Field, isotopic, and chemical studies of tourmaline-bearing rocks in the Belt–Purcell Supergroup: genetic constraints and exploration significance for Sullivan type ore deposits

Abstract

The Sullivan Pb–Zn–Ag massive sulphide deposit (located in the mid-Proterozoic Belt–Purcell Supergroup near Kimberley, British Columbia) is associated with a large tourmalinite alteration zone. A petrologically similar, but barren, alteration zone has recently been discovered at Trestle Creek, Idaho. Because of the importance of the Sullivan deposit, several methods of exploration involving tourmaline have recently been proposed in the literature. To test these proposals, we compared the alteration zone at Sullivan (using literature data) with that at Trestle Creek. The two areas can clearly be distinguished using Mg content in tourmaline and δ18O in albitite, can probably be distinguished using δ18O in tourmaline-bearing rocks, but cannot be distinguished using alteration mineralogy alone. In addition we found that tourmaline occurs in at least eight different geologic settings in the Belt–Purcell Supergroup (one of which includes the alteration zones at Sullivan and Trestle Creek).Assuming a high water/rock ratio, a moderate to very high degree of oxygen-isotope exchange, and a hydrothermal fluid with δ18O ≥ 0, a series of hydrothermal models can be calculated for the alteration zones at Sullivan and Trestle Creek. The most realistic models at both localities involve temperatures of about 200–250 °C and fluids of marine derivation with a variable 18O shift. The isotopic differences between Sullivan and Trestle Creek are probably the result of a greater degree of fluid evolution and higher temperatures at Sullivan. Oxygen isotopes, hydrogen isotopes, and mineral chemistry of tourmaline from other geologic settings in the Belt–Purcell Supergroup suggest deposition from fluids of marine origin under various temperature conditions.

Turmalinitos vulcanogênicos da formação Morro da Pedra Preta do Grupo Serra do Itaberaba (SP): petrografia, composição química da turmalina e implicações metalogenéticas

“…Série Científica Beaty et al (1987), Hellingwerf et al (1994), Slack (1996) e Griffin et al (1996) reforçam a existência da correlação entre turmalina rica em Mg e depósitos de sulfetos, o que pode constituir um guia em trabalhos de exploração mineral. Griffin et al (1996) destacam que certos elementos traços presentes em turmalina (Cu, Pb, Zn, Sn, Ba, Sr e Ga) são também diagnósticos do tipo de depósito de sulfeto maciço.…”

Structural, textural, geochemical and isotopic signatures of synglaciogenic Neoproterozoic banded iron formations (BIFs) at Bafq mining district (BMD), Central Iran: The possible Ediacaran missing link of BIFs in Tethyan metallogeny

“…The mineral is associated with sericite and probably formed by reaction of fluids rich in Fe, Mg and B with plagioclase, alkali feldspar and chlorite. Sericite-tourmaline associations in exhalative ores have been reported to form at 200-250º C (Beaty et al, 1988).…”

Tourmalinization related to Late Proterozoic-Early Palaeozoic lode gold mineralization in the Bin Yauri area, Nigeria

“…Oxide ratios F e O / ( F e O + M g O ) and N a 2 0 / ( N a 2 0 + CaO) are used to evaluate compositional differences in the schorl-dravite tourmaline series (e.g. Ethier and Campbell 1977 1984;Beaty et al 1988). A relatively lower N a 2 0 / ( N a 2 0 + CaO) ratio exists in the altered wall-rock tourmaline, and F e O / ( F e O + M g O ) ratio in the wall-rock and vein tourmaline, c o m p a r e d to the ratios in tourmalinite (Fig.…”

“…At Bin Yauri, there is also the possibility of Fe being partitioned into sulphide minerals (cf. Beaty et al 1988), and some Fe + Mg into carbonates (ferroan dolomite and ankerite). These possibilities may explain the wall-rock tourmaline having less FeO and MgO and more A1203 compared with the vein tourmaline, the latter probably precipitating directly from the mineralizing fluids during vein formation.…”

“…Ethier and Campbell 1977;Slack 1982;Williams and Kennan 1983;Slack et al 1984;Taylor and Slack 1984;Henry and Guidotti 1985;Plimer 1988;Appleby and Williams 1988;Beaty et al 1988;Slack and Coad 1989;Bandyopadhyay et al 1993).…”