View
18
Download
0
Category
Preview:
DESCRIPTION
Tracking Fluid Exhaust from Polymetallic Carbonate Rock-HostedOre Deposits: Examples from Central Perú
Citation preview
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Tracking Fluid Exhaust from Polymetallic Carbonate Rock-Hosted Ore Deposits: Examples from Central Per
A joint project between the Mineral Deposit Research Unit, Anglo American Peru, BHP Billiton, Cia. Minera Antamina;
Cia. Minas de Buenaventura, Falconbridge(Noranda), Phelps Dodge Peru, and Teck ComincoAdditional support from Natural Science
and Engineering Research Council of Canada
Richard Tosdal, Thomas Bissig, Abraham Escalante, Greg Dipple, Shane Ebert, Julio Jurado - MDRU
Manuel Pacheco, Eric Manuel Pacheco, Eric LiptenLipten, , JhonJhon Espinoza Espinoza -- Minera AntaminaMinera Antamina
Angel Angel SabastizagalSabastizagal -- Minas BuenaventuraMinas Buenaventura GervasioGervasio Rodriguez Rodriguez -- Minera CoronaMinera Corona
Gracias a Minera Corona y Volcan CompaniaGracias a Minera Corona y Volcan Compania
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Predictable halos surround skarn, vein, and carbonate replacement deposits that reflect the composition of the host rock as well as the depth of formation and deposit type.
Visual
Mineralogic
Geochemical
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Cretaceous
JurassicPaleozoic and Precambrian
Paleocene to Oligocene volcanic rocks
Miocene volcanic and sedimentary rocks
Coastal Batholith(Late Cretaceous to ~Eocene)
Major Miocene Intrusions
IquitosPiura
LimaIca
Arequipa
Trujillo
SimplifiedSimplified geologygeology of Central Perof Central Per
Cerro de Pasco
Tarma
Huancayo
La Oroya
Producing mine
Antamina
Uchucchacua
Yauricocha
Colquijirca
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Visual mineral zoningDeeper deposits have thermal aureoles and distal Ag-veins
Bleaching of host rocks and conversion to marble nearest the intrusions
Predictable set of veins dispersed laterally and vertically
All deposit surrounded by geochemical halo
Minerals and alteration around deposits dependant on depth of formation and host rocks
.
Antamina
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Cu-Zn skarn core through Marble-hornfels aureole tolimestone
The dominant fluid escape structures are sedimentarylayering and early-stagequartz feldspar porphyrydikes
Skarn environment
Antamina
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
T-16 T-17
West Wall
Bleaching of limestone at depth near stock
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Cachi Cachi
Mina Central
Cordilleran base metal lode (deep)
Yauricocha DistrictRegionally and locally defined 3 broad
alteration zones surrounding the sulfide deposits
Zone A: Inner and adjacent to stock -
Cachi Cachi --Bleached marble
Mina Central -- Mn-flooding of marble
Zone B: Intermediate
Cachi Cachi -- Bedding controlled bleaching
Mina Central - Grey marble with carbonate veins
Zone C: Fresh limestone with some areas of bleached limestone
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Mina Central Zone A - Bleached marble with Mn
Mn in veins and pervasive in rock
Zone A
Zone B
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Zoning around deeper carbonate rock hosted systems
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
NW SE
Upper Jumasha Fm.
Marker horizon
Middle Jumasha Fm.
Lower Jumasha Fm.
Ros
a Ve
in
Ro s
a Ve
in
Ros
a 2
Vein
Ros
a 3
Vei n
4180m
4360m
4450m
4725m
4940m
4400m
4500m
4600m
4700m
4800m
4900m
5000m
4300m
4200m
4100m
Vein, faultAg ore zone
0 100Meters
Surface
4450 m level
Rosa vein
Shallow veins
Uchuccachua
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
3 Visual Alteration Zones Inner Dolomitized Limestone Intermediate White Marble fresh Pucara Limestone
Jasperoid Bodies within dolomitized zoneSulfide-bearing carbonate veins in fresh limestone
Cordilleran base metal lode (shallow)
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Mineral zoningShallow or very distal in marls characterized by dolomite halos and jasperoid
Colquijirca - dark jasperoid with dolomite halo Cerro de Pasco - Irregular jasperoid in dolomitized limestone about 500 m from
ore body; fresh limestone is behind the dark jasperoid body
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Vein zoningVeins surrounding skarn and deeper CRD - characterized by calc-silicate, Mn-oxide, and orange brown carbonate with the latter having the greatest lateral and vertical extent.
