Distal Alteration

8/3/2019 Distal Alteration

1/81

Pallca

Project

Nevado Yerupaja

6617 meters

Traceelementgeochemistry

and distal veins

UBC

MDRU

M i n e r a l D

S. Ebert

April 25 2003


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Outline

1) Trace element dispersion patterns

2) Geology and distal veins

3) Ultraviolet fluorescence of vein calcite

4) Simplified distal vein model

UBC

MDRU

M i n e r a l D


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Trace element dispersion patterns

1) Yauricocha MineMinera Corona

- Reserves of 361,000 tons 7% Zn, 4% Pb, 0.3% Cu 4.9 OPT Ag

- Mineralized zones extend >400m vertically

- District contains CRD-skarn, Carlin-style Au, low-grade

porphyry-Cu, low grade Au, Ag-Cu base metal veins


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SanJuanSan

Antonio

423000E

8640 000N

8638 000N

A

A

B B

N

LakeAcococha

Cu - zone0.3% Cu

Au - zone60 - 264ppb

0 1Km

Quartz monzonite intrusive

Celendine FormationJumasha Formation limestone

Pb-Zn-Ag mineralization

Quartz-sphalerite-pyrite-galena-enargite vein

Purisima Conception

Pass

Cachi-Cachi

421 000E

Lim

ito

fma

rble

Limitofm

arble

Yauricocha District


6/81

Yauricocha, Pass area, looking west


7/81

Prisma Conception area looking east


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Yauricocha Pass - Main Zone traverseWest

East

Simplified geology and sample locations

2800m

2700m

2600m

2500m

CRD mineralization

ConceptionAu zone

Rock sample location

Elevation

(meters)

0 500 1000

? ? ? ?

Quartz Monzonite

Celendin Formation

Jumasha Formation

Bleached marble

Gray marble

Gray limestone

Pb-Zn-Ag orebody

UTM 422385E8639090N

UTM 420600E8638750N


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0

1000

500

0

0

12000

0

500

0

10

Partsp

ermillion


10/81


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SanJuanSan

Antonio

423000E

8640 000N

8638 000N

A

A

B B

N

LakeAcococha

Cu - zone0.3% Cu


0 1Km





Purisima Conception

Pass

Cachi-Cachi

421 000E

Lim

ito

fma

rble

Limitofm

arble

Yauricocha District


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Cachi-Cachi

Looking west


13/81

Yauricocha Cachi-Cachi traverse

West East

Simplified geology and sample locations

2700m

2600m

2500m

Skarn - CRDmineralization

Rock sample location

Elevation(meters)

Quartz Monzonite

Jumasha Formation

Bleached marble

Gray marblePb-Zn-Ag orebody

0 100 200

Meters


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Trace element dispersion patterns

1) Uchucchacua MineBuenaventura

- South Americas largest Ag producer

- High grade silver hosted in veins

- Roughly 2 million ton reserve at 420 ppm Ag, 2.1% Zn


17/81

km

0 1

Uchucchacua surface map

Cia De Minas Buenaventura

S.A.A.


18/81

NW SE

Upper Jumasha Fm.

Markerhorizon

MiddleJumasha Fm.

Lower Jumasha Fm.

Rosa

Ve

in

Rosa

Ve

in

Rosa2Vein

R o s a

3 V

e i n

4180m

4360m

4450m

4725m

4940m

4400m

4500m

4600m

4700m

4800m

4900m

5000m

4300m

4200m

4100m

Vein, fault

Ag ore zone

0 100

Meters

Uchucchacua simplified

Cross section from Cia De

Minas Buenaventura S.A.A.


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22/81

Rosa VeinThin bedded gray footwall limestone

253254255256257258271272273274275276277278279280

XX

X

X259260

261

262

Verticalcliff

White calcite veinlet Grab sample locationWhite +/- gray and brownishcalcite. Crustiform banding

Late Mn-Fe breccia

Breccia

2 meter chip sample

Crustiform banded white-brown-gray calcite vein

Calcite veinlets with Mnand Fe-oxides

X X X XXX XX

Similar calcite veins andveinlets continue for at leastanother 70 meters

270 269 268 267

266

265

X265

264263

Uchucchacua - Rosa Vein 4940m Sectionvein and footwall geochemical traverse

Average width in cm / number per 2m interval

0.1/6 Calcite veins less than 5cm

Calcite veins greater than 5 cm

Calcite vein density in limestone}00000 0 7/1

0.2/30.2/31/6

15/210/1

2/42/4

10/2

3/50.5/3

25/1

0.7/30.1/1

25/1

2/3

40/2

0.5/60.6/7

5/1

1/5

6/1

1/4

280

UTM 316754E8826157N

0 2 4 6 8 10 12 14 16 18 20

Meters

FaultStr. 110 dip 75 S

0 0SouthNorth

North-south section across the Rosa Vein at surface at 4940m elevation. Face of section trends 020 degrees.

