Environmental mineralogy and geochemistry of waste dumps at the Pb(Zn)-Ag Bottino mine, Apuane Alps, Italy

The Serbo-Macedonian Metallogenetic Province, part of the Alpine metallogenic belt, hosts several ore deposits in mainly three geotectonic units: the Vardar Zone, the Serbo-Macedonian massif, and to a lesser extend the Dinarides. This metallogenic province includes the most significant Pb-Zn and Sb deposits in Serbia, as well as smaller Bi, Mo, Cu, Fe, Sn, Au and minor U, Wand Hg deposits, which are genetically related to emplacement of granitoids. The Podrinje Metallogenic District belongs to the Serbo-Macedonian Metallogenetic Province and incorporates several smaller orefields: Cer (Northwest Serbia), Boranja (West Serbia), and Srebrenica (East Bosnia and Herzegovina). Polymetallic deposits in the Boranja orefield are genetically related to the emplacement of the Tertiary Boranja granodiorite complex. The orefield contains a large number of sulfide deposits with Pb-Zn, and Sb with subordinate Cu, As, Bi and Ag. Small magnetite deposits connected to pyrometasomatic (skarn) stage are also significant. Skarns are of calcic type, and were formed along contacts of Triassic limestones and quartz diorites. Ore minerals are similar among the various types of orebodies in the Boranja orefield and consist of sulfides, sulfosalts [Pb-Bi-(Ag)-Te-Cu, Pb-Sb-(As), Sb-Cu-(Ag, Fe, Zn)], tellurides, native metals and alloys, oxides and complex-oxides, and gangue minerals. Minerals of the Boranja orefield were formed in several successive stages, which together correspond to a single regional-scale mineralization event that is genetically related to the subvulcanic-plutonic intrusion of the Neogene-aged magmatic Boranja complex. This can be best demonstrated by the zonal arrangement of several metallic mineral associations [Fe-Cu(Bi) -> Pb(Ag)-Zn -> Sb(As) -> CaF2(Pb-Zn)], with increasing distance from the Boranja granodiorite. Silver occurs as a minor metal principally as Ag-tetrahedrite, with subordinate native silver, Ag-bearing gold and pyrargyrite. Significant quantities of Ag can also be accommodated in galena as it is found to contain varied amounts of Ag, Bi and Sb (0.001-0.936, 0-3.345, and 0.012-0.510 wt%, respectively). The presence of both Ag and Bi in significant amounts in a Pb-rich sulfide system is essential for development of galena [solid solution alpha-(Pb-2, AgSb, AgBi)S-2]. This study demonstrates that silver, the most economic metal in Boranja orefield, is mainly accommodated in the galena structure, with lesser amounts present in the form of visible and/or invisible Pb-Bi-(Ag) sulfosalts.

