Rare Earth Element Resources: Indian Context (Society of Earth Scientists Series) 9783030413521, 9783030413538, 3030413527

Citation preview

Society of Earth Scientists Series

Yamuna Singh

Rare Earth Element Resources: Indian Context

Society of Earth Scientists Series Series Editor Satish C. Tripathi, Lucknow, India

The Society of Earth Scientists Series aims to publish selected conference proceedings, monographs, edited topical books/text books by leading scientists and experts in the field of geophysics, geology, atmospheric and environmental science, meteorology and oceanography as Special Publications of The Society of Earth Scientists. The objective is to highlight recent multidisciplinary scientific research and to strengthen the scientific literature related to Earth Sciences. Quality scientific contributions from all across the Globe are invited for publication under this series. Series Editor: Dr. Satish C. Tripathi

More information about this series at http://www.springer.com/series/8785

Yamuna Singh

Rare Earth Element Resources: Indian Context

123

Yamuna Singh Centre for Earth, Ocean and Atmospheric Science University of Hyderabad Hyderabad, India

ISSN 2194-9204 ISSN 2194-9212 (electronic) Society of Earth Scientists Series ISBN 978-3-030-41352-1 ISBN 978-3-030-41353-8 (eBook) https://doi.org/10.1007/978-3-030-41353-8 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Foreword

India is known since long to possess large reserves of monazite in the Coastal mineral sands of the western and eastern coastal tracts of South Indian peninsular shield. Monazite is rich in light rare earth element. Exploration in India for Rare Earth Element (REE) deposits since the 1950s has brought to light several other significant sources that are rich in both light and heavy rare earths. These rare earth mineral deposits occur in different geological settings, that include inland stream placers, carbonatites, alkaline to sub-alkaline felsic rocks, pegmatite and hydrothermal deposits. Several of these sources are under detailed investigation. There are also several relatively minor natural sources and possibilities of recoveries of REE from industrial wastes like phosphogypsum, coal fly ash and bauxite residue (red mud). To these sources, we may also add possibilities of recovery from waste electrical and electronic materials. All these sources are equally significant to ensure a comprehensive approach to multiple Rare Earth (RE) Industry. In spite of such large potential resources, India’s position in the International Scenario of the RE Industry is a low-cost raw material source and relatively insignificant. Some steps are in progress to ensure the larger expansion of the RE Industry in India largely through the initiative taken by the IREL (India) Limited, the Atomic Minerals Directorate for Exploration and Research and other units of the Department of Atomic Energy, Government of India and some of the Defence Research Institutions. Attempts are in progress to enlarge the research inputs in promoting the two arms of the Rare Earth Industry—the upstream chain of exploration, extraction and production of metal oxides, metals and alloys and the downstream chain of manufacturing intermediate products like permanent magnets, phosphors etc. As against this Indian Scenario, the world RE Mineral Industry has made phenomenal progress through the utilisation of REE in the electronics, lighting, power generation, including Nuclear Power and military applications, imparting to Rare Earth Mineral resources a strategic importance. Future commitments to increasingly utilise clean energy for climate control would further enhance the importance of Rare Earth Mineral resources.

v

vi

Foreword

It is in the above context we have to view the present monograph on RE Mineral Resources in India. Dr. Yamuna Singh has made a yeoman service in meticulously compiling the information we have on the RE mineral deposits in India, systematically classifying them in terms of the geological setting and presenting them in order of their current commercial importance and industrial potential. He has outlined several aspects of the Rare Earth Mineral industry in the international field that need consideration in planning our future developments. We have herein a fairly comprehensive presentation on the Rare Earth Resources of India and their future development, which provide a bird’s-eye view of Indian Rare Earth Resources and the scope for their future development. This book is well illustrated and provides voluminous data mostly in summarised tables and attempts as close a description as possible that will give a good understanding of the resources. I believe that this publication will give further impetus to the ongoing efforts in advancing the RE Mineral Industry in India. The publication would be of interest to all engaged in the RE Industry and to the teaching of courses in economic geology in the Universities. It would be a useful addition to the Libraries in India and abroad. Cochin, India

T. M. Mahadevan

Preface

The beginning of the history of rare earth group minerals may be traced to the discovery of ytterbite (subsequently named gadolinite), in 1787. Lieutenant Karl Axel Arrhenius himself did not realise that his picking of a black rock from near Ytterby, Sweden, will bring a revolution in science. Since then, there has been progressive growth in identifying the individual REEs and their use in the mineral industry. Demand for REEs has also progressively increased. Due to similar and low chemical reactivity in geological environment, REEs rarely formed distinct minerals and thus had to be extracted from minerals having very low concentrations. This involved innovative hydrometallurgical processes for extraction and purification of individual rare earth elements. Various prominent industries where REEs find applications in decreasing order are catalysts (24%), magnets (23%), polishing (12%), other applications (9%), 8% each in metallurgy and batteries, glass (7%), ceramics (6%) and phosphors and pigments (3%). Prevailing thrust on clean energy world over has suddenly accentuated the requirement of REEs to sustain progressive growth without aggravating environmental concerns. Presently, rare earth elements are ruling the mineral market riddled with uncertainty in terms of their supply in the world market due to denial of material by countries, like China, which have large Rare Earth Element (REE) resources. Accordingly, those countries which do not have REE resources have intensified exploration efforts to locate workable resources to ease out dependability in the world market. India is not an exception to this fast-changing scenario. In the backdrop of the great advances India has made in the identification of REE resources and the large number of occurrences of REE concentrations in various geological environment, it was felt imperative to take stock of the situation with respect to rare earth resource position of India. Hence, this task was taken up. We have identified a variety of REE resources in India which include beach placers, inland stream placers, carbonatites, peralkaline-alkaline felsic rocks, hydrothermal veins, pegmatites, potential natural resources and potential industrial (secondary) resources. These have great potential as a resource for REE. Except for Beach Placers, we have only preliminary knowledge of the other resources; these

vii

viii

Preface

are encouraging and point to a large potential. Suggestions have been offered on the need to intensify exploration in several of these areas, on a basis of priority. This book has been divided into ten chapters. In Chap. 1, a brief survey of REE, including history of REE discovery, various applications, trend in demand, geochemical characteristics and mineralogy is given. In Chap. 2, details about placer heavy mineral deposits/occurrences located in various coastal stretches, including a few inland, in parts of Odisha, Andhra Pradesh, Tamil Nadu, Kerala, Maharashtra, Gujarat States and coastline of West Bengal are presented. REE-bearing minerals, monazite, zircon and garnet are present with variable grades in most of the placer deposits of eastern and southern Indian coasts. Monazite resource of 12.45 million tonnes (Mt) is contained mostly in beach placers of India. Some of the deposits in Odisha (Chatrapur), Tamil Nadu (Manavalakurichi, Midalam, Vayakallur) and Kerala (Chavara) are under active exploitation for the recovery of beach sand heavy minerals, including monazite. Recovery of light REE (LREE) is being done by IREL (India) Limited by cracking monazite. In Chap. 3, salient features of heavy REE (HREE) resources occurring as inland placers along the courses of several streams draining through Chhottanagpur Granite Gneiss Complex terrain in central and eastern India have been highlighted. Such occurrences are though small in size, but form most potential resources for Yttrium and HREE-rich polymineral concentrates. Cluster of one such stream placer deposit is under exploitation by AMD for the recovery of Yttrium and associated LREE minerals in central India. Several xenotime-bearing stream placer occurrences identified in other parts of India offer scope for exploration inputs for augmenting xenotime-bearing stream placer resources. Carbonatite-hosted LREE resources have been dealt with in Chap. 4. The results reveal that substantial rare earth resources are contained in the carbonatite complexes of western India, namely, Amba Dongar, Gujarat and Kamthai, Rajasthan. In these areas, minerals which contribute to REE are represented by mainly bastnaesite with other minor phases. AMD has estimated 3.46 lakh tonnes of REO resource in Amba Dongar carbonatite complex, by taking average grade of 1.34% TREO. In the case of Kamthai carbonatite deposit, 7.36 million tonnes of ore has been estimated by M/s Ramgad Minerals and Mining Limited, with an average grade of 1.62% REO. In northeast India, Samchampi carbonatite complex contains very low-grade Yttrium ore. The carbonatites of southern India offer scope for exploration of REE, dominated by monazite content. REE potentiality of many other carbonatite bodies needs to be evaluated. It is necessary to develop dependable flow sheets for economic recovery of REE from carbonatites in a cost-effective way. Chapter 5 provides an account of REE concentrations in peralkaline-alkaline felsic rocks of India. Results of initial investigations reveal that peralkaline fine-grained granite and microgranite bodies occurring essentially in the form of dykes of various dimensions associated with Siwana Ring Complex in western Rajasthan are potential for HREE. A cumulative resource of more than one million tonne is speculated by AMD from Siwana ring complex. In southern India, peraluminous to peralkaline Kanigiri granite also contains substantial REE. Presence of discrete mineral phases like columbite-tantalite, fergusonite, samarskite, allanite, monazite, thorite, bastnaesite and hydroxyl-bastnaesite in Kanigiri granite and

