The A. M. breccia is part of the Giant Copper property of British Columbia, Canada. It is the only well-defined tourmaline breccia pipe (TBP) in the Canadian Cordillera. The A. M. breccia shares similarities with other TBPs, most notably those of South America. The A. M. breccia demonstrates concentric zonation with regard to breccia texture, consisting of an outer rim of shingle breccia surrounding a fragmental breccia core. Copper grades correlate to breccia zonation, with higher Cu grades within shingle breccias relative to the fragmental core. Hypersaline fluid inclusions were identified in quartz cement within the A. M. breccia, which reflects conditions expected in porphyry copper deposits. Breccia textures, mineralization, and fluid inclusions at the A. M. breccia are nearly identical to other well-studied porphyry-related TBPs. The strong similarities suggest the A. M. breccia is a porphyry-related TBP. This interpretation encourages deep drilling to identify further mineralization within the A. M. breccia pipe as well as discovery for conventional porphyry mineralization at depth. Similarities can also be drawn to Ancestral Cascadia arc porphyry copper deposits and associated TBPs. The proximity of Giant Copper to the Ancestral Cascadia porphyry district infers a genetic relationship and the interpretation that the Giant Copper porphyry system developed from magmatism related to the Ancestral Cascadia subduction. Classifying Giant Copper as an Ancestral Cascadia porphyry system extends the district into southern British Columbia, where Giant Copper marks its northernmost extent. La br & egrave;che A. M. fait partie de la propri & eacute;t & eacute; The Giant Copper en Colombie-Britannique, au Canada. Il s'agit de la seule chemin & eacute;e de br & egrave;che & agrave; tourmaline (TBP, de l'anglais tourmaline breccia pipe) bien d & eacute;finie dans la Cordill & egrave;re canadienne. La br & egrave;che A. M. pr & eacute;sente des similitudes avec d'autres TBP, notamment celles d'Am & eacute;rique du Sud. La br & egrave;che A. M. pr & eacute;sente une zonation concentrique en ce qui concerne la texture de la br & egrave;che, consistant en une bordure ext & eacute;rieure de br & egrave;che & agrave; galets entourant un noyau de br & egrave;che fragmentaire. Les teneurs en cuivre sont en corr & eacute;lation avec la zonation des br & egrave;ches, les teneurs en Cu sont plus & eacute;lev & eacute;es dans les br & egrave;ches & agrave; galets que dans le noyau fragmentaire. Des inclusions de fluides hypersalins ont & eacute;t & eacute; identifi & eacute;es dans le ciment de quartz de la br & egrave;che A. M., ce qui correspond aux conditions attendues dans les gisements de cuivre porphyrique. Les textures de la br & egrave;che, la min & eacute;ralisation et les inclusions fluides de la br & egrave;che A. M. sont presque identiques & agrave; d'autres br & egrave;ches porphyriques bien & eacute;tudi & eacute;es li & eacute;s & agrave; des porphyres. Les fortes similitudes sugg & egrave;rent que la br & egrave;che A. M. est un TBP li & eacute; au porphyre. Cette interpr & eacute;tation encourage les forages profonds pour identifier d'autres min & eacute;ralisations dans la br & egrave;che A. M. ainsi que la d & eacute;couverte de min & eacute;ralisations porphyriques conventionnelles en profondeur. Des similitudes peuvent & eacute;galement & ecirc;tre & eacute;tablies avec les gisements de cuivre porphyrique de l'arc Ancestral Cascadia et les TBP associ & eacute;s. La proximit & eacute; de Giant Copper avec le district porphyrique de l'Ancestral Cascadia implique une relation g & eacute;n & eacute;tique et l'interpr & eacute;tation que le syst & egrave;me porphyrique de Giant Copper s'est d & eacute;velopp & eacute; & agrave; partir d'un magmatisme li & eacute; & agrave; la subduction de l'Ancestral Cascadia. La classification de Giant Copper en tant que syst & egrave;me porphyrique d'Ancestral Cascadia & eacute;tend le district au sud de la Colombie-Britannique, o & ugrave; Giant Copper marque son extension la plus septentrionale.

