Craig Hart

Associate Professor

Relevant Degree Programs


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2020)
Distribution of district-scale hydrothermal alteration, vein orientations and white mica compositions in the Highland Valley Copper district, British Columbia, Canada : implications for the evolution of porphyry Cu-Mo systems (2020)

This thesis presents a multi-layer lineament mapping method that integrates topography, geophysical data and geological observations to interpret faults at surface, and demonstrates how magnetic intensity data can be used to estimate the dip of fault-related magnetic anomalies by performing 2D inverse modeling along profiles extracted from a magnetic intensity grid. Dip modeling of magnetic anomalies created in a synthetic 3D magnetic susceptibility model shows that the method is accurate to better than 5° for input dips >60°. Comparison between fault orientations modeled from magnetic data and measured in the field in the Guichon Creek batholith (GCB) confirms that the methodology can be successfully applied to brittle faults in real, albeit relatively simple geological environments.Alteration mapping across the Highland Valley Copper (HVC) district defined zones of K-feldspar-bearing and muscovite-bearing veins, and later and more extensive zones of veins bearing sodic-calcic and propylitic mineral assemblages. A palinspastic reconstruction of the GCB to its Late Triassic geometry shows that: 1) potassic alteration forms a westerly-elongated ~12 x 2 km zone that overlaps with the Valley–Lornex and Highmont deposits, 2) sodic-calcic alteration forms discontinuous zones that cover an area ~17 km by 11 km (southwest) and 5 cm/m) is located in the center of the batholith. Permeability within the batholith was dominantly the result of local stresses induced by magma or magmatic fluid overpressure (i.e., radial aplite and K-feldspar-bearing vein patterns around porphyry deposits), and by thermal contraction (i.e., sodic-calcic and propylitic veins perpendicular and parallel to intrusive contacts). The Late Triassic regional sinistral stress regime only locally contributed to the batholith-scale permeability along favourably-oriented west to west-northwest-trending structures.White mica compositional variations, determined by short-wave infrared (SWIR) spectroscopy, define footprints associated with porphyry mineralization. Sodic-calcic and propylitic alteration are characterized by a zone of increased muscovitic white mica abundance that is detectable within 3 km of the HVC deposits, and a zone of increased phengitic white mica abundance detectable to distances up to ~5 km from the HVC deposits.

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Late Cenozoic post-subduction tectonic, magmatic and metallogenic evolution of the Anatolide-Tauride Orogenic Belt, Turkey (2018)

The termination of the northward subduction of the Southern Neotethyan oceanic slabbeneath the Anatolide-Tauride Block in Turkey led to the onset of the Arabia-Eurasiacontinental collision in the Oligocene. The subducting Southern Neotethyan slab was affectedby post-subduction segmentation manifested by slab break-off (central-eastern Anatolia) andtearing (western Anatolia) during the late Cenozoic. Many igneous complexes formed in thelate Cenozoic and some of them host gold-rich porphyry and epithermal prospects and deposits.New temporal (U-Pb, ⁴⁰Ar/³⁹Ar and Re-Os dates), spatial (field observations and GIS) andgeochemical data (elemental and Sr-Nd-Pb isotopic analyses) provide robust constraints on thegenetic relationship between late Cenozoic slab segmentation tectonic events, Anatolianmagmatism and associated gold mineralization.The newly-defined Eastern Anatolian Magmatic Belt formed in response to the slabbreak-off initiation at ca. 25 Ma, window opening, westward break-off propagation to centralAnatolia and induced asthenospheric flow. The slab break-off-related igneous units weresubsequently covered by widespread volcanic products in eastern Anatolia (12 Ma – Present)that resulted from the long-lived asthenospheric heating, destabilization of the thickenedAnatolian lithosphere root and its partial removal by convective dripping. Magmatic sourcesinclude the shallow melting of the previously-metasomatized Anatolian subcontinentallithospheric mantle and asthenosphere by decompression due to impingement of the Arabianand African sub-slab asthenospheric mantles.Late Cenozoic Anatolian magmatism produced porphyry and epithermal prospects anddeposits that cluster in nine isolated mineral districts controlled by graben, transtensionalcorridors and pull-apart basins. The bulk of gold mineralization (33 Moz Au) peaked at thebeginning of the slab break-off event at 25 Ma in central and eastern Anatolia, and slab tear at15 Ma in western Anatolia.The late Cenozoic trench-parallel and -perpendicular migrations of slab rupture andwindow opening in Anatolia 1) allowed toroidal and poloidal flow of asthenosphere beneathAnatolia, 2) caused the migration of melting source and associated igneous complexes andmineral deposits in the overriding crust, 3) destabilized the Anatolian lithospheric mantle,which reduced the amount of available volatiles and metals, and therefore 4) increased theproduction of barren, drier and mantle-dominant volcanism through time that partially coversfertile igneous units.

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The geology and genesis of the Coffee gold deposit in west-central Yukon, Canada : implications for the structural, magmatic, and metallogenic evolution of the Dawson Rage, and gold deposit models (2018)

