newmont’s reserve history on the carlin trend 1965-2001

7/27/2019 NEWMONT’S RESERVE HISTORY ON THE CARLIN TREND 1965-2001

http://slidepdf.com/reader/full/newmonts-reserve-history-on-the-carlin-trend-1965-2001 1/1135

Reserve History

ABSTRACT

Northeastern Nevada’s Carlin trend contains one of the richest

gold endowments in North America. Newmont Mining

Corporation has explored and produced gold from this region

since discovering the Carlin Mine in 1961. Newmont’s Carlin

trend gold reserves have grown from an initial 3.5-million-

ounce (110-t [metric ton]) reserve in 1965 to nearly 12 million

ounces (373 t) in 1998. Over the same period, Newmont

produced 27.3 million ounces (849 t) of gold. Reserve additions

have come from systematic surface and underground

exploration and expansion of more than 30 deposits, through

new metallurgical processes and changing mining methods.

INTRODUCTION

The central part of the Carlin trend is a 38-mile (60-km) long

alignment of gold deposits in Eureka and Elko Counties,

Nevada, extending from the Rain Mine on the south to the Dee

Mine on the north (fig. C-1). Newmont and other companies

have discovered over 40 gold deposits along this trend. The

Carlin trend is one of the largest concentrations of gold deposits

in North America, estimated to contain over 100 million ounces

(3,110 t) of gold including past production, reserves, and

resources (Teal and Jackson, 1997b).

This paper provides a summary of exploration,

metallurgical developments, changing mining methods, and

their relation to Newmont’s reserve history on the Carlin trend.The reserve history is broken down into three periods starting

with the Early Years from 1965 to 1981 centered on mining of

the Carlin deposit and the early expansion to other deposits.

The Growth Years chronicle the meteoric growth of Newmont’s

reserves in the 1980s and the Going Deeper Years focus on the

development of deeper, higher-grade deposits that have been

developed by or led to the onset of underground mining.

EARLY YEARS 1965–1981

Gold was first mined on the Carlin trend from small placers

located in Maggie Creek, east of the Gold Quarry Mine, in the

1880s (Ryneer, 1985). However, it wasn’t until the 1960s that

modern exploration began to uncover the real potential of this

productive gold trend. Newmont began exploration on the

Carlin trend in 1961 when geologists Alan Coope and John

Livermore began investigating the Blue Star Mine and Maggie

Creek claims (Coope, 1991). After a three-week examination

of Blue Star, a recommendation was made to acquire the

property, but Newmont was unable to negotiate a deal with the

landowner (Coope, 1991). Using the experience gained at Blue

NEWMONT’S RESERVE HISTORY ON THE CARLIN TREND

1965–2001

Dean G. Heitt1

Star, exploration focused on jasperoid outcrops located 2 l

34

l

34 l

34

l

34

l

34

miles (4.5 km) southeast of Blue Star, leading to discovery of the Carlin deposit in late 1961 (fig. C-2). Development drilling

between 1962 and 1965 proved up a reserve of 11 million short

tons (10 Mt) grading 0.320 opt (troy ounces per short ton; 11.0

g/t) gold for a total of 3.5 million ounces (110 t).

Early exploration and development focused around the

Carlin deposit because only high-grade ore was economic at a

fixed gold price of $35.00 per ounce (fig. C-3). With the demise

of the Bretton Woods Monetary Agreement in 1971 and the

subsequent rise in gold price, Newmont began acquiring other

properties in the area. In 1972, the Blue Star and Bootstrap

deposits were acquired and, in 1977, the North Star deposit

was discovered north of Blue Star. Intermittent exploration in

the Maggie Creek claim area, from 1962 to 1979, led to

development of a 359,000-ounce (11-t) reserve in 1979 (Rota

and Ekburg, 1988). Figure C-4 shows the location of new

deposits added to reserves during this period.

The 1965 pre-mine reserve of 3,520,000 ounces (109 t)

steadily decreased to a low of 765,600 ounces (24 t) in 1973 as

mining depleted the Carlin deposit reserves (fig. C-5). By 1981,

new discoveries increased Newmont’s Carlin trend reserve to

1.15 million ounces (36 t). Average grade of the reserves

decreased as higher gold prices made lower grade material

economic (fig. C-6). The average reserve grade of 0.165 opt

(5.6 g/t) gold in 1981 was approximately half of the 1965 grade.

