Metal cations and sulfate anions are released through oxidative weathering of sulfide minerals in the aerated or vadosezone. Supergene enrichment processes in porphyry systems. Veracruz,1, paul ashley,1 nancy vickery,1 and josh leigh2 1earth sciences, university of new england, new south wales, australia 2activex, brisbane, queensland, australia email, jose. Metal cations and sulfate anions are released through oxidative weathering of sulfide minerals in the aerated or vadosezone above the water table. Supergene mineralisation of the boyongan porphyry copper. Controls on supergene enrichment of porphyry copper deposits. Ehph conditions for supergene enrichment in sulfide ore bodies it may be stated, in a very simplified way, that supergene enrichment is a process in which metals of economic value are concentrated near the water table by the following pro cesses.
Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. A presentation on the topic of oxidationsupergene enrichment of sulfide ore deposits. Oxidation supergene enrichment linkedin slideshare. Supergene alteration of uraniumbearing veins in the united states by george w. Supergene enrichment of copper deposits since the mafiadoc. Definition weathering processes and supergene ore deposits conditions that influence supergene enrichment ideal starting material zones. Supergene activity at individual deposits lasted for at least 0. On the other hand, the residual gold enrichment, under supergene conditions, can be formed by ag dissolution from au ag hypogene particles bowell, 1992. Therefore, alteration of primary u minerals during supergene oxidation and enrichment can significantly contribute to the evolution of the landscape and can be used to constrain the physicochemical regime of weathering and hydrology fig. 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. In this work, we present the implication of the discovery. The minerals are altered and the structure is obliterated.
Gossan or the iron cap supergene sulphide ore enrichment. Loglog plot of volume versus f15 values in takhtegonbad deposit. Rna, beeper, failsafe, individual medley, taxi squad superis a prefix occurring originally in loanwords from latin, with the basic meaning above, beyond. Ore deposits formed by oxidation and supergene enrichment. L1 06 b explain the classification of mineral deposits. Supergene enrichment how natural processes have transformed lowgrade copper mineralization into economic ores by david f. This early supergene enrichment event is not represented by supergene alunite in the deposit because. The horizon of secondary enrichment is a zone highly enriched with metal, which is formed as a result of physical, chemical, biological and mechanical. The supergene enrichment blanket is overlain by an intensely altered and leached fe oxiderich gossan the remains of the original massive sulfide that extends.
Controls on supergene enrichment of porphyry copper. An orebody thus becomes oxidized and generally leached of many of its valuable materials down to the. The first stage of supergene enrichment is represented by the copperbearing ferruginous conglomerate unit in the southern little burro mountains. Supergene oxidation leaching and secondary sulfide enrichment in the sarcheshmeh porphyry cumo deposit generated a supergene profile to depths of 20 to 80 meters with oxide ore reserve about 22 mt. Supergene oxidized and enriched porphyry copper and. The process acts on elements with multiple oxidation states in a controlled complex manner related to ev, ph, and ionic matrix. Oof 1q4 supergene enrichment of precious metals by natural amalgamation in 2 the las cruces weathering pro. In a recent contribution to the problem of supergene alteration of copper ore deposits, anderson 195 5, following garrels 1954 summarizes the processes taking place as follows. Typical supergene enrichment phenomena in two of crosscuts are illustrated as in fig.
Initial products of supergene oxidation, copiapo mining. Published models that have strongly influenced exploration policy suggest that supergene enrichment ceased at 14 ma due to an increase in aridity. Yet it is only the very latest mesozoic and cenozoic porphyry copper deposits that have been subject to supergene oxidation and enrichment sillitoe 2005, in spite of the fact that the older. At or near the surface in the zone of oxidation, metal and sulfate ions are freed by the oxidation of sulphide minerals. The descending meteoric waters oxidize the primary sulfide ore minerals and.