Most veins strike 100 to 1100


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Rosa VeinDark gray limestone withwhite calc ite veins and veinlets

315314313312311

X306307

305

316

304

317

308310

Grab sample locationRosa vein.

2 meter chip sampleCalcite vein

XXX309

X308

Uchucchacua - Rosa Vein 4450m SectionUnderground at 754m (along vein)


1/20 1/20Calcite veins less than 5cm


Calcite vein density in limestone }5/1 7/20 25/1

1/200.5/90.4/25

5/115/2

0.5/20

313

0 2 4 6 8 10 12 14 16 18 20

Meters

SouthNorth

North-south section across the Rosa Vein underground at 4450m elevation.

* Most calcite veins strike 90 to 100 or 010 to 0300 0

X

X

X

X

Not accessable

Limit ofexposure

Adit

Str. 90 dip vertical0

* There are some shallow dipping calcite filledtension gashes

X

(Projected 15 to 20m)


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Distal Veins

1) Quartz-carbonate Ag-Mn base metal veins

2) Geochemistry

3) Link to intrusions

UBC

MDRU

M i n e r a l D


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SanJuanSanAntonio

423000E

A

A

B B

N LakeAcococha

Cu - zone0.3% Cu


0 1Km


Celendine Formation

Jumasha Formation limestone



Purisima Conception

Pass

Cachi-Cachi

421 000E

Lim

ito

fmarb

le

Limito

fmarble

Quartz-py-sphal-gal-enargite vein

Ag to 306 ppmCu to 3.3 %Zn to 1.3 %Pb to 0.4 %As to 1.1 %high Sb-Hg

Ag to 66 ppmCu to 0.5 %Zn to 4 %Pb to 3 %

Quartz-py-sphal-enargite

YauricochaDistrict


30/81

Marbl

e

Horn

fels

edlim

estone

X

X245

244XX

X

X

X

X

243242

238

239

240

241

Ag 20 ppmMn 3 %As 623 ppm

Ag 1640 ppmMn 16%As 4090 ppmPb 0.2%Zn 0.6%

Hg >10 ppm

Ag 383 ppmMn 12%As 1910 ppmPb 0.06 %Zn 0.14%Hg 6.3 ppm

0 100 200

Meters

Garnet-pyroxeneSkarn

Intrusive

Limestone

1m veinCalcite-silica with

10% alabandite, 3% pyrite

1m silicified limestonesilica-calcite vein withpyrite-orpiment-realgar

5 to 15 cm vein

Banded carbonate-silica-pyrite

{

{

Calc-silicateveinlets

Silica-carbonateveinlets

AnamaraySkarn

Geology data from

Buenaventura and

a 2002 field visit

Quartz pheric


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0 100 200

Meters

N

65

60

80

65

Geology map of the Contonga Mine area. Simplified andmodified from Bodenlos and Ericksen (1955).

Localized marble and bleachingproximal to the intrusive contact

Sulfide-quartz-calcite veinletsparallel to bedding in limestone

JumashaLimestone

Silicified Limestone Sample location

Quartz phericrhyolite

Sulfide-skarn ore zone

Sulfide-quartz-calcite veins

337

330331

332333

334, 335, 336

5 to 15 cm wide qtz-cal veinswith 20-40% Gal-sphal-py

Ag 257 to 381 ppmMn 1450 ppmCu 0.2 to 1%Pb 12 to 20%Zn 9 to 16%plus Cd-Se-Te

Pb-Zn-Ag-Cu-Cd-Bi-Se-te


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Calcite-gal-sphal-pyto 361 ppm Ag


