Till geochemical signatures of the Sisson W-Mo deposit, New Brunswick

Seaman²,

Parkhill³

et al. 2014

atgeol

A till composition study was carried out around the Sisson W-Mo deposit, New Brunswick, Canada, one of the largest W deposits in the world, to test modern analytical methods for W in till and document glacial dispersal from a significant W source. The <0.063 mm fraction of till defines glacial dispersal down ice of the deposit and use of this fraction is recommended for W-Mo exploration in the region. Metal-rich till overlying the deposit contains up to 816 ppm W and 63 ppm Mo. One km down ice, till contains 75 ppm W and 8 ppm Mo, and till in background areas contains a maximum of 7 ppm W, and 2 ppm Mo. Indicator elements for the deposit include W and Mo, and pathfinder elements include Ag, As, Bi, Cd, Cu, In, Pb, Te, and Zn. This list of elements is more extensive than previously identified for the Sisson deposit or identified in other published till geochemical studies because of the polymetallic nature of the Sisson deposit and the broad suite of elements that can now be determined using modern analytical techniques. Lithium meta/tetraborate fusion inductively coupled plasma-mass spectrometry was used to determine the total concentration of W in till and is a fast and cost effective method as compared to those reported in the older literature. Glacial dispersal of W and Mo from the Sisson deposit is detectable at a regional scale at least 14 km down ice (southeast) using surface till sampling. A 2 km till sample spacing should be sufficient to detect glacial dispersal from a W-Mo deposit of this size. RÉSUMÉUne étude de composition du till a été réalisée autour du dépôt de Sisson, composé de tungstène et de molybdène et situé au Nouveau-Brunswick, au Canada. Il s'agit de l'un des plus importants dépôts de tungstène au monde. L' étude a été réalisée pour mettre à l' essai les méthodes modernes d'analyse du tungstène contenu dans le till et pour obtenir des données sur la dispersion glaciaire d'une importante source de tungstène. La fraction inférieure à 0,063 mm du till dé-finit la dispersion glaciaire du dépôt sous la glace et on recommande l'utilisation de cette fraction pour l' exploration du tungstène-molybdène dans la région. Le till riche en métal sus-jacent au dépôt contient jusqu'à 816 ppm de tungstène et 63 ppm de molybdène. À un kilomètre sous la glace, le till contient 75 ppm de tungstène et 8 ppm de molybdène, tandis que la partie inférieure du till contient tout au plus 7 ppm de tungstène et 2 ppm de molybdène. Parmi les élé-ments indicateurs du dépôt, on trouve du tungstène et du molybdène, et les indicateurs géochimiques comprennent notamment l'argent, l'arsenic, le bismuth, le cadmium, le cuivre, l'indium, le plomb, le tellure et le zinc. Puisque le dépôt de Sisson est de nature polymétallique et qu'il est maintenant possible de définir une vaste gamme d' éléments grâce aux techniques modernes d'analyse, la liste d' éléments est plus longue que celle précédemment établie pour le dépôt de Sisson ou que ce qui a été publié dans d'autres études géochimiques du till. Pour déterminer la conc...

Section: Resultsmentioning

confidence: 99%

Section: Arsenic Zinc and Cadmium In The <0063 MM Fraction Of Tillmentioning

confidence: 99%

Section: Till Samplingmentioning

confidence: 99%

Section: Till Samplingmentioning

confidence: 99%

Section: Till Samplingmentioning

confidence: 99%

See 3 more Smart Citations

Till geochemical signatures associated with the Sisson W-Mo deposit, New Brunswick, Canada

Seaman²,

Parkhill³

et al. 2014

atgeol

Application of portable XRF to the direct analysis of till samples from various deposit types in Canada