Preface

ix

associated soils supports potentiality of the felsic body for REE along with rare metals (Nb, Ta). In Chap. 6, REE resources associated with hydrothermal veins have been highlighted. Some of the resources under this category are associated with apatite–magnetite vines of Singhbum Shear Zone (SSZ), Jharkhand, notably the xenotime concentrations in the Kanyaluka area along the eastern end of the SSZ. Chapter 7 provides an account of rare earth-bearing pegmatites of Bastar, Odisha and Andhra Pradesh. In addition, pegmatites of the Madurai district, Tamil Nadu, also contain REE minerals. Where REE deposits occur in pegmatites and hydrothermal veins in alkaline complexes, there is a repetition of geological setting in the different chapters. In actual exploitation, the distribution of REE in the host alkaline rocks, pegmatites and stream sediments may have to be exploited together. Chapter 8 deals with possible natural resources comprising quartz-pebble conglomerate, iron oxide breccia complex, phosphorite, bauxite, laterite, phosphate ores, sea bed/floor mud and ion adsorption clays. Chapter 9 covers potential industrial (secondary) resources, namely, phosphogypsum, phosphoric acid, coal fly ash, red mud, tin slags, tailings from Pb–Zn–Cu ore, blast furnace slags of steel plants and electronic waste. Initial results, however, appear encouraging in some cases. The final chapter discusses the relative merits and potential of several sources for future development and directions for larger inputs in exploration, on the one hand and the utilisation of the industrial sources, on the other. In addition, it is suggested that “REE balance problem” can be addressed by finding additional uses of those individual rare earths whose surplus production cannot be avoided and also to develop substitutes in domain-specific various applications for those rare earths which are scarce or critical in terms of their availability. It is envisaged that promotion of the REE Industry in India should be an integral part of the present programme of “Make in India”, for which a beginning can be made by the AMD-IREL-BARC-NFC-DMRL-ARCI combine. To achieve this goal, several of the industrial partners like Aluminium extraction, Thermal Power Plants, Fertiliser Plants, different Mining Agencies and Steel Plants can also be involved as partners. Also, India can promote its ties with countries, as has been established now with Japan for improving its domain knowledge and new technologies for both upstream and downstream processes of the “Indian Rare Earth Industry”. I owe a deep sense of gratitude and indebtedness to Shri T. M. Mahadevan, Former Director, Atomic Minerals Division (AMD), Department of Atomic Energy (DAE), Government of India, who painstakingly critically reviewed the manuscript and offered innumerable suggestions, modifications and intense technical inputs during various stages, which transformed overall presentation style and clarity drastically. I also thank him profusely for the foreword to this book. However, I accept the responsibility of any mistakes which might have crept in inadvertently. I shall be thankful to the readers if lapses of any kind are communicated to me ([email protected]). I express my sincere thanks to Director, Atomic Minerals Directorate for Exploration and Research (AMD), DAE, Government of India, and also to many former colleagues in AMD for their encouragement, guidance and influential

x

Preface

discussions and help during the preparation of this book. Much of the information for certain chapters of the book is taken from AMD’s publications, especially Annual Journal, Exploration and Research for Atomic Minerals and Journal of Atomic Mineral Science, including Smarika, and the same is gratefully acknowledged. I am grateful to a host of publishing houses and authors who have generously permitted to use figures in this book. Among various sources which have enriched the book, the considerable source is the Geological Society of India, Bengaluru. I am grateful to Prof. D. P. Dubey for his constant inspiration; and to Dr. Sahendra Singh, Dr. M. Ismaiel, Dr. Amit K. Singh and Dr. D. C. Jhariya for their help. I thank the University of Hyderabad, Gachibowli, Hyderabad, for providing me working opportunity. I sincerely thank the Society of Earth Scientists for inviting me to pen down this book. Time to time valuable suggestions received from Dr. Satish C. Tripathi have been very fruitful in many ways, and I thank him profusely for the same. I also thank each members of the Springer book production team who handled the manuscript smoothly, within a short time, in a most professional way. Last but not the least, this book would not have been possible without the blessings of my mother and continued support of my family members, friends and well-wishers. Hyderabad, India

Yamuna Singh

Contents

1

2

. . . . . . . .

. . . . . . . .

1 1 1 9 10 10 12 12

. . . . . . . .

. . . . . . . .

13 13 14 14 15 15 16 17

. . . . . . . .

. . . . . . . .

17 17 18 19 19 22 23 25

Beach Sand Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 World Coastal Placer Deposits . . . . . . . . . . . . . . . . . . . . . . . . .

31 31 32

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Prologue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Discovery of the Rare Earths . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Crustal Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Mineralogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 World REE Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Major Classification of Rare Earth Deposits . . . . . . . . . . . . . 1.6.1 Carbonatites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 Agpaitic Nepheline Syenites and Peralkaline-Alkaline Felsic Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Hydrothermal Veins and Pegmatites . . . . . . . . . . . . 1.6.4 Quartz-Pebble Conglomerate . . . . . . . . . . . . . . . . . . 1.6.5 Stream Placers and Beach Sands . . . . . . . . . . . . . . . 1.6.6 Residual/Supergene Weathering . . . . . . . . . . . . . . . . 1.6.7 Ion Adsorption Clays . . . . . . . . . . . . . . . . . . . . . . . 1.6.8 Iron-Oxide Copper-Gold Type . . . . . . . . . . . . . . . . 1.6.9 Other Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Classification of Industrial By-Products as Rare Earth Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Classification Followed in This Monograph . . . . . . . . . . . . . 1.9 Exploration for REE in India . . . . . . . . . . . . . . . . . . . . . . . . 1.10 Utilisation of Secondary Industrial Sources . . . . . . . . . . . . . . 1.11 Applications of REE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12 REE Scenario: Present and Future . . . . . . . . . . . . . . . . . . . . 1.13 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

xii

Contents

2.3 Indian Coastal Placer Deposits . . . . . . . . . . . . . . . . 2.4 Beach Sand Deposits of Odisha . . . . . . . . . . . . . . . 2.5 Beach Sand Deposits of Andhra Pradesh . . . . . . . . 2.6 Beach Sand Deposits of Tamil Nadu . . . . . . . . . . . 2.7 Beach Sand Deposits of Kerala . . . . . . . . . . . . . . . 2.8 Beach Placers of Maharashtra and Gujarat . . . . . . . 2.9 Coastline of West Bengal . . . . . . . . . . . . . . . . . . . 2.10 REE Geochemistry of Monazite, Garnet and Zircon 2.11 Beach Sand Mining and Mineral Separation . . . . . . 2.12 REE Recovery from Monazite . . . . . . . . . . . . . . . . 2.13 Exploration and Evaluation . . . . . . . . . . . . . . . . . . 2.14 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

