Mineral Deposits Division

Issue 55 February 1997

PREDICTIVE METALLOGENY − “PREMET”

Proposal for a new NERC Thematic Research Program in the UK

Introduction The science of metallogenesis has Mantle Petrogenesis: Many mineral de- Both of these factors are critical components reached a landmark stage where there are few posits are directly or indirectly associated in ore formation, and integration of a detailed major classes of ore deposits for which a with magmatism ultimately of mantle deriva- mechanistic knowledge of plate tectonic proc- working model of their formation does not tion. And yet only a small fraction of ex- esses with an understanding of the conse- exist. This knowledge permits, in broad posed mantle-derived lithologies host ore de- quent magmatic and heat flow responses will terms, prediction of likely geological envi- posits. Recent advances in the understanding provide both a location- and magma-specific ronments for formation of specific classes of of base and precious metal behaviour in sili- indicator for mineral prospectivity. ore deposit. It may also predict relationships cate and sulphide melts can be used to predict Crustal Environment: The crustal en- to structural or tectonic features, or certain the ways in which ore-forming components vironment consists of: chemical reservoirs lithological facies. Beyond this stage, how- will behave in certain melt compositions such as the wallrock and host lithologies with ever, exploration tends to step rapidly away formed under specific conditions of mantle which magmas or fluids may have interacted; from the underpinning science. As a result, melting. Much work has yet to be done, how- fluids within these sequences; and high-per- there is often an apparent discontinuity be- ever, before a comprehensive understanding meability zones formed by structural and li- tween the logical place of mineral deposits of these processes is achieved. This work will thological features. In many cases it is not within an overall geological framework, and combine experimental studies with petrologi- clear what role the upper crustal environment the actual geology of the deposits themselves. cal and geochemical observations of natural has played in ore formation: in some cases the It is the objective of this research programme mantle products, to provide a predictive role is purely mechanical, providing a con- to integrate existing and future deposit-spe- framework for prospective magma types. venient site for magma emplacement or hy- cific information within this broader geologi- Tectonic Setting: Mantle melting drothermal fluid flow; in other cases, chemical framework in such a way that the forma- events, and subsequent crustal melting, are cal interactions with wallrocks appear to play tion of ore deposits in terms of process, controlled by thermal processes occurring a vital role. Understanding the relative im- location, and size becomes both under- within the mantle, and transmitted to the crust portance of these factors in ore formation is standable and predictable. by plate motions. In many cases, the trans- essential for predictive metallogeny. Approach lithospheric permeability provided by tec- Fluid Interactions: The properties of tonic sutures and structural zones is the key hydrothermal fluids are central to mineral All mineral deposits are formed as a re- to crustal emplacement of mantle-derived transport and deposition in many systems, and sult of common geological processes, nor- magmas, and focused enhanced heat-flow. an understanding of the processes that may mally taken to an extreme or maintained over a long period of time. Moreover, for any given deposit type a number of such proc- Yellowknife Women Geoscientists Calendar esses, either working together or in sequence, are required to efficiently concentrate ore- forming components to form an economic resource. Prediction of mineral prospectivity The Yellowknife Women Geoscientists have put together another of their (in)famous cal- requires a detailed understanding of these endars for 1997. All proceeds from the sale of these calendars goes to the Walter Gibbins various processes and their interactions, and Memorial Fund, established in 1992 in memory of the DIAND District Geologist Walter Gibbins. thus involves a multi-disciplinary approach. Funds are used to purchase scientific texts and other learning materials to promote earth science In this respect, the development of most ore education in schools throughout the Northwest Territories. forming systems is controlled by processes occurring under five broad headings: This year’s offering “Staking Our Claim to Fame: Geo Images” is selling for $10 plus $1 postage if ordering by mail, and can be ordered from: Geocalendar Fund, Bag 9100, Yellowknife, NT, X1A 2R3, or ordered via e-mail from [email protected].

February 1997 1 MEETINGS, WORKSHOPS FIELDTRIPS

March 1997 (IGM). Lab prep, chemistry, optical micros- 5946415; FAX: 44-0-171-5946540; Email: copy etc. Field Trip to Neves-Corvo in the [email protected]. 9-12Prospectors & Developers Asoc of Can- Iberian Pyrite Belt, Sept 11-12. Contact: Dr. ada - International Convention & Trade Orlando C. Gaspar, IGM, Apartado 89, 4465 January 1998 Show. Royal York & Metro Toronto Con- S. Mamede de Infesta, Portugal. Tel: +351- 2-951-19-15; FAX: +351-2-951-40-40. vention Centre, Toronto, Canada. Contact 28 - 30 Exploration Methods ‘98 - Pathways PDAC 34 King St E, 9th Floor, Toronto, 10 - 15 Paleogeographical and Geodynamic to Discovery. Hotel Vancouver, Vanc. BC. M5C 2X8. Tel: 416-362-1969; FAX: 416- Conditions of Volcanic Sedimentary Ore Sponsored by the BC&YCM, SEG, BCGSB 362-0101 Formation. Miass, Russia. Commission on and GSC. This will be a special version of volcanic sedimentary ore genesis the traditional Cordilleran Roundup and April 1997 (COVSOG) of the Russian Academy of will comprise all the traditional events plus Sciences (RAN) in common with the special technical sessions and field trips on 21 - 25 EACM ‘97: East Asian Continental Russian section of IAGOD, the Urals topics of interest to economic geologists. Margin - Geology and Development. Hong branch of RAN and All Russian Geologi- Contact: BC & Yukon Chamber of Mines, Kong. Sponsored by Univ. of Hong Kong, cal Research Institute (VSEGEI). Post 840 W Hastings St., Vancouver, BC, V6C H.K. Geological Survey, & Geological So- Conference field trip (3-4 days) to the fa- 1C8. Tel: 604-681-5328; FAX: 604-681- ciety of Hong Kong. Contact: EACoM ‘97, mous Ilmensky Mineralogical Reserve, to 2363. Earth Sciences Dept, Univ. of Hong Kong, massive sulfide deposits, Fe-Mn, Cu, Mo, Pokfulam Road, Hong Kong. FAX: 852- and other ore fields of the South Urals. Of- 31 - Feb 7 The California Gold Rush 25176912; Email [email protected]. ficial languages will be English, German, Fieldtrip. Mother Lode District & Southern California Desert. Sponsored by MDD- April 27 - 30 CIM ‘97 - . New Frontiers for the and Russian. Registration fees: 200 US$ and 150 US$ for SGA and IAGOD members. SEG-BCYCM. Contact: Dani Alldrick, Next Century. Vancouver, BC. Contact: MDD Fieldtrip Coordinator, Tel: 250-952- Chantal Murphy, Meetings Dept., CIM, Contact: Prof. V.E. Popov, Sredny 74 VSEGEI, 199026 St.- Petersburg Russia; 0412; FAX: 250-952-0381; Email: 3400 de Maisonneuve Blvd. West, Suite [email protected]. 1210, Montreal, PQ, H3Z 3B8. Tel: 514- Fax +7 (812) 213 - 5738; E - mail: 939-2710; FAX: 514-939-2714. [email protected] (for V.E. Popov). 12 - 15 Yellowstone Park Fieldtrip. Sponsored March 1998 May 1997 by MDD. Organized by Rick Hutchinson, Nat’l Park Service - Yellowstone, Gary 15 - April 8 Australia-Tasmania Fieldtrip. 17 - 18 Short Course: Volcanic-Associated Wells - Inmet Mining Corp & D. Alldrick - Sponsored by MDD-SEG-BCYCM. Tour Massive Sulphide Deposits in Ancient and BC Geological Survey. Contact: D. Alldrick, organizers John Thompson, Dick Hutchin- Modern Settings: Classification, Processes MDD Fieldtrip Coordinator, Tel: 250-952- son & Dani Alldrick. Contact: D. Alldrick, & Examples. Sponsored by SEG and MDD 0412; FAX: 250-952-0381; Email: MDD Fieldtrip Coordinator, Tel: 250-952- - immediately preceding the Ottawa ‘97 [email protected]. 0412; FAX: 250-952-0381; Email: GAC-MAC Annual Meeting. Contact: T. [email protected]. Barrie or M. Hannington, GSC, 601 Booth 14 - 18 Exploration ‘97. 4th Decennial Inter- Street, Ottawa, ON, K1A 0E8. Tel: 613-947- national Conf. Geophysical & 2793 or -996-4865; FAX: 613-996-9820; Geochemical Exploration. Toronto. Work- May 1998 E mail: [email protected] r.ca, or shops Sept 8-12th. Contact: Jon Baird, [email protected]. Publicity Chair, c/o CAMESE, 101-345 18 - 20 Mineralized Porphyry-Skarn Systems Renfrew Drive, Markham, ON, L3R 9S9. - Short Course. Quebec City, PQ. Immedi- 11 - 14 NEVES CORVO Field Conference. Tel: 905-513-0046; FAX: 905-513-1834; ately prior to GAC/MAC Annual Meeting. Univ of Lisbon, Portugal. Conference will Email: [email protected]. Ab- Contact: Dave Lentz, NB Geological Sur- be organized around the Neves Corvo mine stracts by Sept 1/96 to Ian MacLeod, Chair, vey, Box 50, Bathurst, NB, E2A 3Z1. Tel: & other points of interest in the Iberian Py- Technical Prgm Comm., c/o Geosoft Inc., 506-547-2070; FAX: 506-547-7694; E- rite Belt. Contact: Geoffrey Snow, Barranca Suite 500, 204 Richmond St. W., Toronto, mail: [email protected]. Resources, c/o SEG Offie, 5808 Rapp Street ON, M5H 2G4; Email: [email protected]. #209, Littleton, CO 80120, USA. Tel: 303- 797-0332; FAX: 303-797-0417; WWW: June 1998 http://NevesCorvo.geo.fc.ul.pt. October 1997 June 29 - July 18 IAGOD/CODMUR 8th In- August 1997 20 - 23 SEG Annual Meeting with Geological ternational Platinum Symposium. Society of America. Salt Lake City, Utah. Johannesburg, South Africa. Field excur- 11 - 13 Fourth Biennial Meeting, Society of Contact: R.W. Schafer, BHP Minerals, sions and technical meeting. Contact: Dr Geology Applied to Mineral Deposits 14062 Denver West Parkway, Suite 150, C.A. Lee, PO Box 68108, Bryanston 2021, (SGA). Turku, Finland. Contact: Congress Golden, CO 80401. Tel: 303-277-0707; South Africa. Tel: +1-2711-411-2253; FAX: Office, SGA Meeting 1997, Lemmnkais- FAX: 303-277-0620. +1-2711-692-3693. enkato 18-18B, FIN-20520, Turku, Finland. 20 - 24 Heavy Mineral Conference. Marshall- Tel: +358-21-333-6342; FAX: +358-21- town, South Africa. Sponsored by SA Future GAC/MAC Meetings: 333-6410; E-mail: [email protected]. Institute of Mining & Metallurgy: Zululand & Natal Branchs. Contact: HM Conference, May 19 - 21, 1997 Ottawa ‘97. GAC/MAC Joint September 1997 SAIMM, PO Box 61127, Marshalltown Annual Meeting. Ottawa Congress Centre, 2107, SA. Tel: +27-11-834-1273; FAX: +27- Ottawa, Ontario. Details: Tel: 613-947- Sept YUKON Fieldtrip. Organized by the Yu- 11-838-5923; E-mail: [email protected]. 7649, FAX: 613-947-7650, Email: kon Chamber of Mines, Sponsored by [email protected] CIMM Geology Division. For details contact: Dennis Ouellette, Yukon Chamber of November 1997 May 18 - 20, 1998 Quebec ‘98 - Quebec Con- Mines, Box 4427, Whitehorse, YT. Tel: 403- gress Centre, Quebec City. Contact: Mme 667-2090; FAX: 403-668-7127; E-mail: 8-9Structural Controls & Genesis of Eco- Agathe Morin, Laval University, Sainte- [email protected]. nomic Resources; Dave Johnston Memorial Foy, PQ, Tel: 418-656-2193; FAX: Meeting. Trinity Cllege, Dublin, Ireland. Or- 418-656-7 3 39 ; e-mai l: q ue- 8-10Modern Approaches to Ore and Envi- ganized by the Tectonic Studies Gp., [email protected]; WWW: ronmental Mineralogy - Short Course: Mineral Deposit Studies Gp., Irish Assoc. http://www.ggl.ulaval.ca/quebec1998.html. Laboratorio do IGM, S. Mamede de Infesta, for Economic Geology, and Irish Geological Portugal. Sponsored by International Min- Association. Contact: J. Wilkinson, Dept May 1999 GAC/MAC 1999 - Sudbury eralogical Assoc./Commission on Ore Geology, Imperial College, Prince Consort Mineralogy, Instituto Geologico e Mineiro Rd, London, SW7 2BP, UK. Tel: 44-0-171- May 2000 GAC/MAC 2000 - Calgary

