Browsing by Author "Lentz, David"

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    Chemostratigraphy and hydrothermal alteration of the Flat Landing Brook Formation, Brunswick Belt, Bathurst Mining Camp
    (University of New Brunswick, 2014) Wills, Alexander Oakley; Lentz, David
    The Flat Landing Brook Formation, northern New Brunswick Bathurst Mining Camp, represents a Middle Ordovician supervolcano of tremendous volume. It consists of subaqueous to subaerial volcanic flows, domes, volcaniclastic deposits, and derived sedimentary rocks, mostly within a very narrow range of original calcalkalic/transitional A-type rhyodacite/rhyolite composition but variably obscured by hydrothermal alteration and multiphase deformation. The objective of the project was accomplished: to interpret the cryptic FLB rocks along the Brunswick Belt together with footwall Upper Nepisiguit Falls Formation and hanging wall Little River Formation via: (a) chemostratigraphy employing alteration-resistant and petrogenetically-sensitive ratios of low-mobility elements with contrasting compatibilities; and (b) alteration quantified from multiple precursor mass balance, alteration reaction vector, and mineral normative calculations. The sample suite from seven diamond-drill holes has whole-rock geochemical data (n = 346; XRF and INAA), core photographs (n = 89), Sm-Nd isotopes (n = 15), and O-isotopes (n = 36). Alumina-normalization of incompatible Zr versus compatible TiO2 (TiO2/Al2O3 vs. Zr/Al2O3) reveals emergent sample groupings, and profiled by downhole core sample depth serve as the basis for the chemostratigraphy. Each division is further classified by magmatic affinity (Zr/Y), alkalinity (Nb/Y), crustal/mantle melt (Th/Hf), Fe-Ti oxides stability (Ti/Ti*), REE enrichment/depletion ([La/Yb]cn, Eu/Eu*), and εNdt-derived crust/mantle melt ratios. The sixteen chemostratigraphic divisions are assigned: Nepisiguit Falls Formation felsic volcanic-derived sedimentary rock (NF SED; Zr/TiO2 = 0.059; Nb/Y = 0.28; Zr/Y = 3.72; Th/Hf = 2.17; Ti/Ti* = 0.072; [La/Yb]cn = 4.47; Eu/Eu* = 0.39) and Brunswick Horizon Member iron formation with tholeiitic andesite input (IF; Zr/TiO2 = 0.024; Nb/Y = 0.32; Zr/Y = 3.53; Th/Hf = 1.58; Ti/Ti* = 0.116; [La/Yb]cn = 6.70; Eu/Eu* = 1.17); Flat Landing Brook Formation effusive Reids Brook Member calc-alkalic rhyodacites (A1, A2, A3; Zr/TiO2 = 0.083, 0.085, 0.094; Nb/Y = 0.33, 0.39, 0.33; Zr/Y = 7.05, 8.10, 8.51; Th/Hf = 2.14, 1.48, 1.36; Ti/Ti* = 0.075, 0.093, 0.097; [La/Yb]cn = 7.54, 6.35, 5.33; Eu/Eu* = 0.47, 0.55, 0.61; εNdt = -3.42, -2.59, -2.20; crust/mantle = 64/36, 55/45, 57/43); younger, more voluminous effusive/explosive Roger Brook Member transitional/calc-alkalic rhyolite/rhyodacite (B1, B2, B3, B4; Zr/TiO2 = 0.153, 0.143, 0.116, 0.125; Nb/Y = 0.34, 0.33, 0.34, 0.34; Zr/Y = 6.04, 6.58, 7.09, 8.87; Th/Hf = 2.41, 1.86, 1.65, 1.21; Ti/Ti* = 0.034, 0.045, 0.063, 0.076; [La/Yb]cn = 7.57, 6.62, 6.05, 5.22; Eu/Eu* = 0.38, 0.48, 0.50 & 0.60); upper FLB unnamed flowbanded effusive rhyodacites (transitional C1 and tholeiitic C2; Zr/TiO2 = 0.089, 0.107; Nb/Y = 0.31, 0.32; Zr/Y = 5.73, 3.46; Th/Hf = 2.34, 3.18; Ti/Ti* = 0.059, 0.028; [La/Yb]cn = 6.95, 6.85; Eu/Eu* = 0.45, 0.37); Little River Formation unnamed tholeiitic andesite sedimentary rock (SED; Zr/TiO2 = 0.023; Nb/Y = 0.41; Zr/Y = 4.00; Th/Hf = 3.11; Ti/Ti* = 0.136; [La/Yb]cn = 8.15; Eu/Eu* = 0.63); unnamed felsic volcanic rocks marking transition into rift-stage (transitional/tholeiitic rhyolite C3 and feldspar porphyritic alkalic trachyandesite/rhyolite D1; Zr/TiO2 = 0.200, 0.153; Nb/Y = 0.38, 0.83; Zr/Y = 4.77, 6.98; Th/Hf = 2.08, 1.38; Ti/Ti* = 0.022, 0.039; [La/Yb]cn = 6.21, 7.51; Eu/Eu* = 0.42, 0.53); Brunswick Mines Member within-plate alkalic gabbro/basalt (ALK GAB; Zr/TiO2 = 0.012; Nb/Y = 0.78; Zr/Y = 6.38; Th/Hf = 0.99; Ti/Ti* = 0.521; [La/Yb]cn = 5.95; Eu/Eu* = 0.77); unnamed enriched mid-ocean ridge basalt (E-MORB) type tholeiitic gabbro (THOL GAB; Zr/TiO2 = 0.007; Nb/Y = 0.26; Zr/Y = 3.49; Th/Hf = 0.31; Ti/Ti* = 0.605; [La/Yb]cn = 1.70; Eu/Eu* = 0.96). A lithostratigraphic progression is observed from crustal toward more mantle melt petrogenetic compositions, extensional continental to rift basin tectonics, corroborated by Sm-Nd isotopes: Nepisiguit Falls Formation (εNdt=460Ma = -8.28 to -4.80; crust = 100 to 74%, mantle = 0 to 26%); Flat Landing Brook Formation (εNdt=460Ma = -4.80 to -1.40; crust = 74 to 49 %, mantle = 26 to 51 %); Little River Formation (εNdt=460Ma = -0.12 to -5.10; crust = 39 to 0 %; mantle = 61 to 100 %). Hydrothermal alteration is determined for each sample in chemostratigraphic hole profile to show the range of pervasive weak/moderate to layer selective intensities, for K-feldspathization/albitization (Na2O vs. K2O antipathy), sericitization/paragonitization (Na2O vs. K2O antipathy, SiO2 mobility), chloritization (gain of Fe2O3T and MgO, loss of alkalis and SiO2), silica leaching/flooding (SiO2 gain/loss), and calcite/ankerite/dolomite/siderite/magnesite alteration (gain of CaO +/- Fe2O3T and MgO). Within these profiled holes, there is no evidence of intense hydrothermal alteration, discordant stockwork zone, or significant massive sulfide accumulation in the Flat Landing Brook Formation. Applying similar chemostratigraphy and quantified alteration elsewhere in the Bathurst Mining Camp will help resolve complex lithostratigraphic relationships to focus mineral exploration.