The Coffee gold deposit, located in the Dawson Range, west-central Yukon, Canada, is an example of structurally-controlled, gold-only mineralization with a global resource of ~4 Moz gold. Establishing the controls on ore distribution enhances exploration potential, and provides implications for the tectonic and metallogenic evolution of the northern Cordillera, and global gold deposit models. The controls on ore distribution were identified by drill core logging, field mapping, petrography, and analytical techniques that included geochemistry, shortwave infrared spectroscopy, and geochronology. The results from these analyses allowed the geological and structural framework, and a hydrothermal model for ore formation to be established. Furthermore, a genetic model for hydrothermal events and exhumation within the Dawson Range was developed.Coffee is hosted in metamorphic rocks of the Yukon-Tanana terrane, and mid-Cretaceous plutonic rocks. Metamorphic rocks include psammitic to semi-pelitic schist and K-feldspar augen-bearing orthogneiss that were metamorphosed to lower amphibolite in the Permian. Plutonic rocks include biotite granite of the ca. 100 Ma Coffee Creek pluton, and coeval intermediate dykes. The east-trending dextral strike-slip Coffee Creek fault exerts an important control on mineralization, which is disseminated in the wall rock of high order faults and fractures, and ~1m wide breccia corridors. Mineralization comprises auriferous sulphides that are associated with an alteration assemblage of quartz-muscovite-illite-kaolinite-carbonate, which sulphidize host rock muscovite and biotite. Age determinations from hydrothermal white mica constrains mineralization to ca. 97 Ma, and the coexistence of alteration and ore minerals constrains the character of the hydrothermal fluid to ~250°C and pH ~5. Isotope data provides evidence for decoupled metal sources, and low temperature thermochronology constrains the depth of mineralization to ~5km. Coffee occurs in close spatial and temporal proximity to orogenic gold mineralization. This spatial association, the ore fluid characteristics, and the mid-Cretaceous tectonic regime argues for ore fluids sourced from metamorphic devolatilization of likely siliciclastic rocks at depth. Coffee is interpreted as an epizonal orogenic gold deposit, the result of a regionally significant gold mineralizing event. This interpretation has implications for the metallogeny and exploration of orogenic gold mineralization in the Dawson Range and northern Cordillera, as well as globally.

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Eocene volcanic response to the tectonic evolution of the Canadian Cordillera (2014)

The Ootsa Lake Group (OLG) represents a voluminous episode of Eocene volcanism across the Interior plateau of British Columbia (BC), in the Canadian Cordillera. Remarkable aspects of the rocks (lithology, texture, volume, extent, and geochemistry) suggest that even though they formed along an active continental margin, the tectonic setting was different from a classic arc. The OLG was defined by field mapping, U-Pb and ⁴⁰Ar/³⁹Ar geochronology, major and trace elements geochemistry, and three-dimensional modelling of the thickness and structure. A new tectonic model for the evolution of the Canadian Cordillera in the Paleogene is proposed using this comprehensive dataset.The OLG stratigraphy comprises a thick sequence of rhyolite and dacite lava, locally capped by andesite. Onset, duration and termination of volcanism are equivalent across the Interior plateau, and are constrained between 54.7 and 46.6 Ma by new U-Pb and ⁴⁰Ar/³⁹Ar geochronology. OLG lavas yield a “volcanic arc” signature (diagnostic high-K calc-alkaline trend, and trace and rare earth elements patterns), suggesting supra-subduction zone contributions from a hydrated mantle wedge. However, a similar signature may be inherited from partial melting of crustal reservoirs composed of older accreted volcanic arc crust. This is supported by Sr isotope data indicating variable crustal contributions to melts across BC. OLG intermediate rocks were likely derived from mantle melting, but dominantly silicic compositions support partial melting of the crust as a dominant magma producing mechanism.Eocene volcanic rocks cover at least 65,000 km² of BC, but their original extent may have been almost continuous from southwestern Yukon to Idaho. Coeval volcanism and extensional deformation contributed to the accumulation and preservation of volcanic products in extensional basins, up to 4000 m thick in some locations. With such dimensions, the OLG may have attained the status of a Silicic Large Igneous Province prior to erosion. The cause of OLG volcanism and coeval extension is attributed to the sudden ingress of hot sublithospheric mantle within a previously metasomatized mantle region, following cessation of subduction and a slab break. The resulting thermal anomaly progressed across a “slab gap” beneath BC, leading to mantle and lower crustal melting, crustal anatexis and magmatism.

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Master's Student Supervision (2010 - 2018)
Evolution of hydrothermal alteration and mineralization at the deformed Kerr and Deep Kerr Cu-Au porphyry deposits, northwestern British Columbia, Canada (2018)

The calc-alkalic Kerr and Deep Kerr Cu-Au porphyry deposits are located in northwestern British Columbia, and are part of the Kerr-Sulphurets-Mitchell (KSM) property. The deposits comprise a steeply dipping tabular intrusive complex extending N-S ~2.4 km, with a vertical extent >2 km. Ore is primarily hosted within syn-mineral intrusions of monzonite (~197 Ma: Bridge, 1993) which intruded volcanosedimentary rocks of the Hazelton group. The Kerr deposit contains probable reserves of 276 million tonnes at 0.43% Cu, and 0.22g/t Au, for a contained total of 2.6 billion lb’s Cu, and 2.0 million oz’s Au (Seabridge Gold, 2016). The Deep Kerr deposit has an inferred resource estimate of 1.92 billion tonnes grading 0.41% Cu and 0.31 g/t Au for a contained total of 17.3 billion lb’s Cu, and 19.1 million oz’s Au (Seabridge Gold, 2017). Hydrothermal alteration assemblages are zoned, from early high-temperature potassic alteration located centrally at depth, outwards into subsequent dark chlorite-sericite and sericite-chlorite alteration assemblages. The upper ~1.5 km of the deposit is largely overprinted by late phyllic alteration. Potassic alteration was initially more extensive, and has been largely overprinted. The vein paragenesis comprises ten main vein types subdivided into syn-mineral and late- to post-mineral veins. Copper and gold mineralization are primarily associated with A and B type quartz-sulphide veins contemporaneous with potassic alteration. High-grade copper and gold mineralization is correlated with quartz vein abundance above 500 m elevation within the deposit, and is of a more disseminated style below this elevation. Phyllic alteration introduces molybdenum.A hydrothermal zonation in both white micas and chlorites was indicated with short-wave infrared spectroscopy. White mica composition becomes more Fe+Mg rich (phengitic) distally from the hydrothermal centre, and is also more phengitic at depth within potassic and dark chlorite-sericite altered rocks. The Mg content of chlorites relative to Fe increases with increasing proximity to the centre of the hydrothermal plume. A zonation in sulphides and suphates was indicated by sulphur isotope analysis. Sulphides are isotopically lighter (lower δ³⁴S values) proximal to the high-grade core of the deposit, and sulphates become isotopically heavier (increasing δ³⁴S values) with decreasing depth in the hydrothermal system.