The A.M. breccia is part of the Giant Copper porphyry deposit in southern British Columbia. It is the only well-defined zoned tourmaline breccia pipe in the Canadian Cordillera. Tourmaline is a common alteration mineral within the A.M. breccia and is spatially associated with Cu mineralization. Observed changes in tour-maline chemistry range from alkali (schorlitic-dravitic) to calcic (feruvitic-uvitic). Tourmaline subspecies vary based on their spatial location within the A.M. breccia. Tourmaline outside of the pipe contains higher concen-trations of Mg, whereas tourmaline preferentially incorporates Fe within the pipe. These chemical variations are indistinguishable in hand specimens. Spectral reflectance data were collected from 587 tourmaline grains to determine if discerning chemical changes in tourmaline can be made field-based and thus more cost-effec-tive. Spectral reflectance differentiates tourmaline associated with mineralization and breccia textures from tourmaline occurring distal to the pipe contact or within barren tourmaline breccia pipes. Fe-rich tourmaline within the A.M. breccia shows spectral characteristics of end-member schorl (Fe-rich) spectra. Tourmaline distal to the A.M. breccia and within barren pipes demonstrates spectra of end-member dravite (Mg-rich). This grouping suggests that tourmaline subspecies can be inferred by spectral reflectance, enhancing the effi-ciency of tourmaline as a mineral vector. Tourmaline was also identified via airborne spectral surveys. However, the airborne spectral survey did not identify the end-member spectral properties identified by in situ analysis. Airborne spectral surveys can rap-idly identify tourmaline breccia pipe exposures and expedite early stages of exploration in ore districts where tourmaline is a known gangue mineral.

Geochemical and geochronological data from the Pinguicula Group and unit PR1 of the lower Fifteenmile Group (Yukon, Canada) provide information on sediment provenance and timing of break-up of supercontinent Columbia and seaway development on Laurentia’s northwestern margin. The older unit PR1, in the Coal Creek inlier, has a near-unimodal detrital zircon population with an age of 1499 ± 3 Ma. The Pinguicula Group detrital zircon data, in the Wernecke and Hart River inliers, display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma. Using detrital zircon signatures, Sm–Nd isotopic data, and C-isotopic signatures, lithostratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers are confirmed, whereas the Pinguicula Group and unit PR1 are no longer considered correlative. The zircon population in unit PR1 requires a proximal source, but sources of this age are not known in western Laurentia. Based on detrital zircon and Sm–Nd data, sediment in unit PR1 was derived from the Mt. Isa inlier in northeastern Australia sometime after 1460 Ma. Unit PR1 correlates with older Mesoproterozoic successions, including the Belt-Purcell, that were deposited during break-up of supercontinent Columbia, and contain sediment from Australia and the Mawson continent. Mesoproterozoic successions deposited after 1.45 Ga, including the Missoula Group, lack North American Magmatic Gap (NAMG)-aged zircon and instead record sediment provenance from southern Laurentia, as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group has few NAMG-aged grains that were probably recycled from older Mesoproterozoic basins.

ABSTRACT The Halo-Shakiso emeralds were discovered near the town of Shakiso in southern Ethiopia in 2016. They are gem quality, Cr-dominant emeralds hosted within ultramafic rocks and associated with Cambrian pegmatite intrusions of the Adola Belt. Aqueous-carbonic primary fluid inclusions hosted within emerald have a composition of approximately 3.0 wt.% NaCl eq. and an XCO2 of 0.06, with minor amounts of N2, CH4, and H2S. Stable isotope thermometry of contemporaneous quartz and emerald yields temperatures in the range of 420 to 470 °C. Combined stable isotope and fluid inclusion data are consistent with emerald precipitation at pressures ranging from 2.0 to 3.0 kbar, corresponding to depths of 5.9 to 8.9 km. Additionally, emerald channel water δD and calculated δ18O isotope values are consistent with an igneous origin for the fluids responsible for emerald precipitation; these fluids are also responsible for the metasomatization of the host rocks in and near the pegmatite, forming the phlogopite schist that is host to the Halo-Shakiso emeralds. The isotopic signatures, combined with the occurrence of adjacent pegmatites, support the classification of the Halo-Shakiso emerald deposit as a Tectonic-Magmatic-Related emerald deposit.