33 34 38 43 46 48 50 50 51 52 52 56 56

Inland Stream Placers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Indian Occurrences of Light and Heavy Rare Earths . . . . . . . 3.3 Eastern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Ranchi-Purulia Area, Jharkhand and West Bengal . . 3.3.2 Simdega District, Jharkhand . . . . . . . . . . . . . . . . . . 3.4 Central India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Jashpur District, Chhattisgarh . . . . . . . . . . . . . . . . . 3.4.2 Sarguja-Balrampur Districts, Chhattisgarh . . . . . . . . 3.4.3 Sarguja District, Chhattisgarh and Sonbhadra District, Uttar Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4 Bastar Cratonic Terrain . . . . . . . . . . . . . . . . . . . . . . 3.4.5 Maharashtra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Western India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Vasva River, Vadodara District, Gujarat . . . . . . . . . 3.5.2 Ujol River, Panchmahal District, Gujarat . . . . . . . . . 3.6 Southern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Telangana State . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 Karnataka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 Tamil Nadu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 North Eastern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Kameng River, East Kameng District, Arunachal Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.2 Fossil Placer, East Kameng District, Arunachal Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.3 Residual Granitic Soil, Mandalagiri, Garo Hills, Meghalaya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . .

. . . . . . . . .

61 61 61 62 63 63 67 67 81

. . . . . . . . . . .

. . . . . . . . . . .

91 92 108 109 109 111 112 112 121 122 126

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . 126 . . 126 . . 129

Contents

3.8 Exploration Guide . 3.9 Future Outlook . . . 3.10 Summary . . . . . . . References . . . . . . . . . . . 4

xiii

. . . .

. . . .

. . . .

129 130 130 131

Carbonatites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 World Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Indian Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Western India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Amba Dongar Carbonatite Complex (ACC), Chhota Udaipur District, Gujarat . . . . . . . . . . . . . . . 4.4.2 Siriwasan-Nakal Carbonatite, Chhota Udaipur District, Gujarat . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Panwad-Kawant Carbonatite, Chhota Udaipur District, Gujarat . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.4 Kamthai Carbonatite, Barmer District, Rajasthan . . . 4.4.5 Mer-Mundwara Carbonatite, Sirohi District, Rajasthan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.6 Niwania Carbonatite, Udaipur District, Rajasthan . . . 4.5 North-East India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Samchampi Carbonatite, Karbi Anglong District, Assam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Barpung Carbonatite, Mikir Hills, Karbi-Anglong District, Assam . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3 Jasra Carbonatite, Karbi-Anglong District, Assam . . 4.5.4 Sung Valley Carbonatite, Jaintia Hills District, Meghalaya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Southern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Samalpatti, Dharmapuri District, Tamil Nadu . . . . . . 4.6.2 Pakkanadu-Mulakkadu, Salem District, Tamil Nadu . 4.6.3 Sevattur, North Arcot District, Tamil Nadu . . . . . . . 4.6.4 Other Areas in Tamil Nadu . . . . . . . . . . . . . . . . . . . 4.6.5 Elchuru Carbonatite Complex, Prakasham District, Andhra Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.6 Syenites, Dancherla Area, Anantpur District, Andhra Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Eastern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7.1 Beldih-Kutni Carbonatite, Purulia District, West Bengal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Synoptic Scenario of REE Concentrations in Selected Indian Carbonatites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Methods of Exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . .

. . . . .

137 137 138 139 139

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . 139 . . 144 . . 144 . . 144 . . 151 . . 151 . . 151 . . 151 . . 153 . . 156 . . . . . .

. . . . . .

156 156 158 163 164 164

. . 165 . . 165 . . 165 . . 165 . . 169 . . 171

xiv

Contents

4.10 Future Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 4.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 5

6

Peralkaline-Alkaline Felsic Rocks . . . . . . . . . . . . . . . . . . . . . . . 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 World Occurrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Indian Occurrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Western India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Siwana Granites, Barmer District, Rajasthan . . . . . 5.4.2 Granites from Nakora Ring Complex, Barmer District, Rajasthan . . . . . . . . . . . . . . . . . . . . . . . . 5.4.3 Rhyolite Dykes, Dhorio Nes, Jamnagar District, Gujarat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.4 Acid Igneous Complex, Alech Hill, Jamnagar and Junagarh Districts, Gujarat . . . . . . . . . . . . . . . 5.4.5 Granites, Sudasna Area, Mehsana District, Gujarat . 5.4.6 Sodoari, Gir Forest, Gujarat . . . . . . . . . . . . . . . . . 5.4.7 Kinwat Granite, Nanded and Yeotmal Districts, Maharashtra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Southern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1 Kanigiri Granite, Prakasham District, Andhra Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Central India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1 Dongargarh Granite, Chhattisgarh . . . . . . . . . . . . . 5.7 Eastern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.1 Pala Lahara Granite, Odisha . . . . . . . . . . . . . . . . . 5.7.2 Kumarkunti-Jharnomal, Nuapada District, Odisha . . 5.7.3 Kuilapal Granite, West Bengal . . . . . . . . . . . . . . . 5.8 North-Eastern India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.1 Nongpoh Granite, Meghalaya . . . . . . . . . . . . . . . . 5.8.2 Karbi Hills Granite, Assam . . . . . . . . . . . . . . . . . . 5.9 Himalayan Granites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10 Exploration Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrothermal Veins . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Indian Occurrences . . . . . . . . . . . . . . . . . . . . 6.3 Eastern India . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Singhbhum Shear Zone . . . . . . . . . . . 6.3.2 South Purulia Shear Zone . . . . . . . . . 6.3.3 Kasipatnam, Visakhapatnam District, Andhra Pradesh . . . . . . . . . . . . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

179 179 179 180 181 181

. . . 198 . . . 200 . . . 200 . . . 200 . . . 202 . . . 203 . . . 205 . . . . . . . . . . . . . .

. . . . . . . . . . . . . .

. . . . . . . . . . . . . .

205 210 210 211 211 216 216 219 219 219 220 220 222 222

. . . . . .

. . . . . .

. . . . . .

227 227 228 228 228 235

. . . . . . . . . . . . . 237

Contents

xv

6.4

Western India . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Sendra Complex, Ajmer District, Rajasthan 6.4.2 Albitite Belt, Rajasthan and Haryana . . . . . 6.5 Southern India . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.1 Gogi, Bhima Basin, Karnataka . . . . . . . . . 6.6 REE Potential in Proterozoic Unconformity-Related Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Other Occurrences . . . . . . . . . . . . . . . . . . . . . . . . 6.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

8

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

240 240 242 262 262

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

264 264 264 265

Pegmatites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Indian Pegmatites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Chhattisgarh-Odisha Region . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Bastar Region, Chhattisgarh . . . . . . . . . . . . . . . . . 7.3.2 Odisha Region . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Chhotanagpur Granite Gneiss Complex Terrain . . . . . . . . . 7.4.1 Sarguja-Sonbhadra Region, Chhattisgarh and Uttar Pradesh . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Bihar-Jharkhand Region . . . . . . . . . . . . . . . . . . . . 7.4.3 West Bengal Region . . . . . . . . . . . . . . . . . . . . . . . 7.5 Rajasthan Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Gujarat Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 Maharashtra Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.8 Andhra Pradesh Region . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.9 Karnataka Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.10 Tamil Nadu Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.10.1 Karatupatti-Kalluttu, Madurai District, Tamil Nadu 7.10.2 Kullampatti, Salem District, Tamil Nadu . . . . . . . . 7.10.3 Angalakuruci, Coimbatore District, Tamil Nadu . . . 7.11 Kerala Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.12 Arunachal Pradesh Region, North-Eastern India . . . . . . . . . 7.13 Future Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.14 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

269 269 271 272 272 275 281

. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . .

281 283 287 287 290 290 290 294 295 295 296 298 298 301 303 303 304

Potential Natural Resources . . . . 8.1 Introduction . . . . . . . . . . . . 8.2 Quartz-Pebble Conglomerate 8.2.1 World Occurrences . 8.2.2 Indian Occurrences . 8.2.3 Exploration . . . . . .