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The genesis and post-ore modification of the migmatized Carmacks Copper Cu-Au-Ag porphyry deposit, Yukon, Canada (2018)

No abstract available.

Magmatic-hydrothermal evolution and post-ore modifications of the Halilağa porphyry cu-au deposit, NW Turkey (2017)

The Biga Peninsula of northwest Turkey is an emerging copper-gold province characterized by numerous epithermal and porphyry-type deposits and prospects associated with Eocene to Oligocene calc-alkaline post-collisional magmatism. Neotectonics in the Biga Peninsula are dominated by a NE-SW dextral strike slip regime that is associated with the southern branch of the North Anatolian Fault System (NAF) and a N-S extensional regime. The Halilağa Cu-Au deposit, in central Biga Peninsula, is a porphyry system that also includes other mineralization types such as high-sulfidation and skarn prospects. The deposit is bounded by two transtensional faults, which have a relevant post-mineralization role. The Halilağa porphyry Cu-Au system comprises two dominant intrusive phases: a mineralized quartz monzonite porphyry with crowded phenocrysts of plagioclase and rounded quartz, and a poorly-mineralized, phenocryst-poor, quartz monzonite to granodiorite porphyry. Andesitic dykes cut and post-date the porphyry intrusions. Porphyry Cu-Au mineralization is spatially associated with biotite + magnetite ± K-feldspar alteration and intense quartz veining. This alteration assemblage has been variably overprinted by pervasive sericite±quartz alteration, in particular at shallow levels. At depth, selective pervasive chlorite+sericite alteration has overprinted the early biotite + magnetite ± K-feldspar assemblage. Epidote + chlorite + calcite alteration occurs at the edges of the system. Sulphide mineralogy is dominated by chalcopyrite, pyrite, and minor pyrrhotite as inclusions in pyrite. Faults that bound the porphyry stock display evidence of syn- and post-mineral activity, suggesting that these faults have protracted displacement histories. U-Pb zircon geochronology from the Halilağa district, in this study, constrained the emplacement of the porphyry intrusions to Middle Eocene (40 to 37 Ma) and also indicated another magmatic event of ca. 28 Ma is spatially related to a high-sulfidation epithermal system. Middle Eocene and Oligocene magmatism is coincident with the ages of epithermal and porphyry mineralization in the Biga Peninsula (e.g. Kuscayir, Kartaldağ, Ağı Dağı, Tepeoba), suggesting a favorable setting for porphyry systems generation during that time. In Halilağa, the porphyry mineralization is associated with the Eocene magmatic event, confirmed by a Re-Os analysis of molybdenite yielding a mineralization age of 39.56 ± 0.21 Ma.

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Structural, mineralogical and fluid evolution of the Shahumyan intermediate sulphidation vein deposit, Kapan district, Armenia (2017)

The Kapan District located in the Syunik province of SE Armenia is part of the Lesser Caucasus. The district consists of multiple vein type deposits that were emplaced in the Middle-Upper Jurassic. The Shahumyan deposit is the only actively producing deposit within the district. Understanding vein geometry, and hydrothermal fluid evolution is fundamental in establishing the genesis and exploration significance within an epithermal vein district, providing both near mine and district scale targets.Over 120 veins of varying thicknesses (20cm to 3 m) are identified at the Shahumyan deposit. The veins are sub-vertical, south-dipping and trend east to northeast. Veins comprise of small bends, extensional jogs, soft and hard linked step-overs, pinch and swell structures and cymoid loops. These features are observed along both strike and down-dip of individual veins and contain higher metal grades relative to the rest of the vein. Along strike and down-dip connectivity of these structural features define high-grade ore-shoots within mineralized veins.Three main hydrothermal stages associated with mineralization are defined: Stage 1, pyrite, fine grained quartz ±chlorite; Stage 2a & b, pyrite, chalcopyrite, sphalerite, galena, sulfosalts, Au-Ag tellurides, fine and coarse white quartz, ±calcite; Stage 3; calcite, quartz, pyrite. Au-Ag-Pb tellurides are associated with localized brecciation. Tellurides are predominantly present in fractured sphalerite, pyrite, chalcopyrite and galena. Based on textures and fluid inclusion studies, Au-Ag-Pb tellurides are linked to boiling mechanisms.The epithermal event at The Shahumyan deposit is characterised by punctuated periods of hydrothermal brecciation interspersed with more quiescent periods when coarsely banded vein material was precipitated. Localized brecciation provide increased fluid permeability and ideal fluid pathways for mineralizing fluids. Localized brecciation corresponds with continued propagation or re-opening of the fracture-vein system. Localized boiling is interpreted to be the primarily driver for Au-Ag telluride precipitation.