Petrology, geochemistry, fluid inclusions and U-Pb dating of a wide (30 cm) calcite vein in Upper Ordovician (Sandbian) limestone characterize a hydrochemical microcosm of changing fluid sources and carbon pathways related to burial, then uplift during the Phanerozoic along the Ottawa-Bonnechere graben, central Canada. U-Pb dating of the host limestone produces an age younger than its chronostratigraphic age suggesting the impact of diagenesis, otherwise well-defined petographically. An interred calcite fragment dated as Cambrian may highlight a platform source in this part of the graben hitherto unrecognized stratigraphically. The vein was initiated with extension across a high-angle narrow (2 cm) fault gouge allowing incursion of hot (80-125 degrees C) basinderived (Mg, Ca)-Cl-2 brine recorded by a saddle dolomite-dedolomite-calcite succession, not isotopically datable. Microbial methanogenesis occurred in initial narrow structural recesses giving way to recycled sedimentary bicarbonate with fracture widening. The oldest datable vein calcite (122 +/- 5 Ma) consists of microcrystalline geopetal cumulates of vadose meteoric origin demarcating renewed carbonate formation following a period of near-surface alteration, dissolution, and microfracturing of the prior vein calcite during uplift. Initial Pb-207/Pb-206 ratios are consistent with average crust (0.819 +/- 0.003), and delta O-18 signatures identify a meteoric signature similar to the host rock. Subsequent interlayering of isopachous calcite and pyrite, with an age of 105 +/- 3 Ma for the calcite, defines onset of a meteoric phreatic environment. The role of microbial sulphate reduction is characterized isotopically. Initial Pb-207/Pb-206 ratios scatter below the crustal average (0.84-0.76) that, along with a meteoric delta O-18 signature, suggest incursion of a new fluid reservoir. A subsequent Sr, Mn, Ba-bearing-magnesium calcite marks the beginning of sustained phreatic meteoric dilution for the remaining vein history. Stable (C, O) isotopes document varying temperature and bicarbonate mixtures of sedimentary and bacterial (sulphate reduction) origins associated with a meteoric fluid. This calcite has a mean age of 94 +/- 2 Ma and displays the widest range of initial Pb-207/Pb-206 ratios, which scatter down to 0.65. Stable and radiogenic isotopic compositions suggest a meteoric setting largely influenced by a crustal fluid reservoir of long residence time and-or transport resulting in leaching of radiogenic minerals. The final vein calcite, also of meteoric origin, has an Sr-87/Sr-86 ratio similar to that of the initial basin brine, yet with C-13 signatures that characterize a source of oxidized methane. U-Th series analysis delimits an age older than 0.5 Ma. This stage of vein calcite likely arises through meteoric fracking of Ordovician source rocks during continued basin inversion. In summary, initial brine influx followed by a shallow-crustal meteoric realm document structurally focused fluid migration with and following early Mesozoic graben exhumation. The phreatic meteoric regime of Early Cretaceous age spans a similar to 20 Ma period coincident with transient magmatism arising from near passage of the Great Meteor Hotspot. Regional paleohydmlogy appears to have been influenced for similar to 10 Ma after plume passage.

