Exploration in the central Tethys region of Turkey, Armenia, Azerbaijan, Georgia, Iran, and western Pakistan has led to the identification of the giant Reko Diq (24 Mt Cu and 1300 t Au), Sar Cheshmeh (8.9 Mt Cu and 0.46 Mt Mo), Sungun (5.1 Mt Cu and 0.20 Mt Mo), and Kadjaran (4.6 Mt Cu, 0.94 Mt Mo, and 1100 t Au), and 10 other large (1-2 Mt Cu) porphyry deposits including Saindak, Cevizlidere, Teghout, Meiduk, and Halilaga. Continued exploration efforts have also resulted in the development of porphyry-related gold deposits such as Kisladag (9.6 Moz Au), copler (3.7 Moz Au), Agi Dagi (1.7 Moz Au), and Sary Gunay (3.0 Moz Au), and in the generation of several other promising exploration projects. The distribution in space and time of porphyry deposits in the central Tethys region was shaped by complex pre- to post-mineral tectonic, igneous, collisional, uplift and burial events. These events are represented by a partially-overlapping and variably exhumed and covered collage of twenty-six Early Jurassic to Holocene magmatic belts permissive for the occurrence of porphyry deposits (porphyry tracts and sub-tracts). Twelve tracts or sub-tracts are characterized by compressional continental arcs that formed on drifting terranes or continental margins, 10 developed in compressional to extensional infra-oceanic arc and backarc-rift settings, and 4 formed in extensional post-collisional environments over amalgamated terranes. Eight of these belts were variably affected by coeval and younger metamorphic, fold-and-thrust, and extensional faulting events. Fifty-four porphyry Au-(Cu), Cu-Au, Cu-Mo, Mo-Cu deposits, 15 porphyry-related Au, Au-(Mo) and W-(MoAu) deposits, 239 porphyry prospects, and 68 other porphyry-related mineral sites were identified in the study region. Of the 376 porphyry and porphyry-related sites, about 11% formed in island arc, 42% in continental arc, 20% in backarc, and 27% in post-collisional settings. Of the 69 porphyry and porphyry-related deposits, 7% developed in infra-oceanic arc, 41% in continental arc, 27% in backarc, and 25% in post-collisional settings. The largest occur in either compressional continental arc (18 deposits including the Reko Diq and Sar Cheshmeh giants) or post-collisional (13 deposits including the Kadjaran and Sungun giants) environments. Ninety percent of the largest porphyry or porphyry-related deposits occur in only 9 of the 26 permissive porphyry tracts or subtracts. Moreover, 88, 90, and 77% of the identified Cu, Mo, and Au resources are contained in porphyry deposits that occur in only 4 of these 9 tracts. Of these 4 tracts, 3 outline arc settings, and one delimits a post-collisional environment. The compositional diversity of porphyry intrusions in these tectono-magmatic environments generally varies from island arc settings with the most restricted range (partly alkaline but mainly calc-alkaline dioritic to granodioritic-tonalitic), to continental arc (calc-alkaline dioritic-quartz dioritic, granodioritic, quartz monzonitic-granitic, and less commonly mildly alkaline), to backarc (mildly alkaline and calc-alkaline dioritic to granitic), to post-collisional settings with the most expansive range (alkaline and calc-alkaline mafic to felsic, and weakly peraluminous). Metal associations also vary broadly as a function of porphyry intrusion composition from weakly peraluminous to metaluminous felsic (Mo[ +/- W +/- Cu]; < 2% of porphyry-related systems [i.e., Tyrnyauz]), to metaluminous felsic and intermediate (Cu-Mo[ +/- Au]; 85% [i.e., Cevizlidere, Haft Cheshmeh, Kahang, Sar Cheshmeh, Sungun, Teghout, Reko Diq, Saindak]), to mildly alkaline felsic and intermediate (Cu-Au +/- Mo] [i.e., Agarak, Kadjaran, Kale Raft]) and mafic (Au-Cu; 12% [i.e., copler]), and to alkaline felsic (Au-Mo; 1% of porphyry-related systems [i.e., Kisladag). Tectonic changes were critical in triggering the formation of large porphyry deposits in the region. Large porphyry deposits were preferentially emplaced in continental arc settings shortly before major collisional events (Dar Mu, Kahang, Meiduk, Now Chun, and the giant Sar Cheshmeh and Reko Diq deposits), or in postsubduction environments shortly after collision (Bakircay, Giizelyayla, Haft Cheshmeh, Masjed Daghi, and the giant Kadjaran and Sungun deposits) or during periods of prominent extension (Agi Dagi, Halilaga, Kisladag, Sari Gunay, and Zarshuran porphyry-related deposits). Collision-induced uplift, erosion, and removal of coeval volcanic rocks favorably exposed the hypabyssal level of subduction-related porphyry deposits. Extensional structures that developed parallel and orthogonal to the compressional principal stress component along transtensional or transpressional strike-slip faults or in pull-apart basins commonly controlled porphyry-related deposits in post-collisional settings. The latter deposits typically exhibit shallow epithermal levels of emplace. ment because of preservation by burial. Seventeen porphyry deposits and one porphyry-related deposit in the study region are reported to contain significant supergene resources. Relatively mature levels of secondary copper enrichment in dominantly granodioritic to granitic porphyry deposits occur in areas where large pyrite-rich quartz-sericite alteration zones have been preserved and exposed to surface oxidation (Guzelyayla and Ulutai in northeastern Turkey; Agarak, Ankavan, Dastakert, Kadjaran, and Teghout in Armenia; Ali Javad in northern Iran; Kale Kafi in central Iran; Darreh Zar, Meiduk, Now Chun, and Sar Cheshmeh in southeastern Iran; and Tanjeel in southwestern Pakistan). Chalcocite blankets also developed over porphyry deposits in regions where significant post-mineral faulting has occurred (Muratdere and Saricayiryayla in western Turkey). Normal faulting also enhanced secondary enrichment of gold in the Halilaga porphyry and Sary Gunay porphyry-related deposits located respectively in western Turkey and northern Iran. Evaluation of provincial as well as local controls strongly suggests that continued exploration in the region will lead to the identification of additional porphyry and porphyry-related deposits. These deposits will likely be found under younger cover formations in porphyry belts that are already known, and in association with superjacent high- and intermediate-sulfidation epithermal deposits, or increasingly peripheral skarn, carbonate. replacement, and sediment-hosted deposits. Application of suitable exploration techniques to detect concealed and/or deformed deposits in porphyry belts that remain under-explored may also prove productive.