Newmont’s first mill was commissioned in 1965 to processoxide ore from the Carlin Mine (fig. C-7). Mill #1, as it became

known, later processed ore from other deposits until it was

decommissioned in September 1994. Increasing carbonaceous

ore from Carlin led to the addition of a flash chlorination circuit

in 1971 to pretreat ore prior to cyanidation. A double oxidation

process, added in 1977 to process sulfidic-carbon ores, allowed

the conversion of 285,000 ounces (8.8 t) from waste to ore.

Newmont’s first leach facility began at Bootstrap in 1979

processing ore averaging 0.028 opt (1.0 g/t) gold stockpiled

during mining. Heap leaching using reusable asphalt pads

began at Maggie Creek in 1981. Large-scale leaching having

been proved economic, leach-grade ore would contribute

significantly to Newmont’s reserves in the future.

Production decreased steadily during the Early Years, as

the Carlin Mine was depleted and lower grade ore from new

deposits was processed, reaching a low of 110,000 ounces (3.4

t) in 1980 (fig. C-8). Ironically, this is the same year gold hit

$800 per ounce and averaged over $600 per ounce (fig. C-3).

From 1965 to 1981, Newmont produced 3,291,700 ounces

(102.4 t) from the Carlin trend, the vast majority coming from

the Carlin Mine (fig. C-9).

1Newmont Mining Corporation



36

South AreaOperations

Rain AreaOperations

North AreaOperations

Winnemucca

Elko

Carlin

Ely

Reno

Lovelock

Las Vegas

80

80

H U M B O L D T E L K O

N Y EM I N E R A L

ESMERALDA

LYON

L I N C O L N

C L A R K

P E R S H I N G

C H U R C H I L L W H I T E

P I N E E

U

R

E

K

A

L A

N D

E

R

W

A S H O E

80

80

80

EmigrantPass

GoldQuarry

M ac

Tusc

PeteCarlinUniversal

Gas Pit

Lantern

BeastBlue Star

Bobcat

North Star

W est Leevil le

Four CornersTurf

Genesis

Deep Star

Betze-Post

Rodeo (Goldbug)

Meikle

Dee

Capstone

Bootstrap

Tara

Rain

Emigrant

Carlin

E u r

e k

a C

o u

n t y

E l k

o C

o u

n t y

Mike

0 2 4 6 miles

0 42 6 8 10 kilometers

Figure C-1. Map of the Carlin trend showing the major gold deposits and Newmont’s major operation areas.



37

Reserve History

TailingsFacility

Popovich Hill

Mill 1

Figure C-2. A 1966 view of the Carlin Mine and Mill complex, looking east.

Photo courtesy of Newmont Mining Corporation.

U . S .

d o l l a r s

1 9 6 6

$0

$100

$200

$300

Year

$400

$500

$600

$700

1 9 9 8

2 0 0 0

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

1 9 9 6

159

612

317

387

273

35

Figure C-3. London yearly average gold price from 1965 to 2001. Source: www.kitco.com.



38

Winnemucca

Elko

Carlin

Ely

Reno

Lovelock

Las Vegas

80

80


N Y EM I N E R A L

ESMERALDA

LYON

L I N C O L N

C L A R K

P E R S H I N G


P I N E E

U

R

E

K

A

L A

N

D

E

R

W

A S H O E

80

80

80

EmigrantPass

M aggieCreek

Carlin

Blue Star

North Star

Bootstrap

Carlin

E u

r e k a

C o u

n t

y

E l k

o C

o u n

t y

0 2 4 6 miles


Figure C-4. Location of deposits added to gold reserves during the Early Years (1965–1981).



