The Enterprise Deposit Northwestern Zambia a New Style of - - PowerPoint PPT Presentation

The Enterprise Deposit Northwestern Zambia

a New Style of Nickel-Sulfide Mineralization First Quantum Minerals Ltd.

Outline

• Enterprise Profile
• Exploration History
• Regional Setting
• Lithostratigraphy
• Alteration
• Mineralization & Strucuture
• Fluid Chemistry-Microthermometry & LA-ICP-MS
• Geophysical and geochemical expressions
• Key Components
• Concluding Remarks

What is Enterprise?

• Sediment-hosted hydrothermal nickel(-iron)

sulfide deposit

– Mineralization hosted in carbonates and silicified sediments

• Located in the western portion of the Domes

region in the Northwestern Province of Zambia

• Represents a new style of nickel-sulfide

mineralization

Exploration History

• 1950s – Area prospected by RST Technical Services

– Soil surveys and 31 drillholes resulted in identification of Enterprise (Kawako) and Sentinel (Kalumbila) targets

• 1960s – Hiatus in exploration due to Zambian political instability and

nationalization of mining industry

• 1990s – Anglo America Corporation resumed exploration in the area, drilled

6 RC holes at Enterprise

• 2007 – Kiwara PLC did downhole electromagnetic surveys at Enterprise and

resampled and twinned Anglo America’s holes-intersected Ni rich saprolites

• 2010 – First Quantum Minerals Ltd. acquired Kiwara PLC

– Initiated an aggressive drilling program (>300 Boreholes by 2012) – Identified substantial amounts of Ni mineralisation – Announced a maiden measured and indicated min res of 40.1Mt of 1.07% Ni

• 2014 – pre-stripping of Enterprise deposit began

Location

Zambian Copperbelt Domes Region Congolese Copperbelt

Capistrant et al., 2015

Domes Region

Capistrant et al., 2015

Trident Area

Capistrant et al., 2015

• Located on the

southern limb of shallow plunging syncline of Katangan sediments

Enterprise Bedrock Map

Capistrant et al., 2015

• Generalised Stratigraphy of Neoproterozoic Katanga Supergroup (Colours link

Lith equivalent sequences)

• Exact correlation is unclear, Enterprise Sequence could belong to either UR or

LR

Basement Rocks

• Foliated to porphyroblastic to granoblastic schists
• Quartz-biotite-muscovite(-plagioclase) -(epidote)(-

K feldspar)

• Increased talc, Mg-chlorite, and kyanite content

toward Enterprise deposit

Lower Roan Subgroup

Basal Siliciclastic Sequence

• Immature arkosic meta-

conglomerate

• Bedded quartz-rich

meta-sandstone

• Talcose and hematitic

meta-siltstone

– Talc and hematite vary in abundance with proximity to orebody

Enterprise Graben Sequence Dark-Grey Quartz-Rich Unit

• Laminated with elongate bands of fine-

grained kyanite

• Composed of quartz-kyanite-Mg chlorite-

pyrite-rutile-tourmaline

• Hosts a majority of Ni sulfides

Enterprise Graben Sequence Carbonaceous Quartz-Rich Rocks

• Isolated pods of carbonaceous “shale”
• Composed of quartz-amorphous carbon-kyanite

with minor rutile, Mg chlorite, and pyrite

• Hosts minor Ni sulfides

Total Organic Carbon (TOC) Analysis

Sample Description Total Organic Carbon (wt%) Carbonate (wt%)

Dark-grey quartz-rich rock, laminated, unmineralized (ENTDD0010, 205m)

0.03 0.40

Dark-grey quartz-rich rock, laminated, unmineralized (ENTDD0010, 212.8m)

0.05 0.29

Dark-grey quartz-rich rock, laminated, mineralized (ENTDD0019, 138m)

0.05 0.30

Dark-grey quartz-rich rock, laminated, mineralized (ENTDD0120, 165.3m)

0.05 0.10

Dark-grey quartz-rich rock, laminated, mineralized (ENTDD0120, 251.3m)

0.06 0.75

Black carbonaceous quartz-rich rock, mineralized (ENTDD0120, 165.3m)

16.90 0.10

Black carbonaceous quartz-rich rock, mineralized (ENTDD0120, 251.2m)

13.80 0.49

Black carbonaceous quartz-rich rock, mineralized (ENTDD0087, 203m)

