P.J. Potts Handbook of Silicate Rock Analysis AH an~~ook of SlliCAII HOCK ANAlYSIS To Barbara, Edmund, Esther, Samuel and Tessa AH andbook of ANAlYSIS P. J. POTTS Research Fellow in Earth Sciences The Open University Milton Keynes, UK Springer Science+Business Media, LLC © 1987 Springer Science+Business Media New York Originally published by Blackie & Son Ltd. in 1987 Ali rights reserved. No part ofthis publicat ion may be reproduced, stored in a retrieval system, or transmiued, in any form or by any means, electronic, mechanical, recording or otherwise, without prior permission of the Publishers. British library Cataloguing in Publkation Data Potts, P.J. A handbook of silicate rock analysis. 1. Silicates- Analysis 2. Chemistry, Analytic I. Title 549'.6 QDI81.S6 ISBN 978-94-015-3990-6 ISBN 978-94-015-3988-3 (eBook) DOI 10.1007/978-94-015-3988-3 Library of Congress Cataloging in Publication Data Potts, P.J. A handbook of silicate rock analysis. Bibliography: p. lncludes index. 1. Rocks. Silicate-Analysis. I. Title. QE38.P68 1987 549'.6 86-18868 ISBN 978-94-0 15-3990-6 iv Contents Concepts in analytical chemistry 4.7 Schemes of analysis using flame atomic 1.1 Introduction absorption 122 l.2 Terms and definitions in analytical chemistry 4.8 Interference suppression 123 !.3 Units of measurement: the international system 4.9 Detection limits 127 (Sl) of units 4 4.10 Routine performance 128 1.4 Statistics 7 4.11 Electrothermal atomization !28 l.5 Detection limits 15 4.12 Atomization in the hollow graphite furnace 130 l.6 Sampling strategies: inhomogeneity effects 18 4.13 Background correction 138 1.7 Contamination effects 20 4.14 Geological applications of furnace AAS 144 l.8 Reporting analytical data 27 4.15 Cold vapour and hydride generators 146 l.9 Standard additions calibrations 28 4.16 Solid sampling and novel atomization devices 150 1.10 Rock reference materials 28 l.ll Which technique for which element? 42 5 Inductively coupled plasma-atomic emission spectrometry 2 Classical and rapid methods of analysis 5.1 Historic development and analytical capabilities 153 2.1 Rock dissolution techniques: acid attack 47 5.2 The inductively coupled argon plasma !53 2.2 Rock dissolution procedures: fusion with alkali 5.3 Nebulizers and spray chambers !56 salts 52 5.4 Physical structure of the plasma !63 2.3 Classical methods of rock analysis 55 5.5 Temperature distribution in the plasma !65 2.4 Evolution of rapid methods of analysis 58 5.6 Atomization and excitation processes 165 2.5 Photometry 58 5.7 Interferences in the argon plasma 167 2.6 Flame photometry 62 5.8 Measurement and analysis of emission spectra 169 2.7 Titrations involving ethylenediaminetetra- 5.9 Some instrument considerations-simultaneous acetic acid (EDTA ) 64 v. sequential monochromators !73 2.8 A rapid scheme of analysis 66 5.10 Optimizing operating parameters !75 2.9 Determination of ferrous iron 67 5.!! Calibrations for ICP-AES 179 2.10 The determination of water and carbon dioxide 70 5.12 Silicate rock analysis 183 2.11 The auto-analyser 75 5.13 Direct current plasma-optical emission spectrometry 192 3 Optical spectrometry: principles and instrumentation 6 Arc and spark source optical emission spectrometry 3.1 Principles 71 6.1 Historical perspective 198 3.2 The nature of light 78 6.2 Instrumentation 198 3.3 Atomic spectroscopy 80 6.3 Sample preparation 200 3.4 The electronic structure of atoms: quantum 6.4 Behaviour of elements in an arc discharge 201 theory 80 6.5 Simultaneous multi-element analysis 205 3.5 Spectroscopic notation for electron orbital 6.6 Conclusions 212 configura lions: the Russell-Saunders coupling scheme 82 7 Ion-selective electrodes 3.6 The absorption of light 86 7.1 Analytical perspective 2!3 3.7 The emission of light 88 7.2 Instrumentation 213 3.8 Instrumentation for optical spectroscopy 90 7.3 The Nernst equation 216 3.9 Monochromator 91 7.4 Interference effects: non-ideal Nernst behaviour 217 3.10 Optical filters 97 7.5 Schemes for the analysis of geological samples 3.1! Slits 98 for fluorine 218 3.12 Photon detectors 99 7.6 Determination of chlorine by ion-selective 3.13 Classical monochromator designs 100 electrodes 219 3.14 Stray light effects 103 7.7 Other techniques for the determination of 3.15 Errors in spectrometric measurements 103 chlorine and fluorine 222 4 Atomic absorption spectrometry 8 X-ray fluorescence analysis: principles