February 1997 11 MASSIVE SULPHIDE OCCURRENCES OF CAMPO MORADO A MID-CRETACEOUS, PRECIOUS METALS ENHANCED VMS DISTRICT, GUERRERO STATE, MEXICO

By J. L. Oliver, C. M. Rebagliati, D. S. Jennings, 0.58% Cu, 1.88 % Pb, and 4.53 % Zn. Gold grades within the Farallon Resources Ltd. structural footwall zone frequently exceed 10 g/t. Gold occurs as electrum and in association with tetrahedrite-tennantite. Barite is An integrated exploration program by Farallon Resources Ltd. is not identified macroscopically within the Reforma drill core but being conducted over a series of volcanogenic massive sulphide (VMS) barium is strongly geochemically anomalous in the structural foot- deposits and occurrences near Campo Morado, northwestern Guerrero wall, (stratigraphic hangingwall) to mineralized zones. State, Mexico. Recognition of structural style, stratigraphic position and The stratigraphic column at Reforma exhibits spectacular fa- alteration vectors are currently being used to successfully guide and direct cies variations. Depositional environments range from proximal, ongoing exploration programs for the many occurrences within Faral- high energy debris flows supporting massive sulphide fragments to lon’s Campo Morado concessions. distal, quiescent black clastic turbidites and calcareous argillites. In the Campo Morado district, a series of precious metals enhanced Although the Reforma massive sulphide bodies are definitively VMS deposits, including Reforma, Naranjo, La Lucha, San Rafael and precious metals enhanced, alteration and sulphide mineralogy La Suriana occur at or near the contact of a sequence of felsic to inter- strongly suggests that this deposit has been formed under low, not mediate volcanic rocks and heterolithic debris flows with fine grained high, sulphidation conditions in a below wave base, subaqueous chemical and clastic sediments. These rocks are part of a deformed, depositional environment. Fluid inclusion observations of quartz mid-Cretaceous oceanic arc, called the Guerrero Terrane. Regionally, within the deposit indicate deposition at less than 220oC. they form a classical fold and thrust belt. Structural inversions occur Similar stratigraphic controls are being defined for the newly across east-verging, recumbent folds and north-south trending thrust discovered South Naranjo deposit, located one kilometre to the faults. Between thrust bounded rock panels, continuity of both mineralized zones and lithology is excellent. Upper Plate Lower Plate At the Reforma deposit, historical reserves were 2.7 million tonnes Stratigraphic Column of 4.87 g/t Au, 247 g/t Ag, 1.14 % Cu, and 4% combined Pb and Zn. Stratigraphic Column ...... Sub-Areal ......

. . . . Hematitic Wackes .

. . Diamond drilling has shown that this deposit, in excess of 600 metres . . . Felsic Pyroclastics

. . . . .

. . .

. . . .

. . . . and Shales . . . . and Flows . . . . . strike length, 60 metres thick, and laterally continuous for up to 400 ...... Hematitic Wackes Eocene metres down dip, is located in a structurally inverted panel. Historical ...... Limestones Shales and reserves have been significantly increased by the current drill program. Black Clastics Within this inverted rock panel, the section is dominated by pervasively altered volcanic and sedimentary rocks. Rock alteration in the structural Shales hangingwall (stratigraphic footwall) distal to massive sulphide bodies Cherty Argillites consists of sericite-pyrite-quartz, and proximal to massive sulphide bod- Massive Sulphides ies it consists of chlorite-ankerite-albite. Well Bedded Limestones Heterolithic Debris The massive sulphides at Reforma are themselves strongly zoned. Flows Chalcopyrite, as discordant stockwork veins and as bedded massive sul- Shales Quartz Eye phides, is preferentially lo- Porphyritic Flows and Tuffs calized along the structural Lower Cretaceous and Older Grey,Well Bedded Limestones hangingwall and lead, zinc, Shales Cherty Argillaceous United States gold and silver are en- Orthoquartzites Sediments and and Quartz Rich hanced near the structural Black Quartzites Lower Cretaceous and Older Conglomerates footwall contact. The

Mexico Gulf of Mexico structural hangingwall Shales and P Black Clastics a zone averages 8.6 m thick c i f i in 19 holes and grades c Pillowed Volcanics O Campo Mexico City ce morado 2.10% Cu with 49.2 g/t Ag, FARALLON RESOURCES LTD. a CAMPO MORADO PROJECT n ACAPULCO while the structural foot- MEXICO Volcanic Wackes wall zone averages 7.1 m Reforma Deposit Area

Stratigraphic Column 200 m Intermediate thick in 37 holes and grades Fragmentals 4.73 g/t Au, 238 g/t Ag, After Oliver, 1996

Assay Results from Discovery Holes - South Narano Deposit Hole # From To Analyzed Au Ag Cu Pb Zn Interval (metres) (m) (grams/tonne) (percent) N133 18 11 19 899 9 1 N137 11 1 9 8 1 19 1 1 N145 19 1 18 1 1 9 9 18 191 1 1 91 8 8 1 N149 188 19 88 8 8 1 1 N152 1 19 1 1 11 1 8 1 N155 1 8 1 1 9 1 1 1 1

12 The Gangue No. 55 south of the Reforma deposit. At South Naranjo, chalcopyrite-rich massive sulphides in excess of 75 m in thickness occur at or near 100°10' the same time stratigraphic rock interval which hosts the Reforma massive sulphides.

CAMPO FARALLON At Naranjo, massive sulphides develop in close spatial association with rocks which are interpreted as intrusive hyaloclastites which Reforma West LA PAROTITA have dissected their way through a wet sedi- B CAMPO MORADO mentary pile. Like Reforma, important stra- Reforma tigraphic markers include thin bedded cherty turbidites in the structural footwall and debris flows, highly altered volcanic rocks and intrusive hyaloclastites in the structural hang- EL PINZAN ingwall. Naranjo San Rafael Current drill delineation of the South Naranjo deposit is indicating a length of at La Lucha least 800 m with a true thickness of massive A sulphides ranging from 7 m to 77 m. New assay results from the discovery holes include: At the La Suriana deposit, 8 km south of XOCHICALCO Reforma, surface exploration is just getting underway and diamond drilling will start early in 1997. Previous operators reported a re- 18°10' 18°10' source of 6 million tonnes grading 3 g/t Au, 574 g/t Ag, 0.4% Cu, 3% Pb and 4.6% Zn. Canita

La Surface exploration is also progressing at La Lucha, San Rafael and other occurrences where mapping, soil geochemistry and geo-

100°10' physics are being used to guide initial drilling. 0 1 2 Miles LEGEND After Oliver, 1996 *** 0 121 3 Kilometres Limestone

Clastic Sediments Undifferentiated - Upper Plate Looking Northwest (305º) Clastic Sediments Undifferentiated - Lower Plate A B Mafic Volcanics 1600m Felsic Tuffs 1L Orthoquartzitic Sediments 1500m MS Quartz-Feldspar Porphyritic Intrusions 2L Intermediate Feldspar Porphyritic Intrusions 3L 4L 1400m Volcanic Wackes Naranjo Limb Intermediate Tuffs 5L Reforma Limb Subareal Felsic Pyroclastics MS 6L 1300m

Fault Syncline Axis 7L 1200m Thrust Fault Anticline Axis MS Massive Sulphide Village Deposits MS 1100m

1000m Postulated Deep Limb FARALLON RESOURCES LTD. CAMPO MORADO PROJECT 0 500 1000 Feet Fault MEXICO 0 100 200 300 Metres Thrust Fault Syncline Axis Property Geology and LEGEND Major Mineral Occurrences Limestones Heterolithic Felsic Breccias FARALLON RESOURCES LTD. and Massive Felsic Flows CAMPO MORADO PROJECT Shales - Black Clastics Orthoquartzites and Quartz MÉXICO Rich Conglomerates Reforma Deposit Area MS Massive Sulphides Conceptual Cross-Section After Oliver, 1996

February 1997 13 An Update on the Voisey’s Bay Story: Models Verified & Reserves Growing

MDD - 1996 Julian Boldy Award Winner the interpretation of the relationships between them. For details please refer to Naldrett et al., (1996) and to Ryan (in press). By Bruce Ryan, Geological Survey, Nfld Dept of Mines & Energy The original discovery is within an east-west trending troctolitic dike (Figure 1), which has a variable dip to the north and a maximum Introduction thickness on the order of 100 metres. Mineralization in the dike occurs In a 1995 contribution to this newsletter (Gangue #48, April 1995) both as disseminated sulphide within a troctolitic groundmass, and as and at the GAC/MAC Winnipeg meeting of the GAC/MAC in May of pockets of semi-massive to massive sulphide that locally enclose con- 1996, I presented an overview of the magmatic Ni-Cu-Co sulphide temporaneous silicate minerals (plagioclase, olivine, pyroxene). mineralization near Voisey’s Bay, Labrador, outlining the plutonic set- The Ovoid, to the east of the initial discovery dike (Figure 1), is ting of the mineralization and speculating on the potential controls on an exceptional ore body, a bowl-shaped accumulation of sulphides, in the generation of the sulphides. Both of these contributions were predi- places over 100 metres thick, separated from underlying gneiss by a cated on information presented in a discussion paper by Ryan et al., rind of troctolite containing numerous fragments of gneiss. This sul- (1995) prepared shortly after the initial announcement of the Voisey’s phide mass is roughly elliptical in plan view and is approximately Bay discovery. 450x250 metres in size. The reserves in the Ovoid are estimated to be The setting of the mineralization was given as being in the pre- at 31.7 million tonnes, having an overall grade of 2.83% Ni, 1.68% served remnants of a partly eroded troctolitic pluton, the Reid Brook Cu, and 0.12% Co. The Ovoid is interpreted by Naldrett et al., (1996) intrusion, of the Mesoproterozoic Nain Plutonic suite. The sulphides to be the down-faulted base of the overlying magma chamber - the part were considered to be a product of the crustal contamination of the that is missing from the dike setting. metal-enriched precursor magma to the Reid Brook intrusion by an Drilling of massive troctolite to the east of the Ovoid has encoun- underlying sulphide-bearing Tasiuyak paragneiss unit. tered a significant linear zone of sulphide near the contact between the The basic notions in that contribution have been confirmed in troctolite and the underlying gneiss, at a depth of over 600 metres. This recent papers by Naldrett et al., (1996) and Li et al., (1996). At the discovery is referred to as the Eastern Deeps (Figure 1), and is inter- time of preparing my earlier Gangue contribution the known minerali- preted by Naldrett et al., (1996) to correspond with the line of inter- zation was confined to a dike west of the main troctolite and to a section between the sulphide-bearing feeder dike and the base of the bowl-shaped body (the ovoid) in the intervening drift-covered area Reid Brook magma chamber. This discovery verified the geological between the dike and the intrusion. The dike was considered to repre- reasoning of Ryan et al., 91995) that the massive troctolitic rocks east sent the feeder conduit to the (eroded) base of the intrusion, but the of the discovery dike represented a preserved higher stratigraphic level connection between the Ovoid and its surroundings was not firmly in the Reid Brook intrusion, and that sulphides might be resident at the established. base of the intrusion in that area. The indicated resources for the Eastern Deeps deposit are on the It has now been shown that the Ovoid is also part of the Reid order of 50 million tonnes containing 1.36% Ni, 0.67% Cu, and 0.09% Brook intrusion (Naldrett et al., 1995). Additional massive sulphide Co. The Eastern Deeps deposit has not been fully delineated at present, has been discovered in the troctolite to the east of the Ovoid, a setting but the geometry of the base of the magma chamber in this area indi- referred to as the Eastern Deeps. Geological considerations auger well cates that there may well be an extensive zone of sulphides present for more discoveries in the same area. along strike of the known ore. Similarly, the dike-hosted part of the The Voiseys Bay Deposit deposit, west of the initial discovery outcrops, has the potential for hosting more ore, especially in appropriate traps within this part of the The sulphide mineralization at Voisey’s Bay comprises predomi- sub-chamber plumbing system. nantly pyrrhotite, pentlandite and chalcopyrite; magnetite is also widely developed within the sulphide mineralization. The ore minerals Epilogue are locally exceptionally coarse grained. The Reid Brook intrusion and its sulphide ore deposit straddles As noted above, the Voisey’s Bay mineralization is disposed in the Nain Province - Churchill Province boundary. A major, 1.8 Ga several different settings. Without exception, however, the host rock collisional suture in Labrador. The main controls on the formation of to the sulphides is massive troctolite, one of two major units that the deposit are proposed to be the rapid transport of a sulphur-under- comprise the Reid Brook intrusion, as I outlined in my previous com- saturated mantle magma into the crust, perhaps aided by suture-related munication. The following is an overview of the geological features deep-crustal faults, and the subsequent in-transit sulphur or silica-con- of the three major concentrations of sulphides known at this time, and tamination of that magma by interaction with underlying Tasiuyak

? ? P.E.L.

