Porphyry copper deposit

Morenci Mine quarry 2012. Red rocks on the upper ledges and outcrops in the background are in a leached cap.
The bottom of the quarry appears to be in a mixed oxide-sulphide zone, and this is also what the two tractors in the foreground are hauling. Click to enlarge photo. Bingham Canyon Mine in 2005. The gray rocks visible in the quarry are almost all primary sulfide ore zones. Porphyry copper deposits

are copper ore bodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Preceding these fluids or associated with them are vertical dikes, porphyritic intrusive rocks from which the name of this type of deposit comes. In later stages, circulating meteoric fluids may interact with magmatic fluids. Successive envelopes of hydrothermal alteration typically involve a core of disseminated ore minerals, often stockwork-forming microfractures and veins. Due to their large volume, porphyry orebodies can be profitable at copper grades as low as 0.15%. copper and may have economical amounts of by-products such as molybdenum, silver, and gold. In some mines these metals are the main product.

The first development of low-grade porphyry copper deposits from large open-pit mines roughly coincided with the introduction of steam shovels, the construction of railroads, and increased market demand in the early 20th century. Some mines develop porphyry deposits that contain ample gold or molybdenum but little or no copper.

Porphyry copper deposits are currently the largest source of copper ore. Most known porphyries are concentrated in: western regions. and North America and Southeast Asia and Oceania - along the Pacific Ring of Fire; then the Caribbean; south central Europe and area around eastern Turkey; scattered areas in China, the Middle East, Russia, and the CIS countries; and eastern Australia.[1][2] Only a few are reported in Africa, in Namibia[3] and Zambia;[4] none are known in Antarctica. The greatest concentration of the largest copper porphyries is found in northern Chile. Almost all mines that exploit large porphyry deposits produce open pits.

Content

1 Geological overview 1.1 Geological background and economic significance
1.2 Magmas and mantle processes
1.3 Tectonic and structural controls

2 Characteristics

3 Examples

3.1 Mexico

3.2 Chile

3.3 Peru

3.4 United States

3.5 Indonesia

3.6 Australia

3.7 Papua New Guinea

3.8 Other

4 Porphyry ore deposits for metals other than copper

5 Recommendations

Geological review

Geological background and economic significance

Porphyry copper deposits represent an important resource and the main source of copper mined today to meet global demand.[5] By summarizing geological data, it was determined that most porphyry deposits are Phanerozoic in age and were deposited at depths of approximately 1 to 6 kilometers with a vertical thickness averaging 2 kilometers.[5] During the Phanerozoic, 125,895 porphyry copper deposits were formed; however, 62% of them (78,106) were removed by uplift and erosion.[5] Thus, 38% (47,789) remains in the crust, of which 574 known deposits are at the surface.[5] Earth's porphyry copper deposits are estimated to contain approximately 1.7 × 1011 tons of copper, equivalent to more than 8,000 years of global ore production.[5]

Porphyry deposits represent an important copper resource; however, they are also important sources of gold and molybdenum, with porphyry deposits being the main source of the latter.[6] In general, porphyry deposits are characterized by a low degree of ore mineralization, a porphyry intrusive complex surrounded by veined stockworks and hydrothermal breccias.[7] Porphyry deposits form in arc-related settings and are associated with subduction zone magmas.[6] Porphyry deposits are clustered in discrete mineral provinces, meaning that there is some form of geodynamic control or crustal influence influencing where the porphyry is formed.[7] Porphyry deposits tend to be linear, orogen-parallel belts (eg the Andes in South America).[8]

There are also discrete periods of time in which the formation of porphyry deposits was concentrated or favored. The formation of copper-molybdenum porphyry deposits is mainly concentrated in three time periods: Paleocene-Eocene, Eocene-Oligocene, and middle Miocene-Pliocene.[7] For both porphyry and epithermal gold deposits, gold deposits are generally dated to the Middle Miocene to Recent period,[7] however notable exceptions are known. Most large porphyry deposits are less than 20 million years old,[7] however there are notable exceptions such as the 438 million year old Cadia Ridgeway deposit in New South Wales. This relatively young age reflects the preservation potential of this deposit type; as they are usually located in areas of highly active tectonic and geological processes such as deformation, uplift and erosion.[7] However, it may be that the bias towards a majority of deposits being less than 20 million years old is at least partly an artifact of exploration methodology and model assumptions, since large examples are known in areas that were previously only partially or partially remaining due to insufficient intelligence. to their supposed older host rock age, but were later found to contain large, world-class examples of much older porphyry copper deposits.[ citation needed

]

Magmas and mantle processes

In general, most large porphyry deposits are associated with calc-alkaline intrusions, although some of the largest gold-rich deposits are associated with high-potassium calc-alkaline magmas.[7] Numerous world-class copper-gold porphyry deposits are located in high-potassium or shoshonitic intrusions, such as the Bingham Copper-Gold Mine in the United States, the Grasberg Copper-Gold Mine in Indonesia, the Northparks Copper-Gold Mine in Australia, the Oyu Tolgoi Copper-Gold Mine in Mongolia and Gerbil copper-gold prospect in Russia.[9]

