scholarly journals Influence of Titaniferous Phases on Tungsten Mineralizing Processes at the Giant Sisson Brook W-Mo Deposit, New Brunswick, Canada: Mineral-Chemical and Geochronological Assessment

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 637
Author(s):  
Aaron L. Bustard ◽  
Wei Zhang ◽  
David R. Lentz ◽  
Christopher R. M. McFarlane
Keyword(s):  
New Brunswick ◽  
Low Grade ◽  
Elemental Mapping ◽  
Metasedimentary Rocks ◽  
West Central ◽  
Icp Ms ◽  
Volcaniclastic Rocks ◽  
Acadian Orogeny ◽  
Host Rocks ◽  
Mineralizing Fluids

The Sisson Brook deposit is a low-grade, large-tonnage W-Mo deposit with notable Cu located in west-central New Brunswick, Canada, and is one of several W-Mo deposits in New Brunswick associated with fluids sourced from granitic plutons emplaced during the Devonian Acadian Orogeny. The younger Devonian-aged stockwork and replacement scheelite-wolframite-molybdenite (and chalcopyrite) mineralization straddles the faulted boundary between Cambro-Ordovician metasedimentary rocks with Ordovician felsic volcaniclastic rocks and the Middle Silurian Howard Peak Granodiorite, with dioritic and gabbroic phases. U-Pb dating of magmatic titanite in the host dioritic phase of the Howard Peak Granodiorite using LA ICP-MS resulted in a 204Pb-corrected concordant age of 432.1 ± 1.9 Ma. Petrologic examination of selected mineralization combined with elemental mapping of vein selvages using micro-XRF and metasomatic titanite and ilmenite grains using LA ICP-MS indicates that saturation of titaniferous phases influenced the distribution of scheelite versus wolframite mineralization by altering the aFe/aCa ratio in mineralizing fluids. Ilmenite saturation in Ti-rich host rocks lowered the relative aFe/aCa and led to the formation of scheelite over wolframite. Altered magmatic titanite and hydrothermal titanite also show increased W and Mo concentrations due to interaction with and/or saturation from mineralizing fluids.

scholarly journals Geochemical signatures of mineralizing events in the Juomasuo Au–Co deposit, Kuusamo belt, northeastern Finland

2021 ◽  
Author(s):  
Mikael Vasilopoulos ◽  
Ferenc Molnár ◽  
Hugh O’Brien ◽  
Yann Lahaye ◽  
Marie Lefèbvre ◽  
...  
Keyword(s):  
Trace Element ◽  
Sulfur Isotope ◽  
Mineral Chemistry ◽  
Chemical Compositions ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Icp Ms ◽  
Stage 1 ◽  
Host Rocks ◽  
Relationship Of

AbstractThe Juomasuo Au–Co deposit, currently classified as an orogenic gold deposit with atypical metal association, is located in the Paleoproterozoic Kuusamo belt in northeastern Finland. The volcano-sedimentary sequence that hosts the deposit was intensely altered, deformed, and metamorphosed to greenschist facies during the 1.93–1.76 Ga Svecofennian orogeny. In this study, we investigate the temporal relationship between Co and Au deposition and the relationship of metal enrichment with protolith composition and alteration mineralogy by utilizing lithogeochemical data and petrographic observations. We also investigate the nature of fluids involved in deposit formation based on sulfide trace element and sulfur isotope LA-ICP-MS data together with tourmaline mineral chemistry and boron isotopes. Classification of original protoliths was made on the basis of geochemically immobile elements; recognized lithologies are metasedimentary rocks, mafic, intermediate-composition, and felsic metavolcanic rocks, and an ultramafic sill. The composition of the host rocks does not control the type or intensity of mineralization. Sulfur isotope values (δ34S − 2.6 to + 7.1‰) and trace element data obtained for pyrite, chalcopyrite, and pyrrhotite indicate that the two geochemically distinct Au–Co and Co ore types formed from fluids of different compositions and origins. A reduced, metamorphic fluid was responsible for deposition of the pyrrhotite-dominant, Co-rich ore, whereas a relatively oxidized fluid deposited the pyrite-dominant Au–Co ore. The main alteration and mineralization stages at Juomasuo are as follows: (1) widespread albitization that predates both types of mineralization; (2) stage 1, Co-rich mineralization associated with chlorite (± biotite ± amphibole) alteration; (3) stage 2, Au–Co mineralization related to sericitization. Crystal-chemical compositions for tourmaline suggest the involvement of evaporite-related fluids in formation of the deposit; boron isotope data also allow for this conclusion. Results of our research indicate that the metal association in the Juomasuo Au–Co deposit was formed by spatially coincident and multiple hydrothermal processes.