During the early decades of the 20 th century, several eminent investigators proposed that silver sulfide enrichment beneath zones of oxidation is a widespread and economically important supergene process in silveronly and other silverrich deposits e. Persistencyfield ehph diagrams for sulfides and their. 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 oxidation and leaching processes have led to significant enrichment of porphyry and stratabound mantotype cu deposits, and the economic viability of these deposits is typically dependent on the size and quality of the supergene enrichment blanket that overlies the hypogene cusulfide zones 5, 6. Figure 2 shows the general succession of sulfide mineral destruction by chalcocite replacement, as observed from. Supergene mineralisation of the boyongan porphyry coppergold.
Arifudin idrus, sukamandaru prihatmoko, ernowo harjanto. Lindgren, 1933, a concept that has since become entrenched in the literature e. Supergene enrichment 11 effects of oxidation on mineral deposits. The supergene enrichment is the only process known to record these events. Supergene enrichment of copper deposits since the onset of. Supergene enrichment and hypogene zones are considered with f15 values 1. Implications for supergene oxidation and enrichment of porphyry copper deposits, transactions of the institution of mining and metallurgy, section b. Supergene processes are all but inactive under the hyperarid climatic conditions now prevailing in the chilean norte chico below ca. Fire enrichment of manganese ore is one of method which deals with high phosphorus, high iron refractory lean manganese ore, and it was known as the manganeserich.
The geologic history of oxidation and supergene enrichment in. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. Supergene oxidized and enriched porphyry copper and related. The green mineral atacamite cu2cloh3 is a major constituent of supergene zones in the atacama desert, and increasing evidence suggests that atacamitebearing oxide assemblages are late products of supergene enrichment, likely to have formed by the replacement of preexisting oxide assemblages during the passage of saline water cameron et. The paleoclimatic signatures of supergene metal deposits. At temperatures prevailing near the earths surface, metastable coexistence of chemical substances is common because chemical reactions that would directly lead to the attainment of thermodynamically. Supergene enrichment increased the grade of ore from i weight percent to as much as 20 weight percent. Persistencyfield ehph diagrams for sulfides and their application to supergene oxidation and enrichment of sulfide ore bodies. 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. Supergene definition and meaning collins english dictionary. Therefore supergene oxidation and enrichment processes were active from the early oligocene to the middle miocene, a minimum of 20 m. 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. Clark et al,1967, and consists entirely of djurleite. The supergene enrichment of gold in deposits may take place by a simple mechanical process, by chemical means, or by a combination of these.
There is only one supergene mineral of gold namely the native metal. Delineation of supergene enrichment, hypogene and oxidation. Pyrite is a ubiquitous mineral in quartz veins and its oxidation can contribute strongly to the oxidation and hydrolysis of iron or ferrolysis mann, 1984. Twentyfive samples of supergene alunite collected from deeply developed supergene profiles in porphyry copper deposits and prospects between latitudes 20 and 27 s in northern chile yield kar ages ranging from about 34 to 14 ma. Nevertheless, supergene silver enrichment certainly occurred at rochester and. 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. L2 06 c explain the origin, occurrence and distribution of copper ore deposits of india. The surface waters oxidize many ore minerals and yield solvents that dissolve other minerals. It forms during the supergene sulphide ore enrichment, when weakly acid surface water perloctaes through the mineral deposit. Other words that entered english at around the same time include. Hartley, aj 2003, neogene climate change in the andes.
Its age is bracketed by upper eoceneoligocene tuffs dated by 40ar39ar at 35. The thickness varies from 0 to 5 m, locally exceeding 10 m. Mature oxidation and enrichment are promoted by the following. The descending meteoric waters oxidize the primary sulfide ore minerals and redistribute the metallic ore elements. 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. The geologic history of oxidation and supergene enrichment. This results in an oxidized zone on top gossan, a supergene zone beneath and the. Geochemical distribution and behavior of trace metals associated with. Located near the surface, the leached cap and enrichment blanket are features that form as a result of the oxidation and weathering of the sulfide. Supergene processes are essentially the result of a form of chemical weathering.