. . . . . .

. . . . . .

. . . . . .

311 311 311 311 312 316

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

xvi

Contents

8.3

Iron-Oxide Breccia Complex . . . . . . . . . . . . . . . . . . . . . . 8.3.1 World Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Indian Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.4 Radioactive Phosphorites and Phosphatic Sediments . . . . . 8.4.1 World Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Indian Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.5 Bauxite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Laterite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Lateritic Cover on Alkaline Rocks . . . . . . . . . . . . . . . . . . 8.8 Phanerozoic Sandstones—Cretaceous Mahadek Sandstone, Meghalaya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Thoriferous Lithounits . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Consolidated Sedimentary Rocks . . . . . . . . . . . . . . . . . . . 8.11 Sea Bed/Floor Mud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Ion Adsorption Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12.1 World Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.12.2 Indian Occurrences . . . . . . . . . . . . . . . . . . . . . . . 8.13 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

Potential Industrial (Secondary) Resources . . . . . . . . . . . . . . . 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Phosphogypsum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Phosphoric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Coal Fly Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Red Mud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Mine Tailings and Slags . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Recovery from Waste Electrical and Electronic Equipment (Urban Mine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

317 317 317 322 322 323 324 328 330

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

331 331 331 332 334 334 334 339 339

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

349 349 350 354 356 360 363

. . . . 364 . . . . 365 . . . . 365

10 The Way Forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Commercial Potentials of Indian REE Deposits/Occurrences 10.3 Exploitation, Exploration and REE Resource Augmentation 10.3.1 Beach Sand Deposits . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Stream Placer Deposits . . . . . . . . . . . . . . . . . . . . . 10.3.3 Carbonatite Deposits . . . . . . . . . . . . . . . . . . . . . . . 10.3.4 Mineralised Peralkaline-Alkaline Felsic Rocks . . . . 10.3.5 Other Resources . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.6 Potential Industrial (Secondary) Resources . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

371 371 372 384 385 385 385 386 387 387

Contents

10.4 Indian Rare Earth Industry . . . . . . . . . . . . . . . . . . . . . . . 10.5 Commercial Demand for REE . . . . . . . . . . . . . . . . . . . . . 10.6 Supply and Demand Chain and Technological Innovation . 10.7 Individual REE Balance and Market Price . . . . . . . . . . . . 10.8 The Takeaways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xvii

. . . . . .

. . . . . .

. . . . . .

. . . . . .

387 389 392 393 393 394

About the Author

Dr. Yamuna Singh was born at Rewa in 1957. He did M.Sc. in Geology from Government Science College, Rewa, Madhya Pradesh (affiliated to A.P.S. University, Rewa); and obtained Ph.D. in the same subject from the Nagpur University, Nagpur. After serving for nearly 36 years, he retired as Senior Scientist from the Atomic Minerals Directorate for Exploration and Research (AMD), Department of Atomic Energy, Government of India. He has edited 16 Volumes of AMD’s annual journals, viz. Exploration and Research for Atomic Minerals, Journal of Atomic Mineral Science and Smarika. He is the recipient of several awards, including the National Geoscience Award for Mineral Discovery and Exploration from Ministry of Mines, Government of India; the S. Narayanswami Award in Economic Geology and the JGSIRadhakrishna Prize from Geological Society of India, Bengaluru; the Prof. S. M. Ramananda Setty Award from Mineralogical Society of India, Mysuru; and the Hindi Sevi Samman Puraskar from Department of Atomic Energy, Government of India. He is an elected Fellow of Telangana Academy of Sciences, Hyderabad. He was responsible for the discovery of several uranium and thorium mineralised horizons associated with Proterozoic sedimentary sequences of Bijawar basin, Indravati basin and Pakhal basin; Precambrian granites and schists of Maharashtra. He discovered several rare metal pegmatites in Kawadgaon area, Bastar craton, which have been commercially mined for Nb–Ta, Be and REE minerals. He also discovered several rare metal pegmatites in Sarguja, Chhattisgarh, xix

xx

About the Author

in Chhoattanagpur Granite Gneiss Complex terrain. His identifications of specific rare earth-bearing source granites, mapping of rare earth placers and REE resource evaluation in central India are well known. He has discovered first Indian occurrences of many rare ore minerals of U and Cu–As. He reported the first world occurrence of metamict mineral “alluaudite” from India. He has innovatively applied several analytical techniques in characterisation of radioactive ores and minerals of U, Th, Nb, Ta, REE Be, Li, Zr from diversified geological settings of India, as evidenced from his innumerable publications in national and international peer-reviewed journals of repute.

Chapter 1

Introduction

1.1 Prologue This chapter presents a brief survey of the history, properties, and applications of the rare earths and highlights the background to their current importance as materials of interest in the laboratory and products of use in technology and industry. Chapters that follow, outline the broader aspects of the both natural and industrial resources. Chapters 2–8 outline the geological, structural, geochemical, petrological, mineralogical and genetic aspects of the natural deposits. Chapter 9 brings out a brief sketch of the available industrial secondary sources. The final chapter discusses the relative merits and potential of the several sources for future development and directions for larger inputs in exploration, on the one hand and the utilization of the industrial sources, on the other.

1.2 Discovery of the Rare Earths The term “rare earths” (also called “lanthanides”) represents the group of 17 geochemically coherent metallic elements, including scandium and yttrium (Spedding 1978). All the elements of the lanthanides series, atomic numbers 57 (La) to 71 (Lu), occur in nature, except promethium (Table 1.1). The rare earth elements (REE) are divided into two groups (Table 1.1; US Department of Energy 2017): La to Sm as Light REE (LREE) and Eu to Lu as Heavy REE (HREE). Both Y and Sc are also clubbed with HREE (Table 1.1; US Department of Energy 2017). Their crustal abundance is projected in Table 1.2. Due to geochemical coherence all the rare earth elements, generally, invariably occur together in complex minerals and behave as a single chemical entity. The rare earths occur as complex polymetallic oxides and hydroxydes, carbonates, fluorocarbonates and hydroxyl-carbonates and silicates, phosphates, arsenates, sulphates and vanadates, uranyl-carbonates and © Springer Nature Switzerland AG 2020 Y. Singh, Rare Earth Element Resources: Indian Context, Society of Earth Scientists Series, https://doi.org/10.1007/978-3-030-41353-8_1

1

2

1 Introduction

Table 1.1 a Periodic table showing positions of rare earth elements. Source researchgate.net: US Department of Energy 2017). b Names and symbols of the light rare-earth elements (La-Sm) and heavy rare-earth elements (Eu-Lu and Sc-Y)

(a)

(b) Atomic number

Symbol

Name

21

Sc

Scandium

39

Y

Yttriu m

57

La

Lanthanum

58

Ce

Ceriu m

59

Pr

Praseodymium

60

Nd

Neodymium

61

(Pm)

(Promet hium) *

62

Sm

Samarium

63

Eu

Europium

64

Gd

Gadolinium

65

Tb

Terbium

66

Dy

Dy sprosium

67

Ho

Holmium

68

Er

Erbium

69

Tm

Thulium

70

Yb

Ytt e rbi u m

71

Lu

Lute tium

1.2 Discovery of the Rare Earths

3

Table 1.2 Crustal abundances (ppm) of rare earth elements (After Mason and Moore 1982; Weaver and Tarney 1984; Taylor and McLennan 1985; Shaw et al. 1986; Condie 1993) Element

Mason and Moore (1982)

Weaver and Tarney (1984)

Crustal average

Taylor and McLennan (1985)

Upper Crust

Bulk continental crust

Shaw et al. (1986)

Condie (1993)