scholarly journals U-Pb, Ar-Ar, and Re-Os Geochronological Constraints on Multiple Magmatic–Hydrothermal Episodes at the Lake George Mine, Central New Brunswick

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 566 ◽  
Author(s):  
Carlin Lentz ◽  
Kathleen Thorne ◽  
Christopher R. M. McFarlane ◽  
Douglas A. Archibald
Keyword(s):  
New Brunswick ◽  
Zircon Geochronology ◽  
Weighted Mean ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Icp Ms ◽  
Step Heating ◽  
Geochronological Constraints ◽  
Lake George

The Lake George antimony mine was at one time North America’s largest producer of antimony. Despite being widely known for the antimony mineralization, the deposit also hosts a range of styles of mineralization such as multiple generations of W-Mo bearing quartz veins as well as a system of As-Au bearing quartz–carbonate veins. In situ U-Pb zircon geochronology, using LA ICP-MS, of the Lake George granodiorite yielded a weighted mean 206Pb/238U age of 419.6 ± 3.0 Ma. Step heating of phlogopite separated from the lamprophyre dykes produced a 40Ar/39Ar plateau segment date of 419.4 ± 1.4 Ma. Single molybdenite crystal analysis for Re-Os geochronology was conducted on two W-Mo-bearing quartz veins, which cross-cut altered granodiorite and altered metasedimentary rocks and yielded two dates of 415.7 ± 1.7 Ma and 416.1 ± 1.7 Ma respectively. 40Ar/39Ar geochronology of muscovite from alteration associated with Au-bearing quartz–carbonate veins yielded one representative plateau segment date of 414.1 ± 1.3 Ma. The dates produced in this study revealed that the different magmatic–hydrothermal events at the Lake George mine occurred over approximately a 10-million-year period at the end of the Silurian and the start of the Devonian following the termination of the Acadian orogeny.

scholarly journals Early Cambrian U-Pb zircon age and Hf-isotope data from the Guasayán pluton, Sierras Pampeanas, Argentina: implications for the northwestern boundary of the Pampean arc

2016 ◽  
Vol 43 (1) ◽  
pp. 137 ◽  
Author(s):  
Juan A. Dahlquist ◽  
Sebastián O. Verdecchia ◽  
Edgardo G. Baldo ◽  
Miguel A.S. Basei ◽  
Pablo H. Alasino ◽  
...  
Keyword(s):  
Central Area ◽  
Magma Source ◽  
Western Boundary ◽  
Low Grade ◽  
Early Cambrian ◽  
Zircon Age ◽  
Sierras Pampeanas ◽  
Metasedimentary Rocks ◽  
Icp Ms

An Early Cambrian pluton, known as the Guasayán pluton, has been identified in the central area of Sierra de Guasayán, northwestern Argentina. A U-Pb zircon Concordia age of 533±4 Ma was obtained by LA-MC-ICP-MS and represents the first report of robustly dated Early Cambrian magmatism for the northwestern Sierras Pampeanas. The pluton was emplaced in low-grade metasedimentary rocks and its magmatic assemblage consists of K-feldspar (phenocrysts)+plagioclase+quartz+biotite, with zircon, apatite, ilmenite, magnetite and monazite as accessory minerals. Geochemically, the granitic rock is a metaluminous subalkaline felsic granodiorite with SiO2=69.24%, Na2O+K2O=7.08%, CaO=2.45%, Na2O/ K2O=0.71 and FeO/MgO=3.58%. Rare earth element patterns show moderate slope (LaN/YbN=8.05) with a slightly negative Eu anomalies (Eu/Eu*=0.76). We report the first in situ Hf isotopes data (εHft=-0.12 to -4.76) from crystallized zircons in the Early Cambrian granites of the Sierras Pampeanas, helping to constrain the magma source and enabling comparison with other Pampean granites. The Guasayán pluton might provide a link between Early Cambrian magmatism of the central Sierras Pampeanas and that of the Eastern Cordillera, contributing to define the western boundary of the Pampean paleo-arc.