It is generally believed that the magmas responsible for the formation of porphyries are formed by partial melting of the top of post-subduction stuck plates altered by seawater.[10] Shallow subduction of young floating slabs can lead to the formation of adakite lavas through partial melting.[6] On the other hand, metasomatized mantle wedges can produce oxidized conditions that cause sulfide minerals to release ore minerals (copper, gold, molybdenum), which can then be transported to the upper levels of the Earth's crust.[10] Mantle melting can also be caused by transitions from a convergent to a transform margin, as well as by the steepening and retreat of a subducted slab trench.[10] However, recent belief is that dehydration occurs at the blueschist-eclogite transition affecting most subducted plates rather than partial melting.[6]

After dehydration, solute-rich fluids are released from the slab and metasomatize the overlying layers. mantle wedge of MORB-like asthenosphere, enriching it with volatile and large ionic lithophile elements (LILE).[6] It is now believed that the generation of andesitic magmas is multistage and involves crustal melting and assimilation of primary basaltic magmas, accumulation of magma at the base of the crust (covering with dense mafic magma as it rises), and homogenization of the magma.[6] The lower layer magma will add a lot of heat to the base of the Earth's crust, thereby causing melting of the Earth's crust and assimilation of lower crustal rocks, creating an area of intense interaction between mantle magma and crustal magma.[6] This progressively evolving magma will become enriched in volatiles, sulfur, and incompatible elements—the ideal combination to generate magma capable of forming ore deposits.[6] From this point on, the development of a porphyry deposit requires ideal tectonic and structural conditions to transport magma and ensure its placement in the upper layers of the earth's crust.

Tectonic and structural control

Although porphyry deposits are associated with arc volcanism, they are not typical products in this environment. Tectonic changes are thought to be the trigger for the formation of porphyry.[7] There are five key factors that can lead to the development of porphyries: 1) compression preventing magma from rising through the crust, 2) the resulting larger shallow waters. magma chamber, 3) increased fractionation of magma along with saturation of volatiles and formation of magmatic-hydrothermal fluids, 4) compression limits the development of branches into the surrounding rock, thereby concentrating the fluid into a single reservoir, and 5) rapid uplift and erosion promotes decompression and efficient, possible ore deposition.[11]

Porphyry deposits are typically mined in regions that are low-angle (planar) subduction zones.[7] And a subduction zone that goes from normal to flat and then back to normal subduction causes a number of effects that can lead to the formation of porphyry deposits. Initially there will be reduced alkaline magmatism, horizontal shortening, hydration of the lithosphere over a flat plate and low heat flow.[7] Once normal subduction returns, the hot asthenosphere will again interact with the hydrated mantle, causing wet melting, melting of the Earth's crust as the mantle passes through, and thinning and weakening of the lithosphere due to increased heat flow.[7] The subducting plate can be uplifted by seismic ridges, seamount chains, or oceanic plateaus, which can provide favorable conditions for the development of a porphyry deposit.[7] This interaction between subduction zones and the aforementioned oceanic features may explain the development of several metallogenic belts in the region; since whenever a subduction zone interacts with one of these features, it can lead to ore formation.[7] Finally, in oceanic island arcs, ridge subduction can lead to slab flattening or arc inversion; whereas in continental arcs it can lead to periods of flat plate subduction.[7]

Arc reversal has been shown to occur slightly before the formation of porphyry deposits in the southwest Pacific after the impact.[12] An arc overturn occurs due to a collision between an island arc and another island arc, continent, or oceanic plateau.[10] The collision could stop subduction and thus cause mantle melting.[10]

Porphyry deposits generally do not have the necessary structural controls for their formation; although basic flaws and facial features are associated with some.[10][13] The presence of intra-arc fault systems is useful because they can localize porphyry development.[8] In addition, some authors have indicated that the occurrence of intersections between continental-scale transverse fault zones and arcuate structures is associated with the formation of porphyries.[8] This is actually the case of Chile's Los Bronces and El Teniente Porphyry Copper deposits, each of which lies at the intersection of two fault systems.[13]

Gold-molybdenum-copper-porphyry occurrences of the Borgulican ore field

Gold-molybdenum-copper-porphyry occurrences of the Borgulican ore field

In the consolidated works of N.I. Barakov (1988), A.I. Lobov et al. (1996), I.A. Vasiliev and V.P. Kapanin (2000), the presence in the Amur region of a certain potential for the discovery and development of large-volume objects with gold-molybdenum-copper-porphyry type of mineralization. First of all, this applies to the western part of the Umlekano-Ogodzha metallogenic zone, which corresponds to the area of development of the volcanoplutonic belt of the same name. Within this territory, several promising areas are known, the mineralization of which is presumably associated with large copper-porphyry ore-magmatic systems (Borgulikanskoye and Verkhnetygdinskoye ore fields, Taldansky, Umlekano-Yasnensky, Elna-Adamikha ore clusters, etc.). A characteristic feature of these objects is the constant presence of high concentrations of gold (0.2-1.0 g/t) in veinlet-disseminated ores with ordinary contents of copper and molybdenum. Based on a set of characteristics, some of the ore occurrences in the territory under consideration can be compared with known domestic and foreign gold-bearing porphyry copper deposits, primarily in the Philippines, Australia and Canada.

