Geology and Mineralization of the Lushs Bight Group Springdale Peninsula

Kean, B F; Evans, D T W

doi:10.4095/132255

Cited by 5 publications

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“…13; Marshall and Gilligan, 1987). These 390 conditions are consistent with the lower greenschist grade metamorphism recorded 391 elsewhere in the Lushs Bight Group (Kean et al, 1995). 392…”

Section: Sulfide Textural Evolution During Deformation and Remobilizasupporting

confidence: 73%

“…16a-c).measured δ 34 S values, further arguing that leaching from nearby footwall rocks was the 544 most important source for sulfur in the Whalesback deposit. Since the Lushs Bight Group 545 is 3-4 km in thickness (Kean et al, 1995), there is no restriction for the depth at which the 546 sulfur and metals present at Whalesback were extracted. However, given that copper 547 solubility is low below 225°C and greatly increase with increasing temperature 548 (Hannington et al, 2014), it is suggested that the sulfur and the metals were leached from 549 the lower portion of the mafic Lushs Bight Group.…”

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 99%

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Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

et al. 2015

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21The Whalesback Cu-rich VMS deposit in the Newfoundland Appalachians is a 22 highly deformed deposit found on a steep limb of a closed and boudinaged overturned 23 fold. The deposit was intensely deformed at low temperature but medium pressure (>175 24 MPa) during the accretion of the composite Lushs Bight Oceanic Tract-Dashwoods 25 terrane onto the Humber margin at ca. 480 Ma. 26The ore mineralogy consists of chalcopyrite, pyrrhotite and pyrite with lesser 27 sphalerite and trace Ag-, Bi-and Hg-tellurides. Four styles of sulfide mineralization are 28 present: 1) disseminated (5%); 2) vein (50%); 3) breccia (25%); and 4) semi-massive to 29 massive (20%). Independent of mineralization style, massive pyrite and pyrrhotite (and 30 some chalcopyrite) are commonly parallel to main S 2 schistosity in the deposit, whereas 31 late chalcopyrite piercement veins occur at a high angle to S 2 . The progressive increase in 32 pressure and temperature produced a remobilization sequence wherein sphalerite was the 33 first sulfide phase to cross the brittle-ductile boundary, followed by pyrrhotite and finally 34 chalcopyrite. Maximum temperature was not high enough for the pyrite to cross the 35 brittle-ductile boundary. Instead, pyrite grains were incorporated and transported by 36 pyrrhotite and chalcopyrite during the ductile remobilization events, rounding and 37 fracturing them. Remobilization of the sulfides occurred mainly by plastic flow, but some 38 solution transport and re-precipitation is locally observed. 39In situ secondary ion mass spectrometry (SIMS) sulfur isotopes geochemistry of 40 sulfides yielded values of δ 34 S ranging from +2.7‰ to 4.7‰ for pyrite, +2.1‰ to 4.0‰ 41 for pyrrhotite and +1.3‰ to 4.7‰ for chalcopyrite. Sulfur isotopic modeling suggests 42 3 that at least 60% of the sulfur was derived from leaching of igneous rocks (i.e., basalts), 43 with the reminder derived from thermochemical sulfate reduction (TSR) of seawater 44 sulfate during alteration of the basalts by seawater. At the deposit scale, sulfur isotopes 45 retained their original signature and did not re-equilibrate during the secondary 46 deformation and remobilization events. 47

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“…13; Marshall and Gilligan, 1987). These 390 conditions are consistent with the lower greenschist grade metamorphism recorded 391 elsewhere in the Lushs Bight Group (Kean et al, 1995). 392…”

Section: Sulfide Textural Evolution During Deformation and Remobilizasupporting

confidence: 73%

Section: Sulfide Textural Evolution During Deformation and Remobilizamentioning

confidence: 99%

Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

et al. 2015

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“…Although most of these deposits were mined primarily for Cu, Zn-rich zones have been documented in nearly all of the deposits and sphalerite is locally abundant at Betts Cove, Tilt Cove, Little Deer, and Little Bay and references therein). All the deposits comprise stratiform lenses and pods with welldeveloped sulphide stringer zones hosted predominantly by pillow lavas that have been variably deformed and metamorphosed to greenschist-facies mineral assemblages (West 1972;Upadhyay and Strong 1973;Bachinski 1976;Kean 1984). The relative stratigraphic position of VMS deposits within the ophiolite sequences does not appear to be of relevance to their sulphide mineralogy or gold content.…”