DISCOVERY HILL P.E.L. AND WEST EXTENSION EASTERN DEEPS YOUNGER GRANITE YOUNGER OVOID GRANITE

Figure 1. Block diagram of the Reid Brook troctolite intrusion (dark grey) and the setting of the Ni-Cu-Co sulphide mineralization (black). The present erosional level (P.E.L.) is represented by the younger granite to the west of the Discovery Hill Dike.

14 The Gangue No. 55 [Editor’s Note: Inco announced the discovery gneiss (Ryan et al., 1995; Li et al., 1996), thus That is, their distribution straddles the ex- of a new mineralized zone (NM 2/10/97) which generating an immiscible sulphide magma. trapolated Nain-Churchill boundary, and they lies below and partly contiguous with, a shal- It is of considerable interest to note that are within plutons that may have encountered low zone in the deposit’s western extension. new discoveries of sulphide mineralization in Tasiuyak gneiss during emplacement. Cylindrical in shape, the zone plunges gently the northern part of the Nain Plutonic suite, This reinforces the probable importance eastward toward the Ovoid discovery zone. brought to public attention in numerous press of the Nain-Churchill boundary and the Tasi- This new zone has been traced for 500 m along releases from several junior exploration com- uyak gneiss to the localization of such sul- trend and at depths of 250 - 600 m from sur- panies over the past year, are in a similar re- phide mineralization, and maintains this set- face, with an average width of 110 m.] gional geological setting (though apparently ting as a viable exploration target for different hosts) as the Voisey’s Bay deposit. additional discoveries.

International Mining Highlights

• The Voisey’s Bay Nickel Company Presi- • Zambia has offered to provide Nigeria with dent Dr.Steward Gendron recently an- assistance in the development of its mining Large, Furry Ants nounced that their new nickel smelter/re- industry. The offer provides for technical finery complex will be built on the eastern support and training. (MJ 1/24/97) Discover Gold Avalon peninsula of Newfoundland at Ar- gentia. • Geologists in India, according to India’s Current Science, have discovered uranium For more than 2500 years, historians • Students rioting at South Korea’s Yonsei in the southern state of Andhra Pradesh. the have been intrigued by Herodotus’ tale of University during August, apparently discoveries, by the Dept of Atomic Energy, large furry ants that enriched the Persian em- found weapons in short supply and had to are said to contain up to 0.55% uranium pire by burrowing for gold. Herodotus’ story use whatever was available. When police oxide and small amounts of thorium oxide. finally quashed the protest, the geology de- The deposits are in the Palanad sub-basin of “ants bigger than foxes but smaller than partment faculty discovered that about 10 in the northern part of the Cuddapah dis- dogs” inspired generations of treasure hunters 000 rare rock samples, collected over 30 trict and about 300 km from the state capi- and explorers - going back to Alexander the years and considered irreplaceable, were tol of Hyderabad. (MJ 1/24/97) Great. In the absence of proof, some classical missing. A few specimens were recovered scholars concluded that the man many call the chipped or broken from the streets. • The Geological Survey of Canada recently father of history was at best gullible and at • hosted a workshop for Canadian airborne Russia has recently announced new regu- geophysical contractors (Jan 21/97) to dis- worst a liar. lations which require the registration of all cuss improvements in developing con- Now it appears he may have been right foreign mining consultancy firms with the tracts for aeromag and radiometric sur- Gosgortechnadozor state committee if they veys. Major technological advancements - or largely so. Recently returned from a Hi- wish to operate legally in feasibility or in areas such as GIS and data processing malayan expedition, French explorer-anthro- other studies on any exploration/mining now require significant changes in the con- pologist Michel Peissel and British photogra- projects within the Russian Federation. In tractual framework for GSC and its clients. pher Sebastian Guinness say they have North America Gosgortechnadzor has ap- A summary report will incorporate sugges- located the gold-digging ants on Pakistan’s pointed Colorado-based Crossing Point to tions for improvements provided by par- Dansar plain near the tense 1949 cease-fire represent its interests. Crossing Point will ticipants. act as liaison between North American line with India. The “ants”, it turns out, are mining interests and the Russian mining • Kimberlite boulders have been identified actually marmots, cat-size rodents that bur- authorities. (MJ 1/24/97) on the shoreline of a lake in the Maniitsoq row in a gold-bearing stratum of sandy soil a • region of west Greenland. The lake was few feet underground. Peissel believes Hero- The Province of British Columbia has em- identified by geophysics as a possible kim- barked on an aggressive new program to dotus’ confusion came from the ancient Per- berlite target using the model of kimberlite sian word for marmot, which means ‘moun- help level the international playing field for pipes in Canada’s Lac de Gras area. The tain ant’. investment in mining development. At a boulders were found to have originated in loss to stem the tide of companies leaving the diamond stability field, and one carried the province for “greener pastures” over- Peissel first heard about the gold-digging a clear white microdiamond. (Greenland marmots in 1983, while traveling on the In- seas, the Ministry of Employment and In- Minex News #11) vestment has been allowing its senior bu- dian side of the border. Local Minaro tribes- reaucrates to undertake contracts in • Recent results from a Tasmanian-Austra- men told him that their ancestors extracted developing countries. Particular emphasis lian research program indicates that high- gold from sand that stuck to the rodent’s fur has been placed on South America and Af- resolution seismic reflection surveying has and was deposited on the surface. Trouble rica, in order to bring their mining laws, a potential for identifying large prospec- was, the marmots were located on the Paki- regulations and attitudes into line with tive targets at depths below 500m. Initial stani side of the cease-fire line in an area that those already in place in British Columbia. work included a 1.2 km test line over a pro- is regularly strafed with mortar and gunfire. • Brazil’s constitutional amendment No. 6, spective portion of the Mount Read VMS district of Tasmania. The resulting imagery It took Peissel 14 years to get permission to enacted in August, 1995, and which again visit the region under Pakistani military es- allows foreign companies to own 100% of revealed a prominent bulge at a depth of a local mining property has led to a signifi- 1150m at the top of a highly reflective unit cort. He is convinced it was worth the wait. cant growth in mineral exploration. This is interpreted to be the Que-Hellyer vol- “The expedition’s findings at long last vindi- now expected to evolve into what could be- canics. Beneath the bulge weaker internal cate herodotus,” says Peissel, “ending what come the most significant gold-rush in Bra- reflections indicate the possibility of al- may be the longest treasure hunt in history.” zil’s history with the obvious interest from teration. A strong reflector on top implies a high density contrast which may indicate international mining companies. (MJ - By Thomas Sancton/Paris 4/10/96) massive sulphides. (Aus-Geo News #38). Time Magazine Dec 9/96

February 1997 15 CIM Exploration and Mining Geology Now Aailable to Mineral Deposits Diision - GAC members

The MDD and CIM are pleased to remind you that as a member of Mineral Deposits Division, GAC, the CIM Geological Society’s fellow technical association in Canada, you may now become an individual member subscriber to Exploration and Mining Geology. The special MDD-GAC Member subscription rate for 1996 is $60 (US$50). Please note that this subscription is for personal use only. For direct mail delivery of EMG on a quarterly basis, please complete this form and mail it, together with your subscription fee, directly to the CIM at the address below. Name: GAC Membership #: Address: City: Province/State: Country: Postal Code: MDD Member 4 Cheques should be made payable to the “CIM” and sent to: Canadian Institute of Mining, Metallurgy and Petroleum Xerox Tower, Suite 1210 3400 de Maisonneuve Boulevard W Montreal, Quebec, Canada, H3Z 3B8

Special Session on Back Arc Continental Rifts Digital Data for Indonesia May 18 - 1, 199 - Geological Association of Canada/ Mineralogical Association of Canada 9 - Ottawa Indonesia geological consultant Vol- A Special Session entitled “Tectonic, Magmatic and Hydrothermal Evolution of canex International is developing digital geos- Continental Backarc Rifts and Methods of Sulphide Exploration, with Emphasis on the cience information packages for high priority Bathurst Mining Camp”, will be held at the Geological Association of Canada/Mineralogi- exploration regions in Indonesia, including cal Association of Canada Annual General Meeting. A post-conference trip to the Bathurst Mining Camp, northern New Brunswick will be offered as part of the Session. Co-spon- Kalimantan, Sulawesi, Sumatra and Nusa sored by the GAC-Mineral Deposits Division, CIM-Geology Section, and EXTECH-II Tenggara. project:GSC and NB Dept of Natural Resources. The project is being sponsored by a Technical Program: Two days of presentations and one day of posters will run concurrently on the first day. Emphasis will be on new research emanating from EXTECH- number of major Australian and international II in the Bathurst Mining Camp. The session will draw on the extensive research of modern exploration companies. continental rifts, and similar ancient backarc rifts that host seafloor massive sulphides. Over 50% of the presentations are by invitation, and will feature international experts Based on compilations of information in tectonics, and magmatic & mineralizing processes in backarc rifts. Day 1 will focus on from government 1:250 000-scale maps, and the genetic relationship between extensional tectonism, anoxic sedimentation, felsic mag- the geoscience research literature, the pack- matism, metalliferous fluid generation & discharge, and seafloor depositional processes. ages are intended to be used for project gen- Day 2 will focus on the development, testing and application of exploration methods in the Bathurst Camp. eration and tenement assessments by explora- Field Trip: “Geology & Massive Sulphide Deposits of the Bathurst Mining Camp”. tion managers, project geologists and mining This 3-day trip will examine the characteristics of various VMS deposits, and relate their analysts. formation to the stratigraphic and tectonic evolution of the Bathurst Camp, recently re-interpreted as a preserved backarc basin accretionary complex. The packages are available for use with Organizers: Wayne Goodfellow and Cees van Staal - Geological Survey of Canada the Windows-based desktop mapping and GIS applications ArcView and MapInfo, which en- BATHURST MINING CAMP able sophisticated analysis, interpretation and 466 million years ago presentation of the information. Subduction Oceanic Zone and Bac-Arc Rift Shelf Margin For further information contact: Crust sland Arc Sea Level Dr Graeme Wheller, Volcanex International Massive FelsicF Sulphides Pty Ltd., Geological Research and Informa- VolcanicsVololcanics tion Systems, 521 Tinderbox Rd, Blackmans OCEANIC CRUST Bay, TAS, 7052, Australia. Tel/FAX: +61-3- CONTINENTALCON Magma BASEMENT 62298057, or Email: [email protected] CONTACT pet.com.au. Information is also available on Ottawa 97 co GSC their web site at URL: 61 Booth St, Ottawa, ON,K1a E8 http://busker.trumpet.com.au/volcanex/ Tel 61-97-769 FAX 61-97-765 E-mail ottawa97emrca ASTHENOSPHERE ***

16 The Gangue No. 55 Volcanic-Associated Massive Sulphide Deposits in Ancient and Modern Settings: Classification, Processes and Examples