Map model

Restoration model

Sc

22

Y

33

13

22

20

21

29

30

La

30

27

30

16

32.3

25.6

27.3

Ce

60

55

64

33

65.6

55.7

59.3

Pr

8.2

7.1

3.9

Nd

28

23

26

16

25.9

24.6

26.6

Sm

6.0

3.9

4.5

3.5

4.51

5.04

5.43

Eu

1.2

1.07

0.88

1.1

0.937

1.02

1.01

Gd

5.4

3.8

3.3

2.79

4.81

5.11

Tb

0.9

0.64

0.60

0.481

0.76

0.80

Dy

3.0

3.5

3.7

Ho

1.2

0.80

0.78

Er

2.8

2.3

2.2

Tm

0.5

0.23

0.33

0.32

Yb

3.4

1.46

2.2

2.2

1.47

2.33

2.36

Lu

0.5

0.32

0.30

0.233

0.43

0.43

0.50

0.623

uranyl-silicates and borates (Table 1.3). The discovery of all the rare earths took over nearly 160 years from 1788 to 1941 (Szabadvary 1988; Weeks 1956), and was accompanied by problems of separating them from each other for scientific investigations and industrial applications. Obviously, this involved one of the most challenging tasks of rare earth technology. Although Mosander (during 1839–1841) is credited to initiate the separation of the rare earths, substantial work directed to the separation of various rare earths has been performed from 1891 to 1940 (cf. Gupta and Krishnamurthy 2005). Using available mixed and separated compound intermediates many rare earth alloys and metals were prepared and commercial applications were brought out either for mixed or crudely separated rare earths. Effective process development took place during 1940–1960, including modern separation methods, resulting in the availability of adequate quantities of pure individual rare earth compounds (Powell and Spedding 1959) for the studies related to reduction processes to prepare pure metals and alloys (Beaudry and Gschneidner 1978) and assessment of their properties. From the 1960s, much progress was made in the large-scale production of purer rare earths, in the identification of newer properties, and in their

4

1 Introduction

Table 1.3 List of selected rare earth minerals and their general composition (After Clark 1984, 1993; Miyawaki and Nakai 1987; Bayliss and Levinson 1988; Burt 1989; Cesbron 1989; Leigh 1990; Jambor- Puziewicz and Robert 1994; Fleischer and Mandarino 1995; Jones 1996; Gaines et al. 1997) 1 Carbonates Ancylite

SrCe(CO3 )2 OH.H2 O

Baiyuneboite

NaBaCe2 (CO3 )4 F

Bastnaesite

(La,Ce)(CO3 )F

Burbankite

(Na,Ca)3 (Sr,Ba,Ce)3 (CO3 )5

Calkinsite

(La,Ce)2 (CO3 )3 .4H2 O

Carbocernaite

(Ce,Na)(Sr,Ce,Ba)(CO3 )2

Cebaite

Ba3 Ce2 (CO3 )5 F2

Cordylite

Ba(Ce,La)2 (CO3 )3 F2

Daqingshanite

(Sr,Ca,Ba)3 (La,Ce)PO4 (CO3 )3-x (OH,F) x ~ 0.8

Donnayite

Sr3 NaCeY(CO3 )6 .3H2 O

Ewaldite

Ba(Ca,Y,Na,K)(CO3 )2

Gysinite

Pb(La,Nd)(CO3 )3 (OH).H2 O

Huanghoite

BaCe(CO3 )2 F

Hydroxylbastnaesite

(La,Ce,Nd)CO3 (OH,F)

Khanneshite

(Na,Ca)3 (Ba,Sr,Ce,Ca)3 (CO3 )5

Kimuraite

CaY2 (CO3 )4 .H2 O

Lanthanite

(La,Ce,Nd)2 (CO3 )3 .8H2 O

Lokkaite

CaY4 (CO3 )7 .9H2 O

Mckelveyite

Ba3 Na(Ca,U)Y(CO3 )6 .3H2 O

Parisite

Ca(La,Ce,Nd)2 (CO3 )3 F2

Remondite

Na3 (La,Ce,Ca,Na,Sr)3 (CO3 )5

Rontgenite

Ca2 (La,Ce)3 (CO3 )5 F3

Sahamalite

(Mg,Fe2+ )(La,Ce,Nd)2 (CO3 )4

Schuilingite

PbCu(Nd,Gd,Sm,Y)(CO3 )3 OH.1.5H2 O

‘Shormiokite

Na3 Y(CO3 )3 .3H2 O

Synchysite

Ca(La,Ce,Nd,Gd,Y)(CO3 )2 F

Tengerite

CaY3 (CO3 )4 (OH)3 .3H2 O

Thorbastnaesite

Th(Ca,Ce)(CO3 )2 F2 .3H2 O

Zhonghuacerite

Ba2 Ce(CO3 )3 F

2 Oxides Aeschynite

(Ce,Nd,Y,Ca,Th,Fe)(Ti,Nb)2 (O,OH)6

Brannerite

(U,Ca,Y,Ce)(Ti,Fe)2 O6

Calciobetafite

(Ca,REE,Th,U)2 (Nb,Ta,Ti)2 O7

Cerianite

(Ce4+ ,Th)O2

Ceriopyrochlore

(Ce,Ca,Y)2 (Nb,Ta)2 O6 (OH,F)

Cerotungstite

CeW2 O6 (OH)3 (continued)

1.2 Discovery of the Rare Earths

5

Table 1.3 (continued) Crichtonite

(Sr,La,Ce,Y)(Ti,Fe3+ ,Mn)21 O36

Davidite

(La,Ce)(Y,U,Fe2+ )(Ti,Fe3+ )20 (O,OH)38

Euxenite

(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2 O6

Fergusonite

(La,Ce,Nd,Y)NbO4

Fersmite

(Ca,Ce,Na)(Nb,Ta,Ti)2 (O,OH,F)6

Formanite

YTaO4

Hibonite

(Ca,Ce)(Al,Fe,Ti,Si,Mg)12 O19

Ishikawaite

(U,Fe,Y,Ce)(Nb,Ta)O4

Kobeite

(Y,U)(Ti,Nb)2 (O,OH)6

Loparite

(Ce,La,Na,Ca,Sr)(Ti,Nb)O3

Loveringite

(Ca,Ce)(Ti,Fe3+ ,Cr,Mg)21 O38

Lucasite

CeTi2 (O,OH)6

Murataite

(Na,Y)4 (Zn,Fe)3 (Ti,Nb)6 O18 (F,OH)4

Niobo-aeschynite

(Ce,Nd,Ca,Th)(Nb,Ti)2 (O,OH)6

Plumbopyrochlore

(Pb,Y,U,Ca)2-x Nb2 O6 (OH)

Polycrase

(Y,Ca,Ce,U,Th)(Ti,Nb,Ta)2 O6

Samarskite

(Y,Ce,U,Fe3+ )3 (Nb,Ta,Ti)5 O16

Tantalaeschynite

(Y,Ce,Ca)(Ta,Ti,Nb)2 O6

Tanteuxenite

(Y,Ce,Ca)(Ta,Ti,Nb)2 (O,OH)6

Uranmicrolite

(U,Ca,Ce)2 (Ta,Nb)2 O6 (OH,F)

Uranpyrochlore

(U,Ca,Ce)2 (Nb,Ta)2 O6 (OH,F)

Vigezzite

(Ca,Ce)(Nb,Ta,Ti)2 O6

Yttrobetafite

(Y,U,Ce)2 (Ti,Nb,Ta)2 O6 OH

Yttrocolumbite

(Y,U,Fe2+ )(Nb,Ta)O4

Yttropyrochlore

(Y,Na,Ca,U)1-2 (Na,Ta,Ti)2 (O,OH)7

Yttrotantalite

(Y,U,Fe2+ )(Ta,Nb)O4

Yttrotungstite

YW2 O6 (OH)3

Zirconolite

(Ca,Th,U,REE)Zr(Ti,Nb,Fe)2 O7

3 Halides Fluocerite

(La,Ce)F3

Gagarinite

NaCaY(F,Cl)6

Yttrofluorite

(Ca,Y)F2-3

4 Silicates Agrellite

Na(Ca,REE)2 Si4 O10 F

Allanite

(Ce,Y,Ca,Y)2 (Al,Fe3+ )3 (SiO4 )3 OH

Britholite

(Ce,Y,Ca)5 (SiO4 ,PO4 )3 (OH,F)