First posted November 30, 2017 For additional information, contact: Office of the Associate Director for Energy and Minerals U.S. Geological Survey 12201 Sunrise Valley Drive MS 102 Reston, VA 20192 Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly used in magnets and rechargeable batteries. More than 50 percent of primary cobalt production is from the Central African Copperbelt. The Central African Copperbelt is the only sedimentary rock-hosted stratiform copper district that contains significant cobalt. Its presence may indicate significant mafic-ultramafic rocks in the local basement. The balance of primary cobalt production is from magmatic nickel-copper and nickel laterite deposits. Cobalt is present in several carbonate-hosted lead-zinc and copper districts. It is also variably present in Besshi-type volcanogenic massive sulfide and siliciclastic sedimentary rock-hosted deposits in back arc and rift environments associated with mafic-ultramafic rocks. Metasedimentary cobalt-copper-gold deposits (such as Blackbird, Idaho), iron oxide-copper-gold deposits, and the five-element vein deposits (such as Cobalt, Ontario) contain different amounts of cobalt. None of these deposit types show direct links to mafic-ultramafic rocks; the deposits may result from crustal-scale hydrothermal systems capable of leaching and transporting cobalt from great depths. Hydrothermal deposits associated with ultramafic rocks, typified by the Bou Azzer district of Morocco, represent another type of primary cobalt deposit.In the United States, exploration for cobalt deposits may focus on magmatic nickel-copper deposits in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska; also, possibly basement rocks in southeastern Missouri. Other potential exploration targets include—The Belt-Purcell basin of British Columbia (Canada), Idaho, Montana, and Washington for different styles of sedimentary rock-hosted cobalt deposits;Besshi-type VMS deposits, such as the Greens Creek (Alaska) deposit and the Ducktown (Tennessee) waste and tailings; andKnown five-element vein districts in Arizona and New Mexico, as well as in the Yukon-Tanana terrane of Alaska; and hydrothermal deposits associated with ultramafic rocks along the west coast, in Alaska, and in the Appalachian Mountains.

We report the first study of the Re-Os systematics of cobaltite (CoAsS) using disseminated grains and massive sulfides from samples of two breccia-type and two stratabound deposits in the Co-Cu-Au Idaho cobalt belt (ICB), Lemhi subbasin to the Belt-Purcell Basin, Idaho, USA. Using a Re-185 + Os-190 spike solution, magnetic and non-magnetic fractions of cobaltite mineral separates give reproducible Re-Os analytical data for aliquot sizes of 150 to 200 mg. Cobaltite from the ICB has highly radiogenic Os-187/Os-188 ratios (17-45) and high Re-187/Os-188 ratios (600-1800) but low Re and total Os contents (ca. 0.4-4 ppb and 14-64 ppt, respectively). Containing 30 to 74% radiogenic Os-187, cobaltite from the ICB is amenable to Re-Os age determination using the isochron regression approach.Re-Os data for disseminated cobaltite mineralization in a quartz-tourmaline breccia from the Haynes-Stellite deposit yield a Model 1 isochron age of 1349 +/- 76 Ma (2 sigma, n = 4, mean squared weighted deviation MSWD = 2.1, initial Os-187/Os-188 ratio = 4.7 +/- 2.2). This middle Mesoproterozoic age is preserved despite a possible metamorphic overprint or a pulse of metamorphic-hydrothermal remobilization of pre-existing cobaltite that formed along fold cleavages during the ca. 1190-1006 Ma Grenvillian orogeny. This phase of remobilization is tentatively identified by a Model 3 isochron age of 1132 240 Ma (26, n = 7, MSWD = 9.3, initial Os-187/Os-188 ratio of 9.0 +/- 2.9) for cobaltite in the quartz-tourmaline breccia from the Idaho zone in the Blackbird mine.All Mesoproterozoic cobaltite mineralization in the district was affected by greenschist- to lower amphibolite-facies (garnet zone) metamorphism during the Late Jurassic to Late Cretaceous Cordilleran orogeny. However, the fine- to coarse-grained massive cobaltite mineralization from the shear zone hosted Chicago zone, Blackbird mine, is the only studied deposit that has severely disturbed Re-Os systematics with evidence for a linear trend of mixing with (metamorphic?) fluids.The new Re-Os ages and extremely high initial Os-187/Os-188 ratios of cobaltite reported here favor a magmatic-hydrothermal genetic model for a multi-stage REE-Y-Co-Cu-Au mineralization occurring at ca. 1370 to 1349 Ma, and related to the emplacement of the Big Deer Creek granite pluton at ca. 1377 Ma. In our model, deposition of paragenetically early xenotime and gadolinite was followed by an influx of Mesoproterozoic evaporitic brines and magmatic-hydrothermal fluids containing metals and reduced sulfur derived from mafic and oceanic island-arc Archean to Paleoproterozoic rocks in the Laurentian basement. Cobaltite mineralization occurred upon cooling of these fluids at an inferred temperature of 300 degrees C or below. (C) 2017 Elsevier B.V. All rights reserved.

