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 Congolese Copperbelt Domes Region Zambian Copperbelt Capistrant et al., 2015

Domes Region Capistrant et al., 2015

Trident Area • Located on the southern limb of shallow plunging syncline of Katangan sediments Capistrant et al., 2015

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 Total Organic Sample Description Carbon (wt%) Carbonate (wt%) Dark-grey quartz-rich rock, laminated, unmineralized 0.03 0.40 (ENTDD0010, 205m) Dark-grey quartz-rich rock, laminated, unmineralized 0.05 0.29 (ENTDD0010, 212.8m) Dark-grey quartz-rich rock, laminated, mineralized 0.05 0.30 (ENTDD0019, 138m) Dark-grey quartz-rich rock, laminated, mineralized 0.05 0.10 (ENTDD0120, 165.3m) Dark-grey quartz-rich rock, laminated, mineralized 0.06 0.75 (ENTDD0120, 251.3m) Black carbonaceous quartz-rich rock, mineralized 16.90 0.10 (ENTDD0120, 165.3m) Black carbonaceous quartz-rich rock, mineralized 13.80 0.49 (ENTDD0120, 251.2m) Black carbonaceous quartz-rich rock, mineralized 8.98 0.10 (ENTDD0087, 203m)

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 black shale talc-quartz- kyanite-sulphide • composed of a fine grained recrystallised qtz-kyanite ± talc matrix, with laminae- kyanite-sulphide preferring kyanite altered black shale blebs 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 NiS 2 48% Millerite NiS 65% Bravoite (Ni,Fe)S 2 0.88% ACCESSORY SULPHIDES Polydymite Ni 3 S 4 58% Violarite (Fe,Ni) 2 S 4 39% Molybdenite MoS 2 Cu 5 FeS 4 Bornite Chalcopyrite CuFeS 2 SILICATES Garnierite Ni 3 (Si 2 O 5 )(OH) 4 46% ARSENATES Annabergite Ni 3 (AsO 4 ) 2 8H 2 O 30% Cross-cutting relatioship indicate two stage Ni mineralisation: • Vaesite-Millerite-coarse pyrite • Bravoite-millerite-(molybdenite) Table from Stoltze and Goswell, 2013

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 • 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 • 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

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) 3D AMT Model • Enterprise Graben stands out well • Successfully defined the graben architecture of Enterprise Main and SW

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

ENTERPRISE Critical Elements • 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 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

THANK YOU