MDD-SEG Sponsored Short Course • Stable isotopes and VMS systems: A Re- May 17 - 18, 1996, Ottawa 97 view: D. Huston • This will review current studies on critical aspects of VMS formation, with an em- Heat and Fluid flow modelling and VMS phasis on relevance to mineral exploration. It will present results of recent studies on very systems: T. Barrie, L. Cathles and A. Erendi large or important VMS deposits and districts around the globe. There will be an accom- Examples: panying Economic Geology Reviews in Economic Geology volume co-sponsored by the SEG and the MDD/GAC. Emphasis will be on discussion and audience participation. • The giant Kidd Creek deposit: a giant Speakers are from North America, Europe and Australia and include many pre-eminent komatiite-rhyolite associated VMS system: scientists who work on seafloor and land-based VMS systems. T. Barrie, M. Hannington and W. Bleeker Topics for presentation: • The Iberian Pyrite Belt of Portugal and Spain: Examples of bimodal-siliciclastic • Introduction: Classification of VMS deposits, based on world-wide compilation systems: D. de Carvalho, J. Munha and F. • Barriga Processes: • • Subaqueous volcanism: Environments and controls: H. Gibson & R. Morton Eskay Creek: an unusual precious-metal rich bimodal VMS system: T. Roth, J. • Structural aspects of hydrothermal venting in seafloor-ophiolite settings: G. Harper et al. Thompson et al. • Magmatic and hydrothermal controls on seafloor venting: M. Perfit, I. Jonasson et al. • Windy Craggy, BC: a mafic-siliciclastic • Hydrothermal alteration of oceanic crust: J. Alt VMS system: J. Peter and S. Scott • Fluid chemistry, base and precious metal transport and deposition: B. Seyfried et al. • VMS deposits in ophiolites and their mod- • Stratigraphy and alteration of bimodal VMS systems: T. Barrett et al. ern seafloor analogs: R. Koski & A. Galley • Semi-conformable alteration patterns in VMS systems: D. Ames and A. Galley • Metalliferous sediments of the Atlantis II Deeps, Red Sea: R. Zierenberg • Massive sulphide deposits at sediment-covered spreading centres: W. Goodfellow et NEW Geological Map of Canada al. For further information contact: The Geological Survey of Canada announces the release of a new geological map of Canada in both paper and digital formats. T.Barrie, GSC Released as a vibrantly coloured wall map (Map 1860A) in September, 1996, it is 601 Booth Street, Ottawa, ON, K1A 0E8 the latest comprehensive map produced of Canada’s geology. Compiled from published Tel: 613-947-2793; FAX: 613-996-9820; and unpublished materials of the GSC, provincial and territorial geological surveys, and Email: [email protected] other sources, this map reflects new interpretations of the geology resulting from recent or, geological mapping, extensive aeromagnetic and gravity surveys, and improved methods of dating and correlating geological units. M. Hannington, GSC The digital version, released as Map D1860A in January, 1997, presents the new map Tel: 613-996-4865; in a variety of formats which will meet the needs of a wide range of clients. It is provided Email: [email protected] on an IS)-9660 compliant CD-ROM which allows it to be read by most operating systems. The data are provided in Arc-Info formats (native, .E00 interchange, and .SHP ‘shape”), which can be accessed by a variety of GIS and CAD applications on different platforms, including Unix and Microsoft DOS/Windows. The .SHP files have also been packaged MDD Travel Advisory for direct access by SurView (included on the CD-ROM), a data visualization package for Microsoft Windows. The new map and its digital version afford a better display and understanding of • In July, in Cape Town, South Africa, correlations and contextual geological relationships across Canada and into the offshore four cab drivers were killed and sev- areas. They open up new frontiers for learning about Canada, not only providing the eral customers wounded as gunfire opportunity for studying geological patterns and relationships at the scale of the Canadian erupted again in a continuing war landmass, but also forming the foundation for the digital national geoscience knowledge base. As well, the map will be an invaluable educational tool. over competition among taxi compa- Geological Map of Canada; J.O. Wheeler, P.F. Hoffman, K.D. Card, A. David- nies. son, B.V. Sanford, A.V. Okulitch and W.R. Roest (comp.) • In September, in Los Angeles, USA, Map 1860A, scale 1:5 000 000. Bilingual map with English or French legend police said that four of six recently $30.00 ($39 outside Canada) missing boarding house residents had Bilingual map with both English and French legend actually been kidnapped by a rival $40.00 ($52 outside Canada) boarding house. Stealing boarders is Map D1860A. CD-ROM with bilingual documentation $100.00 ($130 outside Canada) apparently an increasingly common competitive tactic to land other Available from: houses’ customers in order to get ac- Geological Survey of Canada Bookstore cess to their government cheques. 601 Booth Street, Ottawa, ON, K1A 0E8 Tel: 613-995-4342; FAX: 613-943-0646 Please submit your interesting travel Email: [email protected] anecdotes to the editor for the next issue of The Gangue.

February 1997 17 Table I Annual Publication Expenses & Revenues MDD Treasurer’s Report for 1996 Year Expenses# Revenues 198 - 98 ,9 , 199 ,8 by Bob Cathro, MDD Treasurer 1991 11,9 ,89 199 1,9 As shown on the attached pro forma fi- Tables I and II, which accompany this 199 1,8 ,8 nancial statement, a $10 142 loss on opera- report have been prepared to summarize the 199 1, 8,919 tions for 1996 resulted in a corresponding re- publishing activities of the MDD by year 199 11,1 11,1 duction in operating surplus. This loss, which since 1984, and by compare the financial suc- was smaller than expected, was due to the cost 199 , 18,9 cess of each. Table II also includes $31 529 of publishing the Alteration Atlas, which, at otal 1, 8, donated to GAC to assist with its efforts. about $29 000 (including some 1995 ex- Aerae 99 ,1 penses) is by far our most ambitious publishing venture to date. The Mineral Deposits Di- # - includes minor advertising & admin costs * - sales net of commission & sales tax vision also shared the cost, along with GAC, ** - annual average excluding grants is $8156 of printing Short Course Notes #12 during 1996. Table II - Financial Results for Each Publication All other revenues and expenses were in Year Title Expenses Revenues Return line with expectations with the most pleasant 198 ighland Valley, BC 1,8 , 1 surprise being a healthy growth in member- 198 emlo, ON 11,9 1, 147.4 ship fees, which cover our annual operating 198 ellownife, NT ,99 ,18 costs, including The Gangue. Our other ven- tures are financed from retained surplus accu- 1988 Newfoundland VMS 1,1 1,98 88 mulated over the years from donations 1991 Greenstone Gold (NNA ) 11,9 n/a (mainly surpluses from field trips). 199 Mid-Continent iamonds ,8 1,118 207.7 In addition to the operating funds cov- 199 Ore eposit Models 1, n/a ered in the financial statement, MDD also (Reprint Series #6) holds endowments of about $47 000 that sup- 199 Alteration Processes 1, 1, 160.4 port the Gross, Derry and Boldy awards. (Short Course Notes #11) The current strong health of MDD is due 199 Mineral eposit Modelling 1, n/a almost entirely to the dedicated volunteer ef- (Special Paper #40) forts of those responsible for our last three 199 Trace-Element Geochem ,81 ,1 8 publications, Short Course Notes #11, by Dave Lentz, Short Course Notes #12 by D.A. (Short Course Notes #12) Wyman, and the Alteration Atlas, by Anne & 199 Alteration Atlas 9,9 1, 8 John Thompson, as well as our recently re- tired Publications Chair, Kathryn Dunne. It is Totals: 1, 8, 88 quite remarkable that the Atlas, prepared by (excluding grants) 9,9 8, 918 Anne and John Thompson, recovered almost * - outright grant to GAC; ** - 50% MDD / 50% GAC 60% of its costs in only two months. MDD printed 2000 copies, sold 455 by the end of Pro Forma Statement of Revenue & Expenses 1996 and will break even with about 775 sales. For the Year Ended December 31, 1996 Almost as remarkable is the popularity of 1996 1995 Short Course Notes #11 on Alteration Proc- essess, which was priced very low to make it Revenue easily available to students (far below GAC Interest Income$ 4,882.00 $ 5,282.00 pricing policy) and has now made a handsome Membership Fees$ 8,315.00 $ 6,970.00 profit. For the first time in many years, MDD currently has no new publications planned. Publication Sales$ 18,729.00 $ 11,051.00 Donation - S Africa Field Trip$ 175.00 When I replaced Al Sinclair as Treasurer in 1989, one of the principal sources of in- $32,101.00 $ 23,303.00 come came from interest on bank deposits. Expenses For example, Gross funds were invested in a Accounting$420.00 479.00 $ 5-year GIC at an interest rate of 11.5%. As Advertising$ 248.00 interest rates declined, the annual membership fee was increased from $5 to $10. One Bank Charges$93.00 115.00 $ of the other main changes has been the disap- Convention (AGM)$ 547.00 $ 1,766.00 pearance of donations (mainly field trip reve- Newsletter (The Gangue)$ 6,242.00 $ 4,678.00 nue) as an important source of income as field trips have become more expensive and have Computer Upgrade (newsletter) $ 2,008.00 been budgeted to break even. Thus, successful Office & Misc$195.00 248.00 $ publications have emerged as the only signifi- Publication$ 34,364.00 $ 11,156.00 cant source of income other than fees and re- $42,243.00 $ 20,316.00 main, in the opinion of most of the donors of the funds and myself, the most suitable way Net Surplus (loss )($10,142.00 )$ 2,987.00 to provide a vital and low-cost service to all Operating Surplus - Beginning of year$ 83,236.00 $ 80,249.00 members, particularly students, and to the science itself. Operating Surplus - End of year$ 73,094.00 $ 83,236.00

18 The Gangue No. 55

eray1997 February 19

ATER EEO/STAGE / EPOC PERO TERTIARY -NAR

PALEOGENE NEOGENE

Pleistocene olocene

Paleocene Eocene Oligocene Miocene Pliocene

Piacenian

Serravallian

Auitanian

Burdigalian

Priabonian

Messinian

Langhian

Chattian

Tortonian

Rupelian

Calabrian

Zanclian

Thanetian

Bartonian

presian

Lutetian

anian

1 1

118 1

18 1

81 8

1 1

91 9

118 1

Age

Ma EEO/STAGE / EPOC PERO

TRIASSIC URASSIC CRETACEOUS

Santonian

immeridgian

Turonian

ienerian

Spathian

Pliensbachian

Maastrichtian

Cenomanian

Campanian

auterivian

ettangian

Sinemurian

Valanginian

Barremian

Bathonian

Callovian

Berriasian

Toarcian

Aalenian

Baocian

Ladinian

Carnian

Aptian

Norian

Albian

Griesbachian

Coniacian

Oxfordian

Tithonian

Smithian

Anisian

11 1

11 11

9 1

11 18

8 1

1 1

8 118

8 11

8 1 18

1 1

1 11

()

9 19

8 88

8 11

Age

Ma ()

CARBONIFEROUS PERO CAMBRIAN ORDOVICIAN SILURIAN DEVONIAN PERMIAN

MSSSSPPAN PENNSLVANAN

Givetian

hulfian

Siegenian/Pragian

Richmondian

Gedinnian/Lochovian

resbachian

Trentonian

Chayan

Trempealeauan

Serpuhovian

ordian

Famennian

Tournaisian

Llandoverian

PC STAGE / EPOC

enlocian

aucoban

asimovian

Moscovian

Gamachian

Bashirian

Placentian

Canadian

Ludlovian

Pridolian

Samarian

Visean

Ghelian

Artinsian

Eifelian

Asselian

Changhsingian

Frasnian

hiterocian

Blacriverian

Franconian

Maysvillian

Edenian

Capitanian

Roadian

Emsian

(1)

()

9 9

8 88

11 9

(8)

()

8 8

()

1 1 1

1 9 11

1 1 1 9 1 9

()

8 1 81

1 9 1

9 9 9 1

9 9

Age

EON 9 nepltdiooi g o tg boundary stage for age isotopic interpolated (9)

8iooi g o tg onayuncertainty boundary stage for age isotopic 18 8 ARCHEAN PROTEROZOIC

hnri aadrvdfrom: derived data Phanerooic rCmra aafrom: data PreCambrian

Paleoarchaean

Mesoarchaean

adrynian

Neoarchaean

)LmesCard Lumbers 1)

)Brade l (199) al et Barland 1)

Eoarchaean

Aphebian

(middle)

eliian

(early)

(earliest)

(middle)

ERA

(late)

(early) (late)

Paleoproterooic Mesoproterooic Neoproterooic

epoeooc Neoproterooic

Calymmian

Cryogenian

Orosirian

Statherian

Ectasian

Rhyacian

Stenian

PERO

Siderian

Tonian

Ga (

Age Ma Contact: D. Alldrick, MDD Fieldtrip Coordinator, FAX: 250-952-0381; Email: [email protected]

20 The Gangue No. 55 1996 – 1997 MDD EXECUTIVE The Gangue No. 55

Following are the MDD Executive and Directors for the 1996-1997 term. Please contact The Gangue is published quarterly by the Mineral Deposits Division, GAC, and is dis- any of these individuals for enquiries, or to suggest initiatives for MDD. tributed to members as part of their membership. Chairperson: Cominco Ltd., David Moore 7th Floor 409 Granville St. Vancouver, BC, V6C 1T2. Tel: 604-685-3064; FAX: 604-685-3069 MDD Goals and Objectives The Mineral Deposits Division of the Geo- Vice Chairperson Geological Survey of Canada logical Association of Canada is Canada’s fore- Al Galley 661 - 601 Booth Street most society for promoting the study of mineral Ottawa, ON, K1A 0E8 deposits by supporting local and national meet- Tel: 613-992-7867 E-mail: [email protected] ings, symposia, short courses and field trips. We sponsor the publication of research relating to Past Chairperson & Membership DIAND ore deposits and metallogeny and recognize the Jennifer Pell 4-4914 50th Street, Bellanca Bldg. contributions of outstanding Canadian eco- PO Box 1500, Yellowknife, NT, X1A 2R3 nomic geologists by annually awarding the Tel: 403-669-2640 FAX: 403-873-5763; Duncan Derry and William Harvey Gross med- E-mail: [email protected] als and the Julian Boldy Certificate.