The Blackbird cobalt-copper (Co-Cu) district in the Salmon River Mountains of east-central Idaho occupies the central part of the Idaho cobalt belt-a northwest-elongate, 55-km-long belt of Co-Cu occurrences, hosted in grayish siliciclastic metasedimentary strata of the Lemhi subbasin (of the Mesoproterozoic Belt-Purcell Basin). The Blackbird district contains at least eight stratabound ore zones and many discordant lodes, mostly in the upper part of the banded siltite unit of the Apple Creek Formation of Yellow Lake, which generally consists of interbedded siltite and argillite. In the Blackbird mine area, argillite beds in six stratigraphic intervals are altered to biotitite containing over 75 vol% of greenish hydrothermal biotite, which is preferentially mineralized.Past production and currently estimated resources of the Blackbird district total similar to 17 Mt of ore, averaging 0.74% Co, 1.4% Cu, and 1.0 ppm Au (not including downdip projections of ore zones that are open downward). A compilation of relative-age relationships and isotopic age determinations indicates that most cobalt mineralization occurred in Mesoproterozoic time, whereas most copper mineralization occurred in Cretaceous time.Mesoproterozoic cobaltite mineralization accompanied and followed dynamothermal metamorphism and bimodal plutonism during the Middle Mesoproterozoic East Kootenay orogeny (ca. 1379-1325 Ma), and also accompanied Grenville-age (Late Mesoproterozoic) thermal metamorphism (ca. 1200-1000 Ma). Stratabound cobaltite-biotite ore zones typically contain cobaltite(1) in a matrix of biotitite +/- tourmaline +/- minor xenotime (ca. 1370-1320 Ma) +/- minor chalcopyrite +/- sparse allanite +/- sparse microscopic native gold in cobaltite. Such cobaltite-biotite lodes are locally folded into tight F-2 folds with axial-planar S-2 cleavage and schistosity. Discordant replacement-style lodes of cobaltite(2)-biotite ore +/- xenotime(2) (ca. 1320-1270 Ma) commonly follow S-2 fractures and fabrics. Discordant quartz-biotite and quartz-tourmaline breccias, and veins contain cobaltite(3) +/- xenotime(3) (ca. 1058-990 Ma).Mesoproterozoic cobaltite deposition was followed by: (1) within-plate plutonism (530-485 Ma) and emplacement of mafic dikes (which cut cobaltite lodes but are cut by quartz-Fe-Cu-sulfide veins); (2) garnet-grade metamorphism (ca. 151-93 Ma); (3) Fe-Cu-sulfide mineralization (ca. 110-92 Ma); and (4) minor quartz +/- Au-Ag +/- Bi mineralization (ca. 92-83 Ma).Cretaceous Fe-Cu-sulfide vein, breccia, and replacement-style deposits contain various combinations of chalcopyrite +/- pyrrhotite +/- pyrite +/- cobaltian arsenopyrite (not cobaltite) +/- arsenopyrite +/- quartz +/- siderite +/- monazite (ca. 144-88 Ma but mostly 110-92 Ma) +/- xenotime (104-93 Ma). Highly radiogenic Pb (in these sulfides) and Sr (in siderite) indicate that these elements resided in Mesoproterozoic source rocks until they were mobilized after ca. 100 Ma. Fe-Cu-sulfide veins, breccias, and replacement deposits appear relatively undeformed and generally lack metamorphic fabrics.Composite Co-Cu-Au ore contains early cobaltite-biotite lodes, cut by Fe-Cu-sulfide veins and breccias, or overprinted by Fe-Cu-sulfide replacement-style deposits, and locally cut by quartz veinlets +/- Au-Ag +/- Bi minerals.

The U.S. Geological Survey assesses resources (mineral, energy, water, environmental, and biologic) at regional, national, and global scales to provide science in support of land management and decision making. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected to be in the Earth’s crust, which commodities may be present, and estimates of amounts of resources in undiscovered deposits. A probabilistic mineral resource assessment of undiscovered resources associated with porphyry copper deposits in northeast Asia—composed mainly of Far East Russia and a small part of northeasternmost China—was completed as part of a global mineral resource assessment. Porphyry copper deposits are the main source of copper globally. Russia is an important source of copper, consistently ranking as 6th, 7th, or 8th in world production since 2000, and ranked 7th in 2014. Most of this production has been from magmatic copper-nickel-platinum-group element, volcanogenic massive sulfide, and sediment-hosted copper deposit types. The purpose of the assessment was to (1) compile a database of known deposits and significant prospects, (2) delineate permissive areas (tracts) for undiscovered porphyry copper deposits that may be present in the upper kilometer of the Earth’s crust, and (3) provide probabilistic estimates of amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) that could be contained in undiscovered porphyry copper deposits in the tracts. The assessment was completed by the U.S. Geological Survey in collaboration with geologists from the Russian Academy of Sciences and industry consultants. The database of known deposits, significant prospects, and prospects includes an inventory of mineral resources in two known porphyry copper deposits, as well as key characteristics derived from available exploration reports for 70 significant porphyry copper prospects and 86 other prospects. Resource and exploration and development activity are updated with information current through February 2013.