In order for supergene enrichment to occur, oxidation of the surface minerals must occur. Supergene alteration of norwegian sulphide deposits a query. No effects of supergene oxidation, sensu stricto, are observed in the hand. Hypogene and supergene gobaltgopper sllfides, carrizal alto. 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. 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. Copper oxides represent an attractive exploration target because even lowgrade prospects have the potential to produce lowcost copper in an environmentally friendly fashion. Some characteristics of the oxidation zone of sulfide ore. These include giant supergene enriched deposits such as those at morenci in arizona 4. University of nevada, reno tectonic controls, timing and. The metallic substances are leached or are altered to new compounds. Harraz presentation supergene enrichment 2 outline of topic 9. 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.
Age of supergene oxidation and enrichment in the chilean. Contact the manufacturer magnese ore enrichment process vaibhavpackaging. Additionally, the ore deposit must contain iron sulfides and metals such. Highly acid lateritic weathering has caused supergene enrichment of uranium in the aluminum phosphate zone of the bone valley formation. Deep oxidation at boyongan has developed a thick supergene enrichment profile up to 600 meters which has a complex supergene mineralogy, consisting of chalcocite, digenite, pseudocovellite, native copper, cuprite, malachite, pseudomalachite, azurite, chrysocolla, pseudochrysocolla, and pseudoneotocite. Supergene gold enrichment in the castromilserra da quinta. During laterization in a previous wetter climate, au was mobilized in the near surface \ and. Morphology of zoning gossans and cappings oxidation and solution in. Here, we present a new application of the iodine129 isotopic method to iodinerich samples from the worlds largest supergene cu profile at the chuquicamata deposit in northern chile, where anomalous concentrations of this element have been reported. Largerscale mobilisation involved leaching of gold from up to 100mthick zones which were the target of historic mining, with up to 10. The region above the watertable in an ore deposit is. Derived from hypogene andor supergene sulfides, copper oxides comprise a. These episodes correspond to the periods during which sulphide minerals have been present in the zone of oxidation, and reflect the common tectonic history of repeated uplift, erosion and burial which all of the deposits share to varying degrees. The ore thus enriched forms the secondary, or supergene sulfide, zone and overlies the primary, or.
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. Ore deposits formed by oxidation and supergene enrichment when ore deposits are exposed to the oxidation zone they are weathered and altered with the country rocks. The central andes host some of the worlds largest porphyry copper deposits. Model question paper2 with effect from 201920 cbcs. Supergene enrichment how natural processes have transformed. Oxidation and secondary enrichment of gold deposits general principles gold deposits, subjected to oxidation, may become enriched near the surface both as a result of chemical processes involving the migration of gold and by the removal of soluble gangue and sulphides. The case of the booubyjan porphyry coppergold deposit, southeast queensland jose a. 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. In semiarid settings such as those in swa, two supergene enrichment zones of au are present. Supergene enrichment of ilmenite occurs through a complex series of reactions with initial oxidation and hydration followed by leaching and dehydration. Supergene gold in the goldbearing wastes of sulfide deposits.
An investigation into supergene silver enrichment at the rochester. 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. The economic viability of these deposits is dependent on the size and quality of their supergene enrichment blanket. Supergene zinc and residual lead enrichment processes peter k. In this particular case, the variable oxidation state element is copper.
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. As host for the largest and richest porphyry copper deposits. In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Iodine remobilization and supergene enrichment of copper. Gold in the supergene zones is commonly crystalline with octahedral shapes and nuggety forms which fill cavities and coat prismatic quartz crystals. It is known that in the supergene zone of sulfide deposits, as well as in the weathering crust, a horizon of secondary enrichment is formed smirnov 1951. Lateritization appears to be associated with the early phase of the supergene process and if ilmenite grains are encased in iron oxides no further alteration proceeds. Oxidation and secondary enrichment of gold deposits general principles gold deposits, subjected to oxidation, may become enriched near the surface both as a result of chemical processes involving the migration of gold and by the removal of soluble.
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