Carboniferous barite-fluorite mineralization in the Late Devonian Kinsac Pluton, southern Nova Scotia

Abstract

Abundant barite ± fluorite ± quartz veins occur along the eastern margin of the Late Devonian Kinsac Pluton, a peraluminous granite that intruded metasedimentary rocks of the Meguma Group. The barite veins, striking 120° with vertical dip, occur in areas of strongly fractured granite, but the veins are not deformed and may contain lenses of comminuted granite. The veins (< 0.6 m wide) are dominated by coarse, cloudy white barite euhedra with or without a late infill of euhedral clear quartz and pink to dark purple fluorite. 40Ar/39Ar step-wise heating of a K-feldspar megacryst in granite immediately adjacent to a barite vein indicates a 354 Ma plateau age for the high-temperature gas fraction and a ca. 320 Ma age for the lowtemperature gas fraction. The younger age is interpreted to record partial resetting of K-feldspar due to interaction of the mineral with vein-forming fluids.Fluid inclusions (aqueous, L-V types) hosted by vein fluorite have homogenization temperatures of 100° to 130°C. Last melting o f ice indicates salinities of 24 to 28 wt. % equivalent NaCl, but low eutectic temperatures indicate that the fluids are mixed NaCl-CaCl2-FeCl2-MgCl2 brines. Although fluorite-hosted fluid inclusions from the South Mountain Batholith have similar salinities, they homogenize at temperatures of 150° to 160°C. Stable isotopic studies of vein minerals indicate 834Sbarite = +13 ± 2%o, 5 l8Oquartz = +22%oand 8D for fluid inclusion extracts are -123 to -165 %o. The data are interpreted to indicate that: (1) sulphur was derived from dissolution of Windsor Group evaporites rather than from sulphides in basement rocks; (2) the 5 l8Owater of the veins was +8 to +12 %o for 100° to 150°C, which is consistent with either a basinal or metamorphic fluid; (3) the fluids interacted with organic matter to generate the low 8D values. Measured 87Sr/86Sr on barite (0.7120; n=2) and fluorite (0.7086) indicate that the fluids exchanged with a radiogenic source, either the Horton Group or the Meguma Group being the most likely reservoir.Collectively the data indicate vein formation during the Early Carboniferous, when the study area was buried under ca. 2-3 km of Carboniferous strata which have subsequently been eroded. Basinal-type fluids were focused into zones of extension which opened as a result of high Pfluld, in concert with sinistral movement on NW-trending faults that crosscut the Meguma Terrane.On trouve une abondance de filons de barytine ± fluorite ± quartz le long de la marge orientale du pluton du Devonien superieur de Kinsac, granite hyperalumineux qui s'est introduit dans des roches metasedimentaires du groupe de Meguma. Les filons de barytine, orientes selon un pendage vertical de 120°, se trouvent dans des zones de granite fortement fracturees, mais ils ne sont pas deformes et ils pourraient renfermer des lentilles de granite fragments. Les filons (< 0,6 m) sont domines par la presence de barytine automorphe blanc trouble, grossiere, avec ou sans remplissage tardif de quartz transparent automorphe et de fluorite rose a...

Controls on Barite Mineralization in a Major Intracontinental Shear Zone: Carboniferous of the Cobequid Highlands, Nova Scotia

“…The data compare well with other late Carboniferous galenas from the Kennetcook basin (Figure 10). These galenas have Pb isotopes that are similar to those of late mafic rocks, including dykes cutting Horton Group in the Kennetcook basin, late gabbro in the Wentworth pluton, and the youngest basalt in the Fountain Lake Group [7] (excluding outlier values), except [25] for Kinsac; for granites, etc., from [27,28]. [25] for Kinsac; for granites, etc., from [27,28].…”

“…These galenas have Pb isotopes that are similar to those of late mafic rocks, including dykes cutting Horton Group in the Kennetcook basin, late gabbro in the Wentworth pluton, and the youngest basalt in the Fountain Lake Group [7] (excluding outlier values), except [25] for Kinsac; for granites, etc., from [27,28]. [25] for Kinsac; for granites, etc., from [27,28]. Lead isotopes were determined on one galena sample (SFB87-2016) from th fractures at Five Islands.…”

“…Other late Carboniferous analyses from the literature are also shown in isotope plots. These include analyses from barite deposits at the Brookfield [22], Walton [23,24] and Kinsac [25] deposits and Pb-Zn mineralization at those localities and at the Gays River and Jubilee deposits [7,26] (Figure 1a).…”

Granite-hosted mineral deposits of the New Ross area, South Mountain Batholith, Nova Scotia, Canada: P, T and X constraints of fluids using fluid inclusion thermometry and decrepitate analysis

“…In addition, Ca-rich fluid inclusions in vein barite-fluorite hosted by the 370 Ma Kinsac Pluton (Fig. 1) originated from Carboniferous basinal fluids interacting with the Meguma Group or its detrital equivalent, the Horton Group (Kontak et al 1999b). Therefore, in the New Ross area, the Na-Ca trends in Figure 8a are related to interaction of magmatic fluids with contact metamorphic generated fluids originating from metasedimentary rocks of the Meguma Supergroup, particularly from metawackes of the Goldenville Group located in close proximity to several mineral deposits near New Ross (Turner, Walker, Morley's, Millet Brook, Long Lake).…”

U-Pb dating of the Musquodoboit Batholith, southern Nova Scotia: evidence for a protracted magmatic-hydrothermal eventin a Devonian intrusion

“…Reynolds et al (1981) reported plateau ages of 373 and 363 Ma for biotite and muscovite, respectively, and 363 Ma for biotite from two monzogranite samples from this intrusion. More recently, Kontak et al (1999b) reported a 354 Ma plateau age for K-feldspar in monzogranite from the same area.…”