Although emerald deposits are relatively rare, they can be formed in several different, but specific geologic settings and the classification systems and models currently used to describe emerald precipitation and predict its occurrence are too restrictive, leading to confusion as to the exact mode of formation for some emerald deposits. Generally speaking, emerald is beryl with sufficient concentrations of the chromophores, chromium and vanadium, to result in green and sometimes bluish green or yellowish green crystals. The limiting factor in the formation of emerald is geological conditions resulting in an environment rich in both beryllium and chromium or vanadium. Historically, emerald deposits have been classified into three broad types. The first and most abundant deposit type, in terms of production, is the desilicated pegmatite related type that formed via the interaction of metasomatic fluids with beryllium-rich pegmatites, or similar granitic bodies, that intruded into chromium- or vanadium-rich rocks, such as ultramafic and volcanic rocks, or shales derived from those rocks. A second deposit type, accounting for most of the emerald of gem quality, is the sedimentary type, which generally involves the interaction, along faults and fractures, of upper level crustal brines rich in Be from evaporite interaction with shales and other Cr- and/or V-bearing sedimentary rocks. The third, and comparatively most rare, deposit type is the metamorphic-metasomatic deposit. In this deposit model, deeper crustal fluids circulate along faults or shear zones and interact with metamorphosed shales, carbonates, and ultramafic rocks, and Be and Cr (±V) may either be transported to the deposition site via the fluids or already be present in the host metamorphic rocks intersected by the faults or shear zones. All three emerald deposit models require some level of tectonic activity and often continued tectonic activity can result in the metamorphism of an existing sedimentary or magmatic type deposit. In the extreme, at deeper crustal levels, high-grade metamorphism can result in the partial melting of metamorphic rocks, blurring the distinction between metamorphic and magmatic deposit types. In the present paper, we propose an enhanced classification for emerald deposits based on the geological environment, i.e., magmatic or metamorphic; host-rocks type, i.e., mafic-ultramafic rocks, sedimentary rocks, and granitoids; degree of metamorphism; styles of minerlization, i.e., veins, pods, metasomatites, shear zone; type of fluids and their temperature, pressure, composition. The new classification accounts for multi-stage formation of the deposits and ages of formation, as well as probable remobilization of previous beryllium mineralization, such as pegmatite intrusions in mafic-ultramafic rocks. Such new considerations use the concept of genetic models based on studies employing chemical, geochemical, radiogenic, and stable isotope, and fluid and solid inclusion fingerprints. The emerald occurrences and deposits are classified into two main types: (Type I) Tectonic magmatic-related with sub-types hosted in: (IA) Mafic-ultramafic rocks (Brazil, Zambia, Russia, and others); (IB) Sedimentary rocks (China, Canada, Norway, Kazakhstan, Australia); (IC) Granitic rocks (Nigeria). (Type II) Tectonic metamorphic-related with sub-types hosted in: (IIA) Mafic-ultramafic rocks (Brazil, Austria); (IIB) Sedimentary rocks-black shale (Colombia, Canada, USA); (IIC) Metamorphic rocks (China, Afghanistan, USA); (IID) Metamorphosed and remobilized either type I deposits or hidden granitic intrusion-related (Austria, Egypt, Australia, Pakistan), and some unclassified deposits.

The Hart River sills are a set of mafic to intermediate intrusions that occur in northern Yukon, Canada. The largest sills are over 500 m thick and over 200 km long. New U-Pb dates of 1382.15 +/- 0.39 Ma and 1382.14 +/- 0.36 Ma were obtained via chemical abrasion thermal ionization mass spectrometry on zircon. Whole rock initial neodymium isotopic compositions of the Hart River sills are juvenile and have epsilon Ndi from +1.5 to +4.0. The primary mineralogy of the Hart River sills is predominated by clinopyroxene and plagioclase. Geochemical modeling indicates that the Hart River sills lie on a common liquid line of descent defined by a fractionating assemblage of plagioclase, clinopyroxene and minor olivine. The Hart River sills have rare earth element and high field strength abundances similar to normal mid-ocean ridge basalts (N-MORB) but are enriched in large ion lithophile elements. The Sm/Yb and Dy/Zr ratios indicate >8% partial melting of spinel-bearing mantle. During the emplacement of the Hart River sills, western Laurentia was juxtaposed with Australia and eastern Antarctica within the supercontinent Columbia. The degree of partial melting, similarity to N-MORB, and juvenile isotopic signature are consistent with an episode of rifting at 1.38 Ga. Coeval magmatism and intracontinental rift basins farther south on Laurentia provide additional evidence for rifting of supercontinent Columbia at 1.38 Ga. (C) 2018 Elsevier B.V. All rights reserved.