First posted November 18, 2015 For additional information, contact: Contact Information, Mineral Resources Program U.S. Geological Survey 12201 Sunrise Valley Drive 913 National Center Reston, VA 20192 http://minerals.usgs.gov/ A probabilistic mineral resource assessment of undiscovered resources in porphyry copper deposits in the Tethys region of western and southern Asia was carried out as part of a global mineral resource assessment led by the U.S. Geological Survey (USGS). The purpose of the study was to delineate geographic areas as permissive tracts for the occurrence of porphyry copper deposits at a scale of 1:1,000,000 and to provide probabilistic estimates of amounts of copper likely to be contained in undiscovered porphyry copper deposits in those tracts. The team did the assessment using the USGS three-part form of mineral resource assessment, which is based on (1) mineral deposit and grade-tonnage models constructed from known deposits as analogs for undiscovered deposits, (2) delineation of permissive tracts based on geoscientific information, and (3) estimation of numbers of undiscovered deposits. The assessment area includes the Asian part of Turkey and Georgia, Armenia, Azerbaijan, Iran, western Pakistan, and southwestern Afghanistan. Selected tracts also extend marginally into southwesternmost Russia and northeasternmost Iraq. This region is located in the central part of the larger Tethyan Eurasian Metallogenic Belt, which extends from western Europe to eastern Asia. Mining in this part of the Tethyan Eurasian Metallogenic Belt has occurred for thousands of years; in 2011 the region produced 420,000 metric tons (t) of copper (2.6 percent of global production), 8,300 t of molybdenum (3 percent), and 29,600 kilograms of gold (1 percent). The assessment team defined 26 tracts permissive for Late Triassic to Holocene porphyry copper-molybdenum and porphyry copper-gold deposits. Permissive tracts range in extent from 2,960 to 194,000 square kilometers (km2) and cover a total area of 924,000 km2. Younger tracts overlap older tracts in several areas. Three permissive tracts include sub-tracts in order to separate tract segments on the basis of geography, data quality, or likelihood of occurrence of undiscovered deposits. About 65 percent of all known porphyry sites occur in only five tracts, which also host most of the identified copper resources. In terms of tectonic setting, 58 percent of the permissive tracts are related to continental arcs; 19 percent to island arcs or back arcs; and 24 percent to postcollisional settings. Of the known porphyry copper deposits, subequal fractions are spread among these three settings. The spatial distribution of known porphyry deposits and prospects is also related to the level of erosion. Magmatic belts with numerous known porphyry sites exhibit subequal areas of coeval plutonic and volcanic units and lesser amounts of cover rocks. Belts with fewer known porphyry sites display either high or low volcanic-to-plutonic ratios and (or) greater cover, indicating crustal levels that are too shallow or too deep for exposure of porphyry deposits. Probabilistic estimates of numbers of undiscovered porphyry copper deposits were made for 18 of the 26 tracts. The undiscovered porphyry copper endowment for 8 tracts is discussed qualitatively. The assessment estimates that the Tethys region contains 47 undiscovered deposits within 1 kilometer of the surface. Probabilistic estimates of numbers of undiscovered deposits were combined with grade and tonnage models in a Monte Carlo simulation to estimate probable amounts of contained metal. The 47 undiscovered deposits are estimated to contain a mean of 180 million metric tons (Mt) of copper distributed among the 18 tracts for which probabilistic estimates were made, in addition to the 62 Mt of copper already identified in the 42 known porphyry deposits in the study area. Results of Monte Carlo simulations show that 80 percent of the estimated undiscovered porphyry copper resources in the Tethys region are located in four tracts or sub-tracts.

The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world's largest orogenic systems. The Central Asian Orogenic Belt is a collage of amalgamated Precambrian through Mesozoic terranes that extends from the Ural Mountains in the west nearly to the Pacific Coast of Asia in the east and records the evolution and final closure of the Paleo-Asian Ocean in Permian time. The eastern Tethysides, the orogenic belt to the south of the Central Asian Orogenic Belt, records the evolution of another ancient ocean system, the Tethys Ocean. The evolution of these orogenic belts involved magmatism associated with a variety of geologic settings appropriate for formation of porphyry copper deposits, including subduction-related island arcs, continental arcs, and collisional and postconvergent settings. The original settings are difficult to trace because the arcs have been complexly deformed and dismembered by younger tectonic events. Twelve mineral resource assessment tracts were delineated to be permissive for the occurrence of porphyry copper deposits based on mapped and inferred subsurface distributions of igneous rocks of specific age ranges and compositions. These include (1) nine Paleozoic tracts in the Central Asian Orogenic Belt, which range in area from about 60,000 to 800,000 square kilometers (km2); (2) a complex area of about 400,000 km2 on the northern margin of the Tethysides, the Qinling-Dabie tract, which spans central China and areas to the west, encompassing Paleozoic through Triassic igneous rocks that formed in diverse settings; and (3) assemblages of late Paleozoic and Mesozoic rocks that define two other tracts in the Tethysides, the 100,000 km2 Jinsajiang tract and the 300,000 km2 Tethyan-Gangdese tract. Assessment participants evaluated applicable grade and tonnage models and estimated numbers of undiscovered deposits at different confidence levels for each permissive tract. The estimates were then combined with the selected grade and tonnage models using Monte Carlo simulations to generate probabilistic estimates of undiscovered resources. Additional resources in extensions of deposits with identified resources were not specifically evaluated. Assessment results, presented in tables and graphs, show amounts of metal and rock in undiscovered deposits at selected quantile levels of probability (0.95, 0.9, 0.5, 0.1, and 0.05 confidence levels), as well as the arithmetic mean and associated standard deviations and variances for each tract. This assessment estimated a total of 97 undiscovered porphyry copper deposits within the assessed permissive tracts. This represents nearly five times the 20 known deposits. Predicted mean resources that could be associated with these undiscovered deposits are about 370,000,000 metric tons (t) of copper, 10,000 t of gold, 7,700,000 t of molybdenum, and 120,000 t of silver. The assessment area is estimated to contain about five times as much copper in undiscovered deposits as has been identified to date. This report includes a summary of the data used in the assessment, a brief overview of the geologic framework of the area, descriptions of permissive tracts and known deposits, maps, and tables. A geographic information system database that accompanies this report includes the tract boundaries and known porphyry copper deposits, significant prospects, and prospects. Assessments of overlapping younger rocks and adjacent areas are included in separate reports available on-line at http://minerals.usgs.gov/global/.