Byelorussite

NaMnBa2 Ce2 Ti2 Si8 O26 (F,OH).H2 O (continued)

6

1 Introduction

Table 1.3 (continued) Cappelenite

Ba(Y,Ce)6 Si3 B6 O24 F2

Caysichite

Y2 (Ca,Gd)2 Si4 O10 (CO3 )3 .4H2 O

Cerite

(Ce,Ca)9 (Mg,Fe2+ )Si7 (O,OH,F)28

Cervandonite

(La,Ce,Nd,)(Fe,Ti,Al)3 (Si,As)3 O13

Chevkinite

(Ca,Ce,Th)4 (Fe2+ ,Mg)2 (Ti,Fe3+ )3 Si4 O22

Dissakisite

Ca(Ce,Y)MgAl2 Si3 O12 (OH)

Dollaseite

CaCeMg2 AlSi3 O16 (OH)F

Eudialyte

Na4 (Ca,Ce)2 (Fe2+ ,Mn,Y)ZrSi8 O12 (O,Cl)

Gadolinite

Y2 Fe2+ Be2 Si2 O10

Hingganite

(Y,Yb,Er)BeSiO4 OH

limoriite

Y2 SiO4 CO3

Ilimaussite

Ba2 Na4 CeFe3+ Nb2 Si8 O28 .5H2 O

Iraqite

K(La,Ce,Th)2 (Ca,Na)4 (Si,Al)16 O40

Joaquinite

Ba2 NaCe2 Fe2+ (Ti,Nb)2 Si8 O26 (OH,F).H2 O

Kainosite

Ca2 (Y,Ce)2 Si4 O12 CO3 .H2 O

Karnasurtite

(Ce,La,Th)(Ti,Nb)(Al,Fe3+ )(Si,P)2 O7 (OH)4. 3H2 O

Keivyite

(Y,Yb)2 Si2 O7

Kuliokite

Y4 Al(SiO4 )2 (OH)2 F5

Melanocerite

(Ce,Ca)5 (Si,B)3 O12 (OH,F).nH2 O

Minasgeraisite

Y2 CaBe2 Si2 O10

Miserite

K(Ca,Ce)4 Si5 O13 (OH)3

Monteregianite

(Na,K)6 (Y,Ca)2 Si16 O38 .10H2 O

Mosandrite

(Ca,Na,Ce)12 (Ti,Zr)2 Si7 O31 H6 F4

Nacareniobsite

NbNa3 Ca3 (La,Ce,Nd)(Si2 O7 )2 OF3

Nordite

(La,Ce)(Sr,Ca)Na2 (Na,Mn)(Zn,Mg)Si6 O17

Okanoganite

(Na,Ca)3 (Y,Ce)12 Si6 B2 O27 F14

Orthojoaquinite

Ba2 NaCe2 Fe2+ Ti2 Si8 O26 (O,OH).H2 O

Perrierite

(Ca,Ce,Th)4 (Mg,Fe2+ )2 (Ti,Fe3+ )3 Si4 O22

Rowlandite

(Y,Fe,Ce)3 (SiO4 )2 (F,OH)

Saryarkite

Ca(Y,Th)Al5 (SiO4 )2 (PO4 ,SO4 )2 (OH)7 .6H2 O

Sazhinite

Na3 CeSi6 O15 .6H2 O

Semenovite

(Ca,Ce,La,Na)12 (Si,Be)20 O40 (O,OH,F)8 .H2 O

Steenstrupine

Na14 Ce6 Mn2+ Mn3+ Fe2 2+ (Zr,Th)(Si6 O18 )2 (PO4 )7 .3H2 O

Stillwellite

(Ce,La,Ca)BSiO5

Strontiochevkinite

(Sr,La,Ce,Ca)4 (Fe2+ ,Fe3+ )2 (Ti,Zr)4 Si4 O22

Tadzhikite

Ca3 (Y,Ce)2 (Ti,Al,Fe)B4 Si4 O22

Thalenite

Y3 Si3 O10 OH (continued)

1.2 Discovery of the Rare Earths

7

Table 1.3 (continued) Thortveitite

(Sc,Y)2 Si2 O7

Tombarthite

Y4 (Si,H4 )4 O12 -x(OH)4+2x

Tornebohmite

(La,Ce)2 Al(SiO4 )2 OH

Tranquillityite

Fe8 2+ (Zr,Y)2 Ti3 Si3 O24

Trimounsite

Y2 Ti2 SiO9

Tritomite

(La,Ce,Y,Th,Ca,Fe2+ )5 (Si,B,Al)3 (O,OH,F)13

Tundrite

Na3 (La,Ce)4 (Ti,Nb)2 (SiO4 )2 (CO3 )3 O4 (OH).2H2 O

Vyuntspakhite

Y4 Al3 Si5 O18 (OH)5

Wohlerite

Na(Ca,REE)2 (Zr,Nb)Si2 O7 (O,OH,F)2

Yftisite

(Y,Dy,Er)4 (Ti,Sn)O(SiO4 )2 (F,OH)6

Yttrialite

(Y,Th)2 Si2 O7

5 Phosphates Belovite

(Sr3 ,Na,Ce)5 (PO4 )3 OH

Brockite

(Ca,Th,Ce)(PO4 ).H2 O

Cheralite

(Ca,Ce,Th)(P,Si)O4

Churchite

YPO4 .2H2 O

Florencite

(La,Ce,Nd)Al3 (PO4 )2 (OH)6

Fluorapatite

(Ca,REE,Na)5 (PO4 )3 (F,OH)

Francoisite

(Ce,Nd,Sm)(UO2 )3 O(OH)(PO4 )2 .6H2 O

Laplandite

Na4 CeTiPO4 Si7 O18 .5H2 O

Monazite

(Ce,La,Nd,Th)PO4

Petersite

(Ca,Fe2+ ,Y,Ce)Cu6 (PO4 )3 (OH)6 .3H2 O

Phosinaite

Na3 (Ca,Ce)SiPO7 .H2 O

Rhabdophane

(La,Ce,Nd)PO4 .H2 O

Vitusite

Na3 (Ce,La,Nd)(PO4 )2

Xenotime

(Y,Er)PO4

6 Arsenates, vanadates and sulphates Agardite

(La,Y,Ca)Cu6 (AsO4 )3 (OH)6 .3H2 O

Arsenoflorencite

(La,Ce,Nd)Al3 (AsO4 ,PO4 )2 (OH)6

Chernovite

YAsO4

Chukhrovite

Ca3 (Ce,Y)Al2 (SO4 )F13 .10H2 O

Gasparite

(REE)AsO4

Goudeyite

Cu6 (Al,Y)(AsO4 )3 (OH)6 .3H2 O

Kemmlitzite

(Sr,Ce)Al3 AsO4 SO4 (OH)6

Retzian

(Mn,Mg)2 (La,Ce,Nd)AsO4 (OH)4

Wakefieldite

(Ce,Pb2+ ,Pb4+ )VO4

8

1 Introduction

applications in diversified important commercial fields. The usable forms of rare earths include naturally occurring oxide mixtures, and their synthesized products, high purity individual metals, alloys, and compounds. The discovery of REE was made through cerite, gadolinite and samarskite routes (cf. Gupta and Krishnamurthy 2005). After initial discovery and extraction, the applications of REE have drastically changed to high-purity separated rare earth metals being used in advanced electronics, lighting, power generation and military applications. Consequently, demand for REE has gone up from 75,500 tonnes (t) of rare earth oxides (REO) in 2000 to 123,100 t REO in 2016 (Roskill 2016a). Due to change of end-users, the types of REE products needed have also changed. It is the case with respect to use of Eu and Tb and lately Lu in lighting; the use of La in specialist glass products, and the development of REE permanent magnet alloys that accentuated the consumption of Sm, Nd and Dy. REE are integral to many industrial, commercial and residential appliances and in the growing electrification of vehicles. Though REE may only be used in very small volumes, they can provide performance or longevity benefits that some products rely upon, often making them difficult to substitute (Smith Stegen 2015). In the years to 2026, traditional applications will continue to lead demand growth for REE, though the development of new products and technologies could alter the demand for REE, both in terms of volume and the specific consumption of the individual elements used. In the coming decade, a large consumption of REE is predicted to meet the need of the production of hybrid electric vehicles (HEVs) and full electric vehicles (EVs) needing a lot of REE (Weng et al. 2015; Goodenough et al. 2017). The anticipated growth of HEVs and EVs is from 2.3 million units in 2016 to over 10.1 million units in 2026 (Roskill 2016b). This increased growth is likely to accentuate the demand for neodymium-iron-boron (NdFeB) magnets (Fig. 1.1). Electric vehicles are expected