کانسار Cu-Zn-As باقرق در شمال شرق شهر انارک و در استان اصفهان قرار دارد. کانی‌سازی به‌صورت دیرزاد، ماهیت چینه‌کران و بافت و ساخت پرکننده فضای خالی در سنگ میزبان کربناتی رخداده است. کانی‌شناسی بخش درون‌زاد شامل کالکوسیت، کالکوپیریت، پیریت، اسفالریت، گالن، انارژیت، باریت و کلسیت و کانیهای بخش برون‌زاد شامل مالاکیت، آزوریت، کوولیت، کریزوکولا، کالکوسیت، سروزیت، اسمیت‌زونیت، مس طبیعی، هماتیت، گوتیت و لیمونیت می‌باشد. سنگ میزبان کربناتی در اطراف زون‌های کانه‌دار متحمل دگرسانیهای دولومیتی‌شدن و کلسیتی‌شدن شده است. مس به‌عنوان عنصر اصلی ذخیره (با میانگین 28/20 درصد وزنی) و پس از آن عناصر روی (با میانگین تقریبی 1 درصد وزنی) و آرسنیک (با میانگین تقریبی 1 درصد وزنی) می‌باشند. مطالعات سیالات‌درگیر روی کانی باریت نشان می‌دهد سیال کانه‌دار سولفیدی دارای محدوده دمای همگن شدن بین 259 تا 354 درجه سانتی‌گراد و میزان شوری بین 8 تا 13 درصد وزنی معادل NaCl می‌باشد. سیال کانه‌دار در مراحل پایانی کانی‌سازی با آبهای جوی دچار اختلاط شده و فاز تأخیری غیر سولفیدی کلسیتی با محدوده دمای نسبتا پایین ‌(78 تا 112 درجه سانتی‌گراد) و درجه شوری پایین (بین 3 تا 6 درصد وزنی معادل NaCl) را تشکیل داده است. محدوده مقادیر 34Sδ کانی‌ باریت کانسار باقرق بین 13+ تا 14+ در هزار بوده در حالی‌که محاسبه مقدار 34Sδ مربوط به سیال کانه‌دار پس از تصحیح دمایی بین 7- تا 8- در هزار به‌دست آمد. منشأ گوگرد باقرق با توجه به شباهت ایزوتوپ باریت با سولفات‌های دریایی کرتاسه، احتمالا از لایه‌های تبخیری این دوره زمانی تأمین شده است. این سولفا‌ت‌ها توسط فرآیند‌های ترموشیمیایی به‌صورت بخشی به گوگرد احیایی با مقدار ایزوتوپی سبک‌تر (حدود 21 در هزار) تبدیل و جهت ته‌نشست سولفیدها مورد استفاده قرار گرفته است. کانسار باقرق با توجه به خصوصیاتی همچون سنگ میزبان کربناته، غیاب فعالیت آذرین، بافت پرکننده فضای خالی، دگرسانی دولومیتی،کانی‌شناسی، ژئوشیمی ماده‌معدنی (وجود As و Sb بالا و عدم حضور Bi)، داده‌های دماسنجی و مقادیر ایزوتوپ گوگرد، شباهت زیادی با کانسارهای مس با سنگ میزبان کربناته در افریقا و به‌ویژه نوع سومب (Tsumeb) در نامیبیا نشان می‌دهد. کانسار باقرق احتمالا مرتبط با سیالات دگرگونی آزاد شده در حین فازهای کوه‌زایی مرتبط با بسته‌شدن اقیانوس نئوتتیس می‌باشد.

The George Fisher deposit (107 Mt @ 11.1% Zn, 5.4% Pb, and 93g/t Ag) is the northernmost significant Mount Isa-style deposit hosted by the -1653Ma Urquhart Shale in the Western Mount Isa Inlier. It is distinguished from the Mount Isa and Hilton Mines by a paucity of syn-late tectonic Cu. This has enabled recognition and examination of a previously ·unrecognized, syndiagenetic, hydrothermal Zn-Pb-Ag mineralization-system, despite superposition of intense deformation during the Diamantinan and Isan Orogenies. George Fisher contains eleven west-dipping, stacked, anastomosing, stratabound ore lenses contained within rhythmically laminated pyritic siltstones intercalated with banded mudstones, and separated by barren stylolitic mudstones. The ore-bearing sequence contains abundant carbonate banding including partly coalesced carbonate nodules in pyritic siltstones and planar white carbonate bands in siltstones and banded mudstones. The deposit is zoned from stratigraphically lower Zn-rich to higher Zn+Pb-rich ore bodies. Subeconomic Cu occurrences are coincident with Zn+Pb zones, but are predominantly restricted to upper portions of the sequence. This zonation was developed within two hydrothermal systems separated by 75-125Ma. Emplacement of Zn-Pb-Ag at George Fisher was the culmination of a complex, syndiagenetic, hydrothermal alteration system. Calcite is a major constituent of texturally distinct carbonate banding and its formation post-dates earliest dolomite-ferroan dolomiteankerite alteration. At George Fisher, these carbonates are distinguished by unique stable isotope geochemistry within the Urquhart Shale (δ¹⁸O = 17.1-18.5‰, δ¹³C = 4.1 to -1.7‰) and are enriched in (Fe,Mn)CO₃ relative to paragenetically equivalent carbonates located away from economic Zn-Pb-Ag. These carbonates formed during infiltration of warm, basin-derived fluids into cool sedimentary rocks, prior to stylolitization and at depths of a few hundred metres. Chemical zonation of early carbonates over 10-20km provides vectors for Zn-Pb-Ag-bearing fluid influx zones. Pyritization by thermochemical sulphate reduction of in situ organic material post-dated stylolitization. Infiltrating fluids lacked ore metals at the time. Bedding-parallel carbonate±quartz±celsian-hyalophane-K-feldspar vein development was localized in the immediate vicinity of, preceded and structurally prepared the sequence for, economic Zn-Pb-Ag mineralization. Sphalerite, galena, hydrophlogopite and bitumen were codeposited. Bitumen reflectance data and mesophase textures constrain maximum temperatures of mineralization and peak thermal conditions during burial to 200°C. Metals were transported in slightly oxidized, near-neutral fluids. Sulphur was either sourced from a separate reduced fluid or was transported as sulphate in the same fluid. Metal precipitation occurred via fluid mixing or sulphate reduction. Much sphalerite is preserved in primary depositional sites whilst galena occurs in syn-late tectonic veins and breccias but retains its primary spatial association with sphalerite at deposit scale. Nineteen galena samples, from a range of paragenetic settings, display homogeneous Pb isotope compositions. A Pb-model age of -1653 Ma is interpreted to reflect the timing of Zn-PbAg mineralization. Key characteristics of the syn-late tectonic Cu system include pyrrhotite, biotite-chloritedominant and ferroan dolomite-ferroan ankerite -dominant alteration. Phyllosilicates occur in stratabound lenses superimposed on Ba-K-feldspar alteration zones, whilst ferroan carbonate alteration is pervasive throughout the deposit hanging wall. These carbonates are texturally, chemically and isotopically (δ¹⁸O = 13.0-17.3‰, δ¹³C = 4.6 to -1.3 ‰) distinct from syndiagenetic carbonates. Copper-bearing fluids had temperatures of 250- 300°C based on phyllosilicate mineral stability relationships. The temporal-spatial-temperature zonation of the Zn-Pb-Ag and Cu systems at George Fisher is not preserved at Mount Isa and Hilton. Mineralogical and geochemical characteristics of carbonate and phyllosilicate alteration assemblages throughout Zn-Pbbearing strata at the latter deposits are products of syn-late-tectonic Cu mineralization, reflecting greater influx of Cu-bearing fluids at these sites. Poor preservation of syndiagenetic hydrothermal signatures at Mount Isa and Hilton has undoubtedly contributed significantly to the long-standing controversy surrounding the origin of Mount Isa-style Zn-Pb-Ag deposits.

