Sphalerites from the Kootenay Arc in British Columbia and Washington State were selected to represent three types of carbonate-hosted massive sulfide deposits, including Mississippi Valley-type (MVT), Irish-type, and fracture-controlled replacement type (FCR). These deposits were variably deformed and metamorphosed during the Cordilleran orogen. Laser ablation inductively coupled plasma mass spectrometric (LA-ICP-MS) analyses of the trace element distributions within the sphalerites are combined with petrography and sulfur isotope analyses to evaluate the influence of primary trace element signatures, along with the variable influence of post-ore metamorphism and deformation on sulfide remobilization and trace element redistribution. Mississippi Valley-type (Josephine orebodies) and Irish-type (Yellowhead orebodies) at Pend Oreille mine are only weakly deformed and recrystallized, so their sulfide minerals commonly retain primary ore textures. The sphalerite from the Irish-type deposit has positive narrow range of & delta;34S values (17.9-20.5%o, mean 19.2%o), and it is enriched in Ge, Tl and Pb, but depleted in Cd, Mn, and Cu relative to MVT and FCR deposits. Germanium is concentrated in dark-brown acicular-colloform bands where micro-inclusions of a germanium oxide mineral (argutite (GeO2)) and galena have been detected. Other MVT deposits of the Kootenay Arc (Reeves MacDonald, Jersey-Emerald, HB, Jackpot-Lerwick, Duncan) are more deformed and metamorphosed than the Irish-type deposit of the Pend Oreille mine and primary ore textures are only locally preserved. There is a progressive increase in deformation and degree of recrystallization from Reeves MacDonald, located away from intrusions, to deposits within the contact metamorphic aureoles of intrusions (HB, Jersey-Emerald, Jackpot-Lerwick). Sphal-erite from the least metamorphosed Reeves MacDonald deposit has high Cd, Ga, Pb, and Tl contents, high Cd/Ge and Ga/In values, and the lowest & delta;34S values (7.4 to 11.1%o, mean 8.8%o). In contrast, sphalerites from contact metamorphosed HB, Jersey-Emerald and Jackpot-Lerwick deposits have higher & delta;34S values (13.3 to 28.5%o, mean 19.2%o), are enriched in Mn and Fe, with higher Zn/Cd and Mn/Fe values relative to Reeves MacDonald deposit. These enrichments and fractionations correspond to the breakdown of pyrite and pyrrhotite and the thermal annealing of sphalerite caused by contact metamorphism. Sulfide minerals from the FCR deposit (Abbott-Wag-ner) are undeformed (except for microfractures) and only weakly recrystallized. Sphalerite from the FCR Abbott-Wagner deposit is enriched in Cu, Ga, In, and Sn as primary source signatures relative to sphalerite from MVT and Irish-type deposits. This reflects the more complex mineral assemblage of galena, sphalerite, pyrite, chal-copyrite, and tetrahedrite in this deposit. The presence of chalcopyrite and tetrahedrite is consistent with a higher-temperature origin of the FCR deposit relative to the lower-temperature MVT and Irish-type deposits. This study demonstrates that the high spatial resolution of in-situ LA-ICP-MS analyses of trace element within sphalerites, in combination with petrography and other analytical techniques (e.g., electron microprobe, sec-ondary ion mass spectrometry, field emission scanning electron microscopy) characterizes the behavior and distribution of trace elements in sphalerite for three deposit types and variable conditions of regional and contact metamorphism. Understanding the effects of metamorphism and deformation on trace elements can be very useful in exploration for deposits rich in critical metals.

The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t) of gold. The deposit is hosted in the 2699–2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699–2696 Ma) Mooshla Intrusive Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked, contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host rocks. The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusite-kyanite-pyrophyllite argillic to advanced argillic-style tabular envelope that is up to a few tens of meters thick. The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillic-style alteration assemblage is associated with both corridors. The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic-hydrothermal system that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system. The Westwood Au deposit represents one of the very few documented examples of an Archean magmatic-hydrothermal system—or at least of such systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor Au-rich VMS-type mineralization.