Orange brown carbonate veins Mn-oxide rich veins
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Vein typesType 1 - Calc-silicate
a. Garnetb. Wollastonitec. Calc-silicate
Type 1a: Garnet pods
Type 1b: Wollastonite network
High-temperature veins near to
magmatic source
Cachi Cachi, Yauricocha
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Vein typesa. Orange-brown carbonate
calcitequartzpyrite
b. Orange-brown carbonatecalcitequartzpyriteMnoxides
400 m from Mina Central, Yauicocha
500 m above and lateral from Antamina
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Vein types
a. Mn-oxideorange-browncarbonatecalcitequartzpyrite
b. Pervasive Mn-oxide-orange-brown carbonate
c. Mn-oxidequartzpyrite
Concentrated close to cordillera base metal lode
Mina Central, Yauicocha
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
NW SE
Upper Jumasha Fm.
Marker horizon
Middle Jumasha Fm.
Lower Jumasha Fm.
Ros
a Ve
in
Ro s
a Ve
in
Ros
a 2
Vein
Ros
a 3
Vei n
4180m
4360m
4450m
4725m
4940m
4400m
4500m
4600m
4700m
4800m
4900m
5000m
4300m
4200m
4100m
Vein, faultAg ore zone
0 100Meters
Surface
4450 m level
Rosa vein
Shallow veins
Uchuccachua
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Shallow barren calcite veins
Uchucchacua
White comb calcite cut by Mn-oxide cemented veins and breccia, Rosa
Vein
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Recrystallization of limestone, Cerro de Pasco
Introduction of silica (creamy distal and darker with presence of increase
sulfide)
Colquijirca
Cordilleran base metal lodes (shallow)
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
UV FluorescenceWhite, yellow, green, blue, and red-orange fluorescence with UV light associated with distinct elements in calcite.
Red-orange fluorescence associated with Mnand Ag, and is spatially associated with sulfide deposits
Seen up to 1-km from Antamina
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Ag
Surface 4725m
0.001
0.01
0.1
1
10
100
0 30 60 90 120 150
openA
g
(
p
p
m
)
4180 Level
0.001
0.01
0.1
1
10
100
0 30 60 90 120 150
A
g
(
p
p
m
)
A
s
(
p
p
m
)
As
Surface 4725m
1
10
100
1000
0 30 60 90 120 150
open
Brecciated limestone
Gray limestonesAilcocha limestones
Limit of geochemical haloThreshold
Distance from the vein (m)Distance from the vein (m)
Trace elemental changes with depth
Uchucchacua (Escalante unpublished)
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Cachi Cachi(Jurado, 2006)
Element distribution
As increases in rocks and veins away from bleached marble and the intrusion.
As enriched in marble over limestone
As enriched in orange-brown carbonate and Mn-rich veins over high T calc-silicate veins
Lateral elemental dispersion
Similar patterns for Sb
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Geochemical halosElements distributed in regular arrangements both vertically and laterally.
Forms 1-km scale halo
High temperature elements found closer to thermal source
Low temperature elements found farther away.
Elemental distribution is vertical and lateral.
Distribution dependant on the permeability structure.
Uchucchacua
Fortuna
Antamina
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Sr removal accompanied recrystallization of host limestone to dolomitic limestone
Sr depletion potential to discriminate hydrothermal dolomite from diagenetic dolomite
Shallow Cordilleran base metal lodes
Cerro de Pasco (Bissig et al, unpublished)
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Jasperoid in shallow cordilleran base metal
lodes
Jasperoid - replaces dolomitized limestone accompanied by As, Sb, Hg, Tl and maybe Cs
Can distinguish hydrothermal from diagenetic silica replacement
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Distal Alteration Synopsis
Vertical and lateral zonation dependant on host rocks and permeability structure
Halos can extend to 1000m along fluid pathways. Much shorter across permeability.
Key is to recognize the pathway
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Predictable halos surround skarn, vein, and carbonate replacement deposits that reflect the composition of the host rock as well as the depth of formation and deposit type.
Visual
Mineralogic
Geochemical
discovery through researchdiscovery through researchMineralMineral Deposit Research UnitDeposit Research Unit
Fluid pathways around carbonate hosted polymetallic deposits
Geochemical guias Fluid escape structures are sedimentary layering, intrusive contacts, faults, cleavage
and fracture mesh. High T elements (Cu, Bi and Mo) form large halos close to the skarn Moderate to low T elements (Mn, Hg and Tl) define halos at higher levels around
veins. Sr depletion accompanies shallow cordilleran base metal lodes
As, Sb, Hg, Tl and maybe Csdistinguishes hydrothermal jasperoid from diagenetic replacementOrange-red UV fluorescence (high Mn) up to 1 km awayPeripheral veins have characteristic colors, chemistry, and spatial distribution around deposits; up to 1 km but mostly
Recommended