The mineralization processes in the Peloritani Belt (Southern Sector of the Calabria- Peloritani Arc) prevalently developed during the Variscan orogenesis producing Pb, Zn, Fe, As, Sb, Cu, Ag, W, etc. polymetalliferous ore-bearing horizons. This paper focuses on the polymetalliferous mineralization recognised in the ancient S. Carlo Mine, which has already been subject of some studies and is part of an important discordant vein deposits system that are widespread in the Mandanici Unit (MaU). This Unit is characterized by a Variscan low-P, polyphasic and plurifacial metamorphic basement, exhibiting a prograde zoning, from chlorite zone of greenschist facies to oligoclase-almandine zone of amphibolite facies. The Variscan main foliation (Fv2) is irregularly cut by mineralized veins of decimetric to metric width. They are also perpendicular to the Alpine mylonitic shear zones of metric thickness developing along the sub-horizontal tectonic contacts between the tectono-stratigraphic units. These vein deposits formed along late-Alpine systems of fractures and faults, after Peloritani nappe emplacement. Minerographic study reveals a metalliferous mineral association mainly composed of tetrahedrite associated with, in order of decreasing abundance, chalcopyrite, bournonite, pentlandite, stromeyerite, arsenopyrite, scheelite, galena, sphalerite, pyrite, bismuthinite, boulangerite, jamesonite, covellite, bornite and argentite. Quartz, siderite and ankerite among non-metalliferous minerals are predominant. This work has been supported by mineralogical studies and chemical analyses carried out by Atomic Absorption and Inductively Coupled Plasma-Mass Spectrometry on powdered and separated samples of minerals. Geochemical data (major and trace elements) have allowed a detailed characterization of the minerals. They have revealed that the most significant minerals with Au contents around 1 ppm are tetrahedrite, sphalerite, chalcopyrite and bournonite. The presence of this noble metal in all minerals is important and shows that the mineralizing event is late and widespread. The Ag content is generally about 2000 ppm in all metalliferous minerals, and is higher than those found in the same minerals of other Peloritani deposits in which this content is around 1000 ppm. Sphalerite and carbonates show very low Ag content. Chalcopyrite, sphalerite, bournonite and tetrahedrite show high contents of Ni, As, Bi. Cd and Mn are concentrated in sphalerite. Fe content in sphalerite is on average > 6%, in agreement with pressure-temperature conditions (pressure from 2 to 3 kbar and temperature from 420 to 550 C).