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Fortuna

Antamina

Ridge Road

Qtz-gal-py-cal-fluor

Ag-Au-As-Pb-Zn

Calcite gal sphal pyAg-Au-Mn-Pb-Zn-As +/- Cd-Hg-Sb

Peak Nine

to 361 ppm Ag

4.1% Mn


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UV Fluorescence

1) Some hydrothermal calcite

associated with skarn-CRD and

distal veins fluoresces red

2) Upper veins at Uchucchacua

fluoresce red and white-blue

3) Syn-tectonic veins do not

fluoresceUBC

MDRU

M i n e r a l D


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Contonga Ag-Pb-Zn vein

Yauricocha CRD ore

17.77

11.09

C

D


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Antamina - Fortuna calcite vein

Antamina - Fortuna Ag vein

13.64

14.49

12.34

6.02

A

B


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Uchucchacua 4940 m level

Uchucchacua 4940 m level

16.17

15.94

15.84

B

C


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UV Fluorescence

1) A hand held UV lamp may be useful in distinguishing

calcite related to mineralization vs. syn-tectonic calcite

2) Can UV help distinguish level in the system?

3) What are the compositional variations affecting fluorescence?

UBC

MDRU

M i n e r a l D


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Simplified distal vein model

1) Geology, geochemistry,

UV fluorescence

(and isotopes) link distalveins and mineralization

2) A model for larger veins

hosted by pure limestone

UBC

MDRU

M i n e r a l D

Surface 0 km


40/81

Limito

fhorn

fels

Limit

ofma

rble

1 km

2 km

Skarn

Graymarble

Bleachedmarble

Fortuna veins

Uchucchacua Ag zone

Barren calcite vein

Surface

Carbonate host rocks

Low-gradeporphyry Cu-Mo

CRD

0 km

Antamina

Milpo

Yauricocha

Dec

reasin

gquartz

inv

eins

Ag-Mn-Pb-Zn-As

Ag-Mn-Pb-Zn-As-Sb-Hg

Cu-Pb-Zn-Ag

(Very weak Mn-Hg-Tl-Ag-Zn)


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Conclusions

1) There are large and variable geochemical anomalies incarbonate rocks around skarn-CRD at Yauricocha, largely

veinlet controlled.

2) Field relationships and geochemistry indicate distal

Ag-Mn-base metal veins are directly related to intrusion/skarn systems.

3) The proposed simplified vein model has important

exploration implications. Additional work to test/improve

the model us ongoing.

4) Combined trace element, oxygen isotopes, and UV

fluorescence may provide exploration guides.

UBC

MDRU

M i n e r a l D


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Stable Isotopic Studies

225 Analyses Antamina (130)

Chacua (37)

Yauricocha (49)

Milpo (9) Sedimentary protolith:

21 to 25 d18O (VSMOW) 1 to 3 d13C (VPDB)

Mineralized zones and distal halos recorddepletion of d18O +/- d13C

UBC

MDRU

M i n e r a l D


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Overview

Deposits span a continuum within amagmatic hydrothermal system and allowdevelopment of a conceptual model

Distal alteration controlled by stratigraphyand structure

Lateral alteration haloes are narrow whenhosted by steeply dipping strata (Milpo)

Wider haloes are associated with gentlydipping strata

UBC

MDRU

M i n e r a l D


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Vertical Zonation of Targets Shallow: 0.5 km (above Chacua)

No distal alteration

18O and 13C of veins retains magmatic-hydrothermal signature

Intermediate: 1 km (ore zone at Chacua,

Fortuna - top of Antamina)

18O and 13C halo (> 10 m) around veins provideslargest target (larger than trace elements)

Deep: 1.5 to 2 km (Antamina and Yauricocha) Advective bleaching of marble provides largest

target (larger than 18O and 13C)

UBC

MDRU

M i n e r a l D

Surface

0 km

?


47/81

Limito

fhornfe

ls

L

imitof

marble

1 km

2 km

Skarn

Graymarble

Bleachedmarble

Fortuna Ag-Pb-Zn veins

Uchucchacua Ag zone

Barren calcite vein

d

d

18

13

O 18

C -2

d

18

O depletion inadjacent wall rock

Small O depletionin adjacent wall rock

d18

Strong O depletionin adjacent wall rock

d18

Large zones with variableO depletion halos mostly

within bleached limestoned

18

d

d

18

13

O 16

C -6

d

d

18

13

O 13

C -1 to -3

d

d

18

13

O 10 to 14

C -1 to -9

Background limestone

O 22.5

C +2

d

d

18

13



Skarn and CRD

CRD

Narrow O depletion halowithin bleached limestone

d18

Antamina

Milpo

Yauricocha

Decreasin

gqua

rtz in

veins

Simplified outline ofdepletion halod

18O

?