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Establishing the stable isotope and geochemical footprints associated with carbonate-hosted Zn-Pb deposits of the Kootenay Arc (2016)

Carbonate-hosted Zn-Pb deposits of the Kootenay Arc in southeastern British Columbia and northeastern Washington typically have narrow and poorly developed alteration footprints, and so generate significantly smaller visible and geochemical haloes when compared to many other mineral deposit systems. However, these carbonate-hosted deposits can have invisible alteration footprints that are much broader when detected with analyses of light stable isotopes. The intensity of this isotopic alteration increases from peripheral regions into the centre of mineralization with greater shifts towards lighter, or more depleted, isotopic values as a result of more fluid:rock interaction. These depleted stable isotope values can therefore provide information about fluid flow during mineralization and have potential value in the search for sulphide mineralization. Studies of C and O isotopes from the host rocks of four Zn-Pb mines within the Kootenay Arc (H.B., Jersey, Remac and Pend Oreille) in addition to geochemical analyses have revealed at least two separate isotopic alteration signatures. These two different isotopic alteration signatures are inferred to represent two different hydrothermal fluids; the Remac Mine exhibits a much lower temperature isotopic signature when compared to the H.B., Jersey and Pend Oreille mines. Despite the difference in isotopic signature, all four mines are thought to represent Mississippi Valley-type mineralization. The most depleted isotopic values have been interpreted to reflect the highest temperature and most permeable systems. At the mine-scale, isotopic depletion highlights permeable rock-types and proximity to fault zones rather than proximity to Zn-Pb mineralization. At this scale it is therefore necessary to utilize additional geological information, such as geochemistry, to delineate rock-types that could be potential hosts of Zn-Pb mineralization. These two distinct isotopic signatures, in addition to geochemistry and other geological information, could therefore be utilized to vector towards, or re-evaluate, similar Mississippi Valley-type Zn-Pb mineralization within this region.

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Stratigraphic and petrographic characterization of HS epithermal Au-Ag mineralization at the TV Tower district, Biga Peninsula, NW Turkey (2016)

The Biga Peninsula in northwestern Turkey is part of the Western Tethyan Metallogenic Belt, known to be one of the most prospective belts for porphyry and epithermal style copper and gold deposits in the world. However, the limited spatial extent of mineral tenure boundaries around many deposits encumbers the correlation of geological and structural features beyond tenure boundaries and to a district and regional scale. High sulphidation epithermal Ag-Au-Cu and Au-Cu porphyry deposits in the Biga Peninsula are hosted by two temporally discrete magmatic rock formations and are structurally reconfigured by neotectonic faulting. New geological mapping between epithermal and porphyry deposits in the central Biga Peninsula, coupled with petrographic characterization and geochronological constraints on magmatism and mineralization, is used to correlate the Küçükdağ and Kirazlı high sulphidation epithermal Au-Ag-Cu deposits across the TV Tower District and regionally. Identifying prospective magmatic formations and relating structural controls on ore mineralization to regional structures will increase the probability of new discoveries.

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Geology, alteration, mineralization and magmatic evolution of the Southeast Zone (Cu-Mo) and Deerhorn (Cu-Au) porphyry deposits, Woodjam, central British Columbia, Canada (2015)

The Woodjam district is part of the porphyry deposits of Late Triassic to Middle Jurassic age (216–183 Ma) located in the Quesnel terrane in central British Columbia. Porphyry centers include the large Cu-Mo Southeast Zone (SEZ), hosted in the calc-alkalic Takomkane batholith, and the Au-Cu Deerhorn, Megabuck and Takom deposits. The latter are peripheral to the margin of the batholith and are associated with smaller monzonitic bodies of more mafic affinity that intrude and mineralize Nicola Group strata.The Takomkane batholith, host to the SEZ, intrudes and underplates the Nicola Group strata. The main phases include coarse-quartz-monzonite (CQM; 197.48±0.44 Ma) and a later, fine-grained-quartz-monzonite (FQM). Alteration is zoned from intense K-silicate in the center, weaker towards the margins, surrounded by albite alteration at the margins. Mineralization is zoned from chalcopyrite to pyrite-dominated at the margins. The Deerhorn deposit is centered on narrow monzonite bodies with “pencil” geometry and intrudes the Nicola Group volcanic sequence. Main stage of mineralization is hosted in Monzonite-A and is cut by Monzonite-D. Alteration is characterized by intense magnetite and K-silicate in Monzonite-A and adjacent volcaniclastics. Monzonite D displays moderate to weak K-silicate alteration. Mineralization is hosted in banded quartz-magnetite-hematite-chalcopyrite veins in Monzonite A and adjacent volcanic host-rocks.SEZ and Deerhorn intrusive units share geochemical characteristics. The early Takomkane units have higher SiO₂ and incompatible element concentrations, less-fractionated HREEs, negative Eu anomalies, and more radiogenic Nd isotope ratios than the Deerhorn monzonites. The latter are themselves similar to the late SEZ FQM which suggests that the latter and the Deerhorn monzonites are co-magmatic.Differences between alteration and mineralization of both deposits are partially attributed to the depth of emplacement; Cu-Au mineralization at Deerhorn represents a shallower expression of the magmatic hydrothermal system and Cu-Mo mineralization in SEZ represents the deeper segment of the partially contemporaneous system. Geochemical and isotopical affinities between the FQM/Monzonite-A/Monzonite-D intrusions and the plagioclase-phyric andesite of the Nicola Group indicate that these intrusions were partially coeval, and that mineralization in the Woodjam area is tightly connected to the Nicola Group volcanism, as age and chemistry of the rocks are similar.

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Geology, mineralization and geochronology of the Conrad Zone carlin-type gold prospect, east-central Yukon Territory, Canada (2015)

The Nadaleen Trend is a recently discovered, 25 kilometer long trend of mineralization along the northern margin of the Selwyn Basin in east-central Yukon. The regional geologic framework and style of mineralization are both analogous to the Carlin trend in Nevada. The Nadaleen Trend is bound structurally to the south by the regional scale Dawson Thrust and the Kathleen Lakes Fault to the north. This structural setting marks the boundary between the dominantly Neoproterozoic to Paleozoic slope and basin facies carbonates, siltstones and clastic rocks of the Selwyn Basin and Mackenzie Platform stratigraphy. Research efforts are focused on the Conrad and Osiris Zones within the eastern Nadaleen Trend, the first Carlin-type discoveries in the area. Mineralization accompanies the process of decarbonatization of host limestone and subsequent silicification and brecciation. This is reflected in mineralized zones occurring as breccias containing jasperoid replacement of carbonate by quartz and late, open space filling calcite and realgar. Mineralization is typically shear- and breccia-hosted, reflecting a strong structural and permeability control on the development of mineralization. Principal host rocks to mineralization are variably decarbonatized silty limestones and siliciclastic rocks along with narrow gabbroic dykes. Geochemical enrichments associated with Au in the Conrad Zone are typical of Carlin-type deposits, with strong correlations between As-Hg-Sb-Tl and Au. Arsenic occurs primarily as widespread and locally abundant realgar and orpiment. Several phases of Arsenic-rich pyrite are found in mineralized zones, typically as rims around earlier pyrite cores or as
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The timing and genesis of the Blackwater gold-silver deposit, central British Columbia : constraints from geology, geochronology and stable isotopes (2015)