Section: Mafic Volcanic Hosted Vms Depositsmentioning

confidence: 89%

“…Pyrrhotite occurs locally in these deposits, but magnetite is common within the chloritized wallrock fragments. At McNeilly, horizons of massive magnetite together with minor chalcopyrite occur in strongly chloritized rocks described as "black cherts" (Kean 1984 to VMS mineralization is not precisely known.…”

Section: Type Iib Pyritic Assemblagesmentioning

confidence: 98%

Characteristics of gold mineralization in volcanogenic massive sulphide deposits of the Notre Dame Bay area, central Newfoundland

Santagulda¹,

Hannington²

1996

Can. J. Earth Sci.

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A reconnaissance study of 19 volcanogenic massive sulphide deposits in the Notre Dame Bay area indicates Au concentrations of up to 30 pprn (Betts Cove), and elevated gold contents (> 1 pprn Au) have been found in samples from 10 additional past producers and developed prospects. Systematic trends in the occurrence of gold are observed in two principal sulphide assemblages: polymetallic, pyrite -sphalerite -chalcopyrite -galena f arsenopy rite assemblages (type I) and pyrite-chalcopyrite + sphalerite f pyrrhotite assemblages (type 11). Type I assemblages occur in deposits with dominantly felsic host rocks, whereas type I1 assemblages are restricted to deposits in mafic-dominated ophiolite sequences. Free gold grains were observed in samples from eight different deposits in both type I and type I1 assemblages. X-ray emission spectra and electron microprobe analyses of the gold indicate that most grains are electrum, although a Au-bearing telluride occurs at Point Leamington. Ion microprobe analyses indicate that as much as 50% of bulk gold may be present as "invisible gold" locked in pyrite or arsenopyrite (up to 140 pprn Au at Point Leamington). Well-preserved primary depositional features in gold-bearing sulphides from several deposits suggest that the gold in type I assemblages is syngenetic. A strong correlation between gold and a polymetallic suite of Zn, Ag, Pb, As, and Sb, similar to that observed in Kuroko-type massive sulphides and in modem seafloor sulphides, supports a primary origin for gold in type I assemblages. In type I1 assemblages primary depositional features have been largely destroyed by deformation and annealing of sulphide grains. Gold is locally enriched in Zn-rich sulphides, and sulphides containing abundant pyrrhotite have the lowest gold contents. However, consistent geochemical associations with other elements are not observed, and this may reflect the strong remobilization of gold during structural deformation. The abundant free gold in some type I1 assemblages is a product of recrystallization during deformation and was derived locally from primary gold originally present in the host sulphides.

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“…Low field strength elements, including SiO 2 , Al 2 O 3 , FeO t , MgO, K, Rb, Sr, Ba, Cs, Pb, Eu, U, P, Ca, Mn and Na, are generally regarded as mobile elements, whereas high field strength elements, including Ti, Y, Zr, Hf, Ta, Nb, Th, Sc, Ni, Cr, V, and Co are generally thought of as being strongly immobile (Kean et al, 1995;Rollinson, 1998). The Zandspruit ultramafic rocks, here regarded as protoliths of the metasomatized rocks, possess notable quantities of V, Cr, Co, Ni, and Sc.…”

Section: Geochemical Plotsmentioning

confidence: 99%

Metasomatized and hybrid rocks associated with a Palaeoarchaean layered ultramafic intrusion on the Johannesburg Dome, South Africa

Anhaeusser

2015

Journal of African Earth Sciences

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Geology and Mineralization of the Lushs Bight Group Springdale Peninsula

Cited by 5 publications

References 0 publications

Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

Styles, Textural Evolution, and Sulfur Isotope Systematics of Cu-Rich Sulfides from the Cambrian Whalesback Volcanogenic Massive Sulfide Deposit, Central Newfoundland, Canada

Characteristics of gold mineralization in volcanogenic massive sulphide deposits of the Notre Dame Bay area, central Newfoundland

Metasomatized and hybrid rocks associated with a Palaeoarchaean layered ultramafic intrusion on the Johannesburg Dome, South Africa

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