48/81

Milpo


49/81

Yauricocha District

Pass transect Variable d18O depletions up to 1400 m Strong d18O depletions within inner 400 m Purisima Conception - meteoric influence?

Depletions in d13C correlate with d18O. Cachi-Cachi transect

Variable d18O depletions coincident withbleached marble (~200 m)

Depletions in d13C correlate with d18O.

UBC

MDRU

M i n e r a l D

Yauricocha District


50/81

SanJuanSanA

ntonio

423000E

8640 000N

8638 000N

A

A

B B

N

LakeAcococha

Cu - zone0.3% Cu


0 1Km





Purisima Conception

Pass

Cachi-Cachi

421 000E

Lim

ito

fm

arble

Limitofm

arble

Yauricocha District


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U h h


53/81

Uchucchacua

Transects sample approx 500 m verticalzonation

Calcite veins have light d18O (14-19 )with lowest values at depth

No lateral alteration halo at highest levels(4950 m)

Lateral d18O depletion halo (> 10 m) atdepth (4450 m)

d13C depletion (values of 0 to -9 )correlates with d18O

Late veins record meteoric influx

UBC

MDRU

M i n e r a l D


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4300

4400

4500

4600

4700

4800

4900

5000

5.00 10.00 15.00 20.00 25.00

Rosa Vein d18O vs depth

d18O

U h h


55/81

Uchucchacua







UBC

MDRU

M i n e r a l D

Rosa vein 4940m surface sectionoxygen and carbon isotopes


56/81

Rosa VeinThin bedded gray footwall limestone

253254255256257258271272273274275276277278279280

XX

X

X259260

261

262

Verticalcliff

X X X XXX XX

Similar calcite veinsandveinlets continue for at leastanother 70 meters

270 269 268 267

266

265 264263


0.1/6 Calcite veins less than 5cm


Calcite vein density in limestone}00000 0 7/10.2/30.2/31/6

15/210/1

2/42/4

10/2

3/50.5/3

25/1

0.7/30.1/1

25/1

2/3

40/2

0.5/60.6/7

5/1

1/5

6/1

1/4

UTM 316754E8826157N

0 2 4 6 8 10 12 14 16 18 20

Meters

SouthNorth

Most veins strike 100 to 1100

20.56, -7.1815.94, -1.9615.84, -1.91

17.67, -1.96

21.15, 2.9319.96, 1.82

18.49, -3.62

21.83, 3.20

18.67, -1.83

Rosa vein 4450m level undergroundoxygen and carbon isotopes

15.84, -1.91

d O per mil C per mil18 13

d

Rosa VeinDark gray limestone withwhite calcite veins and veinlets

315314313312311

X306307

305 304

317

308310XXX

309

0 2 4

Meters

SouthNorth

X

X

X

Not accessable

Limit ofexposure

AditX


Calcite veins less than 5cm


16.60, -5.8815.92, -6.22

15.98, -6.9515.56, -6.86

17.16, 1.23

16.41, -5.73

17.07, 2.37

U h h


57/81

Uchucchacua







UBC

MDRU

M i n e r a l D


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Synthesis

Skarn, CRD deposits have d18O of 11 to 14, indicative of magmatic fluid (~ 11)

Uchucchacua veins formed at 175 to 275 C

(based on fluid inclusions, Bussell et al1990)

Vertical zonation in vein d18O consistent withprecipitation from magmatic fluids at 200-

250 C

UBC

MDRU

M i n e r a l D

LimestoneMagmatic-

hydrothermalMeteoricinfluence?

Ave 22.5 (8 samples)A


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d18O

0 5 10 15 20 25

Contonga

Yauricocha

Antamina (Fortuna)

Anamary

Milpo

Uchucchacua

yue ce

Distal vein calcite

Skarn-CRD calciteor proximal vein

Late calcite vein

400 Co

300 Co

200 Co

(F.I. Temps. Mainly 175 to 275 C, ave. 250 C)o o

A t i


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Antamina

Exposures allow sampling of vertical zonationover 500 m

Highest levels (Fortuna, ~ 1km) probably slightlydeeper than Ag zone at Chacua

Isotope alteration style is similar to Chacua Agzone

Distal alteration target is stable isotope depletionhalo

Deepest levels (1.5 to 2 km) have similarities to

Yauricocha

UBC

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UBC

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63/81

Gray Marble and Limestone


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Gray Marble and Limestone

Gray Marble (G) reflects protolithcomposition

Cryptic distal alteration recorded in somesamples

Gray marble from vicinity of browncarbonate veins (GVB) are depleted to aslow as 11

