Abstract The Chelopech copper-gold mine is located in west-central Bulgaria, 80 km east of Sofia, on the southern flank of the Balkan Range (Fig. 1 ), adjacent to the towns of Zlatitsa and Pirdop. The mineral potential of the Chelopech area was first recognised at the end of 19 th century, and the outcrop area was worked before World War II. The Chelopech deposit was re-discovered in 1953, following drilling by the Bulgarian government. Underground development began in late 1953 to obtain bulk samples and to further evaluate the deposits. Production commenced in 1959 and reached 100,000 t per annum in 1971. It quadrupled in 1976 following an expansion programme and the construction of a new concentrator, and it peaked at 550,000 t per annum in 1988. Total production for the period 1954 to 2002 was 12,965,000 t hoisted at an average grade of 1.10% Cu and 3.12 g/t Au. The Chelopech mine was then operated by a number of state corporations during the period 1953 to 1982, when the mine became a separate entity under the direct control of a State company called Polimet. Prior to 1990, the Pirdop smelter, located 7 km east of Chelopech, accepted the sulphide-rich concentrates from Chelopech and blended them with cupriferous concentrates from the nearby Medet, Elatsite, and Assarel mines. The relatively high content of arsenic in the Chelopech copper concentrates led the Bulgarian government to decree on April 1, 1990, that Chelopech concentrate could no longer be treated at the Pirdop smelter. In

Abstract Today's field trip examines “Carlin-style” gold deposits hosted within Permian-aged sediments of the Copperton anticline. We will visit two gold mines: the now exhausted Barneys Canyon deposit and the active Melco mine. Representative core will be available at the respective sites. The excursion will focus on the structural controls and alteration related to gold mineralization in this group of deposits. Weather permitting, a traverse will be made along the axis of the Copperton anticline from the Melco haul road south to Bingham Canyon. The traverse will pass down section through a sequence of unmineralized Permian to Pennsylvanian siliceous clastic rocks and end in the Bingham pyrite halo. This road log begins at the intersection of the new Bingham Highway with Highway U-111, approximately two miles east of the town of Copperton. The route from downtown Salt Lake City to this junction may be followed on the Day Two Road Log for the Bingham Canyon field trip. The route heads southwest toward Copperton, northwest on a private road toward the Kennecott Utah Copper concentrator, and then continues northwest to the Barneys Canyon and Melco gold mines. 0.0 Begin at the junction of the new Bingham Highway and U-111. Head southwest, toward Copperton, on the new Bingham Highway. 0.5 Dead ahead are the waste-rock piles from the Bingham Canyon mine. 1.5 Turn right, onto a private road, through the entrance gate to the Copperton concentrator. 2.6 Turn right at the fork in the road. Bingham's Copperton concentrator is to the left. The

Abstract Copper-gold skarns peripheral to the porphyry copper deposit in the Bingham mining district, Utah, contain a geologic resource of over 7 million tons of copper and 9 million ounces of gold. The skarn deposits, hosted by Pennsylvanian limestone beds within the contact metamorphic aureole of the Tertiary Bingham stock, have been mined intermittently since 1896. In the late 1960s, two large deposits were discovered at depth on the north side of the district by The Anaconda Company and Kennecott Copper Corporation: the Carr Fork mine, operated by Anaconda from 1979 to 1981, and the North Ore Shoot deposit, which has not entered production. Recent drilling by Kennecott on the eastern flank of the North Ore Shoot has resulted in discovery of the Fortuna deposit. These three areas are all part of the same, continuous skarn system. A remarkable horizontal and vertical extent of skarn is displayed within the Bingham district. Mineralized skarn occurs in a zone roughly 2,000 feet wide around the quartz monzonite porphyry phase of the Bingham stock and extends over a mile vertically from surface exposures to the deepest drill-hole intersection. Skarn ore, delineated by the +1 percent copper grade contour, lies outside the porphyry copper ore shell and extends to a lower elevation. The Carr Fork orebodies consist predominantly of chalcopyrite in retrograde-altered garnetite skarn. In the North Ore Shoot and Fortuna deposits, massive sulfide replacement bodies are the principal ore type, although mineralized garnetite is also present. Pyrite-gold mineralization that crosscuts copper-gold skarn has been found in the Bingham skarn deposits, but its relationship to other gold mineralization in the district is unclear. Beyond the zone of copper-iron-gold mineralization, lead-zinc-silver deposits occur in limestone and other host rocks within a broad halo nearly one mile wide.

Abstract The Crescent deposit is one of several porphyry-style deposits located within the Iron Mask batholith. Other mined deposits in the district include the Afton, Ajax East and West, and Pothook deposits; the Big Onion, DM, and Python zones have published reserves but have had no production (Figure 1; Kwong, 1977). The Iron Mask is a composite intrusion of alkalic affinity which was emplaced at about 207±3 Ma (Ghosh, 1993) into coeval volcanic rocks of the Nicola Group which is part of the Quesnellia oceanic island-arc terrane (Souther, 1992). The copper-gold deposits within the batholiths have been classified within the silica-saturated group of alkalic porphyry deposits (Lang et al., 1992). The Crescent deposit is located 3 kilometres due east of the Afton deposit, the largest orebody in the district (Figure 1), and yielded 1.36 million tonnes of ore with an average grade of 0.46% copper and 0.2 gram per tonne gold during production in 1989 and 1990.