Hall¹,

Pagé

2015

GEEA

In this study, results by direct portable XRF (‘pXRF’) on unsieved till samples were compared with those by established laboratory methods (aqua regia or fusion ICP-MS and ICP-ES) on the <0.063-mm fraction to determine if the application of direct pXRF in the field would serve as an acceptable guide for immediate follow-up work. Four test sites in Canada were chosen: the Halfmile Lake Cu-Pb-Zn VMS deposit; the intrusion-hosted W-Mo Sisson deposit; a Pb-Zn Mississippi Valley–type (MVT) deposit in the Pine Point district; and the Triple B kimberlite. Unsieved till samples from the GSC archive collection were used for this study and included samples from background areas, immediately overlying, and at various distances down-ice of each deposit. Ziploc® and Whirl-Pak® bags that were used to contain the samples in the field were tested for their properties of X-ray attenuation and contamination. In general, the performance of pXRF in the four test areas was very good where concentrations of elements of interest (indicator or pathfinder elements) were substantially above detection limits by this technique (in the low ppm range for many elements). The following elements, shown to be useful indicator elements (important constituents of the ore/commodity) or pathfinder elements (those associated with the commodity elements) by the established methodology, showed similar patterns by pXRF on the unsieved material: Zn, Cu, Pb, and As at Halfmile Lake; W, Mo, Cu, Zn, Pb, and As at the Sisson deposit; Zn, Pb, and Fe at Pine Point; and Ca, Sr, Cr, and Ni at Triple B. Pathfinder elements whose concentrations were too low for determination by pXRF include: Ag and Sb at Halfmile Lake; Ag and Cd at Sisson; Cd, S, and Se at Pine Point; and Co, Mg, P, U, and Th at Triple B. The high background for Bi by pXRF, equivalent to c . 50 ppm, and its noisy signal precluded its use at Halfmile Lake and Sisson. Elements which tended to show poor precision (three analyses each sample) by pXRF in some samples due to sample heterogeneity include Sn, V, and W. Mercury was erroneously reported for the majority of samples in the low ppm range by pXRF whereas its concentration in fact was in the low ppb range. Several Pb-, Zn- ( c . 1% Pb, Zn) and Fe-rich (up to 16% Fe) samples demonstrated spectral interferences by: Pb on As, Th and Se; Zn on Cu; and Fe on Co. Results for six till samples analysed in Ziploc® and Whirl-Pak® bags showed that Ziploc® absorbs fewer low-energy photons and hence is preferable for determining light elements such as Si, K and Ca. Supplementary material: Four data-sets are available at http://www.geolsoc.org.uk/SUP18897

Indicator mineral and geochemical signatures associated with the Sisson W–Mo deposit, New Brunswick, Canada

Parkhill²,

Pronk³

et al. 2017

GEEA

An indicator mineral and geochemical case study was carried out around the Sisson W–Mo deposit to test modern indicator mineral and analytical methods and document glacial and fluvial dispersal from a significant W–Mo source. Indicator minerals in the 0.25 – 2.0 mm non-ferromagnetic heavy mineral fraction of till and stream sediments include the primary ore minerals scheelite, wolframite and molybdenite, as well as chalcopyrite, joseite, native Bi, bismutite, bismuthinite, galena, sphalerite, arsenopyrite, pyrrhotite and pyrite. Indicator minerals in c. 12 – 14 kg samples define glacial dispersal of at least 10 km down ice (SE) of the deposit and fluvial dispersal at least 4 km downstream. The presence of very coarse (0.5 – 2.0 mm) indicator minerals in till and stream sediments marks proximity (<1 km) to the mineralized source. Indicator elements for the deposit in the <0.063 mm fraction of till, the <0.177 mm fraction of stream sediments, and in stream water include W and Mo, and various combinations of pathfinder elements Ag, As, Bi, Cd, Cu, In, Pb, Te and Zn. This list of elements is more extensive than previously identified for the Sisson deposit or other studies around W mineralization in glaciated terrain. The study demonstrates that indicator mineral methods, so well known for diamond and gold exploration, have a broader application that includes W–Mo exploration.