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. On the other hand, the residual gold enrichment, under supergene conditions, can be formed by ag dissolution from au ag hypogene particles bowell, 1992. 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. 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 metallic substances are leached or are altered to new compounds.
Supergene enrichment 11 effects of oxidation on mineral deposits. The horizon of secondary enrichment is a zone highly enriched with metal, which is formed as a result of physical, chemical, biological and mechanical. L2 06 c explain the origin, occurrence and distribution of copper ore deposits of india. As host for the largest and richest porphyry copper deposits. Iodine remobilization and supergene enrichment of copper. Highly acid lateritic weathering has caused supergene enrichment of uranium in the aluminum phosphate zone of the bone valley formation. Mature oxidation and enrichment are promoted by the following. Persistencyfield ehph diagrams for sulfides and their.
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. 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 gold enrichment in the castromilserra da quinta. 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 geologic history of oxidation and supergene enrichment. At or near the surface in the zone of oxidation, metal and sulfate ions are freed by the oxidation of sulphide minerals. This results in an oxidized zone on top gossan, a supergene zone beneath and the. 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. Therefore supergene oxidation and enrichment processes were active from the early oligocene to the middle miocene, a minimum of 20 m.
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. No effects of supergene oxidation, sensu stricto, are observed in the hand. In this particular case, the variable oxidation state element is copper. In order for supergene enrichment to occur, oxidation of the surface minerals must occur.
Implications for supergene oxidation and enrichment of porphyry copper deposits, transactions of the institution of mining and metallurgy, section b. The minerals are altered and the structure is obliterated. Copper oxides represent an attractive exploration target because even lowgrade prospects have the potential to produce lowcost copper in an environmentally friendly fashion. Supergene enrichment how natural processes have transformed. Other words that entered english at around the same time include. There is only one supergene mineral of gold namely the native metal.
The first stage of supergene enrichment is represented by the copperbearing ferruginous conglomerate unit in the southern little burro mountains. 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. Clark et al,1967, and consists entirely of djurleite. 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. 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. In this work, we present the implication of the discovery. 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. An orebody thus becomes oxidized and generally leached of many of its valuable materials down to the. L1 06 b explain the classification of mineral deposits. Supergene oxidized and enriched porphyry copper and related. The central andes host some of the worlds largest porphyry copper deposits. Model question paper2 with effect from 201920 cbcs. Supergene gold in the goldbearing wastes of sulfide deposits. It forms during the supergene sulphide ore enrichment, when weakly acid surface water perloctaes through the mineral 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. 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. Derived from hypogene andor supergene sulfides, copper oxides comprise a. Nevertheless, supergene silver enrichment certainly occurred at rochester and. Arifudin idrus, sukamandaru prihatmoko, ernowo harjanto. 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. Loglog plot of volume versus f15 values in takhtegonbad deposit. Supergene enrichment of copper deposits since the mafiadoc. 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. A presentation on the topic of oxidationsupergene enrichment of sulfide ore deposits. University of nevada, reno tectonic controls, timing and. 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. 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.
Supergene activity at individual deposits lasted for at least 0. 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. Contact the manufacturer magnese ore enrichment process vaibhavpackaging. In ore deposit geology, supergene processes or enrichment are those that occur relatively near. Initial products of supergene oxidation, copiapo mining. The paleoclimatic signatures of supergene metal 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. Supergene enrichment processes in porphyry systems. 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.
Oxidation supergene enrichment linkedin slideshare. Supergene alteration of uraniumbearing veins in the united states by george w. Supergene enrichment increased the grade of ore from i weight percent to as much as 20 weight percent. Hartley, aj 2003, neogene climate change in the andes. Supergene enrichment of copper deposits since the onset of. Figure 2 shows the general succession of sulfide mineral destruction by chalcocite replacement, as observed from. 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 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. 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. Age of supergene oxidation and enrichment in the chilean. Its age is bracketed by upper eoceneoligocene tuffs dated by 40ar39ar at 35.