کانسار طلای کوه زر در شرق ایران و 35 کیلومتری غرب شهرستان تربت حیدریه (استان خراسان رضوی) قرار دارد. این کانسار نوع اکسید آهن (IOCG) غنی از اسپکیولاریت است. این معدن در کمربند ولکانیکی- پلوتونیکی خواف- بردسکن واقع شده است. پی جوییهای اخیر در این کمربند موجب شناسایی ذخایر مختلف مس- طلای نوع غنی از اکسید آهن (IOCG) از جمله در کوه زر شده است. در ناحیه مورد مطالعه انواع توف و گدازه های اسیدی تا حد واسط مربوط به ائوسن فوقانی گسترش دارند. توده های نفوذی با ترکیب گرانیت، گرانودیوریت، سینوگرانیت و مونزونیت های الیگومیوسن در آندزیت، داسیت و ریوداسیت ائوسن فوقانی نفوذ نموده-اند. توده های نفوذی از سری مگنتیت، غنی از پتاسیم و متاآلومینوس هستند. نمودارهای عنکبوتی گرانیتوئید ها غنی شدگی عناصر لیتوفیل با شعاع یونی بزرگ (Rb, K, Th, Ce) و تهی شدگی درعناصر Ti, Sr, Nb را نشان می دهند. براساس شاخصهای ژئوشیمیایی احتمالا ماگماتیسم در حاشیه قاره ها صورت گرفته است. انواع دگرسانیهای پروپلیتیک (کلریتی)، سیلیسی، آلبیتی، آرژیلیکی، کربناتی و سریسیتی مشاهده شده اند. در توده های نفوذی دگرسانی آلبیتی و در سنگهای آتشفشانی دگرسانی پروپلیتیک (اپیدوتی) نمود بیشتری دارند. سیالات کانه دار با منشأ ماگمایی سبب کانی سازی اسپکیولاریت و طلا در سنگهای نفوذی و آتش فشانی شده اند. کانی سازی در راستای زونهای شکستگی و گسلی امتداد لغز و فضاهای کششی بین آنها رخ داده است. طلای آزاد همراه با کوارتز و اسپکیولاریت یافت می شود. ذخیره کانسار (در یخش اکتشاف شده) بالغ بر 725/0 میلیون تن بوده و هم اکنون درحال بهره برداری و استحصال طلا می باشد.

The mineral aschamalmite, of heyrovskyite-like composition, but different in structure, from the Rudnik Pb–Zn/Cu,Ag,Bi,W polymetallic deposit in the central part of Serbia has been investigated. This polymetallic deposit includes over 90 hydrothermal and skarn-replacement orebody types, primarily hosted by Cretaceous sediments and occassionally by Oligocene dykes and sills of dacitic composition, and contact-metamorphic-metasomatic rocks. These rocks are host to an assemblage of pyrrhotite, colloform pyrite, chalcopyrite, galena, arsenopyrite, native bismuth and scheelite as well as minor pyrite, sphalerite, bismuthinite, argentopentlandite, and native silver. The chemical composition of the ore is very complex, where weight contents of valuable metals range as follows (%): Zn 0.49–4.49; Pb 0.90–5.66; Cu 0.08–2.18; WO3 0.05–1.18; Ag 0.005–0.030; Bi 0.005–0.081; and Cd 0.002–0.016. In reflected light, aschamalmite is optically anisotropic, with moderately high bireflectance ranging from slightly greenish to slightly gray. Electron-microprobe analysis gave an average crystallochemical formulae of (Pb5.82Ag0.20)Σ6.02Bi2.03(S8.93Te0.02Se0.01)Σ8.96. The strongest diffraction maximums of the X-ray powder pattern [d(in Å)(I)] are 3.419(100), 3.382(92), and 3.334(66). Monoclinic unit cell parameters are a=13.727(7); b=4.122(3); c=31.32(2) Å; β=90.72(5) o; and V=1771.8(1) Å3. Mineral assemblages and genesis of the Rudnik polymetallic deposit are discussed in detail and the sulfobismuthite mineralization has been compared with similar well-known global deposits.