Secretary: Inmet Mining Corporation Publication Schedule: Gary S. Wells 3-311 Water Street, Vancouver, BC, V6B 1B8 Tel: 604-681-3771 FAX: 604-681-3360 SUBMISSION PUBLICATION DEADLINE DATE Treasurer: Cathro Exploration Corp. Robert J. Cathro RR#1, Site U-39, Bowen Is., BC, V0N 1G0 December 15 January Tel: 604-947-0038 FAX: 604-947-0038 March 15 April June 15 July Publications: Wolverton Securities September 15 October Art Ettlinger 17th Floor - 701 W. Georgia Street Vancouver, BC, V7Y 1J5 Information for contributors: Tel: 604-662-5248; FAX: 604-662-5205 The objective of this newsletter is primarily to provide a forum for members and other pro- Professional Development Dept. of Earth Sciences, Univ. of Windsor fessionals to voice new ideas, describe interest- Short Courses: Windsor, ON, N9B 3P4 ing mineral occurrences or expound on deposit Iain M. Samson Tel: 519-253-4232 ext 2489; FAX: 519-973-7081 models. Articles on ore deposits, deposit mod- E-mail: [email protected] els, news events, field trips, book reviews, conferences, reprints of presentations to Professional Development BC Geological Survey companies, mining groups or conferences, or Field Trips: 5 - 1810 Blanshard Street; Victoria, BC, V8T 4J1 other material which may be of interest to the Tel: 250-952-0412 FAX: 250-952-0381; economic geology community are welcomed. Dani Alldrick E-mail: [email protected] Manuscripts should be submitted on IBM- Program Chair: Ottawa ‘97 Mineral Resources Division, GSC, 601 Booth St., formatted diskettes in any major word proces- Al Sangster Ottawa, ON, K1A 0E8. Tel: 613-992-8603; sor format. A printed version should be FAX: 613-996-9820; included. Illustrations must be camera-ready E-mail: [email protected]. (ideally as CDR digital files); photos should be of good quality. Short items dealing with news Program Chair: Quebec City ‘98 Sainte-Foy, Quebec events or meetings can be submitted by FAX, Benoit Dubé Tel: 418- 654-2669 FAX: 418- 654-2615; postal mail or E-mail. E-mail: [email protected].

Newsletter Editor The Gangue, PO Box 8076, Victoria, BC, V8W 3R7 Contributions may be edited Brian Grant Tel: 250-952-0454; FAX: 250-952-0451 for clarity or brevity. E-mail: [email protected] For Information & Submissions: MDD DIRECTORS Brian Grant Terence J. Bottrill (1994 - 1997) Oakville, Ontario Editor - THE GANGUE Tel: 905-842-2893; FAX: 905-842-3614 PO Box 8076, Victoria, BC, V8W 3R7 Pamela L. Schwann (1994 - 1997) La Ronge, Saskatchewan Tel: 250-952-0454 FAX: 250-952-0451 Tel: 306-425-4211 FAX: 306-425-4349 E-mail: [email protected] Marcos Zentilli (1994 - 1997) Halifax, Nova Scotia Tel: 902-494-3873 FAX: 902-494-6889; E-mail: [email protected] Dani Alldrick - Associate Editor Dan Brisbin (1995 - 1998) Timmins, Ontario. & MDD Fieldtrip Coordinator Tel: 705-267-1188 ext 253; FAX: 705-264-6080 E-mail: [email protected] E-mail: [email protected] Michael J. Downes (1995 - 1998) Toronto, Ontario. *** Tel: 416-869-3578; FAX: 416-869-3359 E-mail: [email protected] The MDD encourages geoscientists to join Kerry Sparkes (1996 - 1999) St. John’s, Newfoundland the division and contribute to the various Tel: 709-758-1700; FAX: 709-758-1717 programs and activities. Malcolm Robb (1996 - 1999) Yellowknife, Northwest Territories Tel: 403-873-6301; FAX: 403-873-2914 E-mail: [email protected] Paul Archer (1996 - 1999) Quebec City, Quebec Tel: 418-694-9832; FAX: 418-692-3969 Michael Marchand (1996 - 1999) Calgary, Alberta Tel/FAX: 403-282-5105 E-mail: [email protected]

2 The Gangue No. 55 affect such properties is of critical impor- Relevance to the tance from industry in the form of permis- tance in predicting environments and condi- sioning for site access and logistical support. tions conducive to efficient ore formation. NERC Mission Experimental and site-specific investigations The 1993 White Paper “Realizing our Principal Contributors will focus on this issue through study of Potential” emphasized the Government’s physico-chemical and hydrological processes Mr. Gus Gunn, British Geological Survey, commitment to supporting research that Keyworth, Notts, NG12 5GG in the hydrothermal environment. would lead to wealth creation and an im- Surficial Processes: Many mineral de- Dr. Mike Harris, Managing Director provement in the quality of life. We contend Europe/Africa Exploration, RTZ Min- posits only become economic after rework- that the entire fabric of modern life and the ing during weathering and erosion, either by ing & Exploration Ltd., PO Box 695, basis of its wealth are underpinned by the Seventh Floor Castlemead, Lower mechanical reconcentration, or by ground- minerals industry. water redistribution of ore-forming elements. Castle St., Bristol, BS99 1FS This proposal aims to contribute to this Dr. Richard J. Herrington, Dept. Mineral- On the other hand, ore deposits exposed at the equation by improving the scientific basis for surface may be destroyed by erosion or dis- ogy, Natural History Museum, Crom- mineral exploration, thereby reducing its well Rd., London, SW7 5BD solution without reconcentration. The ulti- costs-savings that can be re-invested in envi- mate controls on these surficial processes are ronmental improvements and economic Dr. Jon Naden, British Geological Survey, climate, uplift history, and time, and a clearer growth. We recognize the NERC as the ap- Keyworth, Notts, NG12 5GG understanding of the way these factors inter- propriate body to support this research initia- Professor Jane Plant, British Geological act to affect mineralized lithologies is re- tive, because it has a mandate to support re- Survey, Keyworth, Notts, NG12 5GG quired before predictive models of ore for- search that will create wealth and improve the mation/destruction can be formulated. Dr. Hazel M. Prichard, Dept. Geology, Univ. quality of life. Furthermore, this proposal Wales, PO Box 914, Cardiff, CF1 3YE Despite recent advances we remain dis- will contribute to at least three of the Envi- tant from any comprehensive understanding ronmental Foresight Topics identified by the Dr. Clive Rice, Dept. Geology Univ. Aber- of these key processes outlined above, and in NERC (Fluid Dynamics in Natural Resource deen, Marischal College, Aberdeen, particular the ways in which they interact. Management, Structure and Properties of the AB9 2UE We contend that research in this area is cru- Earth’s Subsurface, and Use of Natural Proc- Dr. Jeremy P. Richards Dept. Geology, cial to the development of a sustainable re- esses and Materials). Univ. Leicester, University Road, source base for the future. Scale of Interest within the UK (and In- Leicester, LE1 7RH ternational) Research Community This pro- Dr. Stephen Roberts, Dept. Geology, Investigative Framework posal has been formulated by members of the Southampton Oceanography Centre, It is proposed that the questions raised Mineral Deposits Studies Group (Geological European Way, Southampton, SO14 under the above headings be addressed in the Society) and Applied Mineralogy Group 3ZH context of a number of regional studies of (Mineralogical Society), and was initiated Dr. Tom J. Shepherd, British Geological metallogenesis, thereby providing a holistic during a special discussion session hosted by Survey, Keyworth, Notts, NG12 5GG framework for investigation. At this time, the Mineral Deposits Studies Group at the Dr. Richard H. Sillitoe, Consulting Eco- three geographical areas have been identified Warwick Applied Geoscience conference in nomic Geologist, 27 West Hill Park, for study, on the basis of mineral endowment, 1996. Thus, it has the support of, and would Highgate Village, London, N6 6ND strategic relevance to national and interna- be of relevance to, the majority of workers in this field within the UK. In addition, this Dr. Noel C. White, Chief Geologist, BHP tional industry, and accessibility: Minerals, Exploration Brook House, • Central Andean Metallogenic Belt: proposal has been discussed with researchers outside the UK, and their involvement would 229 Shepherds Bush Rd., London, W6 Several of the world’s largest Ag, Sn, 7AN and porphyry Cu deposits are located be essential given the inherently international along trench-parallel structural zones in outlook of mineral deposits research. Dr. Jamie Wilkinson, Dept. Geology, Impe- the Central Andes. rial College, Prince Consort Rd., Lon- Scale of Interest don, SW7 2BP • Southwest Pacific: Some of the largest and richest Au discoveries of the last from Users A town meeting was scheduled for two decades have been made in the con- Wednesday, February 19, 1997, at the Uni- Three of the principal contributors to this versity of Leicester, to explore the key issues, tinental margin and island arc terrains of proposal are industry-based scientists, two the Southwest Pacific. challenges, and opportunities in the area of • representing major multinational mining predictive metallogeny. A clear demonstra- Carpatho-Balkan Belt: This belt, companies (BHP and RTZ-CRA), and the tion of interest and impetus at this meeting largely in the former Eastern Bloc, hosts third an independent consultant. Their views important Cu and Au deposits, and is an will endorse the preparation of a draft pro- have helped to focus this proposal on the real posal for thematic research funding, which important new frontier for modern min- needs of industry, thereby ensuring its rele- eral exploration and development. will then be submitted to NERC for its con- vance. The proposal expects extensive assis- sideration later in the year. Issues were to be discussed at workshops, details of which can be viewed on the Mineral Deposits Studies Group internet web-site at URL MEG Luncheon Speakers 1996-1997 {http://www.nkw.ac.uk/bgs/w3/mgs/mpg/m @ Hotel Georgia - Vancouver dsg/PREMET.html}. Note that International collaboration to this proposal is welcome although applica- March 5/97 Jean Pautler, Teck April 2/97 Jack Stanley, tions for NERC funding must be made by UK institutions. Jointly funded proposals are al- Tsacha Project: An Epithermal Au Analytical laboratory Cons. ways popular with funding bodies! Occurrence in the Nechako Plateau Pitfalls of Sample Preparation and Please direct inquires to the Co-ordi- Analysis of Precious Metals nator: Jeremy Richards, Dept. Geology, March 19/97 Peter Laznicka, Univ. Leicester, Leicester, LE1 7RH, UK; U. of Manitoba April 16/97 Yale Simpson email: [email protected]; tel: 0116-2523934 (di- The Gold/Uranium Association in Argosy Mining Corp. rect) 0116-2523933 (main office); FAX: 116- Metallogeny and Politics Slovakian Gold 2523918.