39

Reserve History

M i l l i o n s o u n c e s o f g o l d

1 9 6 6

0

5

10

15

20

25

30

1 9 9 8

2 0 0 0

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

1 9 9 6

Early Years

Growth Years

Going Deeper Years, Open Pit

Going Deeper Years, Underground

3 , 5

2 0 , 0

0 0

7 6 5 , 6 0

0

1 , 1

5 3

, 0 2 0

9 , 8

3 9 , 8

0 9

2 0 , 6

8 4 , 0

0 0

2 3 , 3

3 5 , 0

0 0

1 5 , 9

6 3 , 0

0 0

1 1 , 8

4 1 , 0

0 0

Year-end

T

r o y o u n c e s o f g o l d p e r s h o r t t o n

1 9 6 6

0

0.05

0.10

0.20

0.15

0.30

0.25

0.35

1 9 9 8

2 0 0 0

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

1 9 9 6

Early Years

Growth Years

Going Deeper Years

0 . 3 2 0

0 . 1

6 5

0 . 0

5 1

0 . 1

0 0

Year-end

Figure C-5. Total Newmont reserve ounces of gold on the Carlin trend from 1965 to 2001.

Source: Newmont Mining Corporation and Newmont Gold Company Annual Reports.

Figure C-6. Average grade (opt) of Newmont gold reserves on the Carlin trend from 1965 to 2001.




40

Thickener Tanks Mill Building

Figure C-7. A view of Mill #1 from Popovich Hill in 1968, looking west. Outcrops in the foreground

are Popovich jasperoids. Photo courtesy of Newmont Mining Corporation.

T h o u s a n d o u n c e s o f g o l d

1 9 6 6

0

200

400

600

1,400

1,200

1,000

800

1,800

1,600

2,000

2,200

1 9 9 8

2 0 0 0

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

1 9 9 6

Early Years

Growth Years

Going Deeper Years

1 2 8 , 5

0 0 3

3 7 , 0 0

0

1 1 0 , 0

0 0

1 , 4

6 7 , 8

0 0

1 , 8

6 6 , 0

0 0

Year

Figure C-8. Newmont’s total annual gold production (ounces) from the Carlin trend from 1965 to 2001.




41

Reserve History

GROWTH YEARS 1982–1989

During the 1980s exploration focused on discovery of large,oxide gold deposits amenable to open-pit mining and met with

great success. Twelve new deposits were added to reserves

during the period, nine of them between 1985 and 1988 (fig.

C-10). Geologic mapping, soil and rock chip geochemistry

combined with drilling proved to be the best exploration tools

during this period. Many of the deposits discovered during

the 1980s cropped out at the surface.

The dramatic rise in reserves began with the discovery of

the Gold Quarry and Rain deposits in 1980. Gold Quarry was

discovered approximately 1,000 feet (300 m) east of the

Maggie Creek Mine when drilling encountered gold

mineralization below 250 feet (75 m) of postmineral Tertiary

Carlin Formation (fig. C-11) (Rota and Ekburg, 1988). At about

the same time, Newmont geologists also began investigating

the Rain claims located 12 miles (19 km) south of the town of

Carlin (Knutsen and West, 1984). Although the discovery was

originally staked for barite by local prospector Price “Turk”

Montrose, jasperoid rock chip samples from the discovery

assayed up to 0.480 opt (16.5 g/t) gold (Thoreson, 1988). Gold

Quarry and Rain were classified as reserves in 1982.

Purchase of the TS Ranch in 1982 from Charles Thorton

and Roy Ash was a major milestone in Newmont’s

development of the Carlin trend. Acquisition of these lands

provided Newmont with a substantial private land holding on

the Carlin trend and allowed geologists to explore in areas

previously unavailable.Reserves increased dramatically during the Growth Years

from 1.15 million ounces (36 t) in 1981 to over 20.68 million

ounces (643 t) in 1989 with additions coming from new

discoveries and expansion of existing deposits (fig. C-5). Gold

prices ranging from a high of $460 per ounce in 1982 to a low

of $317 per ounce in 1985 (fig. C-3) meant that lower grade

ore could be included in the reserves. Consequently, the average

grade of 0.051 opt (1.7 g/t) gold in 1982 was a third of the

1981 grade of 0.165 opt (5.7 g/t) gold (fig. C-6). Gold reserves

added throughout the Growth Years averaged approximately

0.050 opt (1.7 g/t) (fig. C-6).