The efficiency of searching and assessing objects of this geological and industrial type within the Umlekano-Ogodzhinsky zone can be increased through the development and application of a regional geological prospecting model. Ore occurrences of the most studied Borgulican ore field can be used as a standard for creating such a model.

The Borgulican potential ore field is confined to the Cretaceous Umlekano-Ogodzhinsky volcanoplutonic belt and is localized on the northeastern periphery of the Gonzhinsky ledge of the Bureinsky middle massif. Zones of hydrothermal-metasomatic alterations and anomalous contents of gold, molybdenum and copper have been known here since the late 50s (Rasskazov et al., 1959). Subsequently, these manifestations were studied by I.P. Volskaya (1978), N.G. Korobushkin (1988), N.I. Barakov (1-995). Thematic work was carried out by N.V. Kotov and L.G. Poritskaya (1995), Yu.K. Kudryavtsev (2000), etc. Currently, search work is continuing here by the FGUGP “Dalgeofizika”.

Previous long-term geological prospecting work made it possible to identify within the ore field the three most promising areas in the rank of ore occurrences (Ikansky, Borgulikansky and Arbinsky) with veinlet-disseminated gold-molybdenum-copper mineralization, presumably attributed to the porphyry type.

We carried out a comprehensive reinterpretation of the accumulated material based on methodological approaches to the study and forecasting of porphyry-type deposits developed at TsNIGRI. In this case, such fundamental patterns of the geological structure of deposits of this type were used, such as the conformity of the morphology of stockwork ore bodies to ore-bearing porphyry intrusions, the concentric zonality of the distribution of ore concentrations, the coincidence of the general orientation of ore bodies with the prevailing orientations of systems of mineralized fractures, the regular structure of zonal ore-metasomatic halos, etc. This approach made it possible to link data from drilling a rare network of exploratory wells and areal geophysical and geochemical surveys and, on this basis, clarify the conditions for localizing predicted ore bodies.

The ore occurrences of the Borgulican ore field are considered together, since the work carried out showed the fundamental similarity of the main features of their composition and structure.

The area of the Borgulikansky ore field is composed of rocks of the Early Cretaceous volcanoplutonic association, including volcanics of the Taldan Formation and intrusive formations of the Burinda complex that break through them. Volcanic rocks vary in composition from dacites to andesites and are classified into effusive, pyroclastic and subvolcanic facies. The main phase of the plutonic complex is represented by porphyritic fine-medium-grained biotite-hornblende quartz monzodiorites, composing a relatively large massif directly to the north of the ore field. The average mineral composition of these rocks is as follows, %: plagioclase (andesine N 40-50) - 40, K-feldspar - 25, dark-colored (hornblende and biotite) - 21, quartz - 13, accessory - 1. The “porphyry phase” of the complex is composed of biotite- hornblende quartz monzodiorite porphyrites, forming an en-echelon system of thick, steeply dipping plate-shaped bodies (“porphyry intrusion”). These are rocks with a clearly defined serial-porphyry structure. In the most common varieties, the amount of porphyry is about 50%. Phenocrysts predominantly 2-6 mm in size (with variations from 0.3 to 8-10 mm) are represented mainly by plagioclase (61%) and hornblende (25%), to a lesser extent by biotite, K-feldspar and quartz. The groundmass is holocrystalline, its structure is microgranite with microhypidiomorphic granular elements. Grain size ranges from 0.01 to 0.03 mm. The composition of the groundmass is predominantly K-feldspar-quartz with subordinate plagioclase, biotite and hornblende. The mineral composition of porphyries, taking into account the quantitative ratios of the main rock-forming minerals of phenocrysts and the groundmass, is as follows, %: plagioclase - 55.9, K-feldspar - 27.7, quartz - 17.3, biotite - 5.3, hornblende -13.5, accessory - 0.3 (quantitative calculations were performed by V.G. Sapozhnikov, TsNIGRI).

In the deep and central parts of porphyry intrusions, the degree of decrystallization of the groundmass increases slightly, and here its composition is dominated by grains measuring 0.02-0.04 mm. As they approach the contacts of the porphyry intrusion, quartz monzodiorite porphyrites gradually transform into contact varieties with poor crystallization of the main mass of the microfelsite, and in some cases micropoikilitic structure, as well as a relatively small amount of phenocrysts (up to 35-40%).

Late formations of the intrusive complex include (biotite)-hornblende quartz monzodiorite porphyrites of the dike series - rare porphyry (20-25%) rocks with a macroscopically observed prismatic-granular structure of the groundmass. Phenocrysts ranging in size from 0.4 to 6 mm are represented by plagioclase, amphibole and biotite. Characteristic is the absence of quartz and K-feldspar phenocrysts. The groundmass is characterized by a distinct hypidiomorphic granular structure and consists of laths (0.05–0.15 to 0.3 mm) of plagioclase, amphiboles and xenomorphic micrograins of quartz and potassium feldspar.