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    Controls on genesis, distribution, and nature of the turbidite-hosted gold deposits, Eastbelt, Southwestern Slave Structural Province, Yellowknife, Northwest Territories
    (University of New Brunswick, 2020) Richardson, Mark Wesley; Lentz, David
    The Ptarmigan and Tom mesothermal gold deposits are located 10 km to the northeast of the city of Yellowknife, Northwest Territories. Both gold deposits comprise a series of en echelon veins. These veins are hosted within upper greenschist to lower amphibolite facies ~2630 Ma rocks. A low-temperature reduced hydrothermal environment during ore deposition formed as either a part of the main arsenopyrite-dominated mineralization or a distinct late-stage ore-formation event. At the deposit scale, the high-grade gold ores are preferentially developed with three contextual scenarios: (1) along contacts, especially the contact between black siltstone host rock and major barren, cleavage-parallel veins; (2) the contact between quartz laminae and carbonaceous host rock slivers; (3) proximity to bismuth telluride mineralization. Thus, competent, barren quartz veins along the axial plane of fold/thrust belts locally host superimposed gold mineralization and provide favourable targets for gold exploration. Hydrothermal apatite is a common accessory mineral in both mineralized and non-mineralized quartz veins in the metasedimentary host rocks that constitute the Ptarmigan and Tom deposits. The apatite in this study likely formed coeval with early stages of sulphide precipitation. The apatite age of 2585 ± 15 Ma is consistent with the intrusions of the 2605 and 2590 Ma two-mica granites of the Prosperous Suite. The near-concordant [superscript 204]Pb-corrected data of the LCT pegmatite hosted apatite reveals two clusters of ages. An older population with an intercept age (N = 4) of 2581 ± 15 Ma, and a younger population with an intercept age (N = 3) of 2519 ± 12 Ma . Furthermore, plotting a regression through all near – concordant data for the pegmatite hosted apatite hints that metamorpic resetting occured around ~2200 Ma. The distribution and abundance of major, minor, and trace elements from in-situ recovered apatite were studied to characterize the nature of mineralizing fluids. Most apatite from mineralized and non-mineralized veins show different Mn, Sr, and Pb contents, as well as chondrite-normalized rare-earth element (REE) and Y abundance patterns. REEs display five unique chondrite-normalized patterns: (1) negative sloped pattern with slight negative Eu anomaly, (2) a flat pattern with a positive Eu anomaly, (3) a positive slope with a negative Eu anomaly, (iv) light rare earth element (LREE) depleted pattern with positive Eu anomaly, and (v) bell-shaped pattern with a negative Eu anomaly. The REE patterns likely reflect both the source of the auriferous hydrothermal fluids and, perhaps, co-precipitating mineral phases. Apatite from the Ptarmigan vein occurs with both: (1) a flat pattern with a positive Eu anomaly and (2) bell-shaped pattern with a negative Eu anomaly. The bell-shaped and flat patterns typify orogenic gold deposits. Vein-hosted apatite commonly displays compositional zoning with a characteristic yellow cathodoluminescence (CL) emission spectra with darker cores and brighter rims. The cores have lower REE, whereas the rims are notably REE higher. It is thought that the darker cores in CL images reflect a transition from an early low REE hydrothermal fluid to one enriched in REE. Lastly, this study breaks ground for conducting a more robust study to classify the trace-element composition of apatite in gold deposits worldwide.
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    Controls on mineralization of the Naartok East gold deposit, Hope Bay volcanic belt, Nunavut
    (University of New Brunswick, 2008) Bernard, Justin; Lentz, David
    The Hope Bay volcanic belt (HBVB), Nunavut, extends about 80 kms long and up to 20 kms wide, within the Bathurst Block of the Archean Slave Province. The HBVB consists mainly of mafic metavolcanic rocks with lesser felsic metavolcanic rocks, with local metasedimentary rocks, and is bounded by Archean granite and gneisses. Three gold deposits are recognized in the belt; these include the northern Doris deposit, the Madrid group of deposits 6 kms to the south, and the southern-most Boston deposit. The Madrid deposits consist of the Naartok East, Naartok West, Rand, and, Suluk deposits, where gold is commonly hosted within Mg-rich basaltic rocks and controlled by complex brittle-ductile deformation zones and splays preferentially developed along the interface between volcanic-sediment horizons. The Naartok East deposit is located wit11in a faulted/sheared hangingwall succession of moderately west dipping, coalesced variolitic pillowed flows that have a Mg-tholeiite composition. The stratigraphic footwall consists of Fe-Ti-tholeiites, which form pillowed to massive flows and flow breccias, with associated interflow sediments. In the hanging wall rocks gold mineralization is spatially associated with zones consisting of with multiphase brecciation, quartz-carbonate stockwork, and pervasive silicification within a broader sericite-albite-ferroandolomite alteration halo; these volcanic rocks have been preferentially altered and sulfidized, indicating that stratigraphy has an important control on the distribution of mineralization. At Naartok East, proximal silicate, carbonate, and sulfide assemblages from the goldbearing hydrothennal breccias and stockwork quartz-carbonate vein systems include; ferroan dolomite, sericite, albite, quartz, chlorite, pyrite, and rntile, +/- chalcopyrite, +/- arsenopyrite, +/Co-rich gersdorffite +/- sphalerite, and+/- electrum. Alteration and sulfide assemblages intermediate to proximal and distal zones include; ferroan dolomite with variations in Fe content (7 .69 to 13 .3 wt. % FeO), chlorite, sericite, muscovite, quartz, albite, pyrite and rutile, +/fuchsite, +/- apatite, +/- chalcopyrite, and +/- monazite. Distal alteration and sulfide assemblages include; chlorite, calcite, ferroan dolomite, quartz, and albite, +/- pyrite, +/- biotite, +/- ilmenite, +/- titanite, and +/ - apatite. Gold-bearing pyrite consistently exhibits strong As zonation with an As-poor core (0 to 0.17 wt.% As) surrounded by an As-rich rim (0.13 to 3.84 wt.% As) and an As-poor outer rim (0.2 to 1.1 wt.% As) containing Au. Electrum, less than 23 μm in diameter, are found in proximal assemblage occurs as rounded to elongated inclusions within growth zones or along grain boundaries and fractures within euhedral to subhedral pyrite; it exhibits notable enrichments in Ag (0.84 to 12.65 wt.% Ag) and Cu (0 to 0.89 wt.% Cu).
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    Distribution, form, and origin of gold and silver related to the Boomerang and Domino volcanogenic massive sulfide deposits, Tulks Belt, Central Newfoundland
    (University of New Brunswick, 2007) Page, Angela M.; Lentz, David
    The Boomerang and Domino volcanogenic massive sulfide (VMS) deposits are hosted within felsic pyroclastic rocks of the Victoria Lake Group located in central Newfoundland's Tulks Belt. The Tulks Belt is a Late Cambrian to Middle Ordovician bimodal volcanic arc and back-arc basin assemblage. Numerous other prospective VMS deposits occur in this belt, e.g., Tulks Hill, Tulks East, Bobby's Pond, Daniel's Pond, Jack's Pond, and Curve Pond. Indicated mineral resources for the Boomerang deposit were recently calculated to be 1.36 million tonnes grading 7.09% Zn, 3.00% Pb, 0.51 % Cu, 110.4 g/t Ag, and 1.66 g/t Au at a cut-off grade of 1 % with similar inferred grades calculated for the nearby Domino deposit, and other deposits with this belt. The Boomerang and Domino massive sulfides commonly occur as lenses hosted within fine to sandy ash tufts of dacitic composition with rare lapilli clasts and intervals of graphitic argillite in the hangingwall. In hand sample, sulfide banding is evident as thin layers rich in sphalerite ranging from nearly massive units to laminated fine-grained sphalerite and galena in association with pyrite, locally with irregular-shaped chalcopyrite forming pressure shadows, up to 5cm in size. In general, the sulfide assemblage consists of intergrown equigranular, subhedral sphalerite, galena, and pyrite with lesser amounts of chalcopyrite, tetrahedrite, and arsenopyrite. Pyrite constitutes over 40% of the total sulfide content at the Boomerang and Domino deposit as primary fine grained, euhedral porphyroblasts within the sulfide assemblage, but is also brecciated to form angular to subangular porphyroclasts. Generally, coarse-grained pyrite and arsenopyrite are intergrown, reflecting recrystallization as a result of regional deformation and possible metasomatically enhanced growth. Late tetrahedrite commonly occurs as interlocking grains, inclusions, and along grain boundaries of the other sulfides. SEM-EDS reveals Ag as a solid solution component within tetrahedrite (up to 16.9 wt. %) and minimal Ag within galena (0.3 wt. %). Multi-element ICP-ES analysis of precious metal-enriched massive sulfides (n= 156) from the Boomerang deposit show positive Spearman Rank correlations between Au and Ag (respectively) with As (r' = 0.91 & r' = 0.81 ), Cd (r' = 0.53 & r' = 0.73), Cu (r' = 0.66 & r' = 0.82), Fe (r' = 0.57 & r' = 0.45), Hg (r' = 0.70 & r' = 0.73), Pb (r' = 0.79 & r' = 0.96), Sb (r' = 0.84 & r' = 0.84), and Zn (r' = 0.59 & r' = 0.79); Au and Ag are also strongly correlated (r' = 0.86). Laser ablation ICP-MS results from selected samples (n = 8) reveal elemental abundance variations from core to rim, complimenting earlier EPMA results. Arsenopyrite rims are enriched in precious metals, averaging 228 ppm Au and 25 ppm Ag with Co richer cores. Precious metal enrichment is evident in the cores of pyrite porphyroclasts, averaging 13 ppm Au and 382 ppm Ag with Co, Ni, and Hg concentrated in the rims. These precious metal and whole-rock element associations reflect a cryptic mineralogic relationship throughout this deposit, i.e., Au is associated with arsenian phases and Ag is associated with tetrahedrite- and galena-rich assemblages
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    Evolution and mineralization of the Moose II Lithium-Tantalum Pegmatite Deposit, Northwest Territories, Canada
    (University of New Brunswick, 2013) Anderson, Melissa O.; Lentz, David; Mcfarlane, Chris R.M.