Abstract The Pothook deposit is one of several alkalic porphyry copper-gold deposits (Afton, Crescent, Ajax East, Ajax West) developed in the Afton mining camp, located 10 kilometres west of Kamloops, British Columbia. These deposits are all hosted by the Iron Mask batholith, a large composite alkalic intrusion of earliest Jurassic age that intrudes latest Triassic Nicola volcanic rocks of the Quesnellia oceanic island arc terrain (Souther, 1992). The Pothook deposit is located on the southwestern edge of the Iron Mask batholith, approximately 750 metres southeast of the much larger Afton copper-gold deposit (Figure 1). It contained a geological reserve of 3.26 million tonnes grading 0.40% copper and 0.16 gram per tonne gold ($0.40 copper equivalent cut-off; Bond, 1985).

Abstract The Bingham Canyon porphyry Cu-Mo-Au deposit is located in the central part of the Oquirrh Mountains, 30 km southwest of Salt Lake City, Utah. The Cu-Au-Mo deposit lies at the center of a large polymetallic district, which includes proximal Pb-Zn-Ag replacement and distal sediment-hosted gold mineralization. Open-pit copper mining commenced in 1906 and through 2011 has produced 2.666 billion tonnes of ore averaging 0.74% Cu, 0.035% Mo, 0.448 g/t Au, and 3.29 g/t Ag. Bingham lies near the west end of an 80-km-long belt of petrochemically similar Eocene to Oligocene intrusions and coeval volcanic rocks, which host base and precious mining districts. The Bingham district is centered on the Bingham stock, a multiphase mid-Eocene intrusion emplaced into a thick succession of folded mid- to upper Paleozoic siliciclastic and carbonate rocks. The 2 × 2 km Bingham stock consists mainly of premineral equigranular monzonite that was intruded successively by a 2-km-long dike-like body of quartz monzonite porphyry (QMP), long narrow dikes and sills of intramineral latite porphyry (LP), and narrower dikes of late-mineral quartz latite porphyry (QLP). The intrusions and associated porphyry-style mineralization dip steeply to the northwest and persist from the pre-mine surface at 2,390 m to below sea level. U-Pb zircon dating indicates a 38.6 Ma age for the equigranular monzonite and suggests that the subsequent porphyry intrusions were emplaced at ∼ 38 Ma. Porphyry intrusion and mineralization were approximately synchronous. Early actinolite-stable alteration in igneous and sedimentary rocks is flanked by distal chlorite-epidote alteration. Magnetite-destructive secondary biotite alteration is pervasive in intrusive rocks that contain > 0.7% copper but typically is fracture-controlled and overprints earlier actinolite alteration in lower grade intrusive rocks and quartzites. K-feldspar alteration accompanies the highest grade copper and gold mineralization. Sericitic alteration is locally pervasive but, more typically, it is restricted to the margins of late quartz-pyrite veins. Late, low-temperature montmorillonite ± kaolinite alteration is ubiquitous in the intramineral porphyries and adjacent equigranular monzonite. An outer zone of 0.35 to > 0.70% Cu mineralization surrounds and overlaps an inner zone of 0.05 to > 0.15% Mo mineralization, which in turn forms a cupola around a barren core. Intense bornite-chalcopyrite-chalcocite-gold mineralization (> 0.7% Cu and > 1 g/t Au) occurred directly above the barren core but has largely been removed by mining. The copper mineralization in the flanks of the deposit is dominated by chalcopyrite. Copper and gold grades decrease downward but quartz-molybdenite stockwork mineralization grading > 0.05% Mo extends to the lower limit of drilling. Equigranular monzonite is the predominant ore host, containing 53% of the ore mined to date. Vein types proceed in a sequence from early biotite through quartz-sulfide to late anhydrite and zeolite. Early copper-bearing quartz veins are truncated by the LP and QLP dikes, but later copper-bearing veins cut the dikes. Cathode luminescence studies indicate that copper-bearing sulfides were deposited within micro-fractures and vugs created by dissolution of earlier quartz. Quartz-molybdenite veins postdate the copper-bearing veins and cut all of the porphyries. Vein densities reach > 10 vol % in the barren core and decrease to ∼ 1 vol % at the outer boundary of the > 0.35% Cu zone. Published fluid inclusion and vein density studies, together with modeled grade distributions, show that mineralization was precipitated by a plume of metal-bearing fluid approximately 2 km in diameter, centered near the southeastern edge of the QMP. The barren core apparently represents an upflow zone near the top of which supercritical fluids separated into vapor and brine. Copper-bearing sulfides and gold precipitated as vapor-dominant fluids cooled from 430° to 350°C. Inclusions in quartz from the deep flanks of the copper deposit indicate similar fluid compositions, but less separation into vapor and brine.