The U.S. Geological Survey collaborated with member countries of the Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) on an assessment of the porphyry copper resources of East and Southeast Asia as part of a global mineral resource assessment. The assessment covers the Philippines in Southeast Asia, and the Republic of Korea (South Korea), Taiwan (Province of China), and Japan in East Asia. The Philippines host world class porphyry copper deposits, such as the Tampakan and Atlas deposits. No porphyry copper deposits have been discovered in the Republic of Korea (South Korea), Taiwan (Province of China), or Japan. Thirteen geographic areas were delineated as tracts that are permissive for porphyry copper deposits in the assessed area. Individual tracts range from about 3,000 to 100,000 square kilometers in area. Permissive tracts are delineated on the basis of mapped distributions of igneous rocks of specific age ranges that define subduction-related magmatic arcs or magmatic belts that might contain porphyry copper deposits. Most of these magmatic arcs are subduction related, although some porphyry deposits and prospects are present in back-arc or poorly understood tectonic settings. Maps at various scales were used in the compilation; however, the final tract boundaries are intended for use at a scale of 1:1,000,000. Numbers of undiscovered deposits were estimated at different levels of confidence for 10 permissive tracts in the Philippines including one area that extends to eastern Taiwan (Republic of China); permissive tracts in South Korea and Japan are discussed qualitatively. Estimates of numbers of undiscovered deposits were combined with grade and tonnage models using Monte Carlo simulation to estimate amounts of undiscovered resources. Grades and tonnages of known porphyry copper deposits in the study area were compared with global grade and tonnage models to determine the appropriate model for simulation of undiscovered resources. Most of the known deposits are best described as copper-gold subtypes of porphyry copper deposits. For some permissive tracts, a general porphyry copper-gold-molybdenum model was used. Thirty-eight porphyry copper deposits are known in the Philippines; the mean number of undiscovered deposits was estimated to be 28. Mean (arithmetic) resources that could be associated with the undiscovered deposits are 90 million metric tons of copper and 5,800 metric tons of gold, as well as byproduct molybdenum and silver. Additional resources that could be discovered in extensions to known deposits were not evaluated. Assessment results, presented in tables and graphs, indicate expected amounts of total contained metal and mineralized rock in undiscovered deposits at different quantile levels, as well as the arithmetic mean for each tract. The Philippines have a long history of porphyry exploration cycles and mine development, interrupted at times by political and social unrest, environmental concerns, and natural disasters. Changes in mining laws within the region and the recent high price of gold on the world market have prompted renewed interest in porphyry copper deposits in the region. South Korea and Japan have been thoroughly explored for many types of mineral deposits. Available data suggest that the permissive rocks in South Korea typically are too deeply eroded to preserve porphyry copper deposits. Porphyry copper systems may be present in Japan, but are likely to lie at depths greater than the 1 kilometer from the surface protocol adopted for this study. Descriptions of the geologic basis for delineating each tract, the data used, the geologic criteria and rationale for the assessment, and results of the assessment are included in appendixes along with the description of a geographic information system (GIS) that includes tract boundaries, known porphyry copper deposits and significant prospects, and assessment results.

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 532-534 Meeting Abstracts Undiscovered Phanerozoic Porphyry Copper Deposits—A Global Assessment Jane M. HAMMARSTROM, Corresponding Author Jane M. HAMMARSTROM USGS, Reston, VA 20192Corresponding author. E-mail: jhammars@usgs.govSearch for more papers by this authorSteve LUDINGTON, Steve LUDINGTON USGS, Menlo Park, CA 94025Search for more papers by this authorGilpin R. ROBINSON Jr., Gilpin R. ROBINSON Jr. USGS, Reston, VA 20192Search for more papers by this authorArthur A. BOOKSTROM, Arthur A. BOOKSTROM USGS, Spokane, WA 99201Search for more papers by this authorMichael L. ZIENTEK, Michael L. ZIENTEK USGS, Spokane, WA 99201Search for more papers by this authorMark MIHALASKY, Mark MIHALASKY USGS, Spokane, WA 99201Search for more papers by this authorLukas ZÜRCHER, Lukas ZÜRCHER USGS, Tucson, AZ 85719Search for more papers by this authorByron B. BERGER, Byron B. BERGER USGS, Denver CO 80225Search for more papers by this authorConnie L. DICKEN, Connie L. DICKEN USGS, Reston, VA 20192Search for more papers by this authorFloyd GRAY, Floyd GRAY USGS, Tucson, AZ 85719Search for more papers by this author Jane M. HAMMARSTROM, Corresponding Author Jane M. HAMMARSTROM USGS, Reston, VA 20192Corresponding author. E-mail: jhammars@usgs.govSearch for more papers by this authorSteve LUDINGTON, Steve LUDINGTON USGS, Menlo Park, CA 94025Search for more papers by this authorGilpin R. ROBINSON Jr., Gilpin R. ROBINSON Jr. USGS, Reston, VA 20192Search for more papers by this authorArthur A. BOOKSTROM, Arthur A. BOOKSTROM USGS, Spokane, WA 99201Search for more papers by this authorMichael L. ZIENTEK, Michael L. ZIENTEK USGS, Spokane, WA 99201Search for more papers by this authorMark MIHALASKY, Mark MIHALASKY USGS, Spokane, WA 99201Search for more papers by this authorLukas ZÜRCHER, Lukas ZÜRCHER USGS, Tucson, AZ 85719Search for more papers by this authorByron B. BERGER, Byron B. BERGER USGS, Denver CO 80225Search for more papers by this authorConnie L. DICKEN, Connie L. DICKEN USGS, Reston, VA 20192Search for more papers by this authorFloyd GRAY, Floyd GRAY USGS, Tucson, AZ 85719Search for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12374_18Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 532-534 RelatedInformation

The U.S. Geological Survey (USGS) conducts national and global resource assessments (mineral, energy, water, and biological) to provide data and scientific analyses to support decision making. Three-part mineral resource assessments result in informed, unbiased, quantitative, and probabilistic estimates of undiscovered mineral resources and deposits. In particular, mineral assessment results inform decisions concerning land-use and mineral-resource development. A probabilistic mineral resource assessment of the sandstone subtype of sediment-hosted stratabound copper deposits in the Teniz Basin, Kazakhstan, was undertaken by the USGS. The Teniz Basin is located in Akmola Oblast, central and western Kazakhstan. With an areal extent of almost 78,000 km2, the basin contains many sediment-hosted stratabound copper prospects, none of which are well described, and the majority of which may belong to the sandstone subtype of sediment-hosted copper deposits. There are no known locations within the Teniz Basin currently mined for copper. Within the basin, however, map units permissive for the sandstone subtype of sediment-hosted stratabound copper deposits include (from oldest to youngest): the Middle Carboniferous Kiery Suite; the Middle to Upper Carboniferous Vladimirov Suite (a stratigraphic equivalent of the Dzhezkazgan Suite, Chu-Sarysu Basin); and the Upper Carboniferous or lowest Permian Kayraktin Suite. The multicolored sedimentary rocks of the Vladimirov Suite, in which 14 potentially ore-bearing horizons of gray beds have been recorded, have the greatest potential for undiscovered, sandstone subtype, sediment-hosted stratabound copper deposits. A quantitative mineral resource assessment has been completed that (1) delineates one 49,714 km2 tract permissive for undiscovered, sandstone subtype, sediment-hosted stratabound copper deposits, and (2) provides probabilistic estimates of numbers of undiscovered deposits and probable amounts of copper resource contained in those deposits. The permissive tract delineated in this assessment encompasses no previously known sandstone subtype, sediment-hosted stratabound copper deposits. However, this assessment estimates (with 30 percent probability) that a mean of nine undiscovered sandstone subtype copper deposits may be present in the Teniz Basin and could contain a mean total of 8.9 million metric tons of copper and 7,500 metric tons of silver.