    The Moose II rare-metal granitic pegmatite is located approximately 115 km east of Yellowknife, NWT, on the north shore of Great Slave Lake. The irregularly zoned dike is -430 m long by 61 m wide, and is discordantly hosted within polydeformed metaturbidites of the Neoarchean Yellowknife Supergroup. This deposit was mined for both lithium and tantalum (1946-1954). The pegmatite formed ca. 2652 Ma (U-Pb columbite ), which corresponds to a late magmatic period following a phase of extensive plutonism in the Slave Province. The size and orientation of the pegmatite suggest that it was emplaced into a dilatant zone along a north-trending shear zone. The dike displays extreme fractionation, manifested by the irregular spatial zonation of mineral assemblages, rare-metal enrichment, and the very high degree of chemical evolution. Mineralogical zones include: a narrow border zone, a fine-grained wall zone, several megacrystic intermediate zones, massive quartz and amblygonitemontebrasite core zones, saccharoidal ( aplitic) al bite zones, and muscovite-rich replacement zones. The degree of chemical evolution of the dike suggests that the pegmatite melt was injected a considerable distance from the progenitor pluton. Detailed internal fractionation trends show progressive evolution from the margins of the pegmatite inwards, and from the south section of the pegmatite towards the north. The economically important minerals present include: amblygonite-montebrasite (Li), spodumene (Li), and columbite-group minerals (Nb-Ta). Processes of niobiumtantalum mineralization are primarily magmatic, with enrichment during magmaticmetasomatism, and minor remobilization during hydrothermal metasomatism.
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    Geochronologic, petrographic, geochemical, and isotopic constraints on the origin of the uraniferous Lac Turgeon Intrusive Complex, Quebec
    (University of New Brunswick, 2014) Beal, Kristy-Lee; Lentz, David; McFarlane, Chris R.M.
    The Lac Turgeon Intrusive Complex (LTIC), along the north shore of the St. Lawrence Seaway in the Grenville Province of Quebec, is host to pegmatite-related uranium mineralization. The main zone has an inferred resource of 81.5 million tons U₃O₈, averaging 0.013% U₃O₈; isolated occurrences, including the Grandroy Zone, have revealed 20 m of 0.174% U₃O₈ in channel sampling and up to 0.213 % U₃O₈ over 5.4 m and 0.089 % U₃O₈ over 10.5 m in drill holes completed in 2009. The intrusion’s main lithologies include granite, pink pegmatite, and white pegmatite that contain biotite, muscovite, zircon, ilmenite, hematite, and magnetite with minor apatite, uranothorite, uraninite, monazite, and xenotime as accessory minerals. Previous mineralogical studies have also noted the presence of pyrochlore, churchite (YPO₄*2H₂O), zoned samarskite, allanite, titanite, bastnaesite, and titanobetafite. The texturally diverse complex has irregular and sharp contacts, highly radioactive late-stage felsic intrusives, local magmatic layering, and breccias. Mineral geochemistry and textures provide evidence of crystallization depths > 4-5 km in a fluid-rich environment and mineral saturation temperatures (monazite, zircon, and apatite) average between 686-894°C. The samples at the LTIC came from the same source with the granite less fractionated than the pegmatite phases (white pegmatite commonly more fractionated than the pink pegmatite) based on the fractionation factors of the large ion lithophile and high field strength elements. The granite and white pegmatite phases towards the outer rim of the complex reveal ages (U-Pb Monazite) of 969 Ma (±7Ma and ±6 Ma, respectively); a Double S Zone granite phase towards the center of the intrusion revealed a concordant age of 941 ± 2.7 Ma (U-Pb Monazite, Xenotime) confirming there are several fractionated intrusive phases present at the LTIC. The dates indicate the LTIC is a post-orogenic complex that crystallized at the current level of emplacement towards the end of the Rigolet orogenic phase but outside the area of penetrative Rigolet metamorphism. Geochemical evidence identify that the LTIC is a peraluminous granite-pegmatite intrusion with a complex mixture of previously melted, lower crustal and more juvenile crustal sources giving a crustal A-type (higher Ga, Nb and lower Ba) to S-type (high Rb, Al) affinity. Similar to other uranium deposits including the Limousin pluton in the French Massif Central, the complex increases in peraluminosity with a slight decrease in fractionation indicative of an L-type granite. L-type granites are the result of low degrees of partial melting of a Proterozoic, metasediment source (high ¹⁸O signature) that contains elevated uranium content. Batch-type melting would have commenced by adiabatic melting during uplift related to the orogenic collapse and reworking of normal-sense shear zones following the completion of the Ottawan orogenic phase of the Grenville Orogen. The U and Th values are highly variable (<2-4485 ppm and 0.7-620 ppm, respectively) with U/Th ratios ranging between 0.28 and 25. The average U/Th for the LTIC is 2.3 (+4.0/-1.5; based on log transform data). In most samples, uraninite is accompanied by increased accessory mineral content explaining the close relationship of uranium with La, Ce, Zr, and Y. The main zones associated with highly uraniferous phases, including the Double S, MA, and MB-zones, have a close association with hybridization that would have occurred during magma ascent or in the magma reservoir prior to ascent, as measured by higher CaO + MgO + FeOt. Hybridization is believed to be the main control for concentrated uranium mineralization for other post-orogenic Grenvillian pegmatites. Fractional crystallization is still a factor related to mineralization elsewhere in the intrusive complex including the J- and Lac Turgeon zones. The Grandroy Zone reveals evidence that albitization or sodium metasomatism (higher Na₂O and lower SiO₂ and K₂O and textural evidence) could play a role in uranium mineralization at that location.