Tectonic implications of 40Ar/39Ar mineral ages from late Precambrian – Cambrian plutons, Avalon composite terrane, southern New Brunswick, Canada

1992 ◽  
Vol 29 (11) ◽  
pp. 2445-2462 ◽  
Author(s):  
R. David Dallmeyer ◽  
R. Damian Nance
Keyword(s):  
New Brunswick ◽  
Quartz Diorite ◽  
Head Group ◽  
Low Grade ◽  
Marine Strata ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Sedimentary Sequences ◽  
Stratigraphic Record ◽  
Isotope Correlation

Within the Avalon composite terrane exposed in southern New Brunswick, late Precambrian, low-grade volcanic–sedimentary sequences are juxtaposed against late Precambrian gneisses (Brookville Gneiss) and older platformal metasedimentary rocks (Green Head Group) along the Caledonia Fault. Both assemblages host petrographically similar suites of calc-alkalic dioritic and granodioritic plutons. Those intruding volcanic–sedimentary sequences (Caledonia terrane) record ca. 615–625 Ma crystallization ages typical of arc-related magmatism throughout the Avalon composite terrane. However, 40Ar/39Ar age data from stocks intruding gneisses and platformal metasedimentary rocks (Brookville terrane) suggest significantly younger crystallization ages.36Ar/40Ar versus 39Ar/40Ar isotope correlation ages recorded by hornblende are interpreted to closely date postmagmatic cooling within six plutons: Fairville Granite (547 ± 1 Ma); French Village Quartz Diorite (539 ± 2 and 537 ± 1 Ma); Rockwood Park Granodiorite (529 ± 2 and 523 ± 3.5 Ma); Musquash Granite (526 ± 2 Ma); Milkish Head Granite (Red Bridge pluton, 520 ± 1.5 Ma); Lepreau Diorite (Talbot Road pluton, 519 ± 2 Ma and Hansen Stream pluton, 518 ± 1.5 Ma. A hornblende isotope correlation age of 530 ± 2 Ma from penetratively foliated amphibolite within the French Village Quartz Diorite suggests that the magmatic activity was locally accompanied by ductile shear. Muscovite within granitic pegmatite in the Brookville Gneiss records a 40Ar/39Ar plateau age of 510 ± 1 Ma interpreted to date final phases of associated magmatic activity.Arc-related magmatism extending into the Cambrian contrasts with the characteristic tectono-stratigraphic record in the Avalon composite terrane where late Precambrian igneous rocks are overstepped by Cambrian–Ordovician shallow-marine strata with only a local and minor record of rift-related volcanic activity. Although the Brookville terrane shows affinities with the Avalon composite terrane during the late Precambrian, the 40Ar/39Ar age data suggest that it was isolated as a distinct tectono-stratigraphic element by the Early Cambrian.

40Ar/39Ar whole-rock phyllite ages from late Precambrian rocks of the Avalon composite terrane, New Brunswick: evidence of Silurian–Devonian thermal rejuvenation

1994 ◽  
Vol 31 (5) ◽  
pp. 818-824 ◽  
Author(s):  
R. David Dallmeyer ◽  
R. Damian Nance
Keyword(s):  
New Brunswick ◽  
Low Grade ◽  
Fine Grained ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Minimum Age ◽  
Tectonic Contact ◽  
Age Constraints ◽  
Gas Fractions ◽  
Thermal Overprint

Several variably deformed and metamorphosed, late Precambrian volcanic–sedimentary successions have been recognized within the Avalon composite terrane exposed in the Caledonian Highlands of southern New Brunswick. Whole-rock samples of metasedimentary phyllite and phyllitic metatuff from the oldest (ca. 600–635 Ma) Avalonian succession display similar, internally discordant 40Ar/39Ar age and apparent K/Ca spectra. Intermediate-temperature gas fractions were experimentally evolved solely from very fine grained, cleavage-aligned white micas. These yield apparent ages between ca. 430 and 410 Ma, and are interpreted to closely date a static Late Silurian – Early Devonian thermal rejuvenation.Evidence for a Silurian – Devonian thermal event has not been previously documented in Avalonian rocks of the Caledonian Highlands (Caledonia assemblage). However, a thermal overprint of similar age (ca. 400 Ma) is recorded by metamorphic muscovite in high-grade gneisses and platformal metasedimentary rocks (Brookville assemblage), which are in tectonic contact with the low-grade Caledonia assemblage. These potentially correlative thermal overprints may provide minimum age constraints on the juxtaposition of these contrasting tectono-stratigraphic assemblages, which are likely to have been palinspastically separate tectonic elements during the earliest Paleozoic.

scholarly journals New deformation, metamorphic and geochronological data on the Aiguilles-Rouges massif (Alpine External Crystallin massifs, France). A reappraisal of the Variscan tectono-metamorphic evolution in the Alpine Western External Crystallin massifs