Abundant magnetite occurs sporadically in variable textural settings within the New Afton Cu-Au porphyry deposit. A study to test the utility of magnetic anomalies as an exploration vector was conducted by analyzing magnetite in drill core samples from a variety of rock types and alteration facies. Magnetite samples from various settings (i.e. disseminated, isolated, vein, breccia grains) were analyzed by a laser-ablation inductively coupled plasma-mass spectrometer for iron and trace elements. New Afton magnetite compositions were compared to previously defined compositional fingerprints of porphyry, iron oxide copper gold, skarn, polymetallic vein, and layered intrusion deposit types. On multi-element plots using bulk continental crust as the normalizing factor, most New Afton magnetite analyses plot within the high-temperature hydrothermal magnetite field, although most samples have elevated V and 6 of 19 samples have notably higher W than other deposit types. A hydrothermal origin is supported by a Ti versus Ni-Cr plot, which discriminates hydrothermal from magmatic magnetite; however, a Ti versus V plot suggests mainly magmatic compositions. Copper is generally depleted relative to bulk crust; gold and platinum values are near their detection limits. Veins, one of the main magnetite habits, define brittle fracture patterns, and trace-element characteristics support formation by pulses of oxidized, high-temperature hydrothermal fluid. The texture and composition of the samples suggest that magnetite crystallized from late magmatic fluids that drove porphyry mineralization.

Orogenic Au deposits require a trigger to transport auriferous fluids from their deep-seated source regions to their depositional site in the mid- to upper-crust. Defining the tectonic trigger of Au ore systems requires precise age constraints. Herein we address that knowledge gap with new Re-Os sulphide (arsenopyrite and pyrite) and U-Pb detrital zircon geochronology results from the Lynn Lake greenstone belt of the Paleoproterozoic Trans-Hudson Orogen, Manitoba, Canada. We document an early-stage of Au-rich veins (ca. 1.82 Ga) that are coeval with syenitic magmatism (1.83-1.82 Ga) and immediately post-date new ages for the opening and closure of synorogenic basins (1.84-1.83 Ga) and late-stage arc magmatism (1.84-1.83 Ga). Together these data point to the importance of stalled subduction and upwelling asthenosphere as possible triggers for fluid release during the earliest stages of continental collision between the Hearne, Superior, and Sask cratons. New dating further documents a second, overprinting generation of auriferous fluids (ca. 1.78 Ga) that post-dates peak metamorphism (ca. 1.81 Ga). These late-stage fluids were driven by a second thermal pulse (ca. 1.78 Ga), which, based on the timing of coeval, crustally derived pegmatitic dykes, may be related to crustal thickening and/or another unrecognized subcrustal heat source. Mineral exploration should focus on the large-scale architecture that is required to focus multiple pulses of auriferous fluids to the same depositional trap over the lifespan of an orogen.

Sedimentary basins that open and close during the last stages of mountain building represent an important exploration criterion for orogenic gold deposits. However, the genetic and/or preservation controls of these synorogenic, or "Timiskaming-type", sedimentary basins and their controlling fault systems on orogenic gold deposits remain unclear. Herein we address that knowledge gap and report new U-Pb detrital zircon and Re-Os sulphide (arsenopyrite and pyrite) geochronology and sulphide Pb isotope results for the Paleoproterozoic Lynn Lake greenstone belt (LLGB), Manitoba, Canada. The youngest detrital zircon from all six meta-conglomerate and-psammite samples of the synorogenic Sickle Group, and previously reported U-Pb zircon ages for post-Sickle Group intrusions, are used to constrain its depositional timing from 1836 +/- 15 to 1831 +/- 4 Ma. Replicate analyses of one highly-radiogenic arsenopyrite sample from an auriferous vein at the MacLellan gold deposit yield a weighted average Re-Os model age of 1824 +/- 12 Ma, which is identical to previously published in situ U-Pb xenotime ages at the same deposit (1827 +/- 8 Ma). Each of these hydrothermal ages demonstrate that early stage auriferous veins immediately post-date deposition of the Sickle Group and most likely occurred prior to peak metamorphism (1814-1801 Ma). This sequence of events is very similar to the Abitibi greenstone belt, suggesting that a synorogenic phase of extension and rapid burial of auriferous veins by Timiskaming-type Sickle Group sediments may have played an important genetic and/or preservation control on early-stage gold mineralization in the LLGB. However, unlike the Abitibi greenstone belt, none of the known gold deposits within the LLGB are hosted within the Sickle Group. Younger Re-Os model arsenopyrite ages at 1782 +/- 16 Ma from the MacLellan gold deposit also post-date synorogenic sedimentary basins by ca. 50 Myr. These late-stage auriferous veins are unrelated to the synorogenic extensional phase and more likely reflect repeated fluid focusing along reactivated structures during a post-peak metamorphic phase of hydrothermal activity. The multistage hydrothermal history of orogenic gold deposits in the LLGB also provides a possible explanation for the mixture of depleted mantle-like and highly radiogenic fluid components that are inferred from age-corrected sulphide Pb isotope compositions (mu(1.8 Ga) = 8.9-10.6). Reworked cratonic margins and their associated greenstone belts thus represent favourable depositional settings for auriferous fluids at multiple stages throughout the lifespan of an orogen.

