研究和数字模拟来重塑。粤北晚古生代沉积盆地存在 3种类型的矿化流体。大宝山型流体与岩浆热动力作用有关 ,形成海底火山热液沉积多金属矿床 ;凡口型流体与深部建造的循环热液有关 ,形成中低温海底热泉喷溢沉积铅锌银汞矿床 ;红岩型流体与盆地成岩压实水有关 ,形成低温单一黄铁矿矿床。红岩地区盆地压实流体系统在盆缘古隆起地段形成红岩型黄铁矿矿带的同时 ,还形成特征的白云岩化作用。白云岩产状和组构、白云石“亮边”和“雾心”特征及地球化学特征表明 ,红岩型诸矿床的成因与盆地沉积物压实过程形成的流体有关     

Selective extraction techniques in exploration for volcanogenic sulphide deposits, Eastern Black Sea region, Turkey

Selective extraction techniques employing 0.05 M EDTA, 1 M hydroxylamine hydrochloride (Hxl) in acetic acid and 0.157 M ammonium oxalate in oxalic acid were used to assess the mode of occurrence of the trace elements in the various geochemical sample media and to increase the anomaly contrast over the concealed massive ore bodies in the the Eastern Black Sea region of Turkey.In hematitized pumice tuffs, an exhalate horizon overlying the Madenköy massive sulphide ore body, the trace elements such as As, Cu, Zn, Pb and Mo are partly associated with sulphides and partly occur in clays, and Fe- and Mn-oxides.The extraction data on stream sediments suggest that a hot nitric acid attack is the best digestion procedure for detecting mechanical dispersion trains in regional geochemical programmes. Comparison of the extractabilities of metals in soils from mineralized areas with those from the background Sirtköy soils by the different extraction procedures demonstrates that EDTA, and to lesser extent Hxl are the best extraction procedures for increasing the anomaly/background ratio. These two extraction procedures were found to also enhance Zn and Pb anomalies over the cover rocks of the Madenköy massive ore body relative to the largely exposed stockwork-impregnation zones.Among the EDTA, Hxl and ammonium oxalate extractions, only the last procedure extracted considerable amounts of As from the soil samples. Vapor-phase analysis suggests that mercury occurs mainly in sulphide form which is leachable only by ammonium oxalate solution that also leaches adsorbed mercury. The EDTA and the Hxl solutions only extracted adsorbed mercury. These three extractants have no effect on either mercuric oxide or mercuric sulphate. Arsenic, a very useful pathfinder in this region, can only be partly extracted from the pumice tuff and soil samples by ammonium oxalate solution.