February 1997 3 MINERAL DEPOSITS DIVISION - GAC Membership Information &Application Regular Member: Associate Member: Corporate Subscription: $10 Cdn/year $20 Cdn/year: $25 Cdn/year: Must be GAC member Non-Residents of Canada Corporate or Library who are not members of GAC The Gangue subscription only

Name: Address:

Country: GAC Member #(see mailing label) : Postal Code: E-mail: Tel: FAX: MC/Visa Card #: I enclose a cheque for: Cdn/US $ Expiry Date: Signature: Mail Application to: Geological Association of Canada, c/o Dept. of Earth Sciences, Memorial Univ. of Newfoundland St. John;s, Newfoundand, A1B 3X5. Tel: 709-737-7660; FAX: 709-737-2532; E-mail: [email protected]

The Modern International Explorationist

By John Thompson, MDRU The Mineral Deposit Research Unit (MDRU) was formed in the graduate level, should teach geoscience students how to think, 1989 to increase interaction between the mineral exploration indus- how to collect and interpret data, and how to solve problems. The try and The University of British Columbia. The major activity at new graduate will not know everything but she/he must have the MDRU has been research projects designed to develop new tech- ability to know when and how to obtain information or expertise, niques, solve problems, or generate new ideas. These are funded particularly as we continue to be inundated with new technology, by company consortia, often with matching funds from govern- data and ideas. Education in earth science must also provide the ment. Normally, projects are judged by the extent to which they breadth of knowledge to allow the modern explorationist to com- influence exploration strategies at property and regional scales, but municate with other technical experts - for example, geologists with the importance of the education and training component in projects geophysicists and vice versa, as well as non-technical decision is often overlooked. Both company personnel and researchers learn makers. Finally, it is widely recognized, but important to emphasize, from interaction through projects, but more importantly, projects that formal education is only the beginning; technical skills are involve graduate students who carry out research in close coopera- enhanced continually by experience during a career of looking at tion with companies. These students represent the explorationists rocks, data and mines, and may be tuned further by professional of the future and it is therefore important to determine what skills courses. these people need and to what extent we are providing them. 3. Non-Technical Skills: Modern global exploration requires There are three components to the modern explorationist. Be- an increasing number of non-technical skills, most of which are not ing outstanding in all three is not necessarily possible nor a prereq- featured in university education. Industry often recognizes the need uisite for success, but clearly competency in all three is desirable. for improved report writing and public presentation to both tech- The three components are as follows: nical and non-technical audiences, but interpersonal skills, accounting and management, flexibility, languages, and an ability to un- 1. Innate Ability: For some reason, a few people, from pros- derstand and work with different cultures are all important. Equally pectors to exploration managers, are involved in the discovery of critical but rarely acknowledged are honesty and integrity. These several ore deposits during their careers, while the majority of may not be attibutes of bureaucratic organizations (private and explorationists are lucky to be involved in one. It is hard to define public) in many countries, but most people at a local level value why such successful explorers have the knack of picking winners, working with someone whom they trust. but tenacity, creativity, and imagination are common characteristics, usually combined with a willingness to take risks. It is We hope to teach and instill these skills and characteristics in difficult to teach these characteristics at any level, although it is the future generation of explorationists. In the final analysis, it will certainly possible to encourage and enhance them. take more than a source of money to maintain Vancouver as a centre of international exploration into the next century. People with the 2. Technical Skills: For the geoscientist, a university education appropriate knowledge and ability are the key. initiates the development of technical skills. These include the basic building blocks of earth science, such as field work and petrology, [comments on the above are welcomed by the author and should be and increasingly emphasize the use of computers and analytical directed to him via email at [email protected] or fax: equipment. More importantly, university education, particularly at 604-822-6136]

4 The Gangue No. 55 INCOMING MDD CHAIRPERSONS REPORT 1996/97

D.W.Moore, MDD Chairperson MDD lost another key figure this year with Dave Lentz retiring from the position of Short Course coordinator. Not one Happy New Year and Greetings from the West Coast. I had to loose his touch, Dave has agreed to organize a short course the good fortune of being snowed-in at a ski-hill during our on skarns sponsored by MAC at Quebec ‘98 meeting. Thanks recent blizzard of the century (tame by Eastern Canadian stand- are due to Dave for his enthusiasm and dedication over the years. ards I might add). This resultant “spare-time” was not directed Iain Samson of the University of Windsor has assumed this to writing this long overdue report, however, so here it is January position and would welcome suggestions particularly on ideas in once again rainy Vancouver. for regional short courses, which some members have expressed Membership in the Mineral Deposits Division of GAC for interest in in the past. 1996/97 stands at 792 of which about 100 are international members. This represents roughly 1/3 (and I believe the most Speaking of Quebec ‘98, Benoit Dubé, MDD program active portion) of the total membership in the parent organiza- chairperson is coordinating an excellent program including a tion. To paraphrase our outgoing chairperson Jennifer Pell’s special session on intrusive related Cu-Au deposits and field comments from last year, it is a privilege for me to act as MDD trips to Gaspe Copper and Chibougamou which should dove-tail Chairperson this year and hopefully to contribute to MDD’s nicely with the skarn short course. enviable track record of achievement. As Jennifer stated how- The strong tradition of MDD field trips continued with the ever, any organization is only as good as its members so I would very successful Central Andes Field trip (reported on elsewhere like to encourage all of you to get involved. If you have any in this issue) organized by Al Sangster and coordinated by Dani ideas or suggestions for new initiatives, projects, or publications Alldrick. The next major international field trip is planned to or have thoughts as to how MDD can better serve your needs, Tasmania and Eastern Australia in March 1998. This trip is please contact me, one of the executive or local directors. being co-sponsored with the SEG and will be run in conjunction This past year was a busy one for MDD with much of the with Exploration Methods ‘98 - Pathways to Discovery an inter- activity as usual centered around the Winnipeg ‘96 GAC-MAC national symposium being organized by the British Columbia meeting last May. The meeting was attended by 820 people of Yukon Chamber of Mines and the SEG. An MDD sponsored which a great many were MDD members. Two special sessions trip to Californian mineral deposits also affiliated with this meet- were sponsored by MDD at the GAC-MAC Winnipeg’96 meeting will be run in early February 1998 and is in the early planning ing, one on Circum-Superior Nickel Deposits and the other on stages. VHMS Deposits in the Flin Flon-Snow Lake areas. These ses- I would like to remind everyone about two awards that are sions were accompanied by three field trips to the Thompson presented by MDD at the GAC Annual Meeting. The Duncan Nickel Belt, Flin Flon Belt and the Sturgeon Lake Caldera. A R. Derry Medal is the highest award bestowed by the Mineral well attended MDD sponsored short course entitled “Trace ele- Deposits Division. It is presented to an outstanding geologist ment geochemistry of volcanic rocks, applications for massive- who has made significant contributions to the science of eco- sulphide exploration” was organized by Dereck Wyman. The nomic geology in Canada. Recipients are recognized for their short course notes were selling like hot-cakes at Winnipeg and skill and stature as professional economic geologists and for are still available through GAC. Thank you to Jamie Robertson, their public contributions to the science. The William Harvey MDD’s Winnipeg ‘96 Chairperson, for doing such a great job. Gross Award is presented to a young geologist (less than age 40) An excellent economic geology program has also been as- who has made outstanding contributions to the field of economic sembled for the Ottawa’97 GAC-MAC Meeting under the lead- geology in a Canadian context. The people chosen for these ership of our program chairman Al Sangster. The program in- awards are nominated by you, the MDD membership. We cur- cludes a symposium “Canadian Contributions to Latin rently have a critical shortage of nominations and I would urge American Mineral Deposits Geology”, three special sessions, everyone to give some thought to who might be suitable recipi- “Tectonic, Magmatic and Hydrothermal Evolution of Continen- ents of these awards and make the effort to put forward a nomi- tal Back Arc Rifts and Methods of Sulphide Exploration with nation so that outstanding individuals may be recognized. Emphasis on the Bathurst Mining Camp, Northern New Bruns- wick”; “Geology of the Kidd Creek Orebody, Timmins, Ontario” MDD is in strong financial shape. We have however, sig- and “Atypical Gold Deposits” as well as a short course entitled nificant calls on these resources such as a major expenditure for “Volcanic Associated Massive Sulphide Deposits”, organized by publication of the “Atlas of Alteration”. Furthermore as our T. Barrie and M. Hannington. Companion field trips are planned treasurer Bob Cathro points out it will be hard to generate much for the special sessions as well as a trip to the Balmat Edwards revenue in the current low interest rate environment. Nonethe- Zinc District. 1997 is the 50th Anniversary of GAC and many less, there has been much discussion over the years by executive special events are planned for the Ottawa meeting: it should be and others as to how MDD should best utilize this financial great, hope to see you there! resource. Is it by providing funding for additional publications, field trips and short courses of direct benefit to members and/or On the publication front; the “Atlas of Alteration”editedby should MDD become involved in broader education initiatives A.J.B Thompson and J.F.H Thompson came to fruition this year. to school children or the public at large? If you have any A total of 330 copies were sold in the pre-publication stage and thoughts on this subject we would be most interested to hear additional 123 copies have been sold since. It is a good looking them. book with lots of excellent photographs and should be an important reference text. This was Kathryn Dunne’s swan song as Well, that about wraps it up, aside from thanking Brian MDD Publications editor. Thank you Kathryn for your efforts Grant who continues to do a terrific job in virtually single-hand- on MDD’s behalf over the last several years. Art Ettlinger is edly putting out The Gangue. MDD’s new Publications person and I know he would welcome any suggestions members might have for new projects. Thanks for your support, David Moore

February 1997 5 OTTAWA ’97 – SHORT COURSE GEOEXPLORE BIOLOGICAL/MINERALOGICAL Mailing List INTERACTIONS Geoexplore, the new electronic mailing list, is a platform for discussion of all aspects Date: 16-17 May 1997 of mineral exploration. Topic choices are lim- ited only to the field of mineral exploration. A two-day Short Course organized by Julie M. McIntosh and Lee A. Groat (De- Everyone is invited to subscribe and contrib- partment of Earth and Ocean Sciences, The University of British Columbia) and spon- ute to this mailserver and there is no charge sored by the Mineralogical Association of Canada, will provide an introduction and for the service. Geoexplore is maintained by review of the rapidly expanding field of geomicrobiology. Robertson Info-Mine in Vancouver, BC. Topics will include a review of bacteria, growing and maintaining bacterial cultures, techniques used to study bacterial/mineralogical interactions, bacteria and the break- To subscribe to the Geoexplore mailing down of sulphide minerals, bacteria and acid rock drainage, bacteria and the weathering list please send an e-mail to: of silicate mineral, biomineralization, and lichens. [email protected] This course will be relevant to researchers from academia and government, and to with the following message: geoscience professionals. Discussion among the speakers and attendees will be an subscribe Geoexplore important component of the course. Participants will include B.S. Davis, M. Easton, F.G. Ferris, G.D. Ferroni, L.G. Leduc, D. Gould, R. Guay, and H.W. Nesbitt. Once subscribed you will automatically Registration $350 CAD for professionals, $200 for students. receive all messages posted on the Geoexplore For additional information; mailing list. If you wish to post a message, article, question, etc. to the list membership Julie M. McIntosh or Lee A. Groat, send an e-mail to:[email protected] Earth & Ocean Sciences, University of British Columbia with your message in the main body of the Vancouver, BC, V6T 1Z4 Tel:604-822-8238; Fax: 604-822-6088; e-mail. Email: [email protected]; or, [email protected] *** Exploration Methods ‘98 - Pathways to Discovery

January 28 - 30, 1998 Sponsored by Society of Economic Geologists, and the B.C. - Yukon Chamber of Mines in conjunction with the annual Cordilleran Roundup - Hotel Vancouver, Vancouver, BC, Vancouver, British Columbia, Canada, will be the site of this international exploration conference in January 1998. The theme for this conference, Pathways to Discovery, will build on the successful meeting in Denver organized by the Society of Economic Geologists in 1993 - Integrated Methods in Exploration and Discovery. The 1998 meeting will combine technical excellence with the atmosphere of the annual Cordilleran Roundup. Vancouver, a centre for worldwide exploration and mining, is an ideal location for a major exploration-focused meeting. Technical sessions (posters and papers), forums, core shacks, short courses and field trips will highlight exploration strategies and pathways to discovery in frontier areas, explored regions, and mature mining districts. The hospitality and entertainment that characterize Roundup will be an important feature of this conference, particularly in celebration of the centenary of the Klondyke Gold Rush. Vancouver is a city that reflects its position on the Pacific Rim. The cultural mix creates a vibrant atmosphere providing excellent restaurants and entertainment. Snow-capped mountains rim the active harbour and nearby is some of the world’s best skiing and sailing. Mark your calendars now - this meeting should not be missed! For further information contact:

BC & Yukon Chamber of Mines E-mail: [email protected] WWW: http://www.eos.ubc.ca/pathways98 Tel: 604-689-5271 FAX: 604-681-2363 Associated Organizations: Mineral Deposits Division - GAC § Association of Exploration Geochemists § Canadian Institute of Mining, Metallurgy & Petroleum § MDRU - University of British Columbia § British Columbia Geological Survey § Geological Survey of Canada

6 The Gangue No. 55 Quebec ’98 MAC Short Course - Mineralized Porphyry-Skarn Systems May 15 - 17, Quebec City Immediately preceding the Quebec GAC/MAC conference on May 18 - 20, 1998 This 2.5 day Short Course, sponsored by the Mineralogical Association of Canada, will review various geochemical systematics involved in the formation of mineralized skarn systems through to regional metallogenic perspectives. The course should be of interest to research economic geologists, explorationists, as well as students interested in understanding these dynamic hydrothermal systems. Topics include: an overview of porphyry-skarn systems; intrusion dynamics; phase equilibria con- straints; reaction models; mineral chemistry; stable and radiogenic isotope systematics; fluid inclusion con- straints; as well as reviews on Au, Sn-W, Cu-Au, Mo, wollastonite & rare-metal skarn systems from various parts of the world. Principle participants include: Tyson Birkett, John Bowman, Phil Brown, Don Burt, Gregg Dipple, Marco Einaudi, Tassos Grammatikopoulos, Jeffrey Keith, Dave Lentz, Lawrence Meinert, Takanori Nakano, Rainer Newberry, Yuanming Pan, Gerry Ray, Jeff Rubin, Robert Wares, and Anthony Williams-Jones. This Short Course will be followed by a 2-day MDD/GAC Special Session entitled: “Systematics of Mineralized Hydrothermal Skarns”, held during the GAC/MAC annual meeting. There will be a post-meeting porphyry-skarn field trip to Gaspe, Quebec, which will include the Gaspe porphyry-Skarn Cu (Mo) deposit. For further information contact: Dave Lentz, New Brunswick Geological Survey PO Box 50, 495 Riverside Drive, Bathurst, NB, E2A 3Z1 Tel: 506-547-2070; FAX: 506-547-7694; Email: [email protected]