The discovery of new mineral deposits is essential to maintain a stable supply of mineral commodities, however, new mineral discoveries are in ever more remote, deeper, and/or covered geological environments, which presents significant challenges. The fifth phase of the Targeted Geoscience Initiative (TGI-5) was developed to address these challenges and to advance our understanding of ore-forming processes at various spatial scales and across geological time. Here we present a selection of highlights from research activities comprising the Gold Project. These research activities, all of which included significant field components, focused on different aspects of the gold mineral systems and included gold districts with variable metal endowment (e.g. southern and northern Neoarchean Abitibi greenstone belt), geological setting (e.g. pre-, syn-, and post-orogenic processes), and geological age (e.g. Paleoproterozoic Trans-Hudson, and Phanerozoic Appalachian orogenic belts). The southern Abitibi is host to many different types of giant gold deposits (e.g. synvolcanic and orogenic gold ore systems), although the sources of ore-components for these mineral systems remained unclear. New TGI research addressed this knowledge gap and demonstrate that (1) diagenetic sulphides (pyrite nodules) and their host sedimentary sequences within the Superior Province are pre-enriched in gold; (2) Archean calc-alkaline felsic volcanic centres associated with large synvolcanic gold deposits further suggest that igneous differentiation in the lower crust may be associated with the generation of synvolcanic gold-rich magmatic-hydrothermal systems; and (3) undocumented upper mantle pathways existed, which were revealed by anomalous ore-forming element concentrations within cratonic mantle samples from the southern Superior Province. Together these research activities provide new insights into the upgrading of ore components from the mantle to the upper crust, although the role of these pre-enriched source rocks to gold ore systems remains unclear. Other research activities focused on the complete source-to-ore pathways of gold-bearing fluids for multiple gold districts across Canada. The similar pacing of events and timing of auriferous vein development within the overall tectonic evolution for several of these gold districts likely reflects a common driver (e.g. upwelling asthenosphere) and/or tectonic triggers (e.g. crustal extension and associated magmatism). However, the contrasting metal endowment of areas with otherwise similar histories (e.g. southern versus northern Abitibi belt) suggests that the prospectivity of gold districts is not entirely related to the large-scale drivers and triggers of ore-forming fluids. Moreover, long-term preservation is another critical factor in gold ore systems, which is promoted by rapid burial; limited post-ore remobilization during hydrothermal and metamorphic overprinting; and long-term craton stability. Indications of preferential preservation, such as the occurrence of synorogenic polymict conglomerate, constitute key exploration criteria. New analytical methods that were developed as part of TGI-5 are also providing new tools (e.g. rapid in situ element mapping and data interrogation approaches; new geochronological methods; clumped isotope thermometers) for recognizing ore-proximal depositional controls from the rock record. An improved understanding of these controls and efficient vectoring tools are increasingly important for mineral exploration targeting.

This study investigates pyrite nodules hosted in argillite horizons within (Zn-Ag-Au-Cu±Pb) massive sulphide ore of the 20N Zn zone at the LaRonde Penna Au-rich volcanogenic massive sulphide deposit, Abitibi greenstone belt, Quebec. Two pyrite nodules are examined in detail: LA-001 and LA-002. These nodules are spherical and oblate spheroidal in shape and display similar textures, including a core (zone 1) composed of fine, equigranular grains with variable amounts of silicate-carbonate inclusions; a rim (zones 2a to c) that varies from inclusion-poor to -rich and consists of equigranular to radially oriented, acicular pyrite grains; and a thin layer of idiomorphic pyrite overgrowth that surrounds the nodules (zone 3). Sulphide inclusions in nodule LA-001 consist predominantly of sphalerite, whereas sulphide inclusions in nodule LA-002 include an assemblage of sphalerite, Zn-bearing stannite (Cu2(Fe,Zn)SnS4), and galena, all of which occur also in the surrounding massive sulphide ore. In nodule LA-002, sphalerite is intimately associated with stannite, and together they are preferentially concentrated along both the concentric zones of the inclusion-rich section of the rim (zone 2b) and within the radially bladed rim (zone 2c), parallel to blade elongation. Whereas textures are similar in the two nodules, compositional maps generated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) reveal important distinctions in element distribution patterns for inclusion-partitioned elements (Cu, Zn, Sn, Pb, Bi), which reflect the mineralogy and bulk abundances for lattice-bound elements (Ni, As, Au). Gold is mainly concentrated in the fine-grained cores, but in different amounts in LA-001 (average of 0.38 ppm Au; n = 6918) and LA-002 (average of 1.04 ppm Au; n = 10,539). Nickel and As values in LA-001 are respectively 10 and 3 times greater than in LA-002. In both nodules, Ni is enriched in the rim relative to the core. The pyrite nodules have in situ delta-34S values (secondary ion mass spectrometry analyses) that range from -0.8 to +5.0 per mille (average +2.1 per mille, n = 50), with the core showing slightly lighter values than the rim. Based on these results, the nodules (zones 1 and 2) are interpreted to have formed by diagenetic processes and the presence of stannite, sphalerite, and galena (enrichment in Zn, Sn, Cu, and Pb) is likely the expression of a previously hydrothermally enriched sediment rather than a direct hydrothermal contribution during crystal growth. While more work is needed, the composition of pyrite nodules could potentially be used as vectors toward syngenetic mineralization.

