Supergene sulphide enrichment pdf

At the ashanti concession, ghana, goldbearing quartz veins and disseminated sulphide lodes occur in narrow m shear zones with altered argillites and metatholeiite host rocks. The descending meteoric waters oxidize the primary sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment of the khanong copper resource, sepon. It forms during the supergene sulphide ore enrichment, when weakly acid surface water perloctaes through the mineral deposit. In situ supergene enrichment of the sulphide protore has resulted in a highgrade chalcociteclay zone 10. In this work, we present the implication of the discovery. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering.

The fact that wellauthenticatedsupergene parageneses have. The ore thus enriched forms the secondary, or supergene sulfide, zone and overlies the primary, or. Definition weathering processes and supergene ore deposits conditions. Domingos massive sulphide orebodies is described and correlated with the supergene kaolinitehalloysite alteration observed. Significance of supergene enrichment supergene sulphide enrichment is the natural upgrading of buried sulphide deposits by the secondary deposition of metals dissolved in waters percolating through the rock generally from surface down. Gold 111 salts of oxyanions are not very stable, but complex auric sulphates of the type auso, are known. These include giant supergene enriched deposits such as those at morenci in arizona 4. The formation of secondary concentrations of ni co significant enough for an economic resource requires a protolith lithology that is primarily enriched in ni.

Definitions definition from evans leaching of valuable elements from the upper parts of mineral deposits and their precipitation at depth to produce higher concentrations definition from guilbert and park supergene enrichment occurs when oxidizing acids dissolve metal ions from the protore and redeposited it in more. Supergene enrichment how natural processes have transformed. The supergene enrichment is the only process known to record these events. Supergene oxidized and enriched porphyry copper and related. Metavolcanic host rocks, mineralization, and gossans of the. In the iberian pyrite belt ipb, most of the volcanogenic massive sulphide deposits and related stockworks are capped by a more or less well developed and preserved gossan. Supergene features and evolution of gossans capping. Concentrating minerals by chemical weathering processes. Introduction ore deposits are crustal concentrations of useful elements that can be exploited at a pro. The supergene enrichment blanket is overlain by an intensely altered and leached fe oxiderich gossan the remains of the original massive sulfide that extends upward to the paleosurface. Detailed descriptions of supergene mineralization in the ipb are scarce. The main nickel and copper supergene enrichment zone is located near the central axis of target 19 positioned roughly over two peridotite layers defined by the recent aircore and diamond drilling. The economic viability of these deposits is dependent on the size and quality of their supergene enrichment blanket.

Definition secondary or supergene enrichment where leaching of materials occurs and precipitation at depth produces higher concentrations. Supergene gold enrichment in the castromilserra da quinta. First, the enrichment may be primarily the result of the chemical removal of a large part of the gangue minerals, in which case the gold migrates slowly downward by gravity or is left behind as a residual. Below the water table is a zone of supergene enrichment in which secondary sulfide minerals such as covellite and chalcocite form from chalcopyrite and copper sulfate in. The earliest mineral workings in the ipb gossans back as far as ca. Occasionally, some of the leachedout soluble metals can reprecipitate below the water table developing zones of secondary sulphide enrichment chavez, 2000, williams, 1990. In the more than 50 years which have elapsed since the recognition and characterization of the phenomena of supergene oxidation and enrichment, this economically significant topic has received remarkably little attention. Metals that have been leached from the oxidized ore are carried downward by percolating groundwater, and react with hypogene sulfides at the supergene hypogene boundary. However, harvesting microorganisms from the supergene zone and using them. The geologic history of oxidation and supergene enrichment in. The mineralisation is concealed by up to 10 m of kaolinitemica forest ochrosol soils, beneath which is a saprolitic zone of leached rock extending down 6070 m to the hypogene ore zone. Multiphase origin of the cuco ore deposits in the western. In ore deposit geology, hypogene processes occur deep below the earths surface, and tend to form deposits of primary minerals, as opposed to supergene processes that occur at or near the surface, and tend to form secondary minerals. Supergene features and evolution of gossans capping massive.