Ottawa ‘97 - Mineral Deposits Program

Symposium Field Trips Canadian contributions to Latin American Mineral Deposit Geology and Mineral Deposits of the Balmat-Edwards District, Geology: M. Zentilli (Dalhousie University) and R. Jannas (Met- New York: W. deLorraine (Zinc Corp of America) and A. Sangster allica Resources Inc.). Canadian based mineral deposit research (GSC). Participants will receive an overview of the geology and and mineral exploration activity are at an all-time high in Latin dolomite marble-hosted zinc deposits in the Sylvia Lake Syncline, America. including an underground visit to the Number 4 Mine. Special Sessions Atypical Gold Deposits of the Abitibi area, Quebec and On- tario: J.-F. Couture (MRN, PQ) and F. Robert (GSC). Field trip Atypical Gold Deposits: A. Sangster (GSC) and J.-F. Couture will focus on Archean gold occurrences that don’t fit well into (MRN, PQ). Session will consist of papers on gold deposits or their existing classifications, and will compliment papers in the Special aspects, plus occurrences that don’t fit well within existing classi- Session. fications. One section of the session will deal with deposits to be visited on the “Atypical Gold Deposits of the Abitibi Area” trip. Geology and Massive Sulphide Deposits of the Bathurst Camp, New Brunswick: S. McCutcheon, J. Langton and D. Lentz (NB Geology of the Kidd Creek Orebody, Timmins, Ontario: M. Dept Natural Resources). This trip will provide an overview of the Hannington, T. Barrie and W. Bleeker (GSC). The results of a joint geology and mineral deposits of the Bathurst Camp, New Bruns- multidisciplinary research project involving the GSC, Falcon- wick, and is designed to compliment the Special Session on back- bridge Ltd. and Laurentian Univ. will be presented, covering the arc basins and massive sulphide deposits. geology, geochemistry, geochronology, alteration and isotope geochemistry of the Kidd Creek deposit. Timmins to Sudbury Transect: New Developments in the Set- ting of Massive Sulphide Deposits: D. Ames, W. Bleeker, K. Tectonic, Magmatic and Hydrothermal Evolution of Back-Arc Heather and N. Wodica (GSC). This trip will highlight new devel- Rifts with Emphasis on the Bathurst Mining Camp, New opments in the geology of massive sulphide deposits within the Brunswick: W. Goodfellow and C. van Staal (GSC). This session Timmins Camp, the Swayze Belt, the Levack Gneiss Complex, and will present a synthesis of the geology of back-arc rifts and their the Early Proterozoic Whitewater Group within the Sudbury struc- role in the formation of massive sulphide deposits as exemplified ture. by the Bathurst Mining Camp. The papers will focus on the joint Geological Survey of Canada and New Brunswick Dept of Natural Resources Extech II project. For further information contact: MDD - SEG Short Course Mineral Deposits Division Program Chair: A.L. Sangster, GSC Volcanic-associated Massive Sulphide Deposits in Ancient & 601 Booth St., Ottawa, Canada, K1A 0E8. Modern Settings: Classification, Processes and Examples: T. Bar- Tel: 613-992-8603; FAX: 613-996-9820; rie and M. Hannington (GSC). E-mail: [email protected] See page 17 for Short Course details -

February 1997 7 INTRUSION-RELATED GOLD-PYRRHOTITE VEINS Type Examples of Dani Alldrick and Trygve Höy due to late magma movement, these rocks tear INTRUSION-RELATED British Columbia Geological Survey apart; producing characteristic en echelon ten- Au-PYRRHOTITE VEINS sion gashes. Circulating hydrothermal fluids The entire mass of this [Johnny] mountain is precipitate gold-rich iron sulfides and gangue. impregnated with mineral, and all the assays Veins may be planar, or, where the stress field ISKUT CAMP which have been made show values. has reoriented during vein growth, s-shaped SNIP JOHNNY MTN. B.C. Minister of Mines Annual Report cymoidal veinsets develop. 1917 p. K63 The brittle-ductile thermal transition oc- STEWART CAMP SCOTTIE GOLD curs at about 400°C or 1/2 Tm (one-half the There’s so much ore in Johnny Mountain even melting temperature of the rock). This zone the marmots have gold teeth. is lies at 8 km to 12 km depth through the continental crust (Fig. 2), but it rises in mag- Vancouver Mining Promoter, 1986 matic arc environments which are locallized Over the past ten years, geologists in- along active convergent plate margins, be- volved in ore deposits studies in British Co- cause it is wrapped around and envelopes the lumbia have recognised similarities between point sources of heat represented by partially- Figure 1 a few gold-bearing sulphide-rich veins (Fig- molten, shallow, sub-volcanic magma bodies. ROSSLAND CAMP ure 1) that previously had been classified The thermal transition envelope is shown in CENTRE STAR among the many examples of “mesothermal Figure 3 as a thin line, but it is really a broad IRON COLT veins” in the province. Deposits include his- layer or zone. In three dimensions, this zone toric producers such as the veins of the is bell-shaped; lying closer in to shallow Rossland camp, and important new discover- stocks, but standing further out from deeper in a single vein is typically less than one mil- ies at the Snip and Johnny Mountain gold plutons which have a broader thermal enve- lion tonnes, the proximal association with mines. lope. other veins in the en echelon set (Johnny These veins display many of the struc- The mineral deposit profile presented on Mountain mine, Scottie gold mine, Rossland tural, textural and mineralogical charac- page 10, has been developed to highlight the camp) and the strong probability of additional teristics of mesothermal veins (Panteleyev, significant features of this important class of vein sets localized elsewhere around the pe- 1991), but ongoing studies progressively re- high-grade gold-bearing veins. These depos- rimeter of the same pluton (Johnny Mountain, vealed features that were inconsistent with the its are attractive exploration targets that offer: Rossland camp) mean that the total tonnage well-established setting for classic mesother- • high profit potential (high grades) potential for the set of veins can be significant mal deposits (Fig. 2). Intrusion-related gold- • relative ease of mining (strong, regular, (Rossland camp). pyrrhotite veins are hosted in volcanic island structural control; gold occurs as free elec- Veins discovered and mined to date have arc complex rocks, and are localized around trum) presented relatively straightforward mining the perimeter, or within the margin, of coeval • relative ease of exploration (predictable re- scenarios. Veins are steeply dipping to sub- subvolcanic plutons. Geochronometry on the stricted geologic setting; characteristic vertical. A significant proportion of the gold plutons and volcanic strata and galena lead geophysical response) can be recovered as free electrum in a shaker isotope analyses of the vein sulfides as well • box or Wilfley table, the remainder reports to as lead isotope analyses from lead extracted high ‘exploration potential’ (deposits occur in clusters or sets of veins; veins have close pyrrhotite-pyrite concentrate. Gold:silver ra- from feldspars in the plutons show that the tios average 1:1, ranging from 5:1 to 1:5. Gold veins are syn-intrusive and synvolcanic in genetic associations with other important mineral deposit types). shows its strongest correlation with copper, age. even though both these elements are in low These moderate tonnage, high-grade concentrations. In addition to recoverable sil- Intrusion-related gold-bearing pyrrhotite gold veins (Table 1) characteristically occur veins occur as a series of parallel, tabular to ver, byproduct copper has been produced at as vein sets. Although the tonnage potential cymoid veins of massive iron sulphide and/or bull quartz, commonly in en echelon fracture sets. Veins may be composed of (i) massive Gold Deposits Associated with the fine-grained pyrrhotite and/or pyrite +/- chalcopyrite, or (ii) massive bull quartz with mi- Brittle-Ductile Transition Zone Magmatic Arc nor calcite and minor to accessory disseminations, knots and crystal aggregates of sulfides. Mesothermal Carlin-Type These two dominant vein types may occur . independently or together. The two minerali- 12 km zation styles may grade into each other along 8 km Brittle a vein (Snip mine), may form parallel to each Brittle o Volcanic 400 C Ductile other in a compound vein (Scottie Gold mine), Ductile Extension Arc or they may occur in adjacent but separate Strike-Slip veins within an en echelon set (Johnny Moun- tain mine).

The subvolcanic setting for these vein HOTSPRINGS VOLCANOGENIC EPITHERMAL 5KM MASSIVE deposits is transitional in depth between the VEINS SULPHIDES setting for porphyry copper systems and the Lake setting for epithermal systems (Fig. 3). Min- 0 Sea Level Sea Level TRANSITIONAL VEINS eralization is synvolcanic and syn-intrusive Zones of Gold PORPHYRY-RELATED MANTOS and forms along the temperature-constrained Mineralization 5KM SKARNS “brittle-ductile transition envelope” that sur- Locus for PORPHYRY INTRUSION-RELATED rounds subvolcanic intrusions (Nesbitt, VEINS 1988). Within this zone, rocks are too warm Figure 2 to shatter in brittle fashion; but not quite hot Modified from Nesbitt, 1988 enough for ductile flow. As stress builds up

