Geophysical methods are well recommended for all types of sub-surface exploration. [6] Alternatively, metasomatised mantle wedges can produce highly oxidized conditions that results in sulfide minerals releasing ore minerals (copper, gold, molybdenum), which are then able to be transported to upper crustal levels. A deposit of basaltic porphyry, which may be used in construction, was discovered in the Nenets Region, the regional administration’s press service said on Thursday. The mineralization frequently forms a halo around the intrusion both in the intrusion itself and in the surrounding host rocks. Min. The Cu-Mo, Cu-Au, and Mo porphyry, and most epithermal lode deposits, usually have reserves in the order of hundreds of Mt or even Gt, if you can delineate a large sufficient volume of these fractured and veined rocks, then you will have a stockwork. I'm looking for a advices of papers, or some comentaries about the tectonic history and structural geology of te Center of Ecuador. The chemical alteration of the rocks surrounding a porphyry are a hint of the presence of ore. Over time, erosion removes the overlying volcanoes, covering the porphyry deposits. Join ResearchGate to find the people and research you need to help your work. Mineral Resource Reviews. [6] Alternatively, metasomatised mantle wedges can produce highly oxidized conditions that results in sulfide minerals releasing ore minerals (copper, gold, molybdenum), which are then able to be transported to upper crustal levels. Economic Geology, 2005. Richards, J.P., Tectono-Magmatic Precursors for Porphyry Cu-(Mo-Au) Deposit Formation. Porphyry copper deposits of the world. Mineralization of Cu ores tend to occur at the tops of porphyry systems in cupolas. I think one of the most important challenge in the future is how can we find hidden deposit on earth!! I ask this, because some colleagues believe these are not stockwork because they are not randomly distributed in the rock. The intrusives also simulates the limestone altering its composition and forming and endo skarns. [7] Finally, in oceanic island arcs, ridge subduction can lead to slab flattening or arc reversal; whereas, in continental arcs it can lead to periods of Flat Slab Subduction. It’s marked in the red hatch pattern in the cross section. The deposits along the Pacific coast of  North and South America are associated with plate subduction while the more gold-rich deposits in Indonesia and Papua New Guinea are associated with island arc volcanism behind the subduction zone. Economic Geology, 2003. Can be related with the compatibility of ore-forming elements or chemical reaction between fluid and hostrock (like boiling mechanism) or remobilization of ore which was transported previous pulses? [5] It is estimated that the Earth's porphyry copper deposits contain approximately 1.7×1011 tonnes of copper, equivalent to more than 8,000 years of global mine production. Solomon, M., Subduction, arc reversal, and the origin of porphyry copper-gold deposits in island arcs. "Mineralization as related to structural deformation, igneous activity and sedimentation in folded geosynclines." The magma then continues to accumulate in a chamber below and it starts to cool. [7] Finally, in oceanic island arcs, ridge subduction can lead to slab flattening or arc reversal; whereas, in continental arcs it can lead to periods of Flat Slab Subduction. Yes, Joshua Ehlich is correct, there is a difference of opinion. Whereas the mafic layered complexes we discussed in the last talk usually develop relatively deep in the earth’s crust porphyries form at a much shallower depth not quite as shallow as epithermal deposits but not much deeper than them either. One plate is forced under the other in what is called a subduction zone. Copper is not the only metal that occurs in porphyry deposits. [6] The current belief is that the generation of andesitic magmas is multistage, and involves crustal melting and assimilation of primary basaltic magmas, magma storage at the base of the crust (underplating by dense, mafic magma as it ascends), and magma homogenization. I will be glad to know if you give me papers or idea about it. The steam you can see rising above the new forming dome in the picture on the left there is leakage of the mineralizing fluids. Some authors (e.g. Skarns are often striking looking rocks containing red garnets and green pyroxenes. Leave your phone number if you would like us to call you. Richards, J.P., Tectono-Magmatic Precursors for Porphyry Cu-(Mo-Au) Deposit Formation. target generation) before you start looking for hydrothermal alteration zones within them. This relatively young age reflects the preservation potential of this type of deposit; as they are typically located in zones of highly active tectonic and geological processes, such as deformation, uplift, and erosion. The rock on the bottom right has suffered this potassic alteration; pink-orange mineral is potassium feldspar. I would like to know what is your idea about this subject? [7] Upon a return to normal subduction, the hot asthenosphere will once again interact with the hydrated mantle, causing wet melting, crustal melting will ensue as mantle melts pass through, and lithospheric thinning and weakening due to the increased heat flow. Dykes and granitic rocks with porphyritic textures. Some of the group members gave their individual opinion but I never even researched on it to understand it myself. Porphyry copper deposits are currently the largest source of copper ore. Economic Geology, 2010. You then have to go back to the early years of the 20th century to find the first properly scientific petrographic and field studies dealing with this particular ore paragenesis. Lis is also a published author of travel and technical books and has written many articles for online websites. This is not a porphyry deposit