Gold-rich zones in the Nadaleen trend (central Yukon) exhibit several characteristics consistent with Carlin-type mineralization: 1) alteration zones with partial to complete decalcification of mineralized intervals and very fine-grained quartz associated with silicification; 2) the association of gold with certain pathfinder elements (Tl, As, Hg, and Sb) and minerals (realgar, orpiment, and fluorite); 3) the low base metal and Ag content of the mineralized intervals; and 4) the 'invisible' nature of gold, which occurs as rims of Au-bearing arsenian pyrite on pre-ore pyrite and/or as sub-micrometre particles. Mineralization styles vary significantly between intervals and even within an interval, attesting to the 'passive' or 'opportunistic' nature of the mineralizing fluids that exploited a variety of porous and permeable pathways regardless of their sedimentary and/or tectonic origin. Alternating finely laminated limestone and siltstone (Conrad zone) and floatstone intervals (Conrad, Sunrise, and Osiris zones) are the most favourable sedimentary units. Pre-mineralization fractures acted as feeders for selective bed replacement and pre-mineralization vein networks were preferentially dissolved by early acidic fluids and channelized later by gold-bearing fluids. With ongoing research, we hope to better constrain the occurrence of gold at the micron scale, the geochemical variations due to alteration, the temperature of the mineralizing fluids, and the timing of the gold mineralization.

The tectonic trigger(s) that controls the formation of large gold deposits hosted within ancient greenstone belts re-main poorly understood. Herein we address that knowledge gap by merging macro- to micro-scale field relationships and multiple mineral chronometers to constrain the timing of magmatism, deformation, metamorphism, and gold in the Lynn Lake greenstone belt, Manitoba. Preliminary monazite and xenotime ages from the MacLellan gold deposit (1.83-1.75 Ga) are coeval with previously reported metamorphic ages for northern Manitoba (1.81-1.78 Ga), which also marks the terminal collision of the composite Hearne-La Ronge-Lynn Lake block and Sask-Superior craton at 1.83 to 1.80 Ga. The peak metamorphic mineral assemblage and dated phosphate minerals define the main structural fabric (D2) of the Lynn Lake greenstone belt, which coupled with the folded, transposed auriferous veins, places a lower limit for the timing of gold at or before 1.75 Ga. However, xenotime within a garnet-hosted and gold-bearing veinlet dated at ca. 1.83 Ga may provide the first evidence for a cryptic early stage of gold mineralization that is coeval with the onset of collisional orogenesis between the composite Hearne and Superior cratons. Ongoing thermo-chronology (e.g. apatite, biotite) and Re-Os pyrite and arsenopyrite dating at gold deposits within the Lynn Lake greenstone belt will further constrain the timing of gold deposition relative to the different stages of the Trans-Hudson orogeny. New ages will inform ore system models by identifying the tectonic trigger(s) for gold and improving exploration targeting in ancient greenstone belts.