8 The Gangue No. 55 Rossland, Johnny Mountain and Chibouga- mau camps. ISLAND ARC 0 5 10 15 KM Intrusion-related gold-pyrrhotite veins ORE POTENTIAL SHALLOW have remarkably predictable exploration SUBAQUEOUS characteristics. Deposits occur in a re- HOTSPRING stricted geologic setting around the perimeter EPITHERMAL (marine) VEINS SUBAERIAL VOLCANOGENIC of coeval subvolcanic plutons in volcanic arc SHALLOW HOTSPRINGS MASSIVE environments. Prospecting, geochemical or 5KM SUBAQUEOUS SULPHIDES geophysical programs can thus be focussed HOTSPRING (crater lake) Proximal Distal on a swath of ground around the perimeter of (Cu, Pb, Zn, Au, Ag) (Pb, Zn, Ag, Ba) these prospective stocks, ranging from 500 metres inboard of the contact to one kilometre Lake Sea Level Sea Level . . outboard of the intrusive contact. Exploration 0 ...... work has shown that these massive pyrrhotite TRANSITIONAL veins are characterized by strongly anomalous magnetometer lows. Two factors contribute PORPHYRY-RELATED Au VOLCANIC-HOSTED MANTOS to this unexpected response: pyrrhotite in Tuffs & Flows these deposits is entirely non-magnetic hex- 5KM SKARNS agonal pyrrhotite; the propylitic alteration en- Limestone velope around these veins is magnetite-de- structive, trace magnetite that is ubiquitous in PORPHYRY Cu-Au the country rock volcanics has been replaced by non-magnetic iron sulphide in the altered Locus for wallrock envelope of the veins. INTRUSION-RELATED Au-PYRRHOTITE VEINS Intrusion-related Au-(Ag-Cu) pyrrhotite veins have high ‘exploration potential’. Figure 3 o 1 NO VERTICAL Since they are emplaced in oceanic or conti- 400 C 2Tm EXAGGERATION nental volcanic arc environments, these deposits have close metallogenetic and predict- ures. Two of these veins subcrop beneath an and finally into thin, discontinuous fracture able spatial associations with other ore deposit adjacent glacier and were discovered by un- controlled veins and veinlets with quartz-car- types that are typical of volcanic arc environ- derground drilling targeted on pronounced bonate gangue. This zonation is a critical ments (Figure 3). High-grade gold-pyrrhotite low aeromagnetic anomalies. guide in exploration and deposit evaluation. veins offer new exploration targets within es- The Snip mine consists of two large en Selected Bibliography tablished arc-related porphyry, skarn and epi- echelon veins that closely overlap. Close- thermal mining camps (e.g.. Stewart, BC) . spaced pre-development drilling could not Alldrick, D.J. (1993): Geology and Metallogeny of the Conversely, where intrusion-related gold- discriminate between these two structures Stewart Mining Camp, Northwestern British Colum- pyrrhotite veins are discovered first, the ex- which were interpreted as a single, but zoned, bia, B. C. Ministry of Energy, Mines and Petroleum ploration potential for other arc-related depos- vein. Underground mapping revealed the two Resources, Bulletin 85, 105p. separate onlapping structures: the upper vein Alldrick, D.J. (1996): Intrusion-related Au-pyrrhotite its types must be high as well and the Veins, I02; in Selected British Columbia Mineral exploration focus must be expanded to in- is massive quartz with accessory sulphides; Deposit Profiles, Volume 2 - Metallic Deposits, Lefe- clude the search for porphyry, epithermal, the lower vein is massive pyrrhotite-pyrite. bure, D.V. and Höy, T., Editors, B.C. Ministry of skarn and hotspring deposit types (e.g. Johnny Both veins constitute ore, but the massive sul- Employment and Investment, Open File 1996-13, Mountain, BC). phide vein segment yields consistently higher p.57-58. gold grades. Alldrick, D.J., Drown, T.J., Grove, E.W., Kruchkowski, The Johnny Mountain and Scottie E.R. and Nichols, R.F. (1989): Iskut-SulphuretsGold; Gold mines are the best examples of en eche- The Rossland camp produced more than Northern Miner Magazine, January, 1989, p.46-49. lon distribution of veins. At Johnny Moun- 84 tonnes of gold and 105 tonnes of silver Drysdale, C.W. (1915): Geology and Ore Deposits of tain mine, four parallel, planar veins have between 1894 and 1941, mainly from massive Rossland, British Columbia; Geological Survey of been delineated. Three economic veins are pyrrhotite-chalcopyrite veins. These veins Canada, Memoir 77. massive quartz with 10 to 15 percent sulphide are preferentially located along the margins Fyles, J.T. (1984): Geological Setting of the Rossland of a synvolcanic intrusion, the Rossland mon- Mining Camp; B.C. Ministry of Energy, Mines, and disseminations and knots. The fourth vein is Petroleum Resources, Bulletin 74, 61p. composed of massive pyrite-pyrrhotite with zodiorite, within a thick pile of Early Jurassic Höy,T., Dunne, K.P.E. andWehrle,D.(1992):Tectonicand significant but sub-economic gold content. volcanic rocks. The camp is unique in that Stratigraphic Controls of Gold-copper Mineralization The entire set of four veins is offset by a post- Tertiary faulting has tilted the vein system, in the Rossland Camp, Southeastern British Colum- ore fault, but each vein can be traced to its producing surface exposures that extend from bia; in Geological Fieldwork 1991, Newell, J.M. and offset continuation. Gold grades were suffi- deeper to more shallow structural levels from Grant, B., Editors, B.C. Ministry of Energy, Mines and ciently high within the fault zone that, despite east to west. Veins with associated wallrock Petroleum Resources, Paper 1992-1, p.261-271. skarn envelopes and disseminated sulphides Klepper, M.R., Ruppel, E.T., Freeman, V.L. and Weeks, dispersion and dilution of crushed vein mate- R.A. (1971): Geology and Mineral Deposits, East rial the relithified fault gouge was mined as that formed at deeper levels grade upward to Flank of the Elkhorn Mountains, Broadwater County, low-grade ore. At Scottie Gold mine, four massive pyrrhotite-chalcopyrite veins with Montana, United States Geological Survey,Profes- parallel, en echelon veins show cymoid flex- only minor gangue and alteration envelopes, sional Paper 665, 65p. EXPLORATION GUIDES RESOURCE TECTONIC SETTING Andesitic to Basaltic Volcanic Arc GEOLOGIC SETTING Subvolcanic ROSSLAND 5.4 m tonnes 15.7 g/t Au Perpheral to Coeval Plutons SNIP 1.3 m tonnes 27.9 g/t Au GEOPHYSICS Strong Magnetic Lows Moderate to Strong EM Response SCOTTIE GOLD 0.3 m tonnes 17.6 g/t Au GEOCHEMISTRY Au, Ag, (Cu, As, Zn) JOHNNY MOUNTAIN 0.2 m tonnes 18.1 g/t Au DEPOSIT GEOMETRY En Echelon Vein Sets Fixed Angular Relationships ASSOCIATED DEPOSITS Full Suite of Arc-Related Ore Types

February 1997 9 Nesbitt, B.E. (1988): Gold deposit Continuum - A Genetic Deposits, Pilote, P.,Editor, Geological Survey of Can- ing, Metallurgy and Petroleum, Special Volume 46, Model for Lode Gold Mineralization in the Continen- ada, Open File 3143, p.31-41. p.838-850. tal Crust, Geology, v.16, p.1044-1048. Rhys, D. A. (1993): Geology of the Snip Mine and its Robert, F. (1994): Timing Relationships Between Cu-Au Panteleyev, A. (1991): Gold in the Canadian Cordillera - a RelationshiptotheMagmaticandDeformationalHis- Mineralization, Dykes, and Shear Zones in the Chi- Focus on Epithermal and Deeper Environments, in tory of the Johnny Mountain Area, Northwestern bougamau Camp, Northeastern Abitibi Subprovince, Ore Deposits, Tectonics and Metallogeny in the Ca- British Columbia; unpublished M.Sc. thesis, The Uni- Quebec; in Current Research 1994-C, Geological nadian Cordillera, B.C.MinistryofEnergy,Minesand Survey of Canada, p.287-294. Petroleum Resources, Paper 1991-4, Chapter 7, versity of British Columbia, 278p. Sinclair, W.D., Pilote, P., Kirkham, R.V., Robert, F., and p.163-212. Rhys, D. A. (1995): The Red Bluff Gold-copper Porphyry Daigneault, R. (1994): A Preliminary Report of Por- Pilote, P. and Guha, J. (1995): Metallogeny of the Eastern and Associated Precious and Base Metal Veins, phyry Cu-Mo-Au and Shear Zone-hosted Cu-Au De- Extremity of the Abitibi Belt; in Metallogenic Evolu- Northwestern British Columbia; in Schroeter, T.G., posits in the Chibougamau Area, Quebec; in Current tion and Geology of the Chibougamau Area - from Editor, Porphyry Deposits of the Northwestern Cor- Research 1994-C, Geological Survey of Canada, Porphyry Cu-Au-Mo to Mesothermal Lode Gold dillera of North America, Canadian Institute of Min- p.303-309. INTRUSION-RELATED Au-PYRRHOTITE VEINS British Columbia Mineral Deposit Profile Number I-02; by Dani J. Alldrick IDENTIFICATION TEXTURE/STRUCTURE: Two dominant have superimposed foliation or brecciation SYNONYMS: Extension veins, transitional vein types may occur independently or to- onto these early-formed veins. veins, contact aureole veins, “mesothermal gether. Veins may be composed of (i) mas- ASSOCIATED DEPOSIT TYPES: Typical veins”. sive fine-grained pyrrhotite and/or pyrite, deposits of a volcanic arc, especially those or (ii) massive bull quartz with minor cal- in the subvolcanic setting: porphyry Cu+/- COMMODITIES (BYPRODUCTS): Au, Ag cite and minor to accessory disseminations, (Cu). Mo+/-Au (L04), skarns, epithermal veins knots and crystal aggregates of sulphides. and breccias (H04, H05), ‘transitional’ de- EXAMPLES [British Columbia (MINFILE These two types of mineralization may posits (volcanogenic Cu-As-Sb-Au-Ag, #) - Canada/International]: Scottie Gold grade into each other along a single vein or L01) and surficial fumarolic hotspring (104B034), Snip (104B250), Johnny may occur in adjacent, but separate veins. (H03) and exhalative deposits. Mountain (104B107), War Eagle Some veins have undergone ductile and (082FSW097), Le Roi (082FSW093), Cen- brittle shearing that complicates textural COMMENTS: The genesis of these deposits tre Star (082FSW094); Copper Rand, Port- and structural interpretations. remains controversial. Many have been interpreted as mesothermal veins; others, in age, Merrill, Main, and Chib-Kayrand ORE MINERALOGY [Principal and subor- mines, Chibougamau, Quebec; Keating deformed terrains, as exhalative massive dinate]: Pyrrhotite, pyrite, chalcopyrite, sulphide deposits. Those in the Chibouga- and Ohio-Keating mine, Elkhorn Moun- native gold, electrum, sphalerite, galena, tains, Montana. mau camp have also been referred to as bornite, argentite, arsenopyrite, magnetite, shear-hosted gold deposits. GEOLOGICAL CHARACTERISTICS ilmenite, tetrahedrite, tennantite, molybde- EXPLORATION GUIDES CAPSULE DESCRIPTION: Parallel tabular nite, cosalite, chalcocite, tellurobismuthite, to cymoid veins of massive sulphide and/or hessite, volynskite, altaite, native bismuth, GEOCHEMICAL SIGNATURE: Elevated bull-quartz-carbonate with native gold, cubanite, valleriite. values of Au, Ag, Cu. (As, Zn). electrum and chalcopyrite are emplaced in GANGUE MINERALOGY (Principal and GEOPHYSICAL SIGNATURE: Electro- a set of en echelon fractures around the subordinate): Quartz, calcite, ankerite, magnetic (ABEM and VLF-EM) anomalies periphery or within subvolcanic plutons. siderite, chlorite, sericite, rhodochrosite, and anomalous magnetometer lows (nega- Many previous workers have called these K-feldspar, biotite, albite. tive anomalies or ‘magnetic troughs’). mesothermal veins. ALTERATION MINERALOGY: Regional OTHER EXPLORATION GUIDES: Intense TECTONIC SETTINGS: Volcanic arcs in chlorite alteration and proximal sericite al- prospecting swath extending from 100 me- oceanic and continental margin settings. teration predominates; pyrite, silica, car- tres inside the intrusive contact to 1000 me- Older deposits are preserved in accreted arc bonate, rhodochrosite, biotite, epidote, K- tres outside the intrusive contact of a pro- terranes. Deposits in Archean greenstone feldspar, ankerite. Alteration occurs as nar- spective sub-volcanic pluton. Detailed soil belts perhaps formed in immature volcanic row (4 cm) vein selvages and as moderate geochemistry and detailed ground geo- arc settings. Local setting is the exten- alteration haloes extending up to several physics could be designed to investigate sional environment developed at moderate metres into the country rock. At deeper this same area. Small, ‘hairline’ mineral- depths around sub-volcanic plutons. structural levels, alteration envelopes are ized fractures are good proximal indicators DEPOSITIONAL ENVIRONMENT / GEO- more extensive and may include skarn min- of a nearby major vein. Increased altera- LOGICAL SETTING: The subvolcanic eral assemblages with diopside, garnet, epi- tion intensity could also be a good proximal setting for these deposits is transitional be- dote, biotite, K-feldspar, plagioclase, am- indicator, but this is a more subtle feature. tween the setting for subvolcanic porphyry phibole and wollastonite. Deposits are commonly located along shear zones. Once the vein orientation on an in- copper systems and for subvolcanic epi- ORE CONTROLS: Well defined faults and thermal systems. itial discovery is determined, additional shears control the mineralization. Veins are parallel veins should be anticipated and in- AGE OF MINERALIZATION: British Co- peripheral to and spatially associated with vestigated with fences of drill holes. lumbia examples are all Early Jurassic; porphyritic intrusive rocks which may host those in Chibougamau camp are Archean. porphyry copper and/or molybdenum min- ECONOMIC FACTORS HOST/ASSOCIATED ROCK TYPES: Hos- eralization and copper-gold skarns. TYPICAL GRADE AND TONNAGE: trocks are andesitic to basaltic tuffs, tur- GENETIC MODEL: Mineralization appears Gold/silver ratios are close to 1:1. Copper bidites or early intrusive phases around the to be related to felsic to intermediate plu- may also be recoverable. Typical grades are periphery of phaneritic, locally porphyritic, tons that record syn to late volcanic arc 10 to 20 g/t Au. felsic to intermediate stocks and batholiths. magmatism. Deposits in British Columbia IMPORTANCE: The Snip gold mine is cur- DEPOSIT FORM: At various deposits the formed along the thermally controlled ‘brit- rently British Columbia’s largest gold pro- form has been described as: planar, en eche- tle-ductile transition envelope’ that sur- ducer and the Rossland veins are the prov- lon vein sets, shear veins, cymoid veins, rounds subvolcanic intrusions. Late ince’s second largest gold camp. Two de- cymoid loops, sigmoidal veins, extension magma movement caused local shear posits in the Chibougamau camp, Copper veins, tension gashes, ladder veins, and stress, and resultant en echelon vein sets Rand and Portage, are currently in produc- synthetic Reidel shear veins. Veins vary in opened and were filled by sulphides and tion. width from centimetres to several metres gangue minerals precipitating from circu- and can be traced up to hundreds of metres. lating hydrothermal fluids. Shearing may ***

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