The Blackwater Au-Ag deposit of central British Columbia is hosted by a lithic-rich, latite lapilli tuff and felsic volcanic rock sequence. U/Pb zircon geochronology shows that these two volcanic rock sequences are Late-Cretaceous, and were deposited at ca. 73.5 and 73.1 Ma, respectively. These host rocks overlie plagioclase to hornblende porphyritic andesite lava flows, mudstone, chert and conglomerate. A monzonite intruded the western portion of the deposit. Felsic dykes or sills are inferred to have intruded felsic volcanic rocks at ca. 68 Ma. A post-mineralization, dacitic sill intruded contacts between sedimentary rocks and lithic-rich, latite tuffs in the south of the Blackwater deposit at ca. 53 Ma. High temperature (>300⁰C), biotite-sericite-sulfide, actinolite-sulfide and garnet-sulfide assemblages alter rocks at the deposit’s perimeter. Low temperature (250-350⁰C), Au-mineralizing fluids precipitated the early main-stage green sericite-quartz-pyrite and the late main-stage green sericite-chlorite-quartz-base metal sulfide assemblages located in the deposit’s centre. ⁴⁰Ar/³⁹Ar geochronology suggests that high temperature alteration minerals precipitated prior to Au-mineralization, between ~68-64 Ma, and that Au-mineralization took place at ca. 65.6-63.9 Ma. The ⁴⁰Ar/³⁹Ar systematics of biotite were reset at ca. 59 Ma during a thermal event.High temperature, barren alteration is attributed to fluids with stable isotope compositions distinct from those that precipitated low temperature alteration. High temperature alteration minerals are enriched in ¹⁸O relative to primary magmatic waters (δ¹⁸OH₂O = 8.9-12.6‰) and have variable δD values (δD =-93.9 to -66.1‰). This, in conjunction with depleted, sedimentary δ³⁴S values (δ³⁴Smineral =-17.7 to -7.7‰) suggests a combination of exchanged meteoric waters, sedimentary formation and/or magmatic fluid sources. A component of magmatic fluids ± evolved meteoric fluids is inferred for low temperature, Au mineralizing fluids. Calculated stable isotope compositions of fluids in equilibrium with green sericite (δ¹⁸O =6.6 - 7.1‰, δD = -79.2 to -62.9‰) plot within the primary magmatic water field while isotopic compositions of associated sulfides (δ³⁴Smineral =-1.8 - 0.3‰) provide evidence for igneous derived sulfur.Blackwater’s host rocks, tectonic environment, metal signature and alteration match those of an intermediate-sulfidation epithermal system with both low- and intermediate sulfidation state sulfide minerals.

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Titanite as an indicator mineral for alkalic Cu-Au porphyry deposits in south central British Columbia (2015)

Exploration success in large parts of the Quesnel and Stikine terranes in south-central British Columbia (BC) has been limited due to extensive coverage by glacial sediments (Ward et al., 2009), where traditional geophysical and geochemical exploration methods have proven to be limited or impractical (Gent et al., 2011). The occurrence of resistate minerals such as apatite, epidote, garnet, magnetite, rutile and titanite as alteration products in porphyry deposits suggests that they could be utilized as porphyry indicator minerals (PIMs) to provide a new tool to increase exploration success in covered terrains (Bouzari et al., 2011). Titanite (CaTiSiO5) is a common accessory mineral in alkalic Cu-Au porphyry deposits that is known to record various magmatic and hydrothermal processes in its texture and chemical composition (). In this research, titanite hosted in bedrock from the Mount Polley, Mount Milligan and Copper Mountain alkalic porphyry Cu-Au deposits of south-central BC, as well as in surrounding till sediments, was characterized based on petrography, heavy mineral separation, and Electronic Microprobe (EMP) and Laser Ablation Inductively Coupled-Plasma Mass Spectrometry (LA-ICP-MS) chemical analyses. The main objective is to determine key diagnostic features of titanite that are related to alkalic porphyry alteration and mineralization. Titanite typically forms as replacement of mafic minerals, such as augite, biotite and magnetite during K-silicate and Na-Ca alterations. Thus, four types of titanite were defined based on key petrographic and chemical features: primary magmatic (MAG), metasomatic (MET), secondary (SEC) and altered (ALT) titanites. Titanite recovered from till sediments near studied alkalic deposits preserve the texture and chemical signatures obtained in the rock, despite surficial weathering. Therefore, the above classification of titanite constitutes a useful mineralogical tool for exploration for alkalic Cu-Au porphyry deposits in covered terrains

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Biogeochemical expressions of buried REE mineralization at the Norra Kärr Alkaline Complex, southern Sweden (2014)