UBC

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M i n e r a l D


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Grey marble and limestone

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00

d 18O (VSMOW)

d

G

GL

GVB

Bleached Marble


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Bleached Marble

Diffusional Bleaching (BS) Planar harline sulfide veins with cm wide

bleaching haloes

Isotopically unaltered

Massive Bleaching (BM) Stratigraphically and structurally controlled

Massive, homogeneous d18O depletion to as lowas 13

Pervasive homogeneous percolation of magmatic-hydrothermal fluids

UBC

MDRU

M i n e r a l D


67/81

Antamina UBC

MDRU

M i n e r a l D


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UBC

MDRU

M i n e r a l D

Antamina


69/81

Antamina UBC

MDRU

M i n e r a l D


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UBC

MDRU

M i n e r a l D

Antamina


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Bleached Marble

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00

d 18O (VSMOW)

d

BS

BL

BM

Veins


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Veins

Early (syntectonic) veins (VE) are similar toprotolith isotopically

Syn-mineralization veins (VM) and browncarbonate mineralized veins (VMB) are low in d18O(11 to 14 )

VM, VMB also depleted in d13C with lighter valuesat depth

Late white and clear calcite (VL) veins locally havemeteoric signature

UBC

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M i n e r a l D


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Veins

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0.00 5.00 10.00 15.00 20.00 25.00

d 18O (VSMOW)

d

VE

VM

VMB

VL

O i


74/81

Overview

Deposits span a continuum within amagmatic hydrothermal system and allowdevelopment of a conceptual model

Distal alteration controlled by stratigraphy

and structure Lateral alteration haloes are narrow when

hosted by steeply dipping strata (Milpo)

Wider haloes are associated with gentlydipping strata

UBC

MDRU

M i n e r a l D

Surface


0 km

?


75/81

Limito

fhornfe

ls

Limito

fmarb

le

1 km

2 km

Skarn

Graymarble

Bleachedmarble


Uchucchacua Ag zone

Barren calcite vein

d

d

18

13

O 18

C -2

d18



d18


d18

Large zones with variableO depletion halos mostlywithin bleached limestoned

18

d

d

18

13

O 16

C -6

d

d

18

13

O 13

C -1 to -3

d

d

18

13

O 10 to 14

C -1 to -9


O 22.5

C +2

d

d

18

13



Skarn and CRD

CRD


d18

Antamina

Milpo

Yauricocha

Decreasin

gqua

rtz in

veins


18O

Vertical Zonation of Targets


76/81

Vertical Zonation of Targets Shallow: 0.5 km (above Chacua)

No distal alteration

18O and 13C of veins retains magmatic-hydrothermal signature

Intermediate: 1 km (ore zone at Chacua,

Fortuna - top of Antamina)

18O and 13C halo (> 10 m) around veins provideslargest target (larger than trace elements)

Deep: 1.5 to 2 km (Antamina and Yauricocha) Advective bleaching of marble provides largest

target (larger than 18O and 13C)

UBC

MDRU

M i n e r a l D

Uchucchacua


77/81

0.1

1

10

100

1000

0 2 4 6 8 10 12

distance from Rosa vein (m)

10

12

14

16

18

20

22

24

d18O(permil)

Ag

18O

Surface


0 km

?


78/81

Limito

fhornfe

ls

Limito

fmarb

le

1 km

2 km

Skarn

Graymarble

Bleachedmarble


Uchucchacua Ag zone

Barren calcite vein

d

d

18

13

O 18

C -2

d18



d18


d18

Large zones with variable

O depletion halos mostlywithin bleached limestoned

18

d

d

18

13

O 16

C -6

d

d

18

13

O 13

C -1 to -3

d

d

18

13

O 10 to 14

C -1 to -9


O 22.5

C +2

d

d

18

13



Skarn and CRD

CRD


d18

Antamina

Milpo

Yauricocha

Decreasin

gqua

rtz in

veins


18O


79/81

Pit West Wall


80/81

Pit West Wall

Massive bleaching over 20 m immediatelyoutboard of skarn

Oxygen isotope depletion is limited to ~ 2 m

Limited lateral percolation of magmatic fluids

Marble cap was an effective seal to the system

UBC

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M i n e r a l D

MDRU


81/81

UBC

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Documents

Distal Alteration