Herin mine (Champdepraz, Aosta, Italy), located in Aosta Valley, approximately between 1600 and 1800 m a.s.l., was exploited for at least 250 years for its Cu-Fe sulfide ore. The deposit host rocks belong to the metaophiolitic Zermatt-Saas unit, the eclogitic lower portion of the Piedmont Western Alpine Nappe. The ore mineral association mainly comprises pyrite and chalcopyrite, along with other sulfides such as pyrrhotite, sphalerite, cubanite and oxides (magnetite, rutile, ilmenite). The deposit consists in lenticular massive bodies and thin layers hosted in various greenschist-facies metamorphosed lithotypes. New data on geometric features, mineralogy, mineral chemistry, petrography, minerography were collected and compared with the existing models for massive-sulfide mineral deposits. We suggest a hydrothermal-volcanogenic primary origin of the mineralization with primary characters largely obliterated by subsequent metamorphic history. On the basis of previous works and our results, we identified two parameters as driving criteria for a comprehension of the multistage process that led to the present configuration of the ore: (a) textural characters of pyrite and (b) distribution of selected trace elements (Co, Ni, As) in sulfides. Spot analyses and atomic maps obtained by electron microprobe provided an integration of these two sets of data. Trace elements, in fact, show a zoned distribution, in particular in pyrite, that can be related to specific textural styles. We selected Co as a useful trace element, due to its high concentration and wide range in pyrite (270-22200 ppm). Besides we determined a critical concentration value for cobalt of 3160 ppm, as discriminating between two generations of pyrite. This led to outline a series of dissolution and crystallization events, that describes the metamorphic history of the sulfide ore.

ناحیه مطالعاتی در شمال استان خراسان رضوی و 45 کیلومتری جنوب نیشابور قرار دارد. رگه های طلادار درون سنگهای گرانیت، گرانودیوریت، گرانودیوریت پورفیری، آندزیت، برش و توف نفوذ کرده اند. رگه ها از جنس کوارتز و کلسیت هستند. مناطق اصلی دگرسانی شامل منطقه سرسیتیک، سیلیسی، پروپلیتیک و منطقه کربنات است. کانی زایی به‌طور نزدیکی با دگرسانیهای سیلیسی و سرسیتیک به شکل رگه‌چه و با منطقه پروپلیتیک به شکل افشان همراه است. کانی شناسی کانیهای باطله کوارتز، کلسدونی، سرسیت، آدولاریا، کلسیت، دولومیت، ایلیت، دیکیت، آلبیت، کائولینیت و کلریت است. کانی زایی رگه ای عمدتا با رگه‌چه ها، برش، افشان و استوک ورک همراه هستند. رگه‌چه ها از پیریت، مارکازیت، آرسنوپیریت و کمتر کالکوپیریت، اسفالریت، گالن، مگنتیت و هماتیت تشکیل شده اند. بیشترین عیار طلا در رگه های سیلیسی دیده می شود. پیریت کانی سولفیدی اصلی در کانی سازی اولیه است. سه نوع پیریت بر اساس ترکیب شیمیایی شناسایی شده است: پیریت خالص، پیریت غنی از آرسنیک و پیریت تیتانیوم- وانادیوم دار. تجزیه های ریزکاوشگر الکترونی بیشترین غلظت آرسنیک، تیتانیوم و وانادیوم را به ترتیب 62/3، 91/3 و 53/0 درصد وزنی در پیریتهای رگه های طلادار نشان می دهند. طلا معمولا همراه با پیریت آرسنیک دار و پیریت تیتانیوم- وانادیوم دار است. براساس مطالعه بافت و ترکیب پیریتها، رگه‌چه‌های پیریت آرسنیک دار همراه با کانیهای سولفیدی آرسنوپیریت، کالکوپیریت، گالن، اسفالریت در دمای بالا و با کاهش دما و فشار، پیریتهای فرامبوئیدال با حاشیه حاوی آرسنیک و طلا شکل گرفته اند و در ادامه پیریتهای درشت تیتان دار به‌وجود آمده اند. پیریتهای خالص و تأخیری درشت بلور آخرین فاز کانی ساز در منطقه هستند.