The U.S. Geological Survey (USGS) conducts national and global assessments of resources (mineral, energy, water, and biologic) to provide science in support of decision making. Mineral resource assessments provide syntheses of available information about where mineral deposits are known and suspected to occur in the Earth's crust and which commodities may be present, together with estimates of amounts of resources that may be present in undiscovered deposits. The USGS collaborated with geologists of the Geological Survey of New South Wales and Geoscience Australia (formerly the Australian Geological Survey Organisation) on an assessment of Phanerozoic-age porphyry copper resources in Australia. Porphyry copper deposits contain about 11 percent of the identified copper resources in Australia. This study addresses resources of known porphyry copper deposits and expected resources of undiscovered porphyry copper deposits in eastern Australia. A three-part form of assessment was used for estimation of undiscovered resources. Using this method, four tracts were delineated that are permissive for porphyry copper deposits. A probabilistic estimate of the expected number of deposits in each tract was prepared on the basis of existing information about geology, geochemistry, geophysics, exploration history, and mineral occurrences. Monte Carlo simulation was used to combine the estimated number of deposits with an appropriate model of grade and tonnage for porphyry copper deposits to provide a probabilistic estimate of metal content and total tonnage for undiscovered deposits. The Delamerian permissive tract comprises igneous rocks of Cambrian age in the Delamerian Orogen, which borders the western margin of the Tasmanides. The Delamerian tract contains no known porphyry copper deposits, but the Adelaide sub-tract, one of three sub-tracts that compose the Delamerian tract, contains four porphyry copper prospects. The Adelaide sub-tract is estimated to contain 2.5±2.2 undiscovered deposits in an area of about 50,700 square kilometers. The Macquarie permissive tract comprises volcanic, volcaniclastic, and minor exposed intrusive igneous rocks of the Macquarie Arc. The nine known deposits in this tract are now estimated to contain a total of about 13.5 million metric tons of copper and 1,700 metric tons of gold. This tract is estimated to contain 6.9±3.5 undiscovered deposits for a total of about 16 deposits in an area of about 41,500 square kilometers. The Yeoval permissive tract includes subequal areas of permissive volcanic and intrusive rocks of Silurian to Devonian age exposed in and around the Cowra-Buchan Rift System, which overlaps the previously accreted Macquarie Arc. The Yeoval tract contains one porphyry copper deposit and several porphyry copper prospects. This tract is estimated to contain 1.3±0.75 undiscovered porphyry copper deposits, for a total of about 2 expected deposits in an area of about 53,200 square kilometers. The East Tasmanide permissive tract includes a semi-continuous belt of plutonic and subordinate volcanic rocks along the eastern margins of Queensland and northeastern New South Wales. The East Tasmanide tract contains 14 known porphyry copper deposits and many porphyry copper prospects, which are all in the Central sub-tract. This sub-tract is expected to contain 4.8±3.3 undiscovered porphyry copper deposits, for a total of about 19 deposits in an area of about 291,000 square kilometers. This assessment estimates that 15 undiscovered deposits contain an arithmetic mean of ~21 million metric tons or more of copper in four tracts, in addition to the 24 known porphyry copper deposits that contain identified resources of ~16 million metric tons of copper. In addition to copper, the mean expected amount of undiscovered byproduct gold predicted by the simulation is ~1,500 metric tons. The probability associated with these arithmetic means is on the order of 30 percent. Median expected amounts of metals predicted by the simulations may be ~50 percent lower than mean estimates.