Objects of the Borgulikansky ore field are confined to a series of complex porphyry intrusions of the Burinda complex, breaking through the thick volcanogenic strata of the Taldan Formation and stretching in a chain along the large Borgulikansky fault with an east-northeast orientation. Along this fault they are separated from the massif located to the north and composed of the main phase of intrusion of the Burindin complex. The thickness of the porphyry intrusions (the width of the outcrop across the strike) is from 400-600 (Ikan) to 1500 m (Borgulican) with a length of 2200 and 1500 m, respectively. At the same time, the available data suggest that they are formed by partially merging en-echelon plate-shaped bodies with a thickness of 200 -250 m. According to a number of sections, the splitting of such bodies according to uprising, dip and extension into even thinner steeply dipping apophyses is established. In general, a fairly consistent predominant east-southeast orientation of the porphyry bodies is outlined, but a number of apophyses change this direction to sublatitudinal, and possibly even northeastern. The estimated dip of the porphyry bodies is steep, in northern directions. This orientation is justified based on an analysis of the structure of the entire ore-magmatic system, taking into account the principle of conformity of mineralized zones to the core ore-bearing porphyry intrusion. Note that the sharp predominance of steeply dipping (to subvertical) fracture orientations observed in borehole cores and trenches suggests a very steep dip in porphyry bodies and ore zones.

The main faults that determine the discontinuous structure of the ore field, Borgulikansky and Limestone, have an east-northeast strike. The block between them, which hosts the Borgulican ore field, is broken by a series of feathering faults, among which two systems predominate: east-northeast, parallel to the main faults, and east-southeast, diagonal to them and consistent with the prevailing orientation of porphyry intrusions . Displacements along these faults (apparently reaching several tens of meters) determined the mosaic-block structure of the ore field territory with alternating raised and lowered tectonic wedges. In addition, a series of low-amplitude tectonic disturbances such as fracture zones is recorded within the ore field. Along them, intensely manifested metasomatites of the acid leaching stage are developed.

The bodies of explosive breccias noted by previous researchers are known mainly within the Borgulican ore occurrence and are currently inaccessible for observation. The interpretation of the geological structure of the occurrence allows us to assume (by analogy with a number of other objects of this type) that breccia bodies gravitate towards areas of pinchout of the porphyry intrusion along the uplift and strike.

The most important elements of the ore-magmatic system and, accordingly, the geological and prospecting model of porphyry-type deposits include the composition and zoning of ore mineralization and near-ore changes. When characterizing the ore-metasomatic formations of the Borgulikan ore field, in addition to microscopic studies, the results of X-ray analysis of samples of the main varieties of metasomatic rocks were used (analyst E.I. Alysheva, X-ray spectral laboratory of TsNIGRI).

The near-ore hydrothermal-metasomatic changes of the objects under consideration are represented by a series of mineral associations (in sequence from high-temperature to low-temperature): quartz-K-feldspar-biotite, albite-epidote-actinolite, quartz-sericite-chlorite (with rutile and sporadic tourmaline, Fe-Mg carbonates, calcite ), argillicite (with kaolinite and smectites); the most recent and low-temperature formations are veinlets of calcite, zeolites and fluorite.

The zoning of near-ore changes is manifested in the regular change of mineral parageneses in space, their overlap (telescoping) and changes in the quantitative relationships between the minerals included in their composition. By analogy with the previously developed standard model of zoning of metasomatic changes in a porphyry copper deposit, we identify the following concentrically replacing generalized zones: 1) potassium-silicon (quartz-K-feldspar-biotite with subordinate albite and actinolite at deeper horizons and insignificant development of superimposed quartz-sericite-chlorite alterations) in the central apical parts of the porphyry intrusion; 2) internal propylitic (quartz-biotite metasomatites with superimposed quartz-chlorite alterations) in the endo-exocontacts of the deep parts of the porphyry intrusion; 3) phyllisite (quartz-sericite with chlorite, tourmaline, carbonates and relics of earlier metasomatic associations) in the exocontacts of the upper parts of the porphyry intrusion and in zones of cross-cutting low-amplitude tectonic disturbances; 4) external propylitic (combined albite-epidote-actinolite and sericite-carbonate-chlorite alterations) in the peripheral parts of the ore field.

In the near-surface zone, hydrothermally altered rocks underwent intense hypergenesis with the development of clayey weathering crust and supergene mudstones.

The ores of the Borgulican ore field have a relatively simple mineral composition. The main ore minerals are pyrite, chalcopyrite, magnetite; minor ones - molybdenite, bornite, sphalerite, galena, fahlores; supergene - iron hydroxides, hematite, bornite, cuprite, chalcocite, native copper and gold.

Hypogenic ore mineralization is manifested in the form of an uneven network of thin veinlets and fine dissemination and is represented by a series of ore mineral associations, concentrically changing in space from the central parts of the mineralized zones to their periphery in the following order: magnetite-bornite-chalcopyrite (in the potassium-silicon zone), pyrite -chalcopyrite-molybdenite (in the inner propylite and partly in the phyllisite zones) and magnetite-pyrite (in the phyllisite and outer propylitic zones). In carbonated tectonic zones, the polymetallic (quartz-carbonate-pyrite-chalcopyrite-galena-sphalerite) association is limitedly developed. In the zone of supergene mudstones above ore-bearing stockworks and along tectonic faults, limonite, hematite, cuprite, bornite, covellite, chalcocite, native copper and gold are present.