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    Geology and geochemistry of sedimentary ferromanganese ore deposits, Woodstock, New Brunswick, Canada
    (University of New Brunswick, 2012) Way, Bryan Curtis; Lentz, David; Keighley, David
    The Early-Silurian Woodstock Fe-Mn Deposits are a series of six, northeast-trending, low grade manganiferous-iron deposits in western New Brunswick that collectively represent the largest Mn resource in North America (194,000,000 tonnes; 13% Fe and 9% Mn). Recent expansion of Route 95 has allowed a more detailed local stratigraphy, mineralogy, and geochemistry of the Fe-Mn deposits within the context of the regional stratigraphy to ascertain the genesis of these deposits. Geological mapping during the field seasons of 2008 and 2009 has revealed six Lithofacies Associations (O, I, II, III, IV, V) within the area, that, generally, are lying conformably on top of each other. However complications due to folding and interbedding have resulting in juxtaposition of the lithofacies associations so they are not always in stratigraphic order. These lithofacies associations are composed of a turbidite-rich section of blue grey calcareous sandstone (O) overlain by black pyritic mudstone (I), associated mineralized and nonmineralized green (II) and red siltstone (III), and laminated to massive grey green calcareous sandstone (IV and V). Na/Mg ratios, chondrite-normalized REE patterns, and mineralogical evidence of rapid changes in ocean redox conditions suggest the Fe-Mn mineralized lithofacies were formed in the offshore zone of a continental shelf on a stable cratonic margin. Al-Fe-Mn ternary and SiO[subscript 2]/Al[subscript 2]O[subscript 3] binary plots developed from archived drill core data indicate the Fe-Mn mineralization was initially derived from hydrogenous-detrital sources without any indication of a hydrothermal input as a source of Fe and Mn.
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    Geology, petrology, and geochemistry of andesite flows and associated intrusive porphyry in the Spences Bridge Belt, Lytton, British Columbia: Implications for precious metal exploration
    (University of New Brunswick, 2008) MacMillan, Mary Theresa; Lentz, David
    The Spences Bridge Gold Belt is host to the Skoonka Creek precious-metal mineral deposit in Lytton. British Columbia. The main mineralization is epithermal style Au-Ag, which is hosted in Cretaceous subaerial malfic to intermediate volcanic rocks. This precious metal mineralization is hosted in the Pimanius Formation in multi-stage massive veins, and stock work vein lets with associated breccia zones with siIica, albite, and argillic alteration round throughout the Skoonka Creek property. The mineralization on the property is highlighted at the J.J showing where Au values grade as high as 20.2 g/t over 12.8 m and 28.6 g/r O\U 3.3 1m. Two outcrops and the Discovery showing diamond drill holes show a geological contact relationship between an amygdaloidal microcrystalline basaltic andesite and an intrusive hornblende porphyry. There is no petrogenetic relationship between the two units; I) because of the distinctly different nature of plagioclase zoning evident; the basaltic andesite has reverse zoning with a sodic interior and a calcic rim, whereas the hornblende porphyry displays normal zoning with a calcic interior and a sodic rim, 2 ) both units have similar groundmass mineralogy containing plagioclase, quartz, calcite and biotite but differ with the presence of clinopyroxene (7%) in the microcrystalline to cryptocrystalline basaltic andesite, and amphibole (Y%), and potassium feldspar (5%) in the microcrystalline hornblende porphyry. Evidence that the extrusive basaltic andesite is older than the hornblende porphyry is supported by the observation of a quenched contact of hornblende porphyry (An content 43-59 wt.%) next to the basaltic andesite (An content 45-56 wt.%). The intrusive hornblende porphyry may be directly genetically associated with the epithermal precious-metal forming hydrothermal system.
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    Influence of mineralogical composition and texture on induced polarization effects in gold-bearing rocks from the Hebert-Brent Showing, Yellowknife Greenstone Belt, Northwest Territories
    (University of New Brunswick, 2017) Richardson, Mark; Butler, Karl; Lentz, David
    In June 2015, geological mapping discovered significant concentrations of gold in the Hebert-Brent (HB) Showing situated within an 11 m-wide highly sulphidized sericite-ankerite schist shear zone, hosted in a 10-15 m-wide, quartz-feldspar porphyry. The HB gold showing is located within the Barney Deformation Corridor of the Yellowknife Greenstone Belt (YGB), Northwest Territories. On July 29th, 2016, two 400 m long IP/resistivity surveys, with 5/10 m electrode spacing were acquired using a multi-gradient array. The survey identified zones of high IP response (chargeability) where expected, in areas of known disseminated sulphide mineralization. In addition, the IP survey exposed a previously undiscovered anomalous IP source. In this study, a prototype two electrode laboratory apparatus was used to investigate factors influencing electrical resistivity and IP effects in selected mineralized and non-mineralized rocks from the survey area. The study revealed information that may be utilized in future geophysical exploration in this area. It was determined that samples from Hebert-Brent are generally less resistive than non-mineralized rocks within this area. However, as a consequence of preferential alignment of silicate layers with foliation, anisotropic effects should be anticipated in this area. The IP response of the mineralized samples was in general greater in magnitude than the non-mineralized samples. It was also determined that there are some IP effects related to highly resistive, non-mineralized rocks in this area. These anomalous IP effects are likely a result of some uncertainty in the measurement apparatus. Normalizing the PFE IP effect by resistivity served to make the mineralized samples standout from highly resistive ones that also exhibited elevated IP responses. Comparison of mineralized and non-mineralized spectral curves were shown to be characteristically different. In addition, the peak phase angle between 0.1 - 10 Hz was found to correlate with increased percent frequency effect. It is recommended that surveys which sense the conductivity of an ore body should be used to aid in delineating massive and electrically conductive parts of a sulphide body. In addition, it is recommended that future IP and resistivity surveys in the area use a measurement of IP effect normalized by resistivity (such as the Metal Factor; MF) to highlight anomalous bodies that are prospective for elevated sulphide (and associated gold) content. Based on the findings in this study, spectral induced polarization (SIP) surveying may aid in identifying mineralized rocks in HB, as the phase maximum (between 0.1 and 10 Hz) is in general greater than that of the non-mineralized country rocks. Testing of the two electrode apparatus was shown to provide accurate and repeatable measurements on both the mineralized and non-mineralized rocks used in this study. However, more testing of the measurement apparatus is recommended to assess its reliability for very highly resistive samples.
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    Influence of mineralogical composition and texture on induced polarization effects in gold-bearing rocks from the Hebert-Brent Showing, Yellowknife Greenstone Belt, Northwest Territories
    (University of New Brunswick, 2017) Richardson, Mark; Butler, Karl; Lentz, David
    In June 2015, geological mapping discovered significant concentrations of gold in the Hebert-Brent (HB) Showing situated within an 11 m-wide highly sulphidized sericite-ankerite schist shear zone, hosted in a 10-15 m-wide, quartz-feldspar porphyry. The HB gold showing is located within the Barney Deformation Corridor of the Yellowknife Greenstone Belt (YGB), Northwest Territories. On July 29th, 2016, two 400 m long IP/resistivity surveys, with 5/10 m electrode spacing were acquired using a multi-gradient array. The survey identified zones of high IP response (chargeability) where expected, in areas of known disseminated sulphide mineralization. In addition, the IP survey exposed a previously undiscovered anomalous IP source. In this study, a prototype two electrode laboratory apparatus was used to investigate factors influencing electrical resistivity and IP effects in selected mineralized and non-mineralized rocks from the survey area. The study revealed information that may be utilized in future geophysical exploration in this area. It was determined that samples from Hebert-Brent are generally less resistive than non-mineralized rocks within this area. However, as a consequence of preferential alignment of silicate layers with foliation, anisotropic effects should be anticipated in this area. The IP response of the mineralized samples was in general greater in magnitude than the non-mineralized samples. It was also determined that there are some IP effects related to highly resistive, non-mineralized rocks in this area. These anomalous IP effects are likely a result of some uncertainty in the measurement apparatus. Normalizing the PFE IP effect by resistivity served to make the mineralized samples standout from highly resistive ones that also exhibited elevated IP responses. Comparison of mineralized and non-mineralized spectral curves were shown to be characteristically different. In addition, the peak phase angle between 0.1 - 10 Hz was found to correlate with increased percent frequency effect. It is recommended that surveys which sense the conductivity of an ore body should be used to aid in delineating massive and electrically conductive parts of a sulphide body. In addition, it is recommended that future IP and resistivity surveys in the area use a measurement of IP effect normalized by resistivity (such as the Metal Factor; MF) to highlight anomalous bodies that are prospective for elevated sulphide (and associated gold) content. Based on the findings in this study, spectral induced polarization (SIP) surveying may aid in identifying mineralized rocks in HB, as the phase maximum (between 0.1 and 10 Hz) is in general greater than that of the non-mineralized country rocks. Testing of the two electrode apparatus was shown to provide accurate and repeatable measurements on both the mineralized and non-mineralized rocks used in this study. However, more testing of the measurement apparatus is recommended to assess its reliability for very highly resistive samples.
