Pining for an anomaly: Biogeochemical mapping of the Cobar Basin for mineral exploration at regional to local scales.

In geochemical mapping for mineral exploration or environmental purposes, the choice of sampling media is influenced by the source, form, mobility and spatial distribution of the elements being mapped. The potential advantages of plant organs over regolith materials include the capacity of plants to sample large volumes of underlying regolith and groundwaters. There have been few regional biogeochemical mapping studies to test the capacity of plants to detect the effects of variations in geology, or the presence of mineralisation or contamination. This study has examined the composition of the needles of cypress pines (Callitris glaucophylla) across the Cobar Basin in New South Wales. With samples collected from over 3,500 individual trees with a 43,000 km2 area, it constitutes one of the largest single-species regional biogeochemical mapping projects undertaken internationally. The sampling includes detailed studies on the response in the needles over a range of precious and base metal mineralisation styles and regolith settings spanning 35 individual deposits. Geochemical analysis has been performed using inductively-coupled plasma-mass spectrometry (ICP-MS) and portable X-ray fluorescence spectrometry (pXRF). Concentrations of most elements in the needles reflect variations in underlying lithology, even in areas with alluvial cover. Concentrations of non-nutrient trace elements Au, Ag, Bi, Pb, As and W are typically higher over Siluro-Devonian clastic sediments than felsic intrusive and volcaniclastic rocks or Ordovician siliciclastic units. Micronutrients Ni, Co and Mn are elevated over ultramafic rocks. The needles display moderate to strong multielement biogeochemical responses to underlying mineralisation for ore-related elements including Au, Ag, Pb, Ni and W. Biogeochemical patterns can differ from those in adjacent soils reflecting influence of different dispersion processes. The pines restrict uptake of Cu and Zn. Seasonal and site variations are not sufficient to substantially alter geochemical contrast between background and mineralisation signatures. The needles display the effects of contamination from current and historical mining operations in some areas. There is no systematic relationship between needle composition and either distance from road edges or road type, except for Fe and Al. In situ pXRF and ICP-MS analyses displays similar patterns for Cu, Pb, Zn, Fe, Mn, Ni, Ca, K, Mg, Al and Si.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2026

Author dc:creator

• Schifano, Joseph

• Biogeochemistry
• Mineral Exploration
• Callitris glaucophylla (white cypress pine)
• pXRF use on vegetation and in situ field use
• Cobar Basin NSW Australia
• anzsrc-for: 37 EARTH SCIENCES

Statement dc:rights

• embargoed access
• CC BY 4.0

Licence

• http://purl.org/coar/access_right/c_f1cf
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/31989

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/106925