The trace element composition of olivine is becoming increasingly important in petrological studies due to the ubiquity of olivine in the Earths upper mantle and in primitive magmatic rocks. The LA-ICP-MS method allows for the routine analysis of trace elements in olivine to sub-ppm levels, but a major drawback of this method is the lack of knowledge about possible downhole fractionation effects when non matrix-matched calibration is used. In this contribution, we show that matrix-matched (i.e., olivine-based) calibration is preferable for small laser spot sizes (<100 mu m) due to significant laser-induced inter-element fractionation between olivine and commonly used silicate glass calibration materials, e.g., NIST SRM 612, GSD-1G and BHVO-2G. As a result, we present two Mg-rich natural olivine standards (355OL and SC-GB) that have been characterized by independent methods (EPMA, solution ICP-MS), and by LA-ICP-MS in four different laboratories. These natural olivines have been used 1) as primary standards for the matrix-matched calibration of olivine samples for most elements of interest (e.g., Li, Na, Al, P, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn), and 2) as secondary standards to assess the accuracy of results. Comparison of olivine- and silicate glass-calibrated results for natural peridotitic olivine reveals that matrix-matched calibration is essential when using small laser spot sizes (<100 mu m) in order to mitigate downhole fractionation effects for certain elements, especially Na, P, Mn, Co, Ni and Zn. If matrix-matched calibration is not feasible, we recommend that spot sizes of >= 100 mu m, laser fluence of <= 4.0 J/cm(2), and total laser shot counts of <= 250 (e.g., 5 Hz repetition rate for 50 s) are used in order to minimize fractionation effects between olivine and silicate glass calibration materials. We demonstrate the applicability of matrix-matched calibration on olivine from a suite of different mantle peridotite xenoliths sampled by kimberlites and alkali basalts from on-craton and off-craton localities.

This research activity investigates the origin of gold-rich (up to approximately 10 ppm) iron sulphide nodules and the timing of gold introduction in Archean carbonaceous metasedimentary rocks near and distal to orogenic gold mineralization in the Timmins-Matheson area, Ontario. It provides insights into the factors controlling gold enrichment and tests the hypothesis asserting a genetic link between sedimentary sulphides and orogenic gold deposits. Preliminary textural examination of numerous iron sulphide (e.g. pyrite) nodules hosted in various sedimentary sequences from assemblages, including Kidd-Munro, Tisdale, Porcupine, and Timiskaming, reveals evidence of nucleation and formation prior to the main regional deformation events. Pyrite grains that are unequivocally metamorphic/hydrothermal in origin (e.g. coarse-grained euhedral porphyroblasts, overgrowths, and cross-cutting stringers) show distinct geo-chemical signatures compared to the nodules, with lower contents of Sb, Tl, Ag and Au. There are also consistent intra-nodule chemical trends, including, for example, systematic decreases in Au and Ni/Tl from core to rim. These trends are observed across the region, regardless of the setting of the nodules (i.e. shear-hosted, proximal or distal to mineralization, stratigraphic depths). The systematic core to rim decrease in gold content may reflect increasing pH and/or redox potential of the ambient fluid during the development of the nodules. Further geochemical and isotopic work is being conducted to better understand the genesis of the gold-rich nodules and any potential genetic link that may exist between orogenic Au mineralization and an earlier gold enrichment event in the Timmins-Matheson area.

Processes operating within mantle source regions likely impact the fertility of ore-bearing melts, although the precise link between mantle conditioning and ore genesis remain poorly understood. New fieldwork and isotopic (Re-Os and Pb-Pb) results for ultramafic samples from young (Mesozoic), ophiolitic mantle near Atlin British Columbia, document ancient (i.e. Paleoproterozoic and younger), refractory mantle domains hosted within variably depleted harzburgite. The metal endowment of these distinct mantle segments and the microscale distribution of gold, platinum group elements and base metals are the focus of on-going study. Field-based research at Atlin complements chemical analysis of kimberlite-hosted mantle olivine and clinopyroxene xenocrysts. These mantle fragments provide a snapshot of the ancient, sub-continental lithospheric mantle beneath the Neoarchean Abitibi sub-province (Kirkland Lake kimberlite field). Geochemical depth profiles, based on preliminary in situ geochemical results of the least-altered xenocrysts, suggest that high temperature olivine is a significant silicate mineral host for some of the so-called chalcophile elements at depth (e.g. Cu and Zn). Other metals, including a rare subset of xenocrysts that yield concentrations for gold and platinum at or above the analytical detection limit (1-5 ppb), occur as micro-inclusions. The distribution of metal-bearing mineral phases within the mantle and, the micro-scale setting of metals within those phases (e.g. mineral inclusions versus lattice substitution), may control the variable metallic endowment of mantle-derived melts in ancient and modern settings.