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    Lithogeochemical analysis of the Heath Steele E zone volcanogenic massive sulphide deposit, Bathurst Mining Camp, New Brunswick
    (University of New Brunswick, 2020) Jimenez-Gonzalez, Josue; Lentz, David
    The Heath Steele E zone Zn-Pb-Cu-Ag volcanogenic massive sulphide deposit lies in the Heath Steele belt in the Bathurst Mining Camp, northeast New Brunswick. The Heath Steele E zone deposit is hosted mainly by felsic volcanic and related volcano-sedimentary rocks of the Nepisiguit Falls Formation (Tetagouche Group), which were deposited in the Tetagouche-Exploits back-arc basin in the Middle Ordovician. The host sequence is affected by locally intense, deposit-related hydrothermal alteration, and polyphase deformation and mid- to upper-greenschist grade regional metamorphism related to inclusion of the host sequence in the Brunswick Subduction Complex. Numerous geological events have affected the E zone deposit and the host rocks, which have complicated a proper stratigraphic interpretation in the area. Furthermore, the similarity among the various volcano-sedimentary units precludes confident unit correlation among adjacent drill cores on the basis of macro-scale observations alone. For this reason, chemostratigraphy is employed to discriminate among the various volcano-sedimentary units, and for assessment of deposit related hydrothermal alteration using a portable X-ray fluorescence spectrometry (pXRF) as the main tool. The pXRF is a useful analytical tool for acquiring high-quality results in real-time with a level of resolution that surpasses most other techniques, thereby providing at least 30 potential variables for use in chemostratigraphic characterization and correlation. The pXRF analysis of eight drill cores of the study area facilitated: 1) the construction of discrimination diagrams that show that the host felsic volcanic rocks in the E zone deposit are rhyodacite/dacite and rhyolite with a tholeiitic magmatic affinity; consistent with an intracontinental back-arc environment, 2) the identification of geochemically distinct rock units in this case, a clear difference between structural hanging wall and footwall was recognized, and 3) qualitative characterization of hydrothermal alteration in the footwall (mainly chlorite-carbonate and chlorite-pyrite-sericite assemblage) and the hanging wall (K-feldspar-sericite and sericite-chlorite-pyrite assemblage).
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    Mineralogical and geochemical examination of the gold mineralization within the silica zone and open pit at Cape Spencer, New Brunswick
    (University of New Brunswick, 2005) Richard, Rob; Lentz, David
    The previously mined open pit at Cape Spencer (NB) is being re-examined as a high-grade, vein-related gold deposit instead of the previously reported low-grade bulk gold deposit. The open pit was mined from 1986-1988, which had proven reserves of 606,790 short tons (550,470 tonnes) grading 2.34 grams per ton (2.12 g/t). The silica zone located 600m northwest of the open pit was explored in 1977 as a possible silica quarry for the purpose of glass making, but the Fe content was too high. Thus far neither research nor exploration has attempted to establish the possible relationship between the silica zone and quartz veins and associated alteration found within the open pit. Detailed geological and structural mapping accompanied by recent 3-D Induced Polarization geophysics of the silica zone and the open pit was carried out to define the trends of the quartz veins, associated gold and sulphide mineralization, and gold depositional controls. Twenty channel samples were taken for petrographic and geochemical analysis, and assaying of selected samples. The multi-element geochemical analyses were done using a multiacid 32 element Inductively Coupled Plasma-Emission Spectroscopy and a 30 element Instrumental Neutron Activation Analysis. A Sulphur bioLeco analysis was also completed to determine the percent sulphur. The quartz veins at the open pit has gold values of up to 100.5 g/t, with the adjacent wall rock containing up to 51.5 g/t gold. The open pit also showed low arsenic values ( <5 ppm) in comparison to the silica zone where gold values ranged from less than 5 ppb to 120 ppb, with arsenic ranging from 3 to 228 ppm, Cu to 1004 ppm, and Mo to 150 ppm. The gold-bearing quartz veins are seen crosscutting the Millican Lake granites (623 Ma), Cape Spencer Formation sediments (post 623 Ma), and Lancaster Formation (310 Ma) suggesting that they were deposited syn- to post-Carboniferious. The silica zone is approximately 200m in length, 50m in width, and greater than 20m in depth. Within this silica body there are at least five different locations that are enriched in sulphides. There has been no age dating done in silica zone, but it is assumed that it is close to the age of the illitic alteration (277 Ma), which is based on previous 40Ar/39Ar ages of illite in altered Precambrian rocks. Previous work, believed that the D2 structures host the gold ores, but recent sampling suggests much later stage deposition of gold.
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    Nomenclature, mineralogy, and geochemistry of a plagioclase kersantite lamprophyre suite, South Eastern Canadian Cordillera; British Columbia.
    (University of New Brunswick, 2002) Adams, Matthew G. L.; Lentz, David
    The newly named Minerva kersantite lamprophyre dikes of the Monashee complex represent the final igneous event in the area. The dikes were emplaced in a north-trending subvertical orientation, where they bisect the acute angle of two sets of regional extensional fractures (D5). This magmatic episode is coincident with Eocene extension (~50.0 Ma), based on the flat 40Ar/39Ar step-heating plateau of contact metamorphic muscovite on the margin of a Minerva dike. Some of the dikes can be delineated with airborne magnetic data and can be correlated with major north-trending extensional faults. These weakly altered mafic dikes have a panidiomorphic texture with phenocrysts (0.5 - 2.0 mm) of phlogopite, augite, amphibole (pseudomorphed by clays), labradorite and both primary and secondary carbonates set in a similar tine-grained groundmass. This is generally consistent with their classification as plagioclase-bearing kersantite lamprophyre. They are weakly silica-undersaturated, ultrapotassic (2.8 wt. % K2O: 7.7 wt.% MgO), with very high large-ion-lithophile element contents(-~300 times primitive mantle) and low highfield- strength element contents similar to E-MORB, as well as a prominent negative Nb anomaly: these geochemical attributes are consistent with the Three Valley Suite being lamprophyres of calc-alkaline affinity that are related to subduction zone magmatism. These dikes are geochemically similar to mafic rocks of the Roman igneous province. On the basis of this relation, it is inferred that subduction of the Juan de Fuca Plate influenced subcrustal mantle wedge metasomatism in the region. Later Eocene extension resulted in decompression melting of this metasomatised mantle, and a short episode of ‘melt ponding’ below the continental lithosphere. Continuing extension enabled the emplacement of this suite of kersantite dikes.