The U.S. Geological Survey collaborated with member countries of the Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP) on an assessment of the porphyry copper resources of Southeast Asia and Melanesia as part of a global mineral resource assessment. The region hosts world-class porphyry copper deposits and underexplored areas that are likely to contain undiscovered deposits. Examples of known porphyry copper deposits include Batu Hijau and Grasberg in Indonesia; Panguna, Frieda River, and Ok Tedi in Papua New Guinea; and Namosi in Fiji. This assessment covers the countries of Cambodia, Indonesia, Lao People’s Democratic Republic, Malaysia, Myanmar, Papua New Guinea, Singapore, Thailand, and parts of southeastern China, India, the Solomon Islands, Vanuatu, and Fiji. Twenty-two geographic areas were delineated as tracts that are permissive for porphyry copper deposits in Southeast Asia. Permissive tracts are grouped into four broadly defined geographic/geologic areas, as follows: (1) the Indochina Peninsula area, (2) Indonesian and Malaysian Islands, (3) New Guinea Island and Papuan New Guinea islands, and (4) Melanesia. Individual tracts range from less than 1,000 to more than 350,000 square kilometers in area. Permissive tracts are based on mapped and inferred subsurface (<1 kilometer depth) distributions of igneous rocks of specific age ranges that define magmatic arcs and magmatic belts that are likely to contain porphyry copper deposits. Most of these magmatic arcs are subduction-related, although some have porphyry-style deposits occurring in postcollisional and (or) poorly understood tectonic settings. Although maps at a variety of different scales were used in the compilation, the final tract boundaries are intended for use at a scale of 1:1,000,000. Global grade and tonnage models for porphyry copper deposits were evaluated. Most of the known deposits are best described as fitting the copper-gold (Cu-Au) subtype of porphyry copper deposit. For some permissive tracts, a general porphyry copper-gold-molybdenum (Cu-Au-Mo) model was used. Assessment participants estimated numbers of undiscovered deposits at different levels of confidence for most of the permissive tracts. These estimates were combined with grade and tonnage models using a Monte Carlo simulation to estimate undiscovered resources. Additional resources in extensions of deposits with identified resources were not evaluated. Assessment results, presented in tables and graphs, show mean amounts of metal and mineralized rock in undiscovered deposits at different quantile levels, as well as the arithmetic mean for each tract. This assessment estimated a mean of 89 undiscovered porphyry copper deposits for the assessed permissive tracts in Southeast Asia and Melanesia. About 288 million metric tons (Mt) of copper and 18,000 metric tons (t) of gold, as well as byproduct molybdenum and silver, could be associated with undiscovered deposits. This represents about four times the number of deposits with identified resources (23) already discovered in Southeast Asia; reliable reported identified resources for those 23 deposits total 84 Mt of copper and 6,000 t of gold. Eleven permissive tracts have no known porphyry copper deposits with reported resources. Three of those 11 tracts lacked sufficient information for a probabilistic assessment and are discussed in qualitative terms. On a regional basis, both the Indochina Peninsula area and the Indonesian-Malaysian Islands area are estimated to contain about 10 times as much in place copper in undiscovered porphyry copper deposits as has been identified to date. For the New Guinea Island areas, the ratio of undiscovered to identified copper resources is about 2. Some parts of the region have a long history of porphyry exploration cycles and mine development, interrupted at times by political and social unrest, environmental concerns, and natural disasters. Changes in mining laws within the region and the recent high price of gold on the world market have prompted renewed interest in porphyry copper deposits in Southeast Asia and Melanesia. However, predicted undiscovered deposits may not be found, and if found, may not be developed. This assessment includes an overview of the assessment results with summary tables. Detailed descriptions of each tract are included in appendixes, with estimates of numbers of undiscovered deposits, and probabilistic estimates of amounts of copper, molybdenum, gold, and silver that could be contained in undiscovered deposits for each permissive tract. A geographic information system (GIS) that accompanies the report includes tract boundaries and a database of known porphyry copper deposits and significant prospects.

The fill of the Mesoproterozoic Belt-Purcell Basin, which straddles the United States-Canada border within the Rocky Mountains of western North America (Fig. 1), consists of marine and nonmarine clastic and carbonate strata 15 to 20 km thick. Three giant metal-producing ore deposits or districts account for the bulk of the known metal endowment within the bounds of the Belt-Purcell Basin: (1) the syndepositional Sullivan Pb-Zn-Ag deposit in southern British Columbia (total production: Pb, 8.4 million tonnes [Mt]; Zn, 7.9 Mt; Ag, 0.0093 Mt; Lydon, 2000), (2) the mesothermal Pb-Zn-Ag veins of the Coeur d’Alene district in northern Idaho (total production: Pb, 7.5 Mt; Zn, 3.0 Mt; Ag, 0.052 Mt; Long, 1998; post-1997 data from USGS Annual Minerals Yearbooks), and (3) the Cretaceous porphyry copper deposit and associated polymetallic veins in the Butte district in Montana (total resource: Cu, 35 Mt; Zn, 4.6 Mt; Ag, 0.044 Mt; Long et al., 1998). The Sullivan Mine closed in 2001 after more than 92 years of production. Mining of 26 major vein deposits in the Coeur d’Alene district began in the 1880s and peaked about 1950. Production in the Coeur d’Alene district continues today from the Galena and Lucky Friday Mines (the latter closed for 2012 to refurbish the mile-deep vertical access shaft). Mining at Butte began in 1875, with copper production peaking in 1917. Mining continues today in the eastern upfaulted portion of the Butte porphyry copper deposit at the Continental Mine. Fig. 1 Locations of major ore deposits within the Belt-Purcell Basin area, along with other ore deposits and mineralized trends that are discussed in this issue. Deposit locations are plotted on a geologic map showing the distribution of five stratigraphic units within the Belt-Purcell Basin in the United States and Canada. Lower Belt formations include the Prichard, Altyn, Appekunny, Chamberlain, Newland, LaHood, …

Cobalt-copper gold deposits of the Idaho cobalt belt, including the deposits of the Blackbird district, have been analyzed for their sulfur, carbon, hydrogen, and oxygen isotope compositions to improve the understanding of ore formation. Previous genetic hypotheses have ranged widely, linking the ores to the sedimentary or diagenetic history of the host Mesoproterozoic sedimentary rocks, to Mesoproterozoic or Cretaceous magmatism, or to metamorphic shearing. The delta S-34 values are nearly uniform throughout the Blackbird district, with a mean value for cobaltite (CoAsS, the main cobalt mineral) of 8.0 +/- 0.4 parts per thousand (n = 19). The data suggest that (1) sulfur was derived at least partly from sedimentary sources, (2) redox reactions involving sulfur were probably unimportant for ore deposition, and (3) the sulfur was probably transported to sites of ore formation as H2S. Hydrogen and oxygen isotope compositions of the ore-forming fluid, which are calculated from analyses of biotite-rich wall rocks and tourmaline, do not uniquely identify the source of the fluid; plausible sources include formation waters, metamorphic waters, and mixtures of magmatic and isotopically heavy meteoric waters. The calculated compositions are a poor match for the modified seawaters that form volcanogenic massive sulfide (VMS) deposits. Carbon and oxygen isotope compositions of siderite, a mineral that is widespread, although sparse, at Blackbird, suggest formation from mixtures of sedimentary organic carbon and magmatic-metamorphic carbon. The isotopic compositions of calcite in alkaline dike rocks of uncertain age are consistent with a magmatic origin. Several lines of evidence suggest that siderite postdated the emplacement of cobalt and copper, so its significance for the ore-forming event is uncertain. From the stable isotope perspective, the mineral deposits of the Idaho cobalt belt contrast with typical VMS and sedimentary exhalative deposits. They show characteristics of deposit types that form in deeper environments and could be related to metamorphic processes or magmatic processes, although the isotopic evidence for magmatic components is relatively weak.