•The WOUS is a ∼1.60 Ga sedimentary succession on northwestern Laurentia.•Detrital zircon ages and isotope geochemistry implies the Gawler Craton as a source.•The WOUS is preserved as clasts within the hydrothermal Wernecke Breccia.•The ∼1.59 Ga Olympic Dam Breccia Complex host clasts of similar sediments.•The Gawler Craton and northwestern Laurentia were connected at 1.60 Ga.

Gold, present as electrum, in the Battle Gap, Ridge North-West, HW, and Price deposits at the Myra Falls mine, occurs in late veinlets cutting the earlier volcanogenic massive sulphide (VMS) lithologies. The ore mineral assemblage containing the electrum comprises dominantly galena, tennantite, bornite, sphalerite, chalcopyrite, pyrite, and rarely stromeyerite, and is defined as an Au-Zn-Pb-As-Sb association. The gangue is comprised of barite, quartz, and minor feldspathic volcanogenic sedimentary rocks and clay, comprised predominantly of kaolinite with subordinate illite. The deposition of gold as electrum in the baritic upper portions of the sulphide lenses occurs at relatively shallow water depths beneath the sea floor. Primary, pseudosecondary, and secondary fluid inclusions, petrographically related to gold, show boiling fluid inclusion assemblages in the range of 123 to 173 °C, with compositions and eutectic melt temperatures consistent with seawater at approximately 3.2 wt % NaCl equivalent. The fluid inclusion homogenization temperatures are consistent with boiling seawater corresponding to water depths ranging from 15 to 125 m. Slightly more dilute brines corresponding to salinities of approximately 1 wt % NaCl indicate that there is input from very low-salinity brines, which could represent a transition from subaqueous VMS to epithermal-like conditions for precious metal enrichment, mixing with re-condensed vapor, or very low-salinity igneous fluids.

