December 2019

Book review: The Geology and Resources of New Zealand Coalfields (AusIMM Monograph 33)

  • By Dean Fergusson MAusIMM CP (Geo)

Edited by Alan Sherwood

It’s rare to see a monograph written by a sole author, but I can’t think of any other practicing coal geologist in New Zealand aside from Alan Sherwood that has the breadth of knowledge, literary skill and professional character to carry this off.

Monograph 33 is an authoritative, some might say overdue, update on NZ coal deposits and the resources they contain. It runs to 279 pages and is supplemented with six appendices. The colour maps, cross-sections and photographs that abound throughout are pleasingly consistent in format and high quality. It is also somewhat pleasing to see that New Zealand Petroleum and Minerals have supported something tangibly connected with its indigenous coal.

Monograph 33 is many things: a dedication to perhaps New Zealand’s greatest coal geologist, Dr Pat Suggate; an overdue consolidation of the NZ Coal Resources Survey (NZCRS) findings; a contemporary classification framework and update of NZ coal resources; a geological overview of the numerous coal deposits, some almost forgotten; and an acknowledgement of the coal geologists who have explored and described our wonderful collection of coal basins since the latter half of the 19th century.

While relatively young and diminutive compared to the continental coal basins that dominate world coal production, I don’t think you’d find the variety of geological settings and variability of NZ coal basins in many other countries. This aspect, along with the unique interplay between dynamic, tectonic controls and the resultant impact on basin structure, stratigraphy, coal rank, type and quality are well captured in Monograph 33.

Throughout the book, Alan demonstrates his comprehensive knowledge of the history of the discovery, exploitation and utilisation of this now maligned, but still necessary ‘transitional’ energy source. Thankfully, it is an irreplaceable ingredient in steel making. The author outlines how coal was intrinsic to the industrialisation of New Zealand and the foundation of its economy through the 20th century, at least up until the discovery of large gas fields in the Taranaki basin in the 1970s. I’m pleased that the work on the non- conventional uses of coal, and lignite, and the need for CO2 sequestration is given some coverage. This account may not be the last word on that front.

Section 1 presents a sub-continental framework for describing the geological setting of the various coal regions and classification of coal quantities they contain, essentially using the Australian Coal Guidelines. This is a commendable attempt to plug the gap in knowledge of NZ’s coal inventory that developed following the NZCRS. The classification is basically sound and the division of Inventory Coal into two sub-categories based on likelihood of becoming JORC Resources is certainly provocative. The many philosophical and practical challenges with presenting an updated inventory are clearly articulated.

Sections 2 and 3 provide a systematic summary of every known coal deposit in the country. This is no mean feat and the abundant references cited are a treasure trove. I can’t help thinking the Monograph would have been more useful, and more representative, had the geological investigations, estimation practices and project assessments that were carried out after the coal resources survey been given more emphasis. Capturing the lessons learned (and not learned) from the several modern coal mines developed, mined through to end-of-life or closed would be highly relevant and beneficial to the current operators. It would also provide a perspective on the level of investigations required to accurately assess the feasibility to operate NZ’s unique coal deposits.

Monograph 33 gets close to being a definitive synthesis of NZ coal deposits and will remain the standard reference for decades ahead. Filling the gaps in the latter part of the story should be the challenge for the current generation of coal geologists, if they’re up for it. The legacy of Alan’s wonderful treatise is that it is a worthy basis for at least one subsequent edition.

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