8.98 0.10

Enterprise Graben Sequence Meta-Carbonates

• Heterogeneous

in composition and texture

• Massive to

banded to brecciated

• Dolomite-calcite-

magnesite with variable amounts Mg-chl, phlogopite, and talc

• Hosts moderate

Ni-sulfide

Altered Mafic Rocks

• Highly altered from original composition
• Composed of Fe-chlorite, actinolite, biotite-

phlogopite, scapolite, rutile, carbonate, magnetite, pyrite

• Does not host Ni sulfides

Upper Roan Subgroup Upper Meta-Carbonates

• Massive marine carbonates
• Dolomitic marbles and biotitic calcareous

carbonates

• Minor pyrite and pyrrhotite

Upper Roan Subroup Polylithic Breccia

• Matrix-supported breccia with variably-

sized, rounded, altered clasts

• Clasts of Upper Roan carbonates, mafic

rocks, minor hematitic siltstones

• Stratiform to discordant

– Related to salt diapirism

Paragensis Summary

• Primary/Diagenetic Assemblages

– quartz, hematite, and pyrite

• Metamorphic Assemblages

– Quartz-biotite-muscovite-rutile-hematite – Epidote-plagioclase – Albite-carbonate(-kyanite)

• Metasomatic assemblages overprinting peak

metamorphic assemblages

– Quartz-kyanite – Ni-sulfide mineralization – Long-lived magnesian alteration event

• Minor retrograde phases

Basal Siliciclastic Meta-Siltstones

• Left to right progression of metasomatic effects with proximity to orebody
• Progressive loss of quartz, hematite, and albite; decrease in kyanite grain size
• Increase in talc

Talc Overprinting

• Destruction of hematite and quartz by talc.

Dark band represent relatively quartz and hematite-rich domains.

• Inclusions of hematite after talc overprinting
• Ragged quartz grains suggest dissolution

Altered Shales

• In places the shale is

barely recognisable- is completely altered to Qtz - Kyanite ± talc

• composed of a fine

grained recrystallised qtz-kyanite ± talc matrix, with laminae- preferring kyanite blebs

black shale talc-quartz- kyanite-sulphide kyanite-sulphide altered black shale kyanite-quartz- talc-sulphide vein

Mineralization

• Enterprise sits in the corner of a graben that

defines a syn-rift sub-basin

• The architecture was identified from the interpreted

drilled sections, as well as the fault system showing up in the geophysical data sets

• Capistrant et al., 2015

Mineralization

PREDOMINANT Ni SULFIDES % Ni Vaesite NiS2 48% Millerite NiS 65% Bravoite (Ni,Fe)S2 0.88% ACCESSORY SULPHIDES Polydymite Ni3S4 58% Violarite (Fe,Ni)2S4 39% Molybdenite MoS2 Bornite Cu5FeS4 Chalcopyrite CuFeS2 SILICATES Garnierite Ni3(Si2O5)(OH)4 46% ARSENATES Annabergite Ni3(AsO4)28H2O 30%

Table from Stoltze and Goswell, 2013

Cross-cutting relatioship indicate two stage Ni mineralisation:

• Vaesite-Millerite-coarse pyrite
• Bravoite-millerite-(molybdenite)

Fluid Chemistry-Microthermometry

A bimodal distribution of moderate (~250-320˚C) and high temperature (370- ~500˚C) FI population with a salinity range of 35 - >50 Wt.% NaClequiv.

Fluid Chemistry-LA-ICP-MS

• Notably, high K fluids are Ca- and

Mg-rich while low-K fluids are Mg-deficient

• Suggestive of halite dissolution

and residual bittern brine origin for Low-K and high K fluids, respectively

• Two fluid types, namely High-K

(K/Na≥0.5) and Low-K (K/Na<0.5) were clearly distinguished based on K/Na ratios

• High-K: Na-K-Ca-Mg- Fe
• Low-K: Na-K-Ca-Fe
• Ni > Cu, Co, Zn in both fluids

Geophysical Expression – Magnetics

• Magnetics were been useful for

pulling out the faults

• But still unsure of the ones bringing

Ni mineralising fluids

Geophysical Expression – EM (Z6)

Geophysical Expression- Audio Magneto-Tellurics (AMT)

• Enterprise Graben

stands out well

• Successfully defined the

graben architecture of Enterprise Main and SW

3D AMT Model

Geochemical expression

• Siltstones have elevated Ni concentrations
• Enterprise does not stand out (1250ppm Ni)

• Sulfur Source – Evaporite
• Seal – carbonate cap
• Trap – reducing horizon,

black shale, mobile HC

• Structure - graben

architecture, deep-tapping conduits

• Ni source – deep-seated?
• Ni-carrying fluids - oxidised,

acidic, and saline

ENTERPRISE Critical Elements

Jack, 2014

Conclusions

• The Enterprise deposit represents a new and unique

style of hydrothermal nickel sulfide deposits

– With mineralization processes broadly similar to those of traditional sedimentary copper deposits of the Zambian Copperbelt

• Deposited in Neoproterozoic Katangan Supergroup

metasedimentary sequence

• Metamorphism and metasomatism affected Lower Roan

Subgroup rocks most intensely

• Nickel sulfides occur predominantly in dark-grey quartz-

rich rocks within the Enterprise graben Sequence

– Mineralization occurs as disseminations, semi-massive replacements, and within quartz-kyanite veins

• Soil geochemistry, geophysics, and drilling were key in

identification and delineation of deposit

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