Fig. 1.1 Projected demand of NdFeB magnet in HEV and EV (after Goodenough et al. 2017)

1.2 Discovery of the Rare Earths

9

Fig. 1.2 Projected demand of NdFeB magnet in renewable energy generation (after Goodenough et al. 2017)

to show the strongest growth in demand. Also, other application for NdFeB magnets is in renewable energy generation, which would become progressively important (Fig. 1.2), as governments and industries tend to meet stringent climate change and emissions standards (Weng et al. 2015; Goodenough et al. 2017). Bulk of the REE ores are dominated by La, Ce and Nd with much lesser contents of the HREE. Accordingly, due to requirements of different beneficiation routes, such ores involve several challenges in beneficiating them to obtain the individual metals needed by the market (Jordens et al. 2013). This also involves of additional steps to separate each of the REE (Xie et al. 2014; Machacek and Fold 2014). Nearly unavoidable, variable contents of different elements in ore is not commensurate with market specification, leading to balance problem (Binnemans et al. 2013; Binnemans and Jones 2015). To handle the balance problem many ways have been outlined, including diversification of the exploited resources, recycling, substitution of other elements for the REE, and seeking new applications for the most abundant REE (Binnemans and Jones 2015).

1.3 Crustal Abundances In the Earth’s crust, REE tends to decrease in abundances with increasing atomic number. Superimposed upon this is the Oddo-Harkins effect of elements leading to more abundance of an even atomic number relative to those with odd atomic numbers. Accordingly, Ce is the most abundant of the REE in the Earth’s crust, with Lu

10

1 Introduction

being distinctly rare. Although crustal abundances of REE are very low, but compared to rarest elements like gold, mercury REE abundances are high. Furthermore, abundances of seven REE, namely, Eu, Tb, Dy, Ho, Er, Tm, Yb, are broadly close to some other elements of economic importance, e.g., W, Sn, As, Br but latter are not designated as rare (Henderson 1996). Additionally, abundances of four REE, namely, La, Ce, Pr, Nd, are in the range of 15 to 100 ppm that are comparable with Cu, Co, Rb and Zn. Among all the REE, estimated content of Ce is ~30 ppm making it most abundant in the crust (Henderson 1996). REE abundances as estimated by various authors are presented (Table 1.2). It is shown that the maximum abundances will be in the Earth’s crust, compared to the Earth’s Mantle and Core.

1.4 Mineralogy There are innumerable REE-bearing minerals. However, only three are important, viz., bastnaesite and monazite for light REE and xenotime for heavy REE. Monazite theoretically contains 70% combined REO (with ~2% yttrium oxide), but generally monazite yields 55–65% REO. The theoretical content of REO in bastnaesite is ~75% (with ~0.05% Y), but floatation concentrates generally yield 60% REO. Contrasting this, xenotime may theoretically comprise ~67% Y2 O3 , but xenotime concentrates on an average show 25% Y2 O3 (Hedrick 1985). A list of selected REE minerals is given for ready reference in Table 1.3.

1.5 World REE Resources Main world occurrences of REE are shown in Fig. 1.3. According to IBM (2018), total estimated REO reserves of world are 121 million tonnes. Out of all the reserves (Table 1.4), China accounts for over 36%, followed by Brazil and Vietnam (~18% each) and Russia (~15%). India’s share of REO reserve is ~5.7%. A number of countries are involved in mining REE, and same is also shown in Fig. 1.3. Out of six main countries involved in REE mining (Table 1.5), a major share of production flows from China (from Baotou), Inner Mangolia and Jiangxi and Sichuan provinces. Bastnaesite constitutes primary ore mineral in Jiangxi and Sichuan, whereas REE is recovered as a by-product of iron ore mining at Baotou (Xie et al. 2017). Substantial world production of yttrium comes from ion adsorption clays located in Jiangxi, Guangdong, Hunan and Jiangsu provinces of China. In Russia, the rare earths are recovered from loparite that is mined from Lovozero massif comprising agpaitic and hyperagpaitic alkaline rocks in the Murmansk region. Titanium-bearing heavy mineral sands of Australia and tin dredging in Malaysia provide sources of REE as by-product.

1.5 World REE Resources

11

Fig. 1.3 World important REE deposits and mines. Source researchgate.net; Barakos et al. (2016) Table 1.4 World REE reserves (in 000 tonnes of REO content) by principal countries S. no.

Country

Reserves

1

World total (rounded)

121,060

2

Australia

3400

3

Brazil

22,000

4

Canada

830

5

China

44,000

6

Greenland

1500

7

India

6900

8

Malaysia

30

9

Malawai

140

10

Russia

18,000

11

South Africa

860

12

Vietnam

22,000

13

USA

1400

Source IBM (2018)

12

1 Introduction

Table 1.5 World production (in tonnes) of rare earths by principle countries S. no.

Country

2013

2014

2015

1

Australia

970

3965

8799

2

China

95,000

140,000

140,000

3

Malaysia

229

292

365

4

Russia

1443

2134

2312

5

USA

3300

3240

2460

6

Vietnam

100

100

100

Source IBM (2018)

1.6 Major Classification of Rare Earth Deposits Rare earth ore deposits have been classified into seven categories with genetic links to igneous, sedimentary and secondary processes of formation (Kanazawa and Kamitani 2006; O’Callaghan 2012). Furthermore, Zhou et al. (2017) categorized REE deposits into six types, namely, carbonatites, alkaline igneous rocks, iron-oxide copper gold (IOCG), placer, ion absorption and other. Although due to uncertainty in genetic affiliations and/or overlapping of many geological processes, categorization of some of the deposits is difficult, yet to make these types broadly consistent in context with Indian scenario, they have been either modified or integrated in conjunction with other classifications (Oris and Grauch 2002; BGS 2011; Weng et al. 2015; Goodenough et al. 2017). Salient features of these are given below.

1.6.1 Carbonatites Carbonatite-hosted deposits comprise the most important rare-earth resource globally, especially for the light rare-earths, constituting between 5 and 15 wt% REO (Neary and Highley 1984), which is manifested in nearly 45 of the some 300 known species of rare-earth minerals in carbonatites worldwide (Wall and Zaitzev 2004; Verplanck and Van Gosen 2011). These occur as inclusions within calcite, dolomite, quartz, strontianite, barite and iron oxide minerals (O’Callaghan 2012). Although these gangue minerals may comprise only traces, rare-earths are essentially concentrated in distinct rare-earth minerals that form in the late stages of magmatic activity (Wyllie et al. 1996; Xu et al. 2010). As perovskite and monazite have the highest melting temperature they crystallise first, followed by various rare-earthbearing carbonate minerals such as carbocernaite, cebaite and burbankite. These anhydrous carbonates are commonly replaced by the fluorocarbonate minerals, bastnaesite, parisite and synchysite and the hydrous carbonate ancylite, which reduce the remaining melt of light rare-earths. Due to this later formed REE-bearing calcite contains primarily residual heavy rare-earths (Wall and Zaitzev 2004; Xu et al. 2010; Ruberti et al. 2008).