Ore intervals from wells, identified according to sampling data, are confined to the upper parts of the potassium-silicon zone (ores of the gold-bearing copper type) and to the adjacent sections of the internal propylitic and phyllisite zones (ores of the molybdenum-copper type).

A characteristic feature of the ore-bearing stockworks under consideration is the presence of reverse geochemical zoning, directed from the contacts of the porphyry intrusion to its center with a change in the maximum concentrations of ore components in the Mo-Cu-Au sequence in this direction. Reverse zoning of this kind (known at a number of industrial sites, for example Kounrad, Kyzata, etc.) is usually interpreted as a result of screening the system by denser host rocks.

Ore bodies within the Borgulican potential ore field are predicted taking into account all available geological, mineralogical, geochemical and geophysical data. On plans and sections, mineralized zones and predicted ore bodies are delineated, respectively, by cut-off copper contents of 0.1 and 0.2% in bedrock. For delineation, in addition to data from deep wells, data from short-length exploratory drilling was used. Taking into account the development of the leaching zone with the removal of copper in the upper horizons of bedrock, noted by all previous researchers, we conventionally carried out areal delineation based on Cu contents in short-length wells of 0.05 and 0.1%, respectively.

The occurrences of the Borgulikan ore field have been studied by a relatively developed network of prospecting wells and mine workings. Currently, the Borgulican manifestation is the most well studied. At the same time, poor natural exposure (along with strong tectonic disturbance and supergene alteration of rocks near the surface) allows for various options for linking the actual geological, geochemical and geophysical data available. The general east-southeast direction of strike of en-echelon mineralized zones, which we adopted when linking the boundaries between prospecting profiles, is substantiated, first of all, by the orientations of geochemical halos and geophysical anomalies, reflecting the position of ore-controlling structures.

A comparison of data from deep drill holes and surface mine workings, analysis of the orientation of fracturing in the core and the zoning of geochemical halos allowed us to assume a steep north-northeast dip (with a gentle east-southeast declination) of the mineralized zones. As can be seen from the presented graphic materials, ore bodies with relatively high concentrations of useful components are localized mainly within the apical endocontact parts of ore-bearing porphyry intrusions, extending in some cases into the exocontact zone.

The outer boundaries of the ore-bearing stockwork and the “pyrite aureole”, obviously, can be outlined in the primary geochemical aureoles according to the boundary concentrations of the main useful components, corresponding to the appearance of their independent ore minerals in noticeable quantities (Cu 0.05%, Mo 0.001%, Au 0 , 1 g/t). The contours of this zone cover both bodies of ore-bearing porphyry intrusions and host volcanic rocks.

In general, both ore bodies and their external halos are clearly conformal to the boundaries of porphyry intrusions, which is typical for porphyry-type deposits. Based on this, a saddle-shaped morphology of mineralized zones and predicted ore bodies (with an en-echelon internal structure) is assumed, repeating the shape of the apophyseal contacts of the porphyry intrusion and merging into a single body in the central part of the ore zones.

The position of halos of elevated (more than 0.005%) Mo contents should be especially emphasized. They are localized in the outer parts of mineralized zones, mainly in the endo-exocontact parts of ore-bearing porphyry intrusions. In this regard, the possibility of identifying three types of ores within the areas under consideration, namely gold-copper, gold-copper-molybdenum and molybdenum-copper, cannot be excluded. Preliminary calculations of the average weighted contents of the main useful components (Cu, Au, Mo) for ore intersections for two leading ore occurrences of the Borgulikan ore field showed that for Ikan, in bodies delineated by a Cu content of 0.2%, they are equal to 0.31% Cu and 0.47 g/t Au, and for Borgulican, where the well profiles probably exposed only the marginal parts of the ore body with mineralization predominantly of the gold-copper-molybdenum type, -0.16% Cu, 0.43 g/t Au and 0 , 005% Mo.

Within the Ikan ore occurrence, a fairly consistent mineralized zone of up to 1300 m in length with a thickness of 400-600 m is outlined by a cut-off Cu content of 0.1%. Within its boundaries, a series of predicted ore bodies with a cut-off Cu content of 0.2% are outlined, discovered by single intersections in prospecting wells to depths of 150-200 m and traced according to magnetic prospecting data.

The Borgulican ore occurrence spatially corresponds to a halo of mineralization, delineated by a Cu content of 0.1% and stretching for 900 m with a thickness of gold-copper-porphyry mineralization with increased concentrations of the main useful components. At the same time, ore intersections with average contents of Cu 0.21-0.27% (up to 0.36%) and Au 0.37-0.45 g/t (up to 0.66 g/t) in the wells of the named profiles can be interpreted like blades of an ore body along strike. It is characteristic that these contents are close to the above values established for the richest ore intersections of the Ikan site. Estimated parameters of the predicted ore body: length up to 400 m with a total thickness of about 300 m; The depth of mineralization may be quite significant.