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    Origin of gold bearing hematitc breccias at the Lake George Antimony Mine, Western New Brunswick
    (University of New Brunswick, 2004) Whaley, Alexander Geoffrey; Lentz, David
    The Lake George Antimony deposit is located in southwestern New Brunswick. The main Au-Sb mineralization is hosted in stock-work veining emplaced into the Kingsclear Group metasedimentary rocks. These veins are believed to be spatially and temporally related to a granodiorite intrusion. To the east, northeast and southeast lies an hematite breccia and alteration zone. Previous studies indicate that this zone is coeval with but not related to, the Au-Sb mineralization event. This study proposes that this zone was formed from Carboniferous faulting, at epithermal to surface depths. The ---.. breccias are divided into three groups, hematite, carbonate-hematite and carbonate-quartz types. Hematite breccias are defined by a dominantly hematite matrix with angular to chemically corroded clasts. Carbonate-hematite type breccias consisting of a wide variety of textures from jigsaw patterns to rotated, rounded, clast supported and collapse. Carbonate-quartz type breccias have a varying abundances of carbonate and quartz, with highly chemically altered clasts. All three breccias are produced from localized faulting, indicating tectonic comminution, fluid assisted, and corrosive wear mechanisms. Carbonate-hematite breccias, also have wear abrasion, collapse, and impact mechanisms, which are produced by stronger and more continuous faulting. Gold, Sb, and other metals are enriched in carbonate-hematite and carbonate-quartz breccia types. This enrichment is likely related to mobilized Sb-Au from the Sb-Au-quartz carbonate veins at the Lake George deposit. Gold appears to be correlated with arsenopyrite or pyrite abundance and deposited on surfaces of iron oxides, iron hydoxides, and Mn oxides.These minerals may have been produced from near surface meteoric water circulation reacted with weathered product.
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    Petrogenesis of Au-BI-As-Cu, Cu-Mo± W, and base-metal-AU-AG mineral occurrences, in the Mountain Freegold Region (Dawson Range), Yukon, Canada
    (University of New Brunswick, 2012) Bineli Betsi, Thierry; Lentz, David
    In order to gaining a better understanding of the evolution of the magmatic systems, as well as processes that combined to form ore minerals across the NFR Freegold Mountain gold-copper project, field observations were combined with reflected and transmitted light microscopy, ChromaSEM-CL and EPMA, whole rock geochemistry, isotope (0, H, C, S, Sr, Nd, and Pb) analyses, and geochronology (U-Pb, Re-Os, and Ar/Ar) and thermochronology (U-Th-He) investigations. Magmatic bodies were emplaced during two protracted episodes, the first from 109.6 to ⁓ 98 Ma and the second between 75.2 and 68.4 Ma. Magma was derived from different sources, as testified by: (i) variations in XMg values of biotite and hornblende (< 0.50-0.65); (ii) the T Al content in least-altered biotite (2.6-2.9); (iii) K values that range from <1 X 10-3 to 33.27 10-3 SI); (iv) least-altered igneous rock O isotope compositions (6.2-10.1 ‰), and; (v) variation in the depth of magma emplacement ( ⁓ 2-7 .1 kb). Magmas differentiated by magma mixing (as indicated by the presence of reversed zoned plagioclase and increase of temperature of crystallization of quartz from the core to the rims) and fractional crystallization (as supported by the presence of normally- zoned plagioclase with Ca-rich core and Na-rich outer rims), thus leading to igneous suites of mostly high-K calcalkaline, spanning from dioritic to granitic compositions, and exhibiting adakitic affinities (depletion in HREE + Y relative to LREE, and high Sr/Y and La/Yb ratios). These magmatic-hydrothermal systems cooled fast, as indicated by the similarity (within analytical error) between zircon U-Pb and zircon (U-Th/He) data, and were slowly exhumed (0.035-0.045 mm/year), favouring the formation and preservation of supergene mineralization, such as that found north of the Mountain Freegold area. Mineral occurrences are of different metal suite of interest, and corresponding style of mineralization (e.g., Ttinta Au-Ag-base-metal-bearing quartz veins, Stoddart Porphyry Cu-Mo± W prospect, and Nucleus Au-Bi-Cu-As deposit). Mineralization within the NFR Freegold Mountain gold-copper project took place over a period of at least 115 Ma and Mineralized systems resulted from the overlapping of multiple volcanoplutonic processes that influenced the Mountain Freegold area, as indicated by 76-78 Ma molybdenite-bearing veins from Nucleus and Revenue, the182 Ma skarn at Nucleus, as well as the 76 Ma Tinta deposit. The 2 Ma difference between the juxtaposed Nucleus and the Revenue mineral occurrences favours not only a long-lived hydrothermal system, but also an evolution from the porphyry to the epithermal environments. Lead and by association all metals, derived from associated magmatic bodies. Sulfur is also of magmatic origin and δ34 S values range from 0.2 to 2.5‰ at Nucleus-Revenue, from -1.4 to 3 .6‰ at Tinta, and from 1.8 to 2.6‰ at Stoddart. The input of meteoric water in the mineralizing process(es) was also notable, as suggested from altered igneous rocks 0 isotope compositions (5.6-5.2‰) and magnetite and quartz O isotope compositions (-6.3‰ and 1.5‰, respectively), as well as sulfate minerals of supergene origin (3.7- 4.3‰ δ34S).
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    Petrogenesis of Cu-Ag skarn mineralization in the Mackenzie Gulch area, Northern New Brunswick, Canada
    (University of New Brunswick, 2017) Massawe, Ronald, Joseph Raphael; Lentz, David
    Northern New Brunswick and the adjacent Gaspé Peninsula of Québec host numerous contact metasomatic Cu–Au skarn deposits commonly in proximity to small Siluro–Devonian intermediate to felsic stocks and/or dikes. In this region, specifically northern New Brunswick, skarn occurrences are principally hosted within the late Ordovician to early Silurian Matapédia Group, which consists of thin-bedded, dark grey argillaceous limestone and calcareous siltstone. This thesis investigated Cu–Ag skarn occurrences at the McKenzie Gulch (MG) area in northern New Brunswick by integrating field observations, petrographic, petrochemical, electron-probe microanalysis (EPMA), laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), fluid inclusions, geochronology (U–Pb zircon and titanite), stable S isotopes, and radiogenic Pb isotopes with the main objective being to understand the petrogenesis of skarn occurrences and establish their relationship to the intrusive rocks. This investigation involved the evaluation of porphyry dikes that are spatially and temporally related to these skarn systems by examining potential parameters that are known to be associated with the genesis of intrusion-related deposits. These magmatic aspects include oxidation state of the magma, water content, P–T conditions, in addition to magma source characteristics, formation, petrochemistry, evolution and emplacement conditions. As a result, two suites of porphyry dikes were recognized in the MG area during this evaluation: (1) plagioclase–hornblende (P–H), and (2) quartz–plagioclase (Q–P) porphyry suites. These Middle Devonian (386.0 ± 2.3 Ma) intrusive rocks are mildly oxidized, I-type granitoids with calc-alkaline affinity that range in composition from granodioritic to tonalitic (with few granitic), based on their petrochemical features. These dikes also exhibit adakite characteristics, a geochemical feature that has been widely associated with many porphyry Cu (and skarn) systems. Petrochemical features and cathodoluminescence (CL) characteristics of quartz crystals from these suites of dikes suggest that two magma chambers were responsible for evolution of these intrusive rocks. The three types of quartz crystals with contrasting CL features have been attributed to at least three different environments of crystallization: 1) a higher temperature environment (up to 915 oC) as recorded by cores of phenocrysts with high Ti concentrations (up to 200 ppm); 2) a moderate to high temperature (≥ 700 ≤ 750 oC) environment as recorded by the transition zones within quartz phenocrysts and microphenocrysts; and 3) a low temperature environment in which groundmass quartz quench crystallized during hypabyssal dike emplacement. Studies of the mineral chemistry showed that composition of calc-silicates (i.e., garnets and pyroxene) have intimate relationship with the dominant metal of the mineralized skarns. These calc-silicate phases plot in their respective compositional fields of Cu-dominated skarns. The investigation conducted on fluid inclusion, geochronology, stable isotope, and mineralization supports field observations, which indicates that skarn formations at the MG area have an association with the intruding porphyry dikes and that this skarn is very similar to and shows no difference with the characteristics of other world-class, intrusion-related skarn systems. Geochronological studies based on U–Pb zircon and hydrothermal titanite indicates a coeval relationship between mineralization and dikes emplacement, suggesting that mineralization in the MG area is short lived or it occurred near the end of magmatic-hydrothermal activity.