The Monte Cristo mining area was discovered in the early days of mining in California, and intermittent attempts have been made to work it to the present time. The gold is localized in lenticular quartz veins replacing fractured country rock along north-south fault zones. Pyrite is the principal ore mineral with magnetite and minor amounts of sphalerite, pyrrhotite, and chalcopyrite also present. Anorthosite is the principal country rock in the areas apparently intruded into diorite. Hornblendite dikes cut the anorthosite before the time of gold mineralization, and late lamprophyre dikes were injected after the vein quartz. Some pegmatite and late aplite dikes are also present. The area on the whole has undergone little metamorphism. Several stages and patterns of faulting are present and an attempt was made to work out their relative ages and the ages of the dikes and veins with respect to them. Joint patterns were mapped but no relation was found between them and the ore control. Economically the mine is considered a bad risk for any sizeable operation. Small scale mining of high grade ore shoots with a minimum of investment capital is believed to offer the best chance of success. The most favorable aspect of the property is the amount of development work done on the Monte Cristo North area where short crosscuts would open up a possible downward extension of the vein exposed at the surface.

Mineralogical, IR-spectral and geochemical monitoring of hydrothermal alteration in a deformed and metamorphosed Jurassic VMS deposit at Arroyo Rojo, Tierra del Fuego, Argentina

Zinc is an important raw material and nonferrous metal that has an extremely important role in the development of national economies. For this reason, countries around the world continue to strengthen their research efforts on the development and utilization of zinc resources. Sphalerite is an important source of zinc metal, which often coexists with chalcopyrite, galena, and pyrite in nature. The flotation separation of complex polymetallic sulfide ore is a difficult problem in the field of mineral processing engineering. To achieve the flotation separation of chalcopyrite, galena, and other minerals from sphalerite, depressants are needed. Due to the difficulty of activation after the depression of galena and other sulfide ores, a zinc depression and lead floatation process is usually used. The choice of the sphalerite depressant is critical when separating zinc and other sulfides. The traditional sphalerite depressants are generally inorganic. Although these depressants significantly improve the hydrophilicity of the sphalerite surface and strongly depress the sphalerite, they have a certain inhibitory effect on other sulfide ores while depressing the sphalerite. In addition, these agents are difficult to degrade and have a negative impact on the environment. To achieve high-efficiency flotation separation of sphalerite and sulfide minerals and improve the quality of the concentrate products, the development of new inhibitors is becoming increasingly important. Thence, the effect of the oxidizer potassium permanganate and organic depressant sodium alginate on the flotation of three kinds of sulfide minerals are studied, including chalcopytite, galena, and sphalerite. The investigations involved flotation tests, X-ray photoelectron spectroscopy (XPS) analysis, adsorption behavior analysis, with an additional focus on the mechanism of potassium permanganate strengthening, and sodium alginate depression of sphalerite flotation. The flotation results show that adding either an oxidizer or sodium alginate alone does not enable the selective depression of sphalerite. However, adding a certain amount of oxidizer and sodium alginate together can realize the selective coordinated depression of sphalerite, with little effect on the flotation of chalcopytite and galena. The XPS analysis results show that sodium alginate is chemically adsorbed on the sphalerite surface with oxidation products such as zinc oxide, zinc hydroxide, or zinc sulfate, but is not adsorbed on an unoxidized sphalerite surface. The adsorption test results show that the preoxidation of potassium permanganate on sphalerite significantly increases the adsorption capacity of sodium alginate on the sphalerite surface. Therefore, potassium permanganate can strengthen the sodium alginate depression of sphalerite flotation.

Three types of base metal occurrences discovered along the Barisan Range, Sumatera are skarn, sedex and hydrothermal styles. The skarn styles include Lokop, Latong and Tuboh, while Dairi and Tanjung Balit belong to sedex and hydrothermal deposits, respectively. The Lokop deposit is dominated by galena with minor pyrite and is hosted within interbedded meta-sandstone, slate, phyllite, hornfels and quartzite of the Kluet Forma- tion. The Skarn Latong deposit consists of galena with minor sphalerite and chalcopyrite with skarn minerals of magnetite, garnet and calcite. It is hosted within the meta-limestone of the Kuantan Formation. The Skarn Tuboh deposit is dominated by sphalerite with minor galena, pyrite, manganese, hematite and magnetite. It is hosted within interbedded meta-sandstone and meta-limestone of the Rawas Formation. The Dairi deposit belongs to the sedimentary exhalative (sedex) type. It is hosted within the sedimentary sequence of the Kluet Formation. Two ore types known are Julu and Jehe mineralization. The Julu mineralization referring to as sediment exhalative (sedex), was formed syngenetically with carbonaceous shale. Ore mineralogies consist of galena, sphalerite and pyrite. The deposit was formed within the temperature range of 236-375°C with salinity ranges from 9,3-23% wt.NaCl. The Jehe mineralization which belongs to the Mississippi Valley-Type, is hosted within dolostone of the Jehe Member. Ores comprise galena, sphalerite, pyrite, chalcopyrite, tetrahedrite and tenantite. The deposit was formed at temperature range from 193-400°C with salinity up to 38.2% wt.NaCl. The Tanjung Balit deposit belongs to the hydrothermal mineralization. The deposit is hosted within the sedimentary sequence of the Silungkang Formation. Ores consist of chalcopyrite, galena and sphalerite with minor gold and silver. Hydrothermal minerals such as silica, illite, montmorillonite, pyropilite, muskovite, siderite, diaspor, dickite, magnesite, chlorite, carbonate, rhodochrosite, analcime, alunite, smectite, ankrite, calcite, dolomite, sericite and zeolite are common found. The Tanjung Balit mineralization is formed at the temperature range from 185-350°C and belongs to meso-epithermal type.