The picture of metasomatic zoning obtained for the Borgulican site corresponds to the typical one for similar objects and is fundamentally similar to that observed at the Ikan site. At the same time, in the central part of the hydrothermal-metasomatic aureole there is also likely the presence of a core of quartz-K-feldspar-biotite alterations and an associated zone of development of a magnetite-bornite-chalcopyrite ore mineral association with high Au and Cu contents.

In conclusion, let us recall that the large-scale and local forecast of porphyry copper ore fields and deposits is based on the concept of a porphyry copper ore-magmatic system. The elements of its structure, acting as predictive criteria and features, and collectively constituting a geological prospecting model, include: the frame of the host rocks, including veneerite intrusions of the main phases of the ore-bearing plutonogenic formation; porphyry intrusions (stocks, dikes), serving as core elements of systems; breccia bodies, usually building up the stocks vertically; metasomatites, naturally zonally located in relation to the contacts of porphyry bodies; ore-bearing stockwork systems conformal to porphyry intrusions and enclosing endo- and exocontact zones; associated lead-zinc, copper-tourmaline, copper-arsenic and other mineralization.

As can be seen from the above brief description of the objects of the Borgulikan ore field, all the essential elements of the porphyry copper ore-magmatic system have been identified here.

Thus, the presence within the Borgulikan ore field of a porphyry-type ore-magmatic system is shown, which includes all the main elements, including ore-metasomatic aureoles with typical zoning and mineralized zones of complex (Cu, Au, Mo) composition with concentrations of useful components reaching industrial values. This confirms the attribution of ore occurrences in the Borgulikan ore field to the gold-molybdenum-copper-porphyry type. The fundamental identity of the composition and zoning of the ore-metasomatic formations of the Borgulican and Ikan areas is substantiated, the visible differences between which are due to differences in the levels of erosion, the size of the aureoles, as well as the difficulties of studying them. The results obtained form the basis of a regional comprehensive geological prospecting model of a gold-molybdenum-copper-porphyry deposit for the search and evaluation of such objects within the Umlekano-Ogodzhinsky belt of the Amur region.

Characteristics

From Cox, (1986) USGS Bulletin 1693
Characteristics of porphyry copper deposits include:

The ore bodies are associated with multiple intrusions and dams of diorite to quartz monzonite composition with porphyry textures.
Breccia intrusions are usually associated with zones with angular or locally rounded fragments. In sulfide, mineralization usually occurs between or within fragments. These breccia zones are typically hydrothermal in nature and may appear as pebble dikes.[14]
Deposits typically have an outer epidote-chlorite zone of mineral alteration.
And quartz is sericite. The alteration zone usually occurs closer to the center and can overlap the imprint.
A central potassic
zone of secondary biotite and orthoclase alteration is commonly associated with most of the ore.
The cracks are often filled or covered with sulfides or quartz. veins with sulfides. Closely spaced fractures of multiple orientations are usually associated with the highest grade ore.
The upper portions of porphyry copper deposits may be affected by supergene enrichment. In this case, the metals in the upper part dissolve and are carried below the groundwater level, where they precipitate.

Porphyry copper deposits are usually mined using quarry methods.

Scheme of the geological structure of the Kounrad deposit

Mineralization is confined to zones of widespread hydrothermally altered rocks, represented by quartz, sericite-quartz, biotite-K-feldspar, kaolinite-montmorillonite metasomatites.

Deposits of this type are formed at greater depths than deposits of the Kounrad type. The outlines of ore bodies are usually unclear. The maximum concentrations of ore mineralization can be confined to the endo- and exocontacts of porphyry intrusions, which is determined primarily by the physical and mechanical properties of the rocks composing them.

At the Kalmakyr deposit, ore stockwork develops mainly in the host syenite-diorites, and in granodiorite-porphyries it becomes poor and only in places do ore minerals form industrial concentrations.

Large cracks, filled with dikes, and smaller ones, to which veinlets are confined, form consistent systems, regularly oriented in relation to the main regional structures.

Deposits of the Kounrad and Kalkamyr types are united by the fact that they are associated with intrusions of gabbro-diorite-granodiorite, gabbro-syenite-diorite and related formations.

Propylite deposits of the Boshchekul type. The molybdenum-copper propylite formation includes less common compared to the two previous groups, significantly copper, less common molybdenum-copper deposits of veinlet-disseminated ores, also associated with porphyry intrusions. Porphyry intrusions, like host effusives, are represented by more basic varieties compared to previous types: diorite porphyrites, plagiogranites, quartz diorites, etc., which are late differentiated intrusions of gabbro-diorite, gabbro-diorite-plagiogranite formations or supply channels of volcanogenic formations [3]. Deposits of this particular type were at one time classified as porphyry copper [4], who noted that in the history of the development of geosynclines, porphyry copper deposits are formed twice: at the end of the early and at the end of the late stages. As an example of the first, he named Boschekul.

