The fluid history of the Seabee mesothermal gold deposit Northern Saskatchewan

The Seabee deposit is a mesothermal, gold-bearinq vein system hosted within mylonitic shear structures in the Glennie Domain of the Proterozoic Trans-Hudson Orogen, northern Saskatchewan, Canada. Field and underground observations indicate that shear structures nucleated at rheological contrasts at the contacts between felsic intrusive dykes, and mafic intrusive lithologies. High-grade ore is located where shear structures intersect to form zones of transtension or dilational jogs. Geochemical patterns for altered mylonites are similar to those of the primary lithologies. Mafic host rocks proximal to the Seabee quartz veins have been altered to biotite, actinolite, epidote assemblages as the result of hydrothermal activity. Two stages of mineralization are present within quartz veins of the Seabee deposit. Stage I consists of quartz, tourmaline, K feldspar, and pyrite. Stage II is confined within microfractures that cut the Stage I assemblage. Stage II is dominated by carbonate, pyrrhotite, chalcopyrite, tellurides, and gold. Quartz adjacent to microfractures was locally recrystallised during the Stage II event. Gold is sited where Stage II microfractures intersect pyrite, whereas the microfractures that transect quartz contain only carbonate with trace quantities of chalcopyrite and tellurides. The occurrence of gold indicates that interaction of an auriferous fluid with Stage I pyrite resulted in gold deposition. In addition, gold blebs locally occur as linear arrays within pyrite proximal to Stage II microfractures, and are interpreted to represent Stage II gold grains about which Stage I pyrite recrystallized. No primary fluid inclusions have been preserved in Stage I quartz veins, although numerous secondary inclusions are present. Secondary inclusions consist dominantly of H₂O(g)-­H₂O (1) or CO₂(g)-CO₂ (1); the occurrence of 3-phase CO₂(g)-H₂O(g)-H₂O(1) is limited. Microthermometric analysis indicates that H₂O(g)-H₂O(1) inclusions were trapped at 212 °C and at pressures of approximately 2.0 kb, suggesting that the Seabee vein system was emplaced at depths of 7.0 km. Stage I barren quartz has δ¹⁸O values of 8.4 -8.9‰, whereas auriferous Stage II quartz has higher values of 10.0-10.6‰. Tourmaline is variably altered, particularly adjacent to Stage II microfractures. This alteration is reflected in the O-­isotope compositions; in unaltered tourmaline the δ¹⁸O is approximately 6.6‰, whereas in altered tourmaline δ¹⁸O ranges from 7.2 to 7.8‰ The O-isotopic compositions of barren quartz and unaltered tourmaline are assumed to preserve the primary isotopic composition of Stage I fluid. The average isotopic fractionation temperature for Stage I quartz­ tourmaline pairs is 430 °C. The O-isotope composition of Stage II fluid is preserved by microfracture quartz and altered tourmaline. The average calculated isotopic fractionation temperatures for Stage II is 360 °C. Although the Stage I and II fluid events differed by 70 °C in temperature, the calculated δ¹⁸Oh₂₀ values for both mineral pairs are in the 5.2 to 5.4‰ range. The mineralization associated with Stage I and II crosscut all lithologies so that the ²⁰⁷Pb/²⁰⁶Pb zircon evaporation age of 1877 ± 10 Ma obtained from a late feldspar porphyry dyke provides an upper limit on the timing of hydrothermal activity. ⁴⁰Ar/³⁹Ar age spectra for hornblende, obtained from mafic rock lithologies, have disturbed patterns signifying that the minerals were reset, likely during the hydrothermalactivity. Biotite from the alteration assemblage of the Seabee deposit has two different ⁴⁰Ar/³⁹Ar plateau ages of 1728 ± 5 Ma and 1769 ± 7 Ma. The 1769 Ma age is correlated with the Stage I event, whereas the 1728 Ma age may date the Stage II event. Younger step ages in both biotite spectra are associated with the distinctly younger fluid event. The initial ⁸⁷Sr/⁸⁶Sr ratio of hydrothermal fluids from Stage I tourmaline is 0.702171 ± 23, whereas ⁸⁷Sr/⁸⁶Sr initial = 0.711093 ± 87 to 0.7078 ± 13 for Stage II sulphides and gold. These results imply that the Stage II gold bearing fluid was either tapping an older Archean source, or selectively leaching Rb-­rich minerals of Paleoproterozoic age. Collectively the field, petrographic, and geochemical results are consistent with the interpretation that the Seabee deposit is a structurally hosted mesothermal lode gold deposit, but not a sedimentary exhalative, or a copper-gold porphyry-type system

Natural Insect Repellents: Activity against Mosquitoes and Cockroaches

Recent research has focused on the repellent properties of extracts from the catnip plant (Nepeta cataria) and the Osage orange (Madura pomifera) fruit. This chapter includes results on German cockroach (Blattella germanica), and house fly (Musca domestica) contact irritancy to catnip essential oil, and its major components, Z,E-nepetalactone and E,Z-nepetalactone, compared with the commercial standard, N,Ndiethyl-m-toluamide (DEET). Both species showed high percentage repellency values when exposed to filter paper treated with catnip essential oil or the individual nepetalactone isomers. Of the two nepetalactone isomers evaluated, German cockroaches were most responsive to the E,Z isomer. House flies showed similar trends in contact irritancy, responding to surfaces treated with the predominant catnip isomer, Z,E-nepetalactone, more intensely than to the catnip essential oil. Catnip and Osage orange essential oils, and a sesquiterpene found in Osage orange, elemol, were evaluated for repellency to the northern house mosquito (Culex pipiens) and are presented here. Two mosquito bioassays were used to measure percentage and contact repellecy. Mosquitoes responded initially with high percentage repellency to surfaces treated with catnip essential oil. From the residual repellency study, this trend in repellency by the catnip oil significantly decreased over the 180-minute test period. Elemol, and DEET initially had lower percentage repellency values than catnip essential oil, but did not show the negative relationship between percentage repellency and time, retaining excellent repellency throughout the 3-hour bioassay. Solutions with elemol and DEET exhibited greater significance in contact repellency compared to catnip essential oil. These results show that catnip essential oil is a potent mosquito repellent, but does not provide the same residual effects as the commercial standard, DEET, Elemol, a sesquiterpene extracted from the fruit of the Osage orange, shows excellent promise as a mosquito repellent with comparable activity to DEET in contact and residual repellency

Team-based Classroom Pedagogy Reframed: The Student Perspective

Postsecondary learning environments often utilize team-based pedagogical practices to challenge and support student learning outcomes. This manuscript presents the findings of a qualitative research study that analyzed the viewpoints and perceptions of group or team-based projects among undergraduate business students. Results identified five pro-team thematic perspectives of team learners’ views including better deliverables, increased ideas, improved learning experiences, reduced workload, and collective security. Responses from students who preferred to work autonomously resulted in three themes centered on self-sufficiency, social loafing, and schedule challenges. Two situational student responses were identified regarding how and why faculty should utilize group and team projects in consideration of individual efficiency and assignment objectives and outcomes conflicts. This study concludes with research-based recommendations for teaching, learning, and further research