Archean greenstones represent a large percentage of worlds total gold endowment and are actively mined on every continent barring Antarctica. Greenstone-hosted gold deposits often have complex deformation and alteration histories, and a general deposit model remains controversial. The aim of this thesis is to improve our understanding of gold mineralisation in Archean greenstone belts, based on a comprehensive case study of the world-class Geita Hill deposit in Tanzania. Geita Hill is one of the largest gold deposits within the Geita Greenstone Belt in north-western Tanzania and has been mined as an open pit since 2002. The deposit is hosted within a greenschist facies metamorphosed and complexly deformed sedimentary package dominated by ironstone and intruded by diorite dykes. The gold mineralisation is spatially associated with the Geita Hill Shear Zone which, is a NE-trending, moderately west dipping deformation zone of discontinuous shear fractures. Detailed structural studies have defined a deformation history for the deposit, providing an opportunity for an in-depth study of the hydrothermal alteration and fluids associated with gold mineralisation. The first component of this thesis builds a paragenetic framework for the Geita Hill deposit. The regional metamorphism is characterised by biotite + chlorite + actinolite + K-feldspar + magnetite ± pyrrhotite ± pyrite indicating upper greenschist facies metamorphism. The gold-related alteration overprints the regional metamorphism and is characterised by silicification and sulfidation fronts that end within one meter of the mineralised zone. Locally, the silicification and sulfidation of the wall rock occurs along a series of mineralised quartz veins which have a sub-vertical dip and tend E-W. Paleostress analysis of the mineralised shear fractures of the Geita Hill Shear Zone suggests vertical maximum compressive stress (σ₁) and northerly extensional stress (σ₃) consistent with the orientation of the mineralised quartz veins and indicating N-S extension. The composition of the mineralised quartz veins is characterised by quartz + biotite + K-feldspar + pyrite, which also overprints the metamorphic mineral assemblage. Gold is closely associated with secondary pyrite and occurs as free gold and gold tellurides (sylvanite, calaverite and nagyagite). It occurs mainly as inclusions in pyrite and as invisible gold in pyrite but gold inclusions in biotite and along quartz grain boundaries are also present. The gold-bearing pyrite is associated with secondary biotite and K-feldspar. Two distinct textural styles of auriferous pyrite can be distinguished: inclusion rich subhedral pyrite and inclusion free euhedral pyrite. It is common for the inclusion rich pyrite to have thick rims of inclusion free pyrite. The mineralising alteration is overprinted by barren, multi-phase quartz-carbonate, and carbonate-chlorite veins. This alteration is characterised by the assemblage calcite + siderite + chlorite ± quartz ± pyrite ± barite. The thesis then builds on the paragenetic framework through silicate and sulfide geochemistry. Biotite was identified as a primary mineral both in the metamorphic assemblage and gold-related hydrothermal alteration assemblage. The study of silicates was conducted through detailed core logging, petrography, SEM mineral identification of alteration assemblages, SWIR measurements and microprobe analyses of biotite in order to identify the nature of the mineralising fluid and its spatial effect across the Geita Hill deposit. Results show that the mineralised assemblage is slightly more oxidized (pyrite + magnetite) compared to the metamorphic background (pyrrhotite + magnetite). The intense sulfidation within the ore zone resulted in the formation of Mg-rich biotite, which grades into more Fe-rich biotite away from the ore zone. This change in biotite composition can be detected using short wavelength infrared spectra, though a shift in the Fe-OH 2250 nm absorption feature to lower wavelengths. This shift is also correlated with an increase in gold grade within the mineralised zone. Halogen chemistry of the biotite implied the presence of multiple hydrothermal fluids during mineralisation, suggesting that within the ore zone a metamorphic fluid in equilibrium with the host rock was overprinted by and mixed with an infiltrating fluid that was enriched in fluorine. Study of the sulfides in the deposit was conducted through laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of pyrite and magnetite grains. The gold distribution correlates well with Te, Ag, Bi and Pb consistent with its occurrence as micro- and nano-inclusions of gold bearing telluride minerals. As, Co and Ni distribution in pyrite grains hosted in quartz veins is patchy, whereas in pyrite grains from ironstone and diorite these elements show zoning characteristic of growth pattern. Elements including As, Ni, Co, Cu and Zn appear to be dominantly locally derived, and remobilised into the pyrite during sulfidation. The concentrations of these elements are highly lithologically controlled, and they are not consistently incorporated into the pyrite after initial stages of growth. Au, Ag, Te, Sn, Bi and Pb appear to be dominantly externally derived, and closely correlate in all varieties of pyrite. The Se content is typical of pyrite from Archean gold deposits (~30ppm) and reflects to an average temperature of ~340°C for the mineralising fluid on the basis of temperature dependent incorporation into pyrite. Lastly, the gold-bearing hydrothermal fluids were studied directly through detailed microthermometry and raman microspectroscopy, and three principle fluids were identified: (1) A low salinity, carbonic-rich (XCO₂ > 0.8) fluid with minor N₂ (XN₂/(XCO₂ + XN₂) 20 wt.%; NaCl/(NaCl+CaCl₂) mass ratio > 0.45), aqueous brine that was interpreted to be magmatic in origin; and (3) A low salinity (NaCl < 5 wt.%) aqueous fluid that was interpreted to be meteoric in origin. Preserved fluid assemblages imply mineralisation occurred at pressures of less than 2 kbar, likely from 1.4 to 1.7 kbar, at temperatures of approximately 350 °C. C-O-H fluid modelling of the carbonicrich fluid has constrained ƒO₂ fluid to 1.5-1.8 log10 units above ƒO₂ FMQ corresponding to absolute values of 10- 30.5 bar. The gold was likely transported in the high salinity brine as Au-bisulfide complexes with tellurium, potentially introduced as a vapour. Deposition of Au was triggered via interaction of gold-bearing fluids with the relatively reduced Fe-rich host rocks and the low salinity CO₂-rich fluid.