Biogeochemical exploration is an effective but underutilized method for delineating covered mineralization. Plants are capable of accumulating rare earth elements (REEs) in their tissue, and ferns (pteridophytes) are especially adept because they are one of the most primitive land plants, therefore lack the barrier mechanisms developed by more evolved plants.The Norra Kärr Alkaline Complex, located in southern Sweden approximately 300km southwest of Stockholm, is a peralkaline nepheline syenite enriched in heavy rare earth elements (HREEs). The deposit, roughly 300m wide, 1300m long, and overlain by up to 4 m of Quaternary sediments, has been well-defined by diamond drilling. The inferred REE mineral resource, over 60 million tonnes averaging 0.54% Total Rare Earth Oxide (TREO), is dominantly hosted within the pegmatitic “grennaite” unit, a eudialyte-catapleiite-aegerine nepheline syenite.Vegetation and soil samples were collected from the surficial environment above Norra Kärr to address four key questions: which plant species is the most effective biogeochemical exploration medium; what are the annual and seasonal REE variations in that plant; how do the REEs move through the soil profile; and into which part of the plant are they concentrated. Athyrium filix-femina (lady fern) has the highest concentration of LREEs and HREEs (up to 125.17ppm Ce and 1.03ppm Dy) in its dry leaves; however, there is better contrast between background and anomalous areas in Dryopteris filix-mas (wood fern), which makes it the preferred biogeochemical sampling medium. The REE content in all fern species was shown to decrease from root > frond > stem, and chondrite normalized REE patterns within the plant displayed preferential fractionation of the LREEs in the fronds relative to the roots. Samples collected from an area directly overlying the deposit had up to five times greater HREE content (0.74ppm Dy) in August than the same plants did in June (0.14ppm Dy).The elevated REE content and distinct contrast to background demonstrate that biogeochemical sampling is an effective method for REE exploration in this environment.

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Evolution of the Late Cretaceous Whistler Au-(Cu) porphyry corridor and magmatic-hydrothermal system, Kahiltna terrane, southwestern Alaska, USA (2014)

The Whistler Corridor is located in the Alaskan Range 150 km northwest of Anchorage. Hosted by the regionally extensive Kahiltna flysch terrane, the Whistler Igneous Suite (WIS) volcano-magmatic sequence is calc-alkalic, metaluminous, and exhibits an arc related trace element signature. Extrusive rocks comprise andesite flows, volcaniclastic rocks, and hypabyssal dykes and sills. Intrusive rocks are dioritic with two major phases. An initial phase associated with porphyry mineralisation was dated by zircon U-Pb (CA-TIMS) at 76.4 ± 0.3 Ma. A later unmineralised phase had previously been determined by hornblende Ar-Ar at 75.5 ± 0.3 Ma. Mineralised diorite exhibits Nb/Y ratios >1.1 distinct from unmineralised diorite (Nb/Y
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Geology, alteration, lithogeochemistry and hydrothermal fluid characterization of the Neoproterozoic Niblack polymetallic volcanic-hosted massive sulfide camp, southeast Alaska, USA (2014)

The Neoproterozoic Alexander terrane Niblack Cu-Au-Zn-Ag volcanic-hosted massive sulfide camp is on Prince of Wales Island, southeast Alaska. Multiple massive sulfide deposits occur at different stratigraphic levels in 565 ±1.25 Ma felsic volcanic strata. Host rocks are vent-proximal felsic pyroclastic volcanic breccia, lapilli tuff, coherent flows (Lookout deposit, Trio zone) and vent-distal felsic ash tuffs (Niblack Mine, Mammoth and Dama zones). New geochemical data and volcanic lithofacies indicate the host stratigraphy was deposited in a juvenile oceanic back-arc basin. Sub-seafloor mineralization (Lookout deposit, Trio zone) consists of 15-75% sulfide with disseminated to net-textured to semi-massive sulfide textures. These ores precipitated in unconsolidated water-laden vent-proximal felsic volcanic stratigraphy. Seafloor exhalative mineralization (Niblack Mine, Mammoth and Dama zones) is comprised of massive (>90%) poorly-banded sulfide. This type of sulfide precipitated on the paleo-seafloor in, or above, less-permeable vent-distal felsic ash tuff stratigraphy.Sub-seafloor sulfide, related hydrothermal alteration assemblages, and variations in metal ratios represent hydrothermal fluid flow and cooling through the host stratigraphy. Temperature estimates from chlorite microprobe data indicate sub-seafloor 1:1 Cu:Zn and 1:10 Au:Ag chlorite-rich alteration (Lookout deposit) formed at 321 ±19°C and seafloor exhalative 3:1 Cu:Zn and 1:10 Au:Ag magnesium-rich chlorite alteration (Niblack Mine) formed at 307 ±16°C.Sulfur, oxygen, deuterium and carbon stable isotope results are used to identify the origin of hydrothermal fluids. Sulfide mineral separates have δ³⁴S values of +6.6 to +10.5‰. Calculated fluid compositions of chlorite and sericite have values of +2.3 to +5.9‰ δ¹⁸O(water) and -24.9 to -77.1‰ δD(water). Calculated δ¹⁸O(water) values of magnetite are +8.1 to +15.5‰ and values of carbonate are -13.5 to +9.0‰ δ¹⁸O(water) and -4.4 to -0.5‰ δ¹³C(calcite).The sulfur isotope results indicate sulfur was derived from leached igneous sulfide and minor seawater sulfate reduction. The oxygen, deuterium and carbon isotopic signatures indicate evolved seawater and magmatic hydrothermal fluid sources. The Lookout deposit is the largest in the camp and has the largest magmatic fluid component. Seafloor exhalative sulfide mineralization (Niblack Mine) formed from an evolved seawater-dominant hydrothermal fluid. This suggests magmatic fluids contributed extra metals and sulfur to the hydrothermal system that enhanced the size of the Lookout deposit.

