Gersdorffite with pentlandite, violarite, pyrrhotite, and pyrite, northwest Nelson, New Zealand

Abstract

Gersdorffite (NiAsS), only reported in New Zealand in 1887 from the Richmond Hill area, has been found in two further localities in northwest Nelson. Gersdorffite has been relocated in a quartz-veined ophicarbonate at Parapara River near Richmond Hill, and has average compositions of (Fe 0.21 , and minor pyrite. The Ni-As-Fe sulphides at Parapara River and Calphurnia Creek are products of talccarbonate facies alteration of ultramafic rock during early Paleozoic (Pre-Baton Event) regional greenschist facies metamorphism, with temperatures of sulphidation ranging between c. 300 and <100°C (below that of associated silicate/carbonate assemblages of 320-490°C), -33 to -30 logƒO 2 , c. -1 to -1.3 logΣS, and between c. -0.9 and -0.11 logƒS in the fluid phase; the presence of gersdorffite requires the introduction of As ± Bi from a carbonate-bearing fluid. At Contact Creek, arsenic was introduced into the fuchsite quartzite by hydrothermal fluids from the nearby Early Cretaceous Onahau Granite that also transported nickel and cobalt scavenged from a lens of antigorite-talc-magnesite within the pluton. Temperatures of gersdorffite and an initial metal solid solution (mss) formation at Contact Creek were between c. 500 and >380°C, the mss subsequently exsolving G98001

The Effects of Galvanic Interactions with Pyrite on the Generation of Acid and Metalliferous Drainage

“…However, a further factor affecting pyrite oxidation in natural systems is its coexistence with other sulfide minerals. ,− When semiconductive sulfide minerals with differing rest potentials are in electrical contact, particularly in acidic solutions, electron transfer occurs from the sulfide with the smaller (anode) to the greater rest potential (cathode). A galvanic cell is formed in which the cathode is galvanically protected and the anode is preferentially dissolved/oxidized. − Among common sulfide minerals, pyrite has a relatively high rest potential (660 mV SHE at pH 4; Table 7 in Li et al, 2013), as compared to other sulfide minerals such as sphalerite (460 mV SHE; pH 4) or galena (400 mV SHE; pH 4).…”

New data on gersdorffite and associated minerals from the Peloritani Mountains (Sicily, Italy)

“…For instance, Henning et al (1997) reported up to 0.12 wt % in gersdorffite from the Eastern Cape province, Republic of South Africa, whereas Voudouris et al ( 2018) found up to 0.18 wt % Bi in samples from the Clemence deposit, in the Kamariza mining district, Greece. The Bi content of gersdorffite from Contrada Zillì (up to 2.76 wt %) can be compared with that reported by Grapes and Challis (1999) from the Calphurnia Creek, northwest Nelson, New Zealand, i.e., 2.80 wt %. However, to the best of our knowledge, the highest Bi content reported in gersdorffite was found by Persuad et al (1988) in samples from the Dawn Lake U-Ni deposit, Saskatchewan, Canada, i.e., 14.53 wt %.…”