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    Petrogenesis of granitoids in the vicinity of the Mactung Tungsten Skarn Deposit, NE Yukon-Northwest Territories: characterization of skarn mineralization and causative plutons through geological, petrochemical, mineralogical, and geochronological analysis
    (University of New Brunswick, 2017) Gebru, Ayalew Legesse; Lentz, David
    Skarn W-(Au-Cu-Bi) deposit at Mactung, Yukon, Canada is situated within the eastern flank of the NW-SE striking poly-deformed Paleozoic Selwyn metasedimentary basin. Two biotite granite stocks occur south and north of the deposit. The northern stock is dominantly porphyritic, cut and rimmed by a more leucocratic medium- to coarse-grained granite. Prominent aplitic dykes outcrop south of the mineralization. Major- and trace-elements strongly discriminate between the various phases of biotite granite and the leucogranite. The biotite granite has an arc-like affinity. The leucogranite is sourced from anatexis of a supracrustal sequence at depth. Tracer Sm-Nd and Rb-Sr isotope systems further indicate the granitoids were sourced from the partial melting of an old continental crust. The δ[superscript 18]O values of Mactung granitoids indicate strong metasedimentary contamination from the source region or during magma ascent. The less evolved biotite granite is directly associated with the W-(Au-Cu-Bi) mineralization, based on field relationships, metallogenic aspects of the intrusion, alteration-mineralization effects, and previously published Re-Os dating of molybdenite and new geochronological data. Multiple dating techniques were used to date various rock types of Mactung, northeast Yukon. Ar-Ar dating reveals the following best ages: 95.6 ± 0.3 to 98.1 ± 2.0 Ma from muscovite grains, and 91.8 ± 0.4 to 95.1 ± 0.8 Ma from biotite grains of porphyritic biotite granite; 93.3 ± 1.2 Ma from biotite grains of coarse-grained leucogranite; 92.9 ± 0.4 and 95.3 ± 0.4 Ma from muscovite grains of medium- to coarse-grained leucocratic granite dyke; 94.0 ± 0.5 Ma from biotite grains of an aplitic dyke; 97.1 ± 1.9 and 96.9 ± 0.6 Ma from biotite grains of biotite hornfels. U-Pb age data for zircon grains were obtained by ID-TIMS analytical techniques for five samples from three rock types of Mactung granitoids: an aplitic dyke south of the Mactung skarn tungsten deposit yields igneous crystallization age of 97.1 ± 0.2 Ma; porphyritic biotite granite from the main phase of the Mactung pluton yielded a crystallization age of 97.6 ± 0.2 and 97 ± 0.1 Ma. A leucocratic granite dyke, a marginal phase in the southeast of the pluton, gives an age of 97.0 ± 0.3 Ma. Combining the Ar-Ar and U-Pb age data, it is proposed that injection of leucogranite magma from 97-92 Ma to have prolonged the thermal regime of the area resulting in overprinting and partial resetting (beyond their blocking temperature) of the Ar-Ar ages. A titanite age from the lower skarn orebody was obtained using laser ablation inductively coupled plasma-mass spectrometry that yielded a less precise [superscript 206]Pb/[superscript 238]U concordia intercept age of 97.1 ± 4.1 Ma that agrees very well with the U-Pb zircon dates (this work) of nearby granite intrusive rocks. Re-Os molybdenite dating of quartz veins, cutting all granitoids, and the lower metasedimentary unit, adjacent the Mactung tungsten skarn yields ages of 97.3 to 106.3 ± 0.4 Ma. Variation of Re-Os age dates, relative to the uniform U-Pb age dates, is likely due to [superscript 187]Os and or [superscript 187]Re heterogeneity in the molybdenite grains. The vein age provides a direct lower timing constraint for granite intrusion and sulphide mineralization events of the area, if the older ages are disqualified. The chemical composition of primary and accessory minerals of Mactung granitoids was determined using Electron Probe Microanalysis (EPMA) and SEM Energy Dispersive Spectroscopy (SEM-EDS). The minerals analysed included biotite, feldspars, muscovite, chlorite, apatite, tourmaline, and monazite. Biotite grains from skarn and hornfels (Unit 3C) were also investigated. Differences in the chemical composition of biotite and feldspar are the most robust means of distinctively characterizing rock types. Aluminium Fe, and Mg are the main distinguishing elements between biotite grains of different lithologies. The Mg, Fe, and Al compositions of biotite from Mactung granitoids and the high Fe and Al contents of tourmaline suggest a peraluminous magma source, derived from the melting of the continental crust, possibly in a collisional tectonic setting. A strongly contaminated and reduced I-type magma is implicated from the log X[subscript F]/X[subscript OH] and log X[subscript Mg]/X[subscript Fe] composition of biotite. Non-mineralizing granites of Mactung (leucogranite and aplitic dykes) have high X[subscript Fe], Al[superscript iv], lower X[subscript Mg], and fO[subscript 2] values relative to the biotite granite and ore zone granites, which are believed to be sources of the skarn tungsten mineralization at Mactung. These latter granitoids are characterized by lower IV(F/Cl) intercept ratios relative to porphyry copper-bearing intrusive systems, and higher IV(F) values relative to porphyry Mo and Sn-W-Be bearing systems. Tungsten mineralization at Mactung is contained in scheelite, associated with or without pyrrhotite, chalcopyrite, and pyrite, in pyrrhotite-pyroxene skarn, (garnet) - pyroxene skarn, and pyroxene-pyrrhotite skarn, with anorthitic plagioclase and quartz. In pyrrhotite skarn, pyrrhotite and chalcopyrite are intimately associated, and their abundance is often indicative of higher grade copper. High Au is directly correlated to Bi. Iron, Ag, Sb, Co, Pb, and Cu are also positively correlated to Au. From SEM and EPMA, Au is associated with native bismuth, Te-bearing bismuth phases as solid solution; native bismuth is the dominant phase. Sphalerite and Aluminum-in-hornblende geobarometry show that skarn formed at 2 kb (200 MPa), which corresponds to a depth of 7-8 km. Mineral assemblages of contact metamorphism in hornfelsic rocks indicate temperatures of 585–635°C for a pressure of 2 kb (200 MPa). The host limestone beds were subjected to about 560–675°C, based on solvus thermometric data obtained from coexisting dolomite and calcite. The temperature of formation of coexisting pyrrhotite and pyrite is about 640oC, which corroborates well with the calcite-dolomite solvus thermometer and contact mineral assemblage in hornfelsic rocks. The oxygen isotope fractionation factor between quartz and scheelite, for samples taken from quartz veins, indicate a corresponding temperature value of 558°C. At this temperature, the early stage pyroxene and scheelite probably crystallized at an oxygen fugacity of 10[superscript -17.5] bars or less. Sulphur isotope analysis of sulphides in the skarn system ranges from 9-19‰ relative to VCDT with an average of 13‰. A mixed source of fluids (magmatic and local sedimentary) is hypothesized for this skarn system.
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    Petrogenesis of the archean Prestige leucogranite and spatially associated LCT pegmatites: insights from whole-rock and muscovite trace element geochemistry and apatite U-Pb geochronology
    (University of New Brunswick, 2018) Palmer, Emily, M; Lentz, David; McFarlane, Chris R.M.