Scheme of the geological structure of the Kounrad deposit. According to A. Poletaev, G. Gilmutdinov, M. Chekhovich and others 1 - slightly altered granodiorite porphyry; 2 – secondary quartzites after granodiorite-porphyry; 3—ignimbrite horizon; 4-5 - effusive. Copper sulfide ores are characterized by both uniform and non-uniform solids of basic composition: 4 - diabase, 5 - lava breccia and tuff; 6—9—secondary quartzites on acidic rocks: c—spherulitic and massive felsite, 7—albitophyre and quartz porphyry, 5—tuff breccia of quartz porphyry, 9—fluidal felsite; 10—dykes of quartz diorites; and, — discontinuity violations; and - Cenozoic loose sediments; з - quarry contour; and - rich and ordinary ores; 15 - poor ores; 16 - boundaries of ore grades under the deposit; large negatively gravitating, apparently granitoid, masses are located. The shape of the stock is complicated by apophyses and blocks of effusive roof rocks deeply sunk into the massif

Hydrothermal (plutonogenic-hydrothermal) deposits form the basis of the mineral resource base of molybdenum. Among them, two main formations stand out: - formation of quartz-molybdenite vein ores; — quartz-molybdenite-chalcopyrite formation of stockwork type. Deposits of the quartz-molybdenite formation gravitate toward granite halos, are often located in the endocontact zone of intrusions, and are represented by veins and stockworks. The length of the main veins is 1000 -2000 m with an average thickness of 0.5 -1.0 m; The veins fall steeply (88 -90°). The veins are accompanied by rims of micaceous, micaceous-quartz and quartz greisens bearing mineralization. In the structure of the veins, three belts are distinguished: above-ore and under-ore. The vertical length of the ore belt is 200 -250 m.

The main ore mineral is molybdenite, sometimes with wolframite; From the surface to a depth of 15 -20 m, molybdenum is almost completely leached; at a depth of 50 m, the proportion of oxidized molybdenum is 20%. The deposit is developed underground using a system of sublevel drifts with a benchtop excavation. minor - cassiterite, scheelite, pyrite, arsenopyrite, bismuthite; veins - quartz, potassium feldspar and plagioclase; minor ones - muscovite, tourmaline, fluorite. The host granites are often greisenized. Vertical zoning usually consists of a change from bottom to top of molybdenum mineralization by tungsten-molybdenum.

The Kounrad deposit is located in the Hercynian fold region of Central Kazakhstan. It is confined to the uplift of the same name, located in the eastern part of the Tokrau Basin - a large superimposed structure formed in the Hercynian on a heterogeneous Caledonian folded foundation. The uplift has an oval shape in plan and dimensions of 40 X 15 km. Almost this entire area is a field of development of intrusive rocks that make up the southern part of one of the largest Ko-unrads in Kazakhstan. Bektauatinsky pluton.

Ecology

The plant is the largest polluter of the environment in the Balkhash region. From the moment the copper production complex began operating until 1995, industrial wastewater was discharged into the lake’s water environment without treatment. As a result, to date, pollution of hydrobiosphere components with heavy metals, according to the Research and Production Center for Fisheries, is becoming dominant. Over the past ten years, in the tissues of fish caught from the lake, the content of zinc has increased by 11 times, chromium by 13 times, and nickel by two times.

The plant is located in close proximity to residential areas of the city of Balkhash.

Process gases are released into the atmosphere without purification from sulfur dioxide and dust containing heavy metals - copper, lead, arsenic, etc. Allergies and asthma are common diseases among residents of the city of Balkhash.

According to numerous testimonies from the city residents themselves, at night, in the summer of 2004, the plant produced a large release of gas into the atmosphere, which led to the massive death of birds in the city. Fishermen also report numerous catches of diseased fish.

At the moment, there is very little data on the current ecological state of Lake Balkhash and the Balkhash region, since in the 1990s the previously conducted standard observations were significantly reduced and scientific research was almost completely stopped.

In September 2005, the Balkhash-Alakol Basin Council (BABC) was created. The creation of BABS in Kazakhstan is provided for in Article 43 of the Water Code of July 9, 2003.

Raw materials

· Ore is delivered to the plant from different mines. The largest is the Kounradsky mine, located 12 kilometers from the plant. The most remote Sayak mine is 250 km to the east.

· Balkhash ore contains many elements from the periodic table. The copper content in it, according to some sources, is about 60%. The ore also contains precious metals - gold, silver and many others.

· In 1967, the London Metal Exchange recognized Balkhash copper as a world standard [3

Here, too, the remains of ancient mining operations have long been known, attributed to the so-called Andronovo culture, dating back to the second half of the second millennium BC. There were also finds of copper items dating back to the fourth millennium BC. In the twenties, the history of mining and metallurgy in Kazakhstan was described by professor of the Tomsk Polytechnic Institute V.A. Pazukhin in the book “Metallurgy in the Kyrgyz Steppe,” published in 1926. And already in 1928, M.P. Rusakov, based on information received from local historian G.P. Amosov, who lived in the territory of the present city of Balkhash, identified and assessed the mineralization developed here as a huge porphyry copper deposit of the Konyrat type, comparing it in size with the largest porphyry copper deposit USA Santa Rita. He called him the Russian Kounrad.

