Mineral resource assessment of the Northland Region, New Zealand A B Christie R G Barker GNS SCIENCE \REPORT 2007/06 May 2007 Mineral resource assessment of the Northland Region, New Zealand A B Christie R G Barker GNS Science Report 2007/06 May 2007 GNS Science BIBLIOGRAPHIC REFERENCE Christie, A.B., Barker, R.G. 2007. Mineral resource assessment of the Northland Region, New Zealand, GNS Science Report, 2007/06, 179 A B Christie, GNS Science, PO Box 30-368, Lower Hutt R G Barker, Consulting Geologist, PO Box 54-094, Bucklands Beach, Auckland © Institute of Geological and Nuclear Sciences Limited, 2007 ISSN 1177-2425 ISBN 0-478-09969-X CONTENTS ABSTRACT............................................................................................................................................vii KEYWORDS ..........................................................................................................................................vii 1.0 INTRODUCTION .........................................................................................................................1 2.0 MINERAL RESOURCE ASSESSMENT FACTORS AND LIMITATIONS .................................7 3.0 PREVIOUS WORK......................................................................................................................9 4.0 METHODS.................................................................................................................................11 5.0 DATA.........................................................................................................................................11 6.0 RESOURCE MAPS...................................................................................................................13 7.0 SETTING ...................................................................................................................................15 7.1. Population and infrastructure ...................................................................................... 15 7.2 Geomorphology........................................................................................................... 15 8.0 GEOLOGY ................................................................................................................................15 8.1 Previous work .............................................................................................................. 15 8.2 Greywacke basement.................................................................................................. 19 8.3 Cretaceous – Cenozoic pre-allochthon sedimentary rocks......................................... 19 8.4 Northland Allochthon ................................................................................................... 19 8.5 Post allochthon rocks .................................................................................................. 23 8.6 Structure ...................................................................................................................... 23 9.0 BULK COMMODITIES: ROCK AGGREGATE, SAND, BUILDING STONE AND LIMESTONE..............................................................................................................................27 9.1 Rock Aggregate........................................................................................................... 27 9.1.1 Northland deposits ......................................................................................... 28 9.1.2 Future potential .............................................................................................. 34 9.2 Sand ............................................................................................................................34 9.2.1 Northland deposits ......................................................................................... 34 9.2.2 Future potential .............................................................................................. 35 9.3 Building and dimension stone ..................................................................................... 37 9.3.1 Northland deposits ......................................................................................... 37 9.3.2 Future potential .............................................................................................. 37 9.4 Limestone .................................................................................................................... 39 9.4.1 Northland deposits ......................................................................................... 39 9.4.2 Future potential .............................................................................................. 43 10.0 COAL AND PEAT.....................................................................................................................45 10.1 Sub-bituminous – bituminous coal .............................................................................. 45 10.1.1 Northland deposits ....................................................................................... 45 10.1.2 Post-1980 exploration (Isaac 1985)............................................................. 45 10.1.3 Future potential ............................................................................................ 46 10.2 Lignite .......................................................................................................................... 48 10.2.1 Northland deposits ....................................................................................... 48 10.2.2 Future potential ............................................................................................ 48 10.3 Peat ............................................................................................................................. 48 10.3.1 Northland deposits)...................................................................................... 48 10.3.2 Future potential ............................................................................................ 48 11.0 MINERAL RESOURCE ASSESSMENT OF METALLIC AND INDUSTRIAL MINERALS......51 11.1 Assessment method.................................................................................................... 51 11.2 Mineral deposit models ............................................................................................... 51 12.0 METALLIC MINERAL DEPOSITS............................................................................................53 12.1 Aluminium.................................................................................................................... 53 12.1.1 Laterite bauxite type aluminium deposits..................................................... 53 12.2 Antimony...................................................................................................................... 55 GNS Science Report 2007/06 i 12.2.1 Hot spring Sb-As type antimony deposits.................................................... 55 12.3 Chromium .................................................................................................................... 57 12.3.1 Podiform chromite type chromium deposits................................................. 57 12.4 Copper......................................................................................................................... 59 12.4.1 Cyprus VMS Cu type copper deposits......................................................... 59 12.4.2 Besshi VMS Cu type copper deposits ......................................................... 61 12.4.3 Porphyry Cu type copper deposits............................................................... 62 12.5 Gold-Silver................................................................................................................... 66 12.5.1 Hot spring Au-Ag type gold-silver deposits.................................................. 66 12.5.2 Low sulphidation epithermal Au-Ag type gold-silver deposits .................... 74 12.5.3 Sediment hosted Au type gold-silver deposits............................................. 77 12.5.4 Au skarn type gold-silver deposits ............................................................... 79 12.6 Iron .............................................................................................................................. 82 12.6.1 Bog iron)....................................................................................................... 82 12.7 Manganese.................................................................................................................. 82 12.7.1 Volcanogenic Mn type manganese deposits ............................................... 82 12.8 Mercury........................................................................................................................ 87 12.8.1 Hot spring Hg type mercury deposits........................................................... 87 12.9 Nickel........................................................................................................................... 90 12.9.1 Lateritic Ni deposits...................................................................................... 90 12.9.2 Gabbroid-associated Ni-Cu type nickel deposits......................................... 90 12.10 Zinc and Lead.............................................................................................................. 92 12.10.1 Zn-Pb polymetallic vein type zinc and lead deposits................................. 92 12.10.2 Zn-Pb skarn type zinc and