it’s one of the Central African copper belt style of deposit. It is likely that this upper chamber is where the hydrothermal fluids are collecting and mineralizing the surrounding rocks. [6] From this point forward in the evolution of a porphyry deposit, ideal tectonic and structural conditions are necessary to allow the transport of the magma and ensure its emplacement in upper-crustal levels. [7] For both porphyry and epithermal gold deposits, they are generally from the time period ranging from the middle Miocene to the Recent period.,[7] however notable exceptions are known. The more details you give on your situation, the better we can help you. [6] Porphyry deposits are clustered in discrete mineral provinces, which implies that there is some form of geodynamic control or crustal influence affecting the location of porphyry formation. As the magma chamber cools from the contact inwards barren feldspars and quartz crystallize out and the remaining melts becomes enriched then melts, volatiles mainly water, carbon dioxide and hydrogen sulfide. [10] The collision may result in the termination of subduction and thereby induce mantle melting. A different but closely related group of deposits to Porphyry Copper Deposits are the skarn deposits. [10][13] The presence of intra-arc fault systems are beneficial, as they can localize porphyry development. Chalcocite has a higher copper content than chalcopyrite and grades of 5 to 10% copper in a laterally continuous horizontal beds are not uncommon. This is Mount St Helens a few years after it blew its top. [7], Arc reversal has been shown to slightly pre-date the formation of porphyry deposits in the south-west Pacific, after a collisional event. Can. make ore, fractures must be closely spaced; generally grades are Keith, J.D., Shanks III, W.C., Archibald, D.A., and Farrar, E., 1986, Volcanic and Intrusive History of the Pine Grove Porphyry Molybdenum System, Southwestern Utah: Economic Geology, v. 81, p. 553-587, https://web.archive.org/web/20100307202424/http://www.mawsonwest.com.au/multimedia/1/ASX%20Chimpantika%20160407.pdf, "Long-lived crustal damage zones associated with fault intersections in the high Andes of Central Chile", "Multi-Stage Construction of the Little Cottonwood Stock, Utah: Origin, Intrusion, Venting,Mineralization, and Mass Movement", https://en.wikipedia.org/w/index.php?title=Porphyry_copper_deposit&oldid=974627296, Creative Commons Attribution-ShareAlike License, The orebodies are associated with multiple intrusions and, Fractures are often filled or coated by sulfides, or by quartz, The upper portions of porphyry copper deposits may be subjected to, Dennis P. Cox, 1986, "Descriptive model of porphyry Cu," in, This page was last edited on 24 August 2020, at 02:24. Economic Geology, 2005. This is a photo from the edge of the pit and you can start to get an idea of the scale for the trucks climbing up the whole roads within the pit but you only really get a full understanding of the scale when you see one of those trucks standing next to a normal SUV. So where does the Au come from in the ore? [12] Arc reversal occurs due to collision between an island arc and either another island arc, a continent, or an oceanic plateau. Glenside, South Australia: Australian Mineral Foundation. Examples of porphyry molybdenum deposits are the Climax, Urad, Mt. Generally, aims of the sampling such as evaluation, geochemistry, mineralogy, isotopes, fluid inclusions or all of them indicate the sampling process. [10] Shallow subduction of young, buoyant slabs can result in the production of adakitic lavas via partial melting. Springer-Verlag Heidelberg, 398 pp. In later stages, circulating meteoric fluids may interact with the magmatic fluids. It is believed that tectonic change acts as a trigger for porphyry formation. Emmons, and Henderson deposits in central Colorado; the White Pine and Pine Grove deposits in Utah ; the Questa deposit in northern New Mexico; and Endako in British Columbia. [10] However, the latest belief is that dehydration that occurs at the blueschist-eclogite transition affects most subducted slabs, rather than partial melting.[6]. The porphyry deposits are low grade but usually very large in size, as a result of the low grade and size few porphyries support expensive underground mining techniques and most are mined by open pit methods. Porphyry copper deposits represent an important resource and the dominant source of copper that is mined today to satisfy global demand. Porphyry deposits are formed when a column of rising magma is cooled in two stages. The only reason these ore bodies are economic is because porphyries are huge, with hundreds of millions of tonnes available in a fairly low-cost mining setting. [6] The current belief is that the generation of andesitic magmas is multistage, and involves crustal melting and assimilation of primary basaltic magmas, magma storage at the base of the crust (underplating by dense, mafic magma as it ascends), and magma homogenization. This creates the higher-grade “cap” mineralisation that found in the upper layers of many porphyry copper mines. you are doing fine. 98: p. 1515-1533. 44(3): p. 373-388. But these […] I have recently visited a mineral occurrence with the following general characteristics: Pervasive argillic alteration in a subvolcanic intermediate rock, sulfide veinlets (partly oxidized), sulfide-bearing quartz veins, mineralized breccia, anomalies (or rather high amounts) of copper and gold, etc. For copper-molybdenum porphyry deposits, formation is broadly concentrated in three time periods: Palaeocene-Eocene, Eocene-Oligocene, and middle Miocene-Pliocene. I saw too many projects and papers ending up as a "flying carpet" . The enormous and remote Grasberg mine, is located in the western half of the island of Papua New Guinea, in the Indonesian province or Irian Jaya.