BACKGROUND:Depression and debt are common in the UK. Debt Counselling for Depression in Primary Care: an adaptive randomised controlled pilot trial (DeCoDer) aimed to assess the clinical effectiveness and cost-effectiveness of the addition of a primary care debt counselling advice service to usual care for patients with depression and debt. However, the study was terminated early during the internal pilot trial phase because of recruitment delays. This report describes the rationale, methods and findings of the pilot study, and implications for future research. OBJECTIVES:The overarching aim of the internal pilot was to identify and resolve problems, thereby assessing the feasibility of the main trial. The specific objectives were to confirm methods for practice recruitment and the ability to recruit patients via the proposed approaches; to determine the acceptability of the study interventions and outcome measures; to assess contamination; to confirm the randomisation method for main trial and the level of participant attrition; and to check the robustness of data collection systems. DESIGN:An adaptive, parallel, two-group multicentre randomised controlled pilot trial with a nested mixed-methods process and economic evaluation. Both individual- and cluster (general practice)-level were was used in the pilot phase to assign participants to intervention or control groups. SETTING:General practices in England and Wales. PARTICIPANTS:Individuals were included who were aged ≥ 18 years, scored ≥ 14 on the Beck Depression Inventory II and self-identified as having debt worries. The main exclusion criteria were being actively suicidal or psychotic and/or severely depressed and unresponsive to treatment; having a severe addiction to alcohol/illicit drugs; being unable/unwilling to give written informed consent; currently participating in other research including follow-up phases; having received Citizens Advice Bureau (CAB) debt advice in the past year; and not wanting debt advice via a general practice. INTERVENTIONS:The participants in the intervention group were given debt advice provided by the CAB and shared biopsychosocial assessment, in addition to treatment as usual (TAU) and two debt advice leaflets. The participants in the control group were given advice leaflets provided by the general practitioner and TAU only. MAIN OUTCOME MEASURES:(1) Outcomes of the pilot trial - the proportion of eligible patients who consented, the number of participants recruited compared with target, assessment of contamination, and assessment of patient satisfaction with intervention and outcome measures. (2) Participant outcomes - primary - Beck Depression Inventory II; secondary - psychological well-being, health and social care utilisation, service satisfaction, substance misuse, record of priority/non-priority debts, life events and difficulties, and explanatory measures. Outcomes were assessed at baseline (pre-randomisation) and at 4 months post randomisation. Other data sources - qualitative interviews were conducted with participants, clinicians and CAB advisors. RESULTS:Of the 238 expressions of interest screened, 61 participants (26%) were recruited and randomised (32 in the intervention group and 29 in the control group). All participants provided baseline outcomes and 52 provided the primary outcome at 4 months' follow-up (14.7% dropout). Seventeen participants allocated to the intervention saw a CAB advisor. Descriptive statistics are reported for participants with complete outcomes at baseline and 4 months' follow-up. Our qualitative findings suggest that the relationship between debt and depression is complex, and the impact of each on the other is compounded by other psychological, social and contextual influences. CONCLUSIONS:As a result of low recruitment, this trial was terminated at the internal pilot phase and was too small for inferential statistical analysis. We recommend ways to reduce this risk when conducting complex trials among vulnerable populations recruited in community settings. These cover trial design, the design and delivery of interventions, recruitment strategies and support for sites. TRIAL REGISTRATION:Current Controlled Trials ISRCTN79705874. FUNDING:This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 35. See the NIHR Journals Library website for further project information. Mark Gabbay and Adele Ring are part-funded by NIHR Collaborations for Leadership in Applied Health Research and Care (CLAHRC) North West Coast and Richard Byng and Rod S Taylor, Vashti Berry and Elizabeth Shaw part-funded by NIHR CLAHRC South West Peninsula.

The sources of emerald-forming fluids and chromophores at the Lened occurrence were assessed using field relationships, Ar-Ar dating, whole rock geochemistry, stable isotopes (O, C, S), and mineral chemistry; the results clearly show that the similar to 100 Ma (Ar-Ar muscovite) Lened emerald occurrence is a Type I (igneous) emerald deposit and relates to the proximal similar to 100 Ma (Ar-Ar biotite) Lened Pluton. Stable isotope analyses suggest the veins formed from a primarily granite-derived fluid with lesser components of meteoric and shale-equilibrated fluids. Beryllium and other incompatible elements (including W, Sn, and F) concentrated in evolved magmatic fluid that exsolved during the last stages of crystallization of the Lened pluton. Local overpressuring of vein-forming fluids under a brittle carapace of early pyroxene-garnet skarn led to fracture and emplacement of quartz-calcite-beryl-scheelite-tourmaline-pyrite veins. Less than 5% of the beryl can be considered pale bluish green emerald. Vanadium concentration in the emerald averages 1563 ppm; Cr averages 75 ppm, and Sc attains concentrations of 782 ppm. The key emerald chromophore vanadium was mobilized by metasomatic breakdown of V-rich black shales (averaging 2000 ppm V) that underlie the emerald occurrence.