    The Yellowknife pegmatite field is host to LCT-family rare-element pegmatites that are associated with Late Archean granitic magmatism. The Prosperous suite, a large plutonic suite composed of 14 two-mica S-type leucogranites, lies in the southwest quadrant of the pegmatite field. The plutons are spatially associated with the rare element pegmatites. Although the geology in this domain is the most thoroughly documented in the Slave Province, the ages of the major plutonic suites are poorly constrained. The Sparrow Lake pluton of the Prosperous suite is the only pluton to have previously been reliably dated at 2596 ± 2 Ma. The Prestige pluton, the focus of this thesis, has been classified as a member of the Prosperous suite and has previously been studied because of its high Li contents. Apatite U-Pb geochronology of the Prestige pluton yielded a concordant age of 2608 ± 4 Ma, which is interpreted to represent the crystallization age of the pluton. Based on geochemical and geochronological similarities, the Prestige pluton is interpreted to be a part of the Prosperous suite. The difference in age between the Sparrow Lake and Prestige plutons is attributed to different crustal levels of emplacement and, therefore, different cooling histories. Upper intercept and concordia ages for apatite from the intra- and inter-pluton pegmatites associated with the Prestige pluton yielded overlapping ages of 2588 ± 6 Ma and 2593 ± 6 Ma, respectively. The whole-rock geochemistry of the intra- and interpluton pegmatites exhibit similar trace element compositions and enrichment of incompatible elements, with averages of 22 ppm Sn, 9.5 ppm Ta, 19.6 ppm Nb, 21.0 ppm Cs, and 453 ppm Rb. Trace element analyses of muscovite via LA-ICP-MS reveal elevated concentrations of Rb, Cs, and Sn within the granite and pegmatites. In general, the rims of muscovite grains are enriched in Li, Cs, Sn, Nb, and Ta, which is attributed to normal magmatic fractionation processes. The whole-rock and muscovite geochemistry reflect increasing fractionation trends from the intra-pluton to inter-pluton pegmatites, as indicated by decreases in K/Rb, K/Cs, and Sr/Rb ratios. The similarity in age, geochemistry, and geothermometry of the intra- and inter-pluton pegmatites suggests they are comagmatic. Distinct differences in fractionation trends, crystallization ages, and muscovite geochemistry, in addition to a lack of field evidence of gradation, suggests that the Prestige granite is not parental to the spatially associated pegmatites. This study emphasizes the importance of geochronological and geochemical work to determine the petrogenesis of pegmatites to spatially related plutons. The source of the pegmatites in this study is not known. However, it is suggested to be a deep-seated magma chamber that has yet to be identified.
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    Petrogenesis of the low sulfidation gold mineralization in the Williams Brook area, Tobique-Chaleur Zone, New Brunswick
    (University of New Brunswick, 2014) Sanchez Mora, Dennis; Lentz, David; Mcfarlane, Christopher
    Gold mineralization in the Williams Brook area occurs within the Siluro-Devonian bimodal volcano-sedimentary rocks of the Tobique-Chaleur Zone in northern New Brunswick (Wapske Formation). Geotectonic discrimination diagrams show A-type signatures. Such compositions indicate a transpressive tectonic setting and suggest that oblique convergence of Gondwana and Laurentia as the driving force for basin formation and coeval magma generation. Gold occurs in two types of mineralization, which show slightly different Ar-Ar (muscovite) ages: 412 Ma from altered rhyolites and 408 Ma from quartz veins. This younger age is supported by similar U-Pb zircon ages determined from the rhyolite host rocks. A -414 Ma age of muscovite from a foliation fabric suggests that there is a structural control to the gold mineralization. Sphalerite, pyrite, and galena are the main hypogene sulfides associated with the gold mineralization; however, supergene oxyhydroxides such as goethite and hematite are also common. Stable isotopic (0, H, S) and radiogenic Pb evidence suggest fluids and metals are from a magmatic source. Fluid inclusions and stable isotope geothermometers suggest gold deposition was at an approximate temperature of 200°C, which is interpreted to be via mixing with meteoric waters. Evidence from different scales determined in this study support the theory that the study area is part of a low sulfidation epithermal style mineralizing system, thus making the Tobique-Chaleur Zone prospective for this style of mineralization.
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    Petrogenesis of tin-tungsten-molybdenum mineralized intragranitic systems within the highly evolved Mount Douglas polyphase intrusive complex, southwestern New Brunswick, Canada
    (University of New Brunswick, 2018) Mohammadi, Nadia; Lentz, David; McFarlane, Chris R.M.
    The Late Devonian Mount Douglas Granite, located in southwestern New Brunswick, is host to endogranitic, granophile-element Sn-, W-, Mo-, Zn-, Bi-, and U-bearing greisen/sheeted veins. It forms the eastern part of the Late Silurian to Late Devonian Saint George Batholith that was emplaced during the Acadian-Neoacadian orogeny. Three units of the highly evolved post-orogenic peraluminous Mount Douglas Granite (Dmd1, Dmd2, and Dmd3) were formed by progressively higher degrees of fractional crystallization. Investigations of these three phases were carried out using a combination of geological field work (mapping), gamma-ray spectrometry, petrographic and geochemical investigations, EPMA, SEM-EDS imaging, Laser ablation ICP-MS measurements, including U-Pb geochronological and radiogenic and stable isotopic studies, supported by Raman spectroscopy on certain minerals. The granite exhibits a hybrid S-type and A-type signature. Whole-rock δ[superscript 18]O (+6.0 to +7.3‰), high initial [superscript 87]Sr/[superscript 86]Sr (mean = 0.70764), positive [subscript εNd(368 Ma)] (+0.3 to +1.1), and Pb isotopic data indicate its derivation by partial melting of a predominately juvenile subducted Avalonian crustal source that was contaminated by supracrustal rocks. Magmatic biotite geochemistry, combined with whole-rock zircon saturation temperature estimates, suggest oxygen fugacity near Quartz-Magnetite-Fayalite (QFM) conditions for unit Dmd1, whereas units Dmd2 and Dmd3 have lower ƒO[subscript 2] and are more reduced. Mineralized greisen/sheeted veins are associated with highly differentiated medium-grained to porphyritic units, Dmd2 and Dmd3, that are the most prospective units of the pluton in terms of metallic mineral deposits. The most fractionated character of Dmd3 is evident by its highest SiO[subscript 2] content (avg. 76.4 wt.%.), higher contents of LILE (e.g., Li, Rb, Cs), HFS (Ta, Th, U), Y (≤ 138 ppm) and REE, and the most pronounced negative Eu anomalies (avg. Eu/Eu* = 0.08). The degree of fractionation in Dmd3 is also manifested by its lowest K/Rb (70-127), Nb/Ta (average = 4.9), and Zr/Hf (average = 23.5), and highest Rb/Sr ratios (average = 42), and also by geochemical compositions of magmatic biotite, K-feldspar, and monazite. The most important indices of magmatic evolution, K/Rb, K/Cs, Rb/Cs, K/Li, and Nb/Ta ratios of co-existing biotite and K-feldspar, decline with increasing degree of fractionation. The estimated K[subscript Rb] suggests a lower equilibration temperature for Dmd3, consistent with whole-rock zircon and monazite saturation temperatures. LA ICP-MS U-Pb geochronology of 157 in situ monazite grains along with 100 mounted zircon grains yielded a Late-Devonian crystallization age of 368 ± 3 Ma. With respect to timing of associated mineralization, there are at least two stages recognized in this system: (I) magmatic-related mineralization, which is recorded by new mineralization ages obtained on uraninite (366.4 ± 4.3 Ma; 2σ; n = 5) and cassiterite (363 ± 9 Ma; 2σ; n = 38), and (II) post-magmatic mineralization defined by hydrothermal monazite, and yielding a younger mineralization age ranging from 344 to 368 with an average of 357 ±7 Ma. The post-magmatic hydrothermal activity can be associated with the High Heat Production (HHP) nature of this pluton, in which the pluton acts as a ‘heat engine’ producing heat by radioactive decay of U, Th, and K that prolonged the hydrothermal fluid circulation (activity).