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Late Jurassic fault-hosted gold mineralization of the Golden Saddle deposit, White Gold district, Yukon Territory (2014)

The Golden Saddle deposit is a lithologically and structurally controlled gold deposit located in west-central Yukon Territory. The deposit is located near the Klondike district, which is best known for its rich history of placer gold mining. The discovery of the Golden Saddle deposit in 2008 was the first significant lode gold discovery in this region. Based upon the geology, structure, and age of the deposit, an amagmatic orogenic model is proposed to describe the genesis of the deposit. The deposit area is underlain by Late Paleozoic amphibolite-grade metasiliciclastic, metavolcanic, metavolcaniclastic and metaplutonic rocks of the Yukon-Tanana terrane. Mineralization occurs at the intersection between a Jurassic east-striking sinistral transpressional fault system and an older north-striking thrust fault. Metavolcanic and metaplutonic rocks occur in the hanging wall of this thrust fault, whereas metasiliciclastic rocks occur in the footwall. Economic gold mineralization is hosted predominantly by a series of subparallel northeast-striking, northwest-dipping faults within the sinistral transpressional fault system. The gold-hosting faults are complex structures comprising early folds and shears that are crosscut by polyphase quartz-carbonate-sulphide veins, fracture zones, and breccias. Gold and related alteration minerals typically occur in brittle, dilational deformation zones. Some gold-bearing brittle deformation zones are oriented parallel to the fold-axial plane of ductile folds. This textural relationship is indicative of gold mineralization occurring near the brittle-ductile transition. Gold mineralization is accompanied by a progression of alteration mineral assemblages, vein mineral assemblages, and vein textures. Pre-gold alteration and veins vary by host rock composition, whereas syn-gold alteration and veins are characterized by quartz-carbonate-illite and gold-bearing pyrite. Mineralization is accompanied by enrichment of Au-Ag-Pb-S-Te, with enrichment of other elements dependent upon host rock composition, and variably including As, Ba, Bi, Cu, Hg, Mo, Sb, Se, and Zn. Values of δ³⁴S for hydrothermal pyrite range from –9.8 to 6.8‰, whereas ratios of ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/ ²⁰⁶Pb range from 2.043-1.933 and 0.828-0.757, respectively. These sulphur and lead isotopic ratios are interpreted to vary in part based upon host rock composition. The age of mineralization is constrained by ¹⁸⁷Re/¹⁸⁷Os model ages of 163–155 Ma for molybdenite in gold-bearing veins within the deposit.

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Surface lithogeochemistry of the Relincho porphyry copper-molybdenum deposit, Atacama region, Chile (2014)

Porphyry copper deposits (PCDs) typically have large alteration haloes that extend several kilometers from economic mineralization providing a geochemical footprint potentially an order of magnitude larger than the deposit. The Paleocene (64±2 Ma) Los Morteros batholith comprises four granodiorite units and hosts four syn-mineralization porphyry units. These units are interpreted as the product of four magmatic differentiation cycles with three magmatic recharges. Alteration assemblages observed within the system include potassic, propylitic and phyllic, with intensities varying between weak to moderate for potassic and phyllic alteration, and weak to strong for propylitic. Lithogeochemical characterization and quantification of alteration is an important exploration tool that has the potential to lead to exploration success. Two hundred and ninety-six surface rock samples were collected in a grid covering 65 km² centered over the Relincho PCD in the Atacama region, Chile to assess the suitability of surface rock lithogeochemistry as a medium for lithological and alteration characterization. Aqua regia ICP-MS, pressed pellet XRF, and fusion-ICP results, combined with shortwave infrared (SWIR) spectra, alkali feldspar staining, petrography and field observations were used to classify lithological units and identify and quantify alteration. Data evaluation and modeling is completed through the use of exploratory data analysis, simple mass balances and molar element ratios (MER) complimented by hand and thin-section observations and SWIR analyses. Gain-loss variations are consistent with spatial element distributions indicating: the addition of SiO₂, K₂O, Ag, Cu and Mo and loss of CaO, Na₂O during potassic alteration; and the addition of Na₂O and loss of SiO₂ during propyltic alteration. Wavelengths of SWIR chlorite features indicate that chlorite is more Fe-rich proximal to mineralization and Mg-rich distally. Simple and molar element ratios are used as proxies for the potassic, propylitic and phyllic alteration assemblages. From these ratios, alteration indices are calculated. The potassic index (K₂O/Th) and propylitic-phyllic index ((18Ca + 14Na + 25K)/(2Si + 7Al + 4(Fe + Mg)) identify and quantify potassic, phyllic and propylitic alteration. Alteration thresholds derived from probability plots indicate that these indices would identify the Relincho deposit as a potential PCD exploration target at a sample spacing of up to 2000 m. Supplementary materials:

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Geology and genesis of the Newton bulk-tonnage gold-silver deposit central British Columbia (2013)

The Newton Au-Ag deposit is located in the Chilcotin Plateau of central British Columbia, Canada. The deposit lacks vein textures typical of magmatic-hydrothermal deposits and its genesis is poorly understood. Investigations focused on drill core logging, petrography, short wave infrared spectroscopy, X-ray diffraction, lithogeochemistry and stable isotopic analyses.The mineralization is hosted within Late Cretaceous age felsic volcanic rocks (U-Pb age of 72.1 ±0.6 Ma). These rocks are interbedded with an intra-arc sedimentary rock sequence that overlies a mafic rock sequence. Porphyritic dykes of felsic to intermediate composition intrude this stratigraphy. The quartz feldspar porphyry yielded a U-Pb age of 70.9±0.5 Ma. Re-Os dating of molybdenite yields an age of 72.1±0.3 Ma and a minimum age for mineralization.The mineralization is stratabound and characterized by pervasive quartz-sericite alteration and disseminated open-space filling sulfides providing strong evidence that the felsic volcanic rocks had high permeability relative to adjacent lithologies. Gold-silver mineralization is associated with two sulfide assemblages 1) pyrite-dominant (pyrite-arsenopyrite) and 2) marcasite–base metal dominant (marcasite-pyrite-chalcopyrite-sphalerite) and rare polymetallic (pyrite-chalcopyrite-sphalerite-arsenopyrite) veins. Siderite has replaced marcasite and chalcopyrite. Variations in Zn-Ag concentrations define a paleothermal gradient that developed in the hydrothermal system.The poorly mineralized felsic porphyry stocks and dykes have quartz-sericite-pyrite-carbonate-kaolinite alteration and minor quartz-calcite-pyrite-molybdenite veinlets. The mafic rocks have propylitic alteration (chlorite-epidote-pyrite-calcite-albite-magnetite).Whole rock lithogeochemistry suggests a calc-alkaline magmatic affinity for the felsic volcanic rocks and the felsic porphyritic intrusions. Alteration intensity is indicated by relative addition of SiO₂, K, C, Fe and removal of Ca and Na. Major rock types show distinct Y-Zr ratios. Hydrothermal fluids in equilibrium with sericite have δ¹⁸O values from 2.5 to 6.8‰ and δD values from -63 to -46.5‰ suggesting a magmatic fluid source that intermixed with meteoric waters. Sulfides have δ³⁴S values from -1.1 to 3.5‰ that indicate a magmatic origin for the sulfur.The results suggest that Newton is a disseminated strata-bound intermediate-sulfidation type epithermal deposit. The Newton deposit is comparable to the Capoose and Blackwater deposits but lacks garnet alteration. The felsic volcanic host rocks at Newton are contemporaneous with the youngest stratigraphy of the Kasalka Group rhyolites (68-71Ma).