2020 ◽  
Author(s):  
Jonas Vanardois ◽  
Pierre Trap ◽  
Françoise Roger ◽  
Fabrice Barou ◽  
Pierre Lanari ◽  
...  
Keyword(s):  
Partial Melting ◽  
Low Grade ◽  
Geochronological Data ◽  
Metasedimentary Rocks ◽  
Time Deformation ◽  
Icp Ms ◽  
Short Period ◽  
Basement Deformation ◽  
Orogenic Plateau ◽  
Variscan Basement

<p>                The Aiguilles-Rouge Massif (ARM) is one of the Western External Crystallin Massifs (ECM) of the French Alps. Similarly to the other ECMs, the ARM exposes a Variscan basement made of migmatitic ortho- and paragneisses and micaschists that hold metric boudins of retrograded eclogites, amphibolites and serpentinites. Upward, low-grade and weakly metamorphosed Late-Carboniferous terrigenous sediments overly the Variscan basement. Deformation and metamorphism occurred between 330 and 300 Ma. The whole ARM is structured by a main N-S to NE-SW trending and vertical foliation formed in response to a regional dextral transpression. The tectonic significance of the ARM’s high-pressure rocks in the Variscan belt realm as relics of a subduction zone, pieces of crustal root of an orogenic plateau or overpressure phenomenon along a high-strain zone is still highly debated. A question that also remains is how eclogite Pressure–Temperature–time-Deformation history (P–T–t-D path) relates to the metamorphic paths recorded in the surrounding migmatitic rocks. In this contribution we present new structural and microstructural (EBSD data) observations that give us a detailed vision of the partitioning of the crustal scale deformation during Late-Variscan time. Three main deformations, named D1, D2 and D3, have been recognized in the gneissic core of the ARM. D1 is relictual and corresponds to a flat-lying S1 foliation that is only visible in the high grade metasedimentary rocks and preserved in low-D2 strain domains. D1 is associated with a partial melting metamorphic event M1. D2 is characterized by three main orientations of planar fabrics that are oriented in directions N160, N0 and N20. These planar fabrics are interpreted as S2-C2-C2’ related to anastomosed system developed under a bulk dextral transpression. D2 shearing becomes more penetrative toward the NE, where it is associated to local partial melting. D3 corresponds to the development of a flat-lying S3 cleavage together with the folding of vertical D2 foliations. The D3 is linked to a regional vertical shortening, associated to few liquid injections. These partial melting conditions occurring during D1, D2 and D3 deformations may unravel a continuum of these three deformations during a short period of time. Processing of new thermobarometric and LA-ICP-MS U-Pb geochronological data on eclogites, surrounding rocks and migmatites are currently in progress. The new obtained results will be presented in addition to the structural and metamorphic data in order to discuss the P-T-t-D path of the deeply buried metasedimentary rocks, migmatites and preserved eclogites.</p>

Zoned epidote nodules from sedimentary rocks of the Eastport Formation, southwest New Brunswick

1978 ◽  
Vol 15 (7) ◽  
pp. 1194-1200 ◽  
Author(s):  
J. A. Percival ◽  
H. Helmstaedt
Keyword(s):  
New Brunswick ◽  
Shallow Water ◽  
Bulk Composition ◽  
Sedimentary Rocks ◽  
Low Grade ◽  
Sodium Potassium ◽  
Grade Metamorphism ◽  
Relative Enrichment ◽  
Host Rocks

Zoned epidote-rich nodules occur in shallow-water sedimentary rocks of the Eastport Formation in southwestern New Brunswick. The host rocks of the nodules are sandstone and shale displaying well preserved clastic texture and minimal metamorphic effects, whereas the recrystallized nodule cores consist of epidote and quartz, with minor proportions of prehnite and actinolite. Whole rock analyses show depletion of sodium, potassium, and magnesium in the nodule relative to the host as well as relative enrichment in calcium and iron. Chemical, mineralogical, and textural similarities to calcareous concretions lead to the conclusion that the nodules represent metamorphosed equivalents of ironstone concretions. The St. George pluton is thought to have been the source of heat for metamorphism. Differences in degree of recrystallization between the nodules and their host rocks are attributed to differences in original bulk composition. Although the primary textures in the pelitic and quartzofeldspathic host rocks remained essentially unchanged during very low grade metamorphism, the nodule cores, richer in calcium and iron, recrystallized into metamorphic assemblages.

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