The U.S. Geological Survey does regional, national, and global assessments of resources (mineral, energy, water, biologic) to provide science in support of land management and decision making. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected to be in the Earth's crust, which commodities may be present, and estimates of amounts of resources that may be present in undiscovered deposits. Canada is an important source of copper, consistently ranking as one of the top 10 world producers during the past decade (2000–2010). The preponderance of this production has been from porphyry-copper-type deposits in the western Canadian Cordillera. A probabilistic mineral resource assessment of undiscovered resources associated with porphyry copper deposits in western Canada was completed as part of a global mineral resource assessment. The purpose of the assessment was to (1) compile a database of known deposits and significant prospects, (2) delineate permissive areas (tracts) for undiscovered porphyry copper deposits that may be present in the upper kilometer (minimally) of the Earth's crust, and (3) provide probabilistic estimates of amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) that could be contained in undiscovered porphyry copper deposits in the tracts. The study was done by the U.S. Geological Survey (USGS) in collaboration with geologists from the British Columbia Geological Survey, Yukon Geological Survey, and industry consultants. The database of known deposits and significant prospects includes an inventory of mineral resources in 89 known porphyry copper (and 2 related copper-bearing polymetallic vein) ore zones, representing 50 porphyry copper deposits, and lists key characteristics of 280 additional porphyry copper and related copper-bearing prospects, as indicated by currently available exploration results, which also are summarized. Resource and exploration and development activity are updated with information current through April 2010. The delineation of permissive tracts and probabilistic estimation of resources in undiscovered deposits were done using the USGS three-part mineral resource assessment approach. Permissive tracts are defined in accordance with descriptive models for porphyry copper deposits to include igneous rocks and known deposits and prospects within magmatic arcs related to convergent plate-margin boundary zones. Frequency distributions of total tonnages and average grades of thoroughly explored deposits were used as models for undiscovered deposits and include a new grade and tonnage model for calc-alkaline porphyry Cu±Mo±Au deposits in western Canada. Five permissive tracts for the occurrence of porphyry copper deposits were delineated: 2 island-arc tracts, 1 tract of transitional, mixed island-arc and continental arc affinities, and 2 continental arc tracts. In permissive tract 003pCu2001, calc-alkaline igneous rocks of Middle Triassic to Late Jurassic age in accreted island-arc terranes of the Intermontane belt are assessed for calc-alkaline porphyry Cu±Mo±Au deposits. The area of this tract is 175,250 km2. In 12 known deposits, the total reported tonnage of ore is 8,100 million metric tons (Mt) containing 24.6 Mt copper. An estimated 6.9 undiscovered deposits contain a calculated mean of 8.9 Mt copper and a median of 6.9 Mt copper. The spatial density for the 18.9 known plus estimated undiscovered deposits in this tract is approximately 11 deposits per 100,000 km2. In permissive tract 003pCu2002, alkaline igneous rocks of Middle Triassic to Late Jurassic age within the Intermontane accreted island-arc terranes are assessed for alkaline porphyry Cu-Au deposits. The area of this tract is 109,290 km2. In 12 known deposits the total reported tonnage of ore is 6,440 Mt, containing 20.9 Mt copper. An estimated 7 undiscovered deposits contain a calculated mean of 22 Mt copper and a median of 13 Mt copper. The spatial density for the 19 known plus estimated undiscovered deposits in this tract is approximately 17 deposits per 100,000 km2. In permissive tract 003pCu2003, calc-alkaline igneous rocks of Late Triassic to Early Cretaceous age within the accreted Insular terranes of mixed island-arc and continental arc affinities are assessed for calc-alkaline porphyry Cu±Mo±Au deposits. The area of this tract is 58,360 km2. The total tonnage of ore reported in the 2 known deposits is 1,160 Mt containing 3.17 Mt copper. An estimated 2.3 undiscovered deposits contain a calculated mean of 3 Mt copper and a median of 1.9 Mt copper. The spatial density for the 4.3 known plus estimated undiscovered deposits in this tract is approximately 7 deposits per 100,000 km2. In permissive tract 003pCu2004, calc-alkaline igneous rocks in continental magmatic arcs of Jurassic to Eocene age are assessed for porphyry Cu±Mo±Au deposits. The area of this tract is 639,500 km2. The total tonnage of ore reported for the 23 known deposits is 6,520 Mt containing 17.9 Mt copper. An estimated 9.6 undiscovered deposits contain a calculated mean of 13 Mt copper and a median of 11 Mt copper. The spatial density for the 32.6 known deposits plus the estimated undiscovered deposits in this tract is approximately 5 deposits per 100,000 km2. In permissive tract 003pCu2005, calc-alkaline igneous rocks in continental magmatic arcs of Oligocene to Pliocene age are assessed for porphyry Cu±Mo±Au deposits. The area of this tract is 32,840 km2. The total tonnage of ore reported for the 1 known deposit is 44.8 Mt containing 0.224 Mt copper. An estimated 1.4 undiscovered deposits contain a calculated mean of 1.8 Mt copper and a median of 0.72 Mt copper. The spatial density for the 2.4 known plus estimated undiscovered deposits in this permissive tract is approximately 7 deposits per 100,000 km2. Western Canada has been thoroughly explored for porphyry copper deposits. The total estimated copper contained in known deposits is about 66.8 Mt (based on 2010 data), as compared to a 49 Mt mean of estimated copper in undiscovered deposits and a 34 Mt median of estimated copper in undiscovered deposits. The copper contained in known porphyry copper deposits represents about 58 percent of the total of known and undiscovered porphyry copper deposits (based on mean values). About 86 percent of the increase in estimated copper resources between 1993 and 2009 resulted from the discovery of extensions to known deposits. Nevertheless, exploration for undiscovered deposits continues, especially in and around significant prospects and in parts of permissive tracts that are mostly hidden beneath younger volcanic, sedimentary, or vegetated surficial cover.