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Evolution of alteration and mineralization at the Red Chris copper-gold porphyry deposit East zone, northwestern British Columbia, Canada (2012)

Located in northwestern British Columbia within the Stikine terrane, the Red Chris Cu-Au porphyry deposit is hosted in the Late Triassic Red Stock (~203.8 Ma). The Red Stock is a quartz monzodiorite to monzonite intrusion hosted in the broadly contemporaneous volcanic rocks of the Stuhini Group. Red Chris has features that are characteristic of calc-alkalic and alkalic porphyry deposits and shares many similarities with the Ridgeway deposit of the Cadia district in New South Wales, Australia. A combined measured and indicated resource of 936 million tonnes at 0.374 % Cu, 0.385 g/t Au, and 1.224 g/t Ag has been outlined from the Main and East zones.Copper and gold are associated with bornite, chalcopyrite and lesser pyrite, hosted in quartz veins and stockworks as disseminations and fracture-controlled veinlets. High-grade mineralization is directly associated with high quartz vein density. Copper-iron sulphide minerals are laterally zoned, with a bornite > chalcopyrite core, grading outward to a chalcopyrite > pyrite shell and outward and upward to a pyrite > chalcopyrite halo. Five major groups of veins are recognized, of which the oldest two sets contain much of the copper and gold.Stable isotopic analysis indicates the presence of magmatic and mixed magmatic-meteoric hydrothermal fluids. Evidence from sulphur isotopes demonstrates a high temperature oxidized magmatic fluid was responsible for transporting and depositing much of the copper and gold. A vertical and lateral zonation in sulphur isotopes exists, whereby deep regions exhibit δ34S values between -1.9 to -0.9 % and transition to near-surface regions in the pyrite halo that exhibit δ34S values between +0.9 to +1.9 %. Isotopic analysis of oxygen and deuterium of hydrothermal alteration minerals provide evidence for a magmatic fluid (secondary biotite and muscovite) and a mixed magmatic-meteoric fluid (illite and kaolinite). Low temperature clay alteration (illite-kaolinite; intermediate argillic assemblage) significantly overprinted high temperature alteration (K-silicate, phyllic) in the upper levels of the system and gradually diminished intensity with depth. Carbonate veins and alteration also characterize the shallow levels and isotopic analysis of carbon and oxygen suggest a magmatic source with the possibility of minor mixing with an external meteoric fluid.

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The age and character of alteration and mineralization at the Buckhorn Gold Skarn, Okanogan County, Washington, USA (2012)

Located in Okanogan County, Washington, USA the Buckhorn mine is one of the largest gold skarns in North America (2.15 Mt at 14 ppm Au).Buckhorn is hosted in Permian Anarchist Group metasedimentary rocks and Jurassic Elise Formation metavolcanic rocks. Monzodiorite comagmatic with the metavolcanic rocks is Jurassic in age (192.4 Ma) confirming the correlation. Two suites of granitoids intrude the local stratigraphy. The Middle Jurassic (170.4 Ma) post-accretionary Buckhorn Intrusive Suite is genetically related to skarn alteration and gold mineralization and comprised of a granodiorite stock, marginal diorite, and several generations of dikes. The Eocene Roosevelt Intrusive Suite (50.5 Ma) is comprised of a small (~0.03 km2) granodiorite stock that post-dates skarn alteration and gold mineralization.Skarn alteration is zoned from dominantly magnetite-garnet in the proximal Magnetic Mine, to equal portions of magnetite-garnet-pyroxene in the Gold Bowl, and pyroxene dominated in the distal Southwest Ore-Zone. The Southwest Ore-Zone contains the majority of the gold mineralization and consists of massive calcic, Fe-rich, reduced skarn alteration along a low-angle shear zone at the contact between the carbonate metasedimentary rocks and the overlying metavolcanic rocks. Skarn alteration is divided into three categories based on the prograde mineralogy: pyroxene, garnet and magnetite skarn. Pyroxene skarn is further subdivided based on the retrograde mineralogy: amphibole-pyroxene, magnetite-pyroxene, and epidote-pyroxene skarn. Gold mineralization occurs in fractures in and intercrystalline space between skarn minerals and is intimately associated with bismuth. Re-Os geochronology of molybdenite bearing skarn confirms the Middle Jurassic age of skarn alteration and gold mineralization (162.8-165.5 Ma).Based on the mineralogy, the hydrothermal fluids that caused prograde alteration were between 430-500° C, fO2=-25 to -20, fS2=-8 to -4.5, and near neutral pH. Fluids responsible for retrograde alteration were cooler (300-430° C), more reduced (fO2
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