1.6 Major Classification of Rare Earth Deposits

13

1.6.2 Agpaitic Nepheline Syenites and Peralkaline-Alkaline Felsic Rocks Agpaitic rocks deficient in calcium host REE concentrations adequately high enough to be economically extractable. REO concentration is normally between 1.5 and 2.5 wt%, which is facilitated by filling of voids by REE in lattice of minerals created by deficiency of calcium (Walters et al. 2011). Such igneous rocks form in areas of continental or back arc rifting (Sorensen 1992), and represent rather rare type of igneous activity, with ~100 reported occurrences worldwide (Oris and Grauch 2002; Walters et al. 2011), some of which are under exploration (O’Callaghan 2012). Such deposits are believed to form possible significant resource-bases particularly for the heavy rare earth elements (Castor and Hedrick 2006). Eudialyte, loparite, steenstrupine and apatite, with lesser abundances of basnaesite and monazite are the main sources of REE minerals (Hedrick 1985; Hedrick et al. 1991; Sorensen 1992), in association with carbonates, quartz, feldspars, micas and pyroxenes as gangue minerals (Oris and Grauch 2002). It is believed that the relative abundance of each of these minerals is linked with ratio of zirconium and thorium in the melt (Andersen et al. 1981), an observation seemingly supported by studies of Sorensen (1992) at the Ilimaussaq complex in Southern Greenland, where it is noted that steenstrupine replaces eudialyte in the upper zones of the cumulate. Compositionally, alkaline igneous rocks are known to show broad variations from ultramafic to felsic (BGS 2011). When they acquire higher molecular proportion of sodium and potassium together more than aluminum they are termed as peralkaline (BGS 2011). Significantly, such rocks distinguish themselves from others by being anomalously enriched in alkali metals (Na, K), high-field strength elements (Zr, Y, Nb, REE). Although REE deposits associated with peralkaline rocks like granites are of normally low grade, they form attractive resource-bases due to Y and HREE concentrations (Castor and Hedrick 2006; BGS 2011).

1.6.3 Hydrothermal Veins and Pegmatites Hydrothermal deposits are spatially and genetically linked with alkaline granite and carbonatite intrusions, and associated rocks. They form extensive, structurallycontrolled, interconnected network of veins (Chao et al. 1992). Generally, they are between 0.5 and 1400 m long, with a width between 1 and 150 cm (O’Callaghan 2012). However, the vein swarm deposits in China (as at the Maoniuping) show continuity for >2 km length with width reaching 20 m (Walters et al. 2011; Castor and Hedrick 2006). The hydrothermal deposit in the Democratic Republic of Congo, at Karonge, is located ~50 km away from the closest related carbonatite intrusive body (Mariano 1989). The REE minerals in veins are represented by allanite, apatite, monazite, euxenite, bastnaesite, parisite, synchysite and fluorite, enrichment being linked with greater mobility of REE in aqueous systems (Leroy and Turpin 1998).

14

1 Introduction

The gangue minerals comprise quartz, feldspars, barite and amphiboles, encircled by an up to 7 m wide wall rock alteration zone (Oris and Grauch 2002). In places where the hydrothermal fluids comprise elevated levels of phosphatic rocks, REE minerals are confined to apatite and monazite, which have extended period of their crystallization. Subsequently, they allow incorporation of more rare earths into their lattice, rather than allowing formation of other REE minerals (Mariano 1989; Wall et al. 2008).

1.6.4 Quartz-Pebble Conglomerate Quartz-Pebble Conglomerate (QPC) or uraniferous quartz-pebble conglomerate represent a type of stratiform palaeo-placers accumulated during period when the oxygen content in the atmosphere was initiated, drastically less than it is today. Two well-known occurrences of uraniferous QPC worldwide are Elliot Lake in Canada, and Witwatersrand in South Africa. These are the products of weathering of the surrounding Precambrian shield granites, and contain uraninite, brannerite and monazite (Neary and Highley 1984) as major heavies. Monazite (±xenotime, ±uranothorite, ±thorite, ±zircon) is a common rare-earth mineral association with these deposits, having concentrations of ~0.01 wt%. Though REE concentration is lower than the other deposit, it is still economic as a by-product of uranium recovery (Jackson and Christiansen 1993; Oris and Grauch 2002). Quartz-pebble conglomerates comprise the main lithounit, with arkose beds of up to 4 m thick between the conglomerate layers (Kimberely et al. 1980).

1.6.5 Stream Placers and Beach Sands Rare earth bearing placer deposits are the product of weathering, erosion, transportation, sorting and concentration of heavy minerals from different types of igneous and metamorphic rocks, deposited in riverine or coastal settings (Long et al. 2010). Nearly 360 placer deposits are known worldwide in Tertiary and Quaternary coastal environment (Oris and Grauch 2002). Coastal placers and beach sands form most important resources for the recovery of rare earths, although high thorium content associated with REE minerals of placers has been a discouraging aspect (Dill 2010; Walters et al. 2011). The grade of the deposits changes according to the nature of source rocks and other environmental aspects, but is reported to be commonly between 0.5 and 8 wt% (Oris and Grauch 2002). The primary rare earth minerals present in the placers include monazite and xenotime. Owing to their presence comparatively as common accessory minerals in various rocks, they are found in varying concentrations in most of the placer deposits all over the world (Long et al. 2010). In addition to monazite and xenotime, florencite and euxenite are also reported in placer deposits associated with lakes in Idaho and Arkansas (Castor and Hedrick 2006).

1.6 Major Classification of Rare Earth Deposits

15

1.6.6 Residual/Supergene Weathering According to Walters et al. (2011) the process of supergene chemical weathering involves in situ remobilisation, enrichment and re-precipitation of minerals or elements, leading to formation of enriched lateritic layers immediately above the mineral source, which happens to be the carbonatites or agpaitic syenites and peralkaline granites in the case of rare earths, including apogranite (Horbe and da Costa 1999). Even the bauxitic layer may also develop in some such zones. Infiltrating groundwater creates secondary supergene monazite and crandallite group minerals by liberating rare earths from carbonate and phosphatic minerals. The supergene monazite tends to accumulate in the centre of the weathering zone, whereas the supergene minerals of crandallite group enrich around the margins of the weathered zone, where percolating groundwater can mix with the country rock and supply aluminum to the system (Mariano 1989). Significantly, in carbonatite-hosted deposit at the Araxá (Brazil), where monazite and xenotime form the primary mineral targets, with the intrusion itself containing between 0.3 and 0.5 wt% REO, the supergene deposits contain between 7 and 14 wt% REO (Walters et al. 2011; Mariano 1989).

1.6.7 Ion Adsorption Clays The genesis of ion adsorption clays is linked with in situ chemical weathering of REErich granitic and volcanic rocks in an environment of limited erosion in a tectonically stable setting with mild, rainy climatic conditions. To help in the adsorption process, which can concentrate the most abundant REE by up to 4 times, it is necessary that weathering produces silica-alumina-rich clay (Clark and Zheng 1991). It was first discovered in the early 1970’s in Jiangxi province in China (Neary and Highley 1984). Presently 214 deposits are known (all located in Southern China), which account for 14% of China’s total REE production (Castor and Hedrick 2006; Wall et al. 2008). The source is traced to 190–135 Ma old granites, overlain by up to 10 m thick deposits containing between 0.05 and 0.2 wt% REO (Clark and Zheng 1991). This forms an attractive resource due to low REE recovery cost despite deposit being of substantially of lower grade relative to other rare earth deposits (Shoamei 1991). From the available profile of the deposits it is apparent that light REE are concentrated in the strongly weathered layer (except Ce, that is retained in the uppermost soil layer), whereas the heavy REE are enriched at the base of the strongly weathered layer and the top of the weakly weathered layer (Fig. 1.4). This stratification is caused by favourable reaction of REE with intensely weathered clay particles (