Onzon-Kanbani area is a western flank of Mogok Metamorphic Belt where gold mineralization is hosted as auriferous quartz-vein with epithermal low-sulphidation characters. Mineralization is closely associated with NE-SW trending fracture or shear zone probably related to the dextral movement of the Sagaing Fault system. Mineralization related hydrothermal alteration is developed as narrow zones beside of the hydrothermal conduit as silicic alteration, sericite-illite alteration, and propylitic alteration. Dominant alteration minerals are quartz, ±adularia, sericite, chlorite, actinolite, epidote, illite, and smectite. The quartz dominant and base metal quartz-carbonate mineralization veins are characterized by open-spaced fracture filling with sharp-walled as well as minor amounts of disseminating nature are also found in marble. Gold occurs as free grains or locked within pyrite, sphalerite, galena, and gangue mineral quartz. In place, large electrum gold grains are associated with sphalerite and pyrite in the gold bearing quartz vein whereas fine-grained inclusions or blebs of native gold are observed in pyrite and sphalerite as disseminated specks. Gold and base metal mineralization are mostly deposited in Stage I ‘mineralization stage’. In place, ‘Stage II’ is a barren stage where veins are barren as quartz or calcite veins with very minor amounts of pyrite. At the last ‘Stage III’, some of the supergene minerals of hematite, goethite, and chalcocite are formed from primary sulphides by oxidation. Mineralogically, the correlation between gold (Au) and silver (Ag) is shown the positive nature as well as in copper (Cu) too. Otherwise, gold (Au) versus any other ore minerals of lead (Pb), zinc (Zn), tin (Sn) and antimony (Sb) are displayed negative correlations. The gold and other ore mineral content are suggested that higher grade mineralization of these metal ores has reduced from mineralization vein to outer alteration zones.

Investigation of contaminant metal dispersal from a disused mine site at Tyndrum, Scotland, using concentration gradients and stable Pb isotope ratios