The Kounrad deposit of disseminated copper ores is located among a huge granite field. Only to the north-west of the deposit, over a relatively large area, Lower Paleozoic arkosic sandstone-shales, the most ancient rocks of the region, occur. Younger rocks are diabases erupted on the surface of sandstone-shales, diabase porphyrites, tuffs and tuff-breccias, quartz albitophyres, their tuffs and tuff-breccias. The primary sulfide minerals were: molybdenite, pyrite, chalcopyrite and bornite. In the oxide enrichment zone, primary copper sulfides were destroyed and malachite, azurite, brochantite, chrysocolla, cyanotrichite and very rarely copper oxides were formed. Below the groundwater level, the formation of a zone of secondary sulfide enrichment and the transformation of chalcopyrite and partially pyrite into chalcocite, less often into covellite, took place. The transition between the zone of secondary sulfide enrichment and the zone of primary ores is gradual (Konradskoye deposit)

Mineralization is confined to zones of widespread hydrothermally altered rocks, represented by quartz, sericite-quartz, biotite-K-feldspar, kaolinite-montmorillonite metasomatites.

At the Kalmakyr deposit, ore stockwork develops mainly in the host syenite-diorites, and in granodiorite-porphyries it becomes poor and only in places do ore minerals form industrial concentrations.

Large cracks, filled with dikes, and smaller ones, to which veinlets are confined, form consistent systems, regularly oriented in relation to the main regional structures.

Deposits of the Kounrad and Kalkamyr types are united by the fact that they are associated with intrusions of gabbro-diorite-granodiorite, gabbro-syenite-diorite and related formations.

Ecology

The plant is located in close proximity to residential areas of the city of Balkhash.

In September 2005, the Balkhash-Alakol Basin Council (BABC) was created. The creation of BABS in Kazakhstan is provided for in Article 43 of the Water Code of July 9, 2003.

Raw materials

· Ore is delivered to the plant from different mines. The largest is the Kounradsky mine, located 12 kilometers from the plant. The most remote Sayak mine is 250 km to the east.

· In 1967, the London Metal Exchange recognized Balkhash copper as a world standard [3

Examples

Mexico

Cananea
La Caridad
Santo Tomas

Chile

Peru

Toquepala
Cerro Verde, southeast of the city of Arequipa

United States

Ajo, Arizona
Baghdad, Arizona
Lavender Pit, Bisbee, Arizona
Morenci, Arizona
Pebble Mine, Alaska
Safford Mine, Safford, Arizona
San Manuel, Arizona
Sierrita, Arizona[15]
Resolution Copper, Superior, Arizona
El Chino, Santa Rita, New Mexico
Ely, Nevada
Bingham Canyon Mine, Utah
Ray Main, Arizona[16]

Indonesia

Batu Hijau, Sumbawa
Grasberg, West Papua, with over 3 billion tonnes of 1 ppm gold, is one of the largest and richest porphyry deposits of any type in the world.
Tujuh Bukit, Java, still being explored, but likely to be larger than Batu Hijau[17]
Sungai Mak and Kabang Kiri, Gorontalo, 292 million tonnes at 0.50 ppm gold and 0.47% copper[18]

Australia

Cadia Ridgeway Mine, New South Wales, is an open pit and block caving copper-gold deposit.
Northparkes porphyry copper deposit, New South Wales, with 63 million tonnes at 1.1% Cu and 0.5 ppm Au.

Papua New Guinea

Ok Tedi
Panguna/Bougainville Copper
Vafi-Golpu Project/Vafi-Golpu Mine

Another

Coclesito, Panama[19]
Majdanpek mine, Serbia[8]
Oyu Tolgoi is one of the largest and richest copper porphyry deposits in the world, Mongolia
La Caridad, Sonora, Mexico
Dizon, Philippines[8]
Saindak copper-gold project, Pakistan[20]

Deposits of porphyry ores for metals other than copper

Copper is not the only metal found in porphyry deposits. There are also deposits of porphyry ores that are mined primarily for molybdenum, many of which contain very little copper. Examples of porphyry molybdenum deposits: Climax, Urad, Emmons and Henderson deposits in central Colorado; the White Pine and Pine Grove fields in Utah[21][22]; then the Questa field in northern New Mexico; and Endako in British Columbia.

The USGS has classified the Chorolque and Catavi tin deposits in Bolivia as porphyry tin deposits

.[23]

Some porphyry copper deposits in oceanic crustal environments, such as those in the Philippines, Indonesia, and Papua New Guinea, are so rich in gold that they are called porphyry copper-gold deposits.[24]

Porphyry-type ore deposits for metals other than copper[edit]

Copper is not the only metal found in porphyry deposits. There are also deposits of porphyry ores, mined primarily for molybdenum, many of which contain very little copper. Examples of porphyry molybdenum deposits are Climax, Urad, Mt. Emmons and Henderson fields in central Colorado; the White Pine and Pine Grove fields in Utah; [21] [22] Questa deposit in northern New Mexico; and Endako in British Columbia.

The USGS classifies the Chorolque and Catavi tin deposits in Bolivia as porphyry tin deposits

. [23]

Some porphyry copper deposits in oceanic crustal environments, such as those in the Philippines, Indonesia and Papua New Guinea, are sufficiently rich in gold that they are called porphyry copper-gold deposits. [24]