During the 1980s, new mines were developed over nearly

the entire length of the trend. These new mines, combined with

increased production from existing operations, required new

process facilities to be located closer to the operation areas

than during the Early Years when all of the mill-grade ore was

shipped to Mill #1. To meet these needs, Newmont

commissioned its second oxide mill (Mill #2) at Gold Quarry

in 1985 followed by Mill #3 at Rain and Mill #5 at Gold Quarry

in 1988, and Mill #4 in the North Area in 1989 (fig. C-1). New

oxide leach pads were constructed at Rain, Gold Quarry, and

the North Area to treat the increased amount of low-grade ore

developed during this time.

C u m u

l a t i v e p r o

d u c

t i o n

( m i l l i o n o u n c e s o

f g o

l d )

Year 1 9 6 6

0

5

10

15

20

25

30

1 9 9 8

2 0 0 0

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

1 9 9 6

3 , 2

9 1

, 7 0 0

7 , 4

0 1

, 2 2 0

2 7

, 3 2 1

, 7 6 7

Figure C-9. Newmont’s cumulative gold production (ounces) from the Carlin trend from 1965 to 2001.Source: Newmont Mining Corporation and Newmont Gold Company Annual Reports.



42

Winnemucca

Elko

Carlin

Ely

Reno

Lovelock

Las Vegas

80

80


N Y EM I N E R A L

ESMERALDA

LYON

L I N C O L N

C L A R K

P E R S H I N G


P I N E E

U

R

E

K

A

L

A

N

D

E

R

W

A S H O E

80

80

80

EmigrantPass

GoldQuarry

M ac

Tusc

Pete

Lantern

Bobcat

Genesis

Post(Newmont Portion)

Capstone

Rain

Emigrant

Carlin

E u r e

k a

C o u

n

t y

E l k o

C o u

n t y

0 2 4 6 miles


SM Z

Figure C-10. Location of deposits added to reserves during the Growth Years (1982–1989).



43

Reserve History

Production rose dramatically from 136,600 ounces (4.25 t)

in 1981 to 1,467,800 ounces (45.5 t) in 1989 (fig. C-8). In 1988,

Newmont became the largest gold producer in North America

(Newmont Gold Company, 1988). Between 1965 and 1989,

Newmont produced 7,407,220 ounces (230.4 t) from the Carlin

trend (fig. C-9).

GOING DEEPER 1990–1998

During the late 1980s exploration and development drilling

began focusing on higher-grade, refractory deposits as near

surface discoveries were exhausted. Refractory material contains

organic carbon and/or unoxidized sulfides and requires

pretreatment of the ore prior to cyanide gold recovery.

Newmont’s first deep discoveries were the Deep Post and Gold

Bug deposits in 1988 near the Post deposit (fig. C-12). The firstdrill hole at Deep Post encountered 470 feet (143 m) averaging

0.930 opt (32 g/t) gold, substantially higher-grade than the typical

oxide deposit discovered in the 1980s. While both Deep Post

and Goldbug would eventually become underground mines, both

were planned originally as open-pit mines.

Barrick Gold Corporation’s 1989 discovery of what would

become the Deep Star deposit started Newmont on the road to

underground mining. Newmont’s first hole intersected 195 feet

(58 m) grading 2.058 opt (70.6 g/t) gold beginning at 1,295

feet (388 m) and subsequent development drilling indicated a

1992 pre-mine reserve of 789,000 ounces (25 t) grading 0.929

opt (31.9 g/t) gold. Early feasibility studies indicated that twin

shafts were the best option for accessing the deposit but startupwas delayed in 1993. Underground mining engineers then

began to evaluate other projects at the Carlin and Rain Mines.

Newmont’s first foray into underground mining had been at

Carlin in 1974 and 1975 when a 2,500-foot (750-m) adit was

driven as a drill platform into the north wall of the pit to test

the down-dip potential of the Main and East orebodies (Kuehn,

1989). Forty-three holes were drilled, and the results justified

an additional layback to the open pit. Underground mining at

Rain was first proposed by Thoreson in 1990 to access high-

grade ore that would have been left in the ultimate pit wall.

Both the Carlin and Rain underground mines began

development in late 1993 with production commencing in 1994

(fig. C-13). Success of both of these projects led to a redesignof the Deep Star Mine from twin shafts to twin declines to

access the deposit. Development for Deep Star began from the

active Genesis open-pit mine in 1994 with production

beginning in 1996 (Clode and others, this volume).