This early supergene enrichment event is not represented by supergene alunite in the deposit because. Supergene processes are all but inactive under the hyperarid climatic conditions now prevailing in the chilean norte chico below ca. Geomorphologic environment and age of supergene enrichment of. The geologic history of oxidation and supergene enrichment in. Metal cations and sulfate anions are released through oxidative weathering of sulfide minerals in the aerated or vadosezone. 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. Gold in the supergene zones is commonly crystalline with octahedral shapes and nuggety forms which fill cavities and coat prismatic quartz crystals. During laterization in a previous wetter climate, au was mobilized in the near surface \ and. In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. 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. 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. Controls on supergene enrichment of porphyry copper. The descending meteoric waters oxidize the primary sulfide ore minerals and. 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.
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. Metal cations and sulfate anions are released through oxidative weathering of sulfide minerals in the aerated or vadosezone above the water table. An investigation into supergene silver enrichment at the rochester. 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. Supergene mineralisation of the boyongan porphyry copper. Largerscale mobilisation involved leaching of gold from up to 100mthick zones which were the target of historic mining, with up to 10. The ore thus enriched forms the secondary, or supergene sulfide, zone and overlies the primary, or. Harraz presentation supergene enrichment 2 outline of topic 9.
Supergene enrichment and hypogene zones are considered with f15 values 1. Persistencyfield ehph diagrams for sulfides and their application to supergene oxidation and enrichment of sulfide ore bodies. Supergene zinc and residual lead enrichment processes peter k. Gossan or the iron cap supergene sulphide ore enrichment. These include giant supergene enriched deposits such as those at morenci in arizona 4. 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 mineralisation of the boyongan porphyry coppergold. The descending meteoric waters oxidize the primary sulfide ore minerals and redistribute the metallic ore elements. Supergene processes are essentially the result of a form of chemical weathering. Supergene oxidized and enriched porphyry copper and. 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. 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. Supergene definition and meaning collins english dictionary. Morphology of zoning gossans and cappings oxidation and solution in. The thickness varies from 0 to 5 m, locally exceeding 10 m.
The process acts on elements with multiple oxidation states in a controlled complex manner related to ev, ph, and ionic matrix. The surface waters oxidize many ore minerals and yield solvents that dissolve other minerals. Supergene enrichment of ilmenite occurs through a complex series of reactions with initial oxidation and hydration followed by leaching and dehydration. Oxidation and secondary enrichment of gold deposits. The supergene enrichment blanket is overlain by an intensely altered and leached fe oxiderich gossan the remains of the original massive sulfide that extends. The supergene enrichment of gold in deposits may take place by a simple mechanical process, by chemical means, or by a combination of these. 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. Some characteristics of the oxidation zone of sulfide ore.
In semiarid settings such as those in swa, two supergene enrichment zones of au are present. Lindgren, 1933, a concept that has since become entrenched in the literature e. The case of the booubyjan porphyry coppergold deposit, southeast queensland jose a. Controls on supergene enrichment of porphyry copper deposits. Published models that have strongly influenced exploration policy suggest that supergene enrichment ceased at 14 ma due to an increase in aridity. The region above the watertable in an ore deposit is. Delineation of supergene enrichment, hypogene and oxidation. Typical supergene enrichment phenomena in two of crosscuts are illustrated as in fig. Geochemical distribution and behavior of trace metals associated with. Additionally, the ore deposit must contain iron sulfides and metals such. 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.
Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. 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. Definition weathering processes and supergene ore deposits conditions that influence supergene enrichment ideal starting material zones. Supergene alteration of norwegian sulphide deposits a query. The economic viability of these deposits is dependent on the size and quality of their supergene enrichment blanket. Hypogene and supergene gobaltgopper sllfides, carrizal alto. Supergene enrichment how natural processes have transformed lowgrade copper mineralization into economic ores by david f. The supergene enrichment is the only process known to record these events.