Verwoerd 1957 recognised that vanadium deposition occurred substantially later than sulphide emplacement. The contrasting sites in this study represent a progression in the development of supergene conditions that occur in relatively high energy fluvial settings. Mineral deposition was controlled mainly by ph conditions, p co2, metal ion activities e. Geological background the lavrion area is part of the attic cycladic crystalline belt, which is a. Formation of supergene minerals took place under near. However, the oftencomplex mineralogy of supergene ores poses serious challenges to extractive metallurgy or mineral processing, and many supergene enrichment blankets will remain unmined or unprocessed until such time as viable metallurgical processes can be developed.

Download limit exceeded you have exceeded your daily download allowance. Initial products of supergene oxidation, copiapo mining. Supergene enriched, intrusion related low suphidation. Supergene gold mobility in orogenic gold deposits, otago schist, new zealand. Age of supergene ore bodies at berg aukas and harasib. Controls on supergene enrichment of porphyry copper. Nico laterites are supergene deposits of ni co formed from the pervasive chemical and mechanical weathering of ultramafic rocks. Supergene oxidized and enriched porphyry copper and. At the contact of oxidised and sulphide ores lies a supergene zone of enrichment which has provided a contrast, not formerly imagined, to eluras primary development and stoping operations. Geology and origin of supergene ore at the lavrion pb.

Metavolcanic host rocks, mineralization, and gossans of. As host for the largest and richest porphyry copper deposits. Supergene gold mobility in orogenic gold deposits, otago schist, new zealand 5 ore, and a substantially greater proportion of that nearsurface gold was free particles fig. Tharsis, rio tinto, were also mined during roman times for precious metals velasco et al. Q for geologists about supergene enrichment supertopo. Since the rio tinto deposits are in many ways analogous with the norwegian massive sulphide deposits, it would seem logical to expect that a supergene enrichment zone, in the case of the latter, would also contain much chalcocite. In this particular case, the variable oxidation state element is copper. Residual mineral deposits an existing mineral deposit can be turned in to a more highly concentrated mineral deposit by weathering in a. The stratiform mineralization form the largest group and can be found mainly in lower roan r2 rocks, which can be identi.

Ore deposits outside the r2 occur along lineaments and result often from supergene enrichment. These results suggest a supergene enrichment in upper zones of the deposit. A very highgrade in situ to exotic limoniteclay cuoxidemineral zone is locally developed above impermeable dolomite at the base of chalcociteclay zone. The characterization of the hydrothermal and supergene alterations was based on detailed mapping, extensive use of the pima short wave infrared spectrometer, petrography, xrd and microprobe. The unusual style of hypogene mineralisation and unique set of conditions have resulted in the development and preservation of a supergeneenriched profile in. Oxidation and secondary enrichment of gold deposits. The development and evolution of supergene gold and. Harraz presentation supergene enrichment 2 outline of topic 9.

The paleoclimatic signatures of supergene metal deposits. Geology and origin of supergene ore at the lavrion pbag. Important gossans developed from primary volcanogenic massive sulfide vms deposits are preserved and described in the iberian pyrite belt ipb, and some of them e. Evidence for the supergene origin of alunite in sediment. This is so because it denotes a concretion of iron hydroxides that has formed on top of sulphide mineral vein, where it reaches the surface. Supergene sulfide enrichment, in geology, natural upgrading of buried sulfide deposits by the secondary or subsequent deposition of metals that are dissolved as sulfates in waters percolating through the oxidized mineral zone near the surface. In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Metal cations and sulfate anions are released through oxidative weathering of sulfide minerals in the aerated or vadosezone.