Exploration for deeper, typically blind deposits required

different techniques than those used in the 1980s. High-grade

gold in the northern Carlin trend is hosted in the lower units of

the Devonian Popovich limestone or in the upper units of the

underlying Devonian-Silurian Roberts Mountains Formation.

Drilling targeted these units below weak geochemical

Maggie Creek

Leach Facility

Gold Quarry

Maggie Creek

Mine

Figure C-11. Aerial view (looking east) of the Maggie Creek Mine and exploration for the Gold Quarry deposit,1982. Photo by Galen Knutsen.



44

Winnemucca

Elko

Carlin

Ely

Reno

Lovelock

Las Vegas

80

80


N Y EM I N E R A L

ESMERALDA

LYON

L I N C O L N

C L A R K

P E R S H I N G


P I N E E

U

R

E

K

A

L

A

N

D

E

R

W

A S H O E

80

80

80

EmigrantPass

Hardie Footwall

Beast

Four Corners

W est Leevil le

Deep Star

Goldbug

Tara

RainUnderground

Carlin

E u r e

k a

C o u

n t y

E l k

o C

o u n

t y

0 2 4 6 miles


Chukar Footwall

Figure C-12. Location of deposits added to reserves during the Going Deeper Years (1990–2001).



45

Reserve History

anomalies and/or favorable structures found in the overlying

barren Ordovician Vinini Formation (D. Groves, 1999, personal

commun.). This exploration method led to the discovery of

the West Leeville deposit in 1994 on lands joint-ventured with

High Desert Mineral Resources about 1.5 miles (2.5 km) north

of the Carlin Mine (Jackson and others, 1997). The West

Leeville deposit lies 1,600 to 1,800 feet (480–540 m) below

the surface and contains a drill-indicated resource of 3.2 million

ounces (100 t) at an average grade of 0.436 opt (15.0 g/t) gold(Jackson and others, 1997a). While most of the exploration

emphasis was on deep deposits, several small, oxide deposits

including Tara and Beast were discovered (fig. C-12).

Newmont’s metallurgical research and development group

played a significant role in increasing reserves during this

period. The Refractory Ore Treatment Plant (Mill #6) was

commissioned in 1994 to roast high sulfide and carbonaceous

refractory ores from all its active operations. Most of

Newmont’s underground ore and a significant portion of the

remaining open-pit ore is refractory and requires pre-treatment

prior to gold extraction. Also in 1994, Newmont began a 3-

year commercial demonstration of its patented bioleaching

technique to process low-grade refractory ore. Bioleaching usesbacteria to oxidize sulfides prior to gold extraction with cyanide

or ammonium thiosulfate. In 1994, Newmont added 2.0 million

ounces (62 t) of Gold Quarry bioleach ore to reserves. In 1999,

bioleach processing was deemed uneconomic due to the low

gold price. Currently only bio-milling ore, which is a

combination of bioleach pretreatment and processing through

an oxide mill, is now included in Newmont’s reserves.

Newmont’s reserves reached a high in 1996 of 23,335,000

ounces (723 t). Figure C-5 illustrates the rising importance of

the underground reserves beginning in 1994. The higher-grade

underground ore has slowly increased the average grade of the

reserves to 0.100 opt (3.4 g/t) gold in 2001 (fig. C-6). Depletionand the revaluing of the reserves at a lower gold price has led

to declining reserves since 1996 (fig. C-7).

Gold production remained relatively constant in the 1990s

reaching a high of 1,866,000 ounces (58 t) in 2000 (fig. C-8).

Between 1965 and 2001, Newmont produced 27,321,767

ounces (849.8 t) from the Carlin trend.

FUTURE

Newmont is confident of continuing to add quality reserves to

its Carlin trend operations in the future. Development is

ongoing to convert known resources into reserves and

exploration continues to look for the next big deposit in thisproductive area. Ongoing metallurgical research of new

processes continues to allow material once considered waste

to be mined and processed economically.

Figure C-13. A 1998 view of the Carlin East underground portal area, looking north. The portal is located in the north

wall of the Carlin East pit. Photo by Matt Breitrick.

Carlin East Portal

BatchPlant

newmont’s reserve history on the carlin trend 1965-2001

Documents