Hill, M.P. 2024 Aggregate opportunity modelling for the Tasman district of New Zealand. Lower Hutt, NZ: GNS Science. GNS Science report 2024/34. 26 p.; doi: 10.21420/98J1-2T63
Abstract
Efficient utilisation of aggregate resources is important for supporting infrastructure development and reducing operational and transport costs related to extraction of hard rock, gravel and sand aggregate materials. Aggregate opportunity has been mapped in Tasman District, encompassing the areas of Richmond, Motueka, the Waimea and Moutere valleys, Takaka and Collingwood, as well as St Arnaud and Murchison and the Ella Range to the south. The presence of aggregate resource potential is a consideration for prioritising future land uses. Delineated aggregate opportunity areas (places that have overlapping spatial data classes favourable for extractive activities) indicate where there is potential that an aggregate resource could be developed, provided that follow-up site-specific investigation confirms the geotechnical suitability of the material and that extractive activities would be compatible with factors such as community and iwi values and land-use zoning. A spatial modelling approach using Geographic Information System (GIS) software forms the basis of aggregate opportunity modelling. The first step of the modelling involves classification of source data into mappable criteria layers. A total of 21 mappable criteria layers were compiled from various source data and classified via aggregate-relevant parameters. Each map class was assigned a class-weighting value that qualitatively ranks its importance as an aggregate indicator using expert knowledge from industry experts and spatial statistics. The second step involved fuzzy logic modelling to combine mappable criteria information and generate four categoriesof predictive model components (source material, land use, quarrying feasibility and cultural sensitivity). The third step combined the four categories of predictive model components into maps of spatial model results, which depict the aggregate opportunity, ranked from low to high, for three types of material (hard rock, gravel and sand). The spatial model results data were analysed and filtered to produce the overall aggregate opportunity model. These map-based GIS datasets of sand, gravel and hard rock aggregate opportunities can be used to manage aggregate resources, generate targets for exploration activities and provide insight into future resource development. This approach acknowledges regulatory, economic and community-sensitivity considerations for aggregate opportunity, while providing insights into aggregate resource distribution and potential extraction sites. Tasman District has large areas of hard rock and gravel deposits that can potentially be utilised for aggregate extraction and supply. Much of this material is exposed at or near the surface. Hard rock aggregate is dominated by sandstone, intrusive rocks and marble; good opportunity for sandstone is located in the Gordon and Barnicoat ranges, intrusive rocks such as granite, gabbro and diorite are located in many parts of the district, and marble opportunity is concentrated within the Arthur Ranges. Gravel and sand are extractable from river and stream deposits, with the best material located within recent river deposits adjacent to the Motueka, Waimea, Wairoa, Wai-iti and Buller rivers and sand is likely to be a companion material within many of the gravel opportunity sites. High-quality, well-sorted gravels need to be prioritised for roading and concrete use and lower-quality gravel and rock should be utilised where suitable to preserve the limited high-quality material. (auth)
Digital appendix is available here: https://doi.org/10.21420/sqq4-rj10