However, the activities of microorganisms in secondary copper deposition sillitoe et al. The khanong supergeneenriched copper resource, 23 mt at 3. Definition of supergene enrichment a mineral deposition process in which nearsurface oxidation produces acidic solutions that leach metals, carry them downward, and reprecipitate them, thus enriching sulfide minerals already present. Sulphide minerals are unstable to highly unstable in surface conditions, as witnessed by the collection curators headache known as pyritedecay, which can turn a freshly collected shiny pyritized ammonite into a pile of stinking, sulphurous fragments within weeks in the worst cases. Supergene px0308 supergene px0309 supergene px0310 supergene px0311 157. The central andes host some of the worlds largest porphyry copper deposits. The ore thus enriched forms the secondary, or supergene sulfide, zone and overlies the primary, or hypogene, zone. Many sulphide ores are oxidised in this process and brought into solution.

Controls on supergene enrichment of porphyry copper deposits. Sulfide oxidation and leaching of ore deposits in the weathering environment, and any attendant secondary sulfide enrichment, are supergene processes ransome, 1912, implying that they are products of descending aqueous solutions of surface derivation. Below the water table is a zone of supergene enrichment in which secondary sulfide minerals such as covellite and chalcocite form from chalcopyrite and copper sulfate in solution. The process acts on elements with multiple oxidation states in a controlled complex manner related to ev, ph, and ionic matrix. Supergene sulphides and related minerals in the supergene. Jul 09, 2015 the main nickel and copper supergene enrichment zone is located near the central axis of target 19 positioned roughly over two peridotite layers defined by the recent aircore and diamond drilling.

The supergene enrichment of gold in deposits may take place by a simple mechanical process, by chemical means, or by a combination of these. The age of the supergene ore is poorly constrained, but presumably pliocene. Published models that have strongly influenced exploration policy suggest that supergene enrichment ceased at 14 ma due to an increase in aridity. Copper sulfide enrichment in supergene deposits has largely been considered an abiotic process brimhall, et al. Report on the ore mineralogy of samples from the lagoa. The development and evolution of supergene gold and sulphide mineralisation that occurs in quartz pebble conglomerates qpcs from two contrasting environments is investigated. The development and evolution of supergene gold and sulphide.

You can see the oxidation zone, consisting of the gossan, the leached zone and the oxidised zone. The enriched ore forms the supergene zone above the primary or hypogene zone. Such complexes may be present where the oxidation potential is high in oxidizing sulphide zones and where h,so, and an. Supergene enrichment is essential for the economic viability of many porphyry copper deposits reich and vasconcelos 2015 this issue, and determining when and how supergene enrichment has occurred is important when exploring for enriched and exotic copper deposits mote et al. Supergene sulphide enrichment is the natural upgrading of buried sulphide deposits by the secondary deposition of metals dissolved in waters percolating through the rock generally from surface down. Mcqueen crc leme, australian national university, canberra, act 0200 and school of rehs, university of canberra, act 2601. Mature oxidation and enrichment are promoted by the following. Although these environments might be distin guished by their geologic characteristics, alunite in sedimenthosted micron gold deposits has been. Oxidation supergene enrichment linkedin slideshare. The enriched ore forms the supergene zone above the primary or hypogene zone and in some cases can hold as much as ten times the original metal. Because of the soft nature of the ore, intense ground support practice has been combined with a panel cut and fill continuous mining system to extract a.

Superposition of the advanced oxidation of colloform pyrite, an enrichment in impurities sphalerite, galena, and tennantite from the primary ores, stagnant water conditions, an elevation of the water table during oxidation, and bacterial activity led to supergene concentrations of the base metals as sulphide, selenides or sulphosalts. Supergene alunite also termed secondary supergene by hayba et al. Gossan or the iron cap supergene sulphide ore enrichment. The geologic history of oxidation and supergene enrichment.

Alunite veins versus supergene kaolinitehalloysite. Supergene sulfide enrichment, also called secondary enrichment, in geology, natural upgrading of buried sulfide deposits by the secondary or subsequent deposition of metals that are dissolved as sulfates in waters percolating through the oxidized mineral zone near the surface. At great depth the pressure is high, and water can remain liquid at temperatures well above 100 c. Aircore drilling doubles nickel and copper supergene. The porphyry copper deposits of southwestern north america were developed in a continental margin cratonic setting, above a subduction zone that was active largely from the early mesozoic to. Supergene alteration of norwegian sulphide deposits a query.