Emerald at the Lened occurrence in the western Northwest Territories is hosted by quartz veins cutting skarn near the Lened granite pluton and older Selwyn Basin strata. Using field relationships, Ar-Ar dating, whole-rock geochemistry, stable isotopes (O, H, C, and B), and mineral chemistry, the sources of the emerald-forming fluids and chromophores have been assessed; the results clearly show that the ca. 100 Ma (Ar-Ar muscovite) Lened emerald occurrence is a Type I (igneous) skarn-hosted emerald deposit related to the proximal ca. 100 Ma (Ar-Ar biotite) Lened pluton. Beryllium and other incompatible elements (i.e., W, Sn, Li, B, and F) in the emerald, vein minerals, and surrounding skarn were derived during the terminal stages of crystallization of the proximal Lened pluton. Decarbonation during pyroxene-garnet skarn formation in the host carbonate rocks probably caused local overpressuring and fracturing that allowed ingress of magmatic-derived fluids and formation of quartz-calcite-beryl-scheelite-tourmaline-pyrite veins. The delta B-11 values of accessory dravite in the emerald veins averages -4.9 + 0.3 parts per thousand (1 sigma, n = 10), which is compatible with a magmatic source, and the Al-Fe-Mg composition is that of tourmaline formed in sedimentary environments, with Mg likely derived from metasomatism of local marine carbonates. The vein fluid was largely igneous in origin, but the dominant emerald chromophore V (emerald vein = avg. 1560 ppm V versus 75 ppm Cr) was mobilized by metasomatism of V-rich sedimentary rocks (avg. 2000 ppm V) that underlie the emerald occurrence.

Emerald from the Binntal occurrence in the Canton of Valais in Switzerland has been studied to determine its chemical zonation, stable isotopic signatures, depositional-fluid characteristics, pressure-temperature emplacement conditions, and formational model. The emerald is vanadium-rich, with optical and blue cathodoluminescence zoning related to chemical variations, primarily in V2O3 concentrations. The hydrogen isotope signature of the emerald channel fluids is unique and in agreement with previously identified high-altitude (deuterium-depleted) Alpine-age meteoric fluids. Field studies, fluid inclusion analyses, and oxygen isotope thermometry are consistent with a metamorphic formational model for the Binntal emerald at temperatures and hydrostatic pressures ranging from 200 to 400 degrees C and 100 to 250 Mpa, respectively. This corresponds to formational depths on the order of 4 to 9 km and fluids consistent with a 10-20 Ma CO2-dominant fluid with approximate mole percentages of 84.0, 11.9, 1.5, 1.3, 0.3, and 0.5 for CO2, H2O, CH4, N-2, H2S, and NaCl, respectively.

Abstract Fluorite is an accessory and a gangue mineral in many metalliferous deposits, and the trace element composition of fl uorite has been used to discriminate different deposit types. We examined fl uorite from 14 North American deposits by performing 514 LA-ICP-MS analyses for thirtyfour elements, to improve our database. This database will be required for future studies aiming to produce reliable discrimination diagrams for use in mineral exploration. Results of this study revealed that fl uorite from sedimentary-hosted deposits (Liard, Kootenay Florence, vein; Hastie Quarry, Barnett mine, Elmwood, Gordonsville, Young mine, MVT) has Sr concentrations less than 200 ppm (with the exception of two outliers), and Y concentrations less than 31 ppm. REE chondrite-normalized patterns are convex or have a negative slope; 75% of the data have a chondrite-normalized REE ratio below 3. Seventy-fi ve percent of fl uorite analyses from peralkaline/alkaline-related deposits (Kipawa, Rexspar, Eaglet, Rock Candy), and Rock Canyon Creek have chondrite-normalized ratios higher than 2 for each lanthanide, and fl at to weakly negative patterns. The 4th tetrad portion of the chondrite-normalized REE plots of sedimentary-hosted deposits has a weakly negative to negative slope, whereas the pattern for alkaline/peralkaline-related deposits varies from weakly negative to positive. Fifty percent of the data (between the 1st and 3rd quartile) from carbonatite-related deposits (Eldor and Wicheeda Lake) show sinusoidal patterns on chondrite-normalized REE plots, with wide element ranges in their fi rst tetrad. Barium, Th, and U also show potential for use in indicator mineral discrimination diagrams. Analyses of single crystals reveals compositional zoning that may not be optically apparent. Fifty analyses on a single Rock Candy fl uorite crystal identifi ed three compositional zones. One of these zones shows variations of trace elements (Ce, 14.5%; Pr, 13.9%; Nd, 14.9%; Sm, 16.9%; Eu 11.4%; Gd, 19.2%; Dy, 18.8%) with similar or lower variability than NIST glass (615). This zone may be useful as a matrix-matched secondary standard. Intra-grain chemical zoning is unlikely to be a major cause of elemental variation within a deposit and, by extrapolation, between deposit types. Our results suggest that Y, Sr and REE are essential for constructing discrimination diagrams that use fl uorite as an indicator mineral.

Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of 335–525 °C and pressures ranging from 70 to 400 MPa. The large range in pressure and temperature likely reflects some post entrapment changes and re-equilibration of oxygen isotopes. Secondary emerald-hosted fluid inclusions indicate subsequent emerald precipitation from higher salinity fluids. Likewise, the δ18O-δD of channel fluids extracted from Poona emerald is consistent with multiple origins yielding both igneous and metamorphic signatures. The combined multiple generations of emerald precipitation, different fluid compositions, and the presence of both metamorphic and igneous fluids trapped in emerald, likely indicate a protracted history of emerald precipitation at Poona conforming to both an igneous and a metamorphic origin at various times during regional lower amphibolite to greenschist facies metamorphism over the period ~2710–2660 Ma.

The Paleoproterozoic Wernecke Supergroup of Yukon was deposited when the northwestern margin of Laurentia was undergoing major adjustments related to the assembly of the supercontinent Columbia (Nuna) from 1.75 to 1.60Ga. U–Pb detrital zircon geochronology coupled with Nd isotope geochemistry and major and trace element geochemistry are used to characterize the evolution of the Wernecke basin. The maximum depositional age of the Wernecke Supergroup is reevaluated and is estimated at 1649±14Ma. Detrital zircon age spectra show a bimodal age distribution that reflects derivation from cratonic Laurentia, with a prominent peak at 1900Ma. Going upsection, the late Paleoproterozoic peak shifts from 1900Ma to 1850–1800Ma, and the proportion of Archean and early Paleoproterozoic zircon decreases. These modifications are a consequence of a change in the drainage system in western Laurentia caused by early phase of the Forward orogeny, several hundred km to the east. The exposed lower and middle parts of the Wernecke Supergroup are correlated with the Hornby Bay Group. Zircon younger than 1.75Ga appear throughout the sedimentary succession and may have originated from small igneous suites in northern Laurentia, larger source regions such as magmatic arc terranes of the Yavapai and early Mazatzal orogenies in southern Laurentia, and possible arc complexes such as Bonnetia that may have flanked the eastern margin of East Australia. Basins with similar age and character include the Tarcoola Formation (Gawler Craton) and the Willyama Supergroup (Curnamona Province) of South Australia, the Isan Supergroup of North Australia, and the Dongchuan–Dahongshan–Hondo successions of southeast Yangtze Craton (South China). Nd isotope ratios of the Wernecke Supergroup are comparable with values from Proterozoic Laurentia, the Isan and Curnamona assemblages of east Australia, the Gawler Craton, and the Dahongshan–Dongchuan–Hondo successions of the Yangtze Craton of South China. These similarities are compelling evidence for a shared depositional system among these successions. Western Columbia in the Late Paleoproterozoic may have had a dynamic SWEAT-like configuration involving Australia, East Antarctica and South China moving along western Laurentia.

Recommended citation: Mao, M., Simandl, G.J., Spence, J., and Marshall, D., 2015. Fluorite trace-element chemistry and its potential as an indicator mineral: Evaluation of LA-ICP-MS method. In: Simandl, G.J. and Neetz, M., (Eds.), Symposium on Strategic and Critical Materials Proceedings, November 13-14, 2015, Victoria, British Columbia. British Columbia Ministry of Energy and Mines, British Columbia Geological Survey Paper 2015-3, pp. 251-264.