There is increasing recognition that there is a variable magmatic component to mineralizing fluids in volcanogenic massive sulphide (VMS) deposit formation. A previous fluid inclusion study conducted on the Windy Craggy Cu-Co-Au deposit in northwestern British Columbia documented primary inclusion fluids salinities that are higher than typical VMS fluids. The previous study concluded that the high salinity indicates a magmatic contribution to the ore-forming system. This makes Windy Craggy an ideal study location to test if there is in fact a magmatic influence on the fluids and to quantify that contribution. Preliminary results of this study show fluids consistent in salinity and temperature with those observed in the previous study. Fluids with salinities between 6.2 and 12.2 weight % NaCl equivalent are documented. Laser ablation ICP-MS analysis of these inclusions detects Na, K, Ca, Cu, Sr, Sn, Sb, Ba and Pb as well as trace elements of potential magmatic origin, including Au, W, Sn, In and Bi. Due to the multiple possible sources of Sn, we will be focusing on other potential magmatic elements such as Au, Bi and In as the study progresses. The small number of samples analyzed to date precludes us from making definitive conclusions. However, the detection of some potential magmatic elements in 17 inclusions is promising.

Evaluating the genetic link between gold, faulting and metamorphism remains a significant challenge at orogenic gold deposits in the absence of precise geochronological constraints with clear paragenetic context. Here we report new field observations and preliminary U-Pb zircon age results from gold deposits hosted within the Paleoproterozoic Lynn Lake greenstone belt. New zircon ages from a faulted, hydrothermally altered and metamorphosed diorite sample intruding the southern edge of the past-producing open-pit constrain the timing of gold, deformation and metamorphism at the Gordon gold deposit to ?1854 Ma. Auriferous veining thus significantly post-dates the age of the volcano-sedimentary host rocks, which are constrained to 1879 to 1892 Ma based on new zircon age dating from two granitic intrusions south of the Gordon gold deposit. Gold thus clearly post-dates some of the earliest deformation events recognized in the La Ronge - Lynn Lake segments of the Trans-Hudson orogeny (ca. 1.87 Ga). The temporal relationship between gold, peak metamorphism and a major deformation phase at ca. 1.81 Ga will be the focus of ongoing Re-Os pyrite and arsenopyrite geochronology of auriferous veins.

The late timing of gold is a characteristic feature of orogenic gold deposits. For many of these deposits, gold and other metals were liberated from the host greenstone belt and/or early sulfides concomitant with the syndeformational and fluid-assisted metamorphic transition of pyrite to pyrrhotite and remobilized into late, high-grade ore shoots. However, this metamorphic-driven gold-upgrading model is usually inferred, at least in part, from mineral textures, which can be equivocal in the absence of geochemical and/or isotopic constraints. Herein, we report new bulk mineral separate and in situ Pb isotope results for minerals in key textures in the Paleoproterozoic Meliadine gold district. Arsenopyrite and pyrite porphyroblasts occur in Paleoproterozoic quartz ± ankerite veins and are enveloped by remobilized pyrrhotite, chalcopyrite, and galena crystals that accompany gold in late, microtextural sites, a texture that forms the basis for the gold-upgrading model. Early, sieve-textured arsenopyrite and pyrite are gold rich and tend to yield the least radiogenic Pb isotope compositions (high 207Pb/206Pb and 208Pb/206Pb ratios), suggesting these relict domains escaped complete recrystallization during later reworking. Late, inclusion-free arsenopyrite and pyrite overgrowths scatter to more radiogenic Pb isotope compositions (low 207Pb/206Pb and 208Pb/206Pb ratios) and are typically gold poor, which we attribute to reworking and precipitation from a younger and more radiogenic fluid prior to and/or during the precipitation of free gold in variably plunging high-grade ore shoots at 1.90 to 1.85 Ga. Remobilized sulfides are the youngest sulfide phases, but locally yield low 206Pb/204Pb and 207Pb/204Pb ratios and, thus spurious old model mp;lt;"ages,mp;gt;" which overlap with the least radiogenic, sieve-textured arsenopyrite/pyrite domains. The isotopic signature of these remobilized sulfides was likely inherited from Pb liberated during reworking of early arsenopyrite and pyrite and a second, crustal Pb source that was introduced during late remobilization. Our results highlight the importance of element recycling from early sulfides and/or the Neoarchean deposit host rocks during significantly younger Paleoproterozoic reworking and gold remobilization. The in situ Pb isotope results of early and remobilized sulfides document the transition of gold from source to sponge to sink, which is likely a feature that occurred during the formation of other orogenic-style gold deposits.