and practice of 4.1 Introduction 106 wavelength dispersive spectrometry 4.2 Instrumentation 107 8.1 Analytical characteristics 226 4.3 Properties of flames 114 8.2 Energy and wavelength of x-rays 226 4.4 Flame chemistry and atomization interferences 8.3 The origin of x-ray spectra 227 in the flame: atomization processes in the flame 117 8.4 Competing de-excitation routes 233 4.5 Instrumental and spectral interferences 120 8.5 Excitation of x-ray spectra 236 4.6 Instrument optimization for routine analysis 121 8.6 Interaction of x-rays with matter 239 v CONTENTS 8.7 Matrix effects in geological samples 142 11.6 Transmission electron microscopy: the 8.8 Mathematical procedures for the correction of chemical analysis of thin foils 396 absorption-enhancement effects 249 8.9 Instrumentation for wavelength dispersive 12 Neutron activation analysis XRF analysis 253 12.1 Introduction 399 8.10 Experimental considerations 271 12.2 The growth and decay of radioactivity 399 8.11 Routine operating conditions and statistical 12.3 Radioactive decay schemes 402 considerations 278 12.4 Instrumentation 405 8.12 Performance in routine analysis 282 12.5 Pulse-processing electronics 409 8.13 Concluding remarks 285 12.6 Interaction of gamma radiation with germanium detectors 411 9 Energy dispersive X-ray spectrometry 12.7 Typical spectrum 413 9.1 The development of energy dispersive XRF 286 12.8 Detector characteristics 414 9.2 The Si(Li) detector 286 12.9 Practical considerations-instrumental neutron 9.3 Detector configuration and characteristics 289 activation 416 9.4 Pulse processing electronics 293 12.10 Determination of photopeak areas 419 9.5 Interaction of x-rays with the silicon detector 297 12.11 Other analytical considerations 422 9.6 Comparison of ED and WD spectrometers 299 12.12 Interferences and systematic errors 424 9.7 Silicate rock analysis by ED-XRF using direct 12.13 Routine schemes of analysis 429 tube excitation 300 12.14 Chondrite normalized abundances 430 9.8 Spectrum analysis procedures 307 12.15 Epithermal u. thermal irradiations 432 9.9 Routine analysis using direct tube excitation 308 12.16 Short-lived isotopes 435 9.10 Indirect excitation methods 315 12.17 Radiochemical separation procedures 435 9.11 Monochromatic polarized excitation using 12.18 Prompt gamma neutron activation analysis 438 Bragg diffraction at 21) = 90°C 321 12.19 Concluding remarks 439 9.12 Radioisotope excitation 322 9.13 Total reflection of primary beam 323 13 Nuclear techniques for the determination of uranium 9.14 Concluding remarks 325 and thorium and their decay products 13.1 Techniques for uranium/thorium determination 440 13.2 The uranium-thorium decay chain 441 10 Electron probe microanalysis 13.3 Delayed neutron fission activation analysis 441 10.1 The development of microprobe techniques 326 13.4 Fission track analysis 445 10.2 Microbeam techniques 326 13.5 Other autoradiography techniques for locating 10.3 Instrumentation for the electron probe and analysing specific elements in thin section 448 microanalyser 327 13.6 Gamma spectrometry 452 10.4 Electron column design 331 13.7 Alpha spectrometry 459 10.5 Vacuum requirements 335 13.8 Secular equilibrium with particular reference to 10.6 Interactions between the electron beam and uranium/thorium disequilibrium sample: the excited volume 336 me as uremen ts 461 10.7 Phenomena within the excited volume 337 13.9 Uranium and thorium series disequilibrium 462 10.8 X-ray production 343 10.9 Matrix correction procedures 348 10.10 X-ray spectrometers 353 14 Ion exchange preconcentration procedures 10.11 Calibration and routine operation 358 14.1 Introduction 472 10.12 Energy dispersive spectrometers 360 14.2 Ion exchange techniques 472 10.13 Sample preparation requirements 364 14.3 Characteristics of ion exchange resins 474 10.14 Microprobe mineral standards 364 14.4 Some theoretical aspects of ion exchange 477 10.15 Routine analytical performance 366 14.5 Optimizing column separations 480 10.16 Analysis of non-silicate minerals: uranium, 14.6 Applications of ion exchange chromatography thorium and rare-earth elements 371 to rare-earth element separations 480 10.17 Bulk rock analysis by electron microprobe 378 14.7 Chelating ion exchange resins 484 10.18 The SEM as a microprobe 380 14.8 Other preconcentration procedures 485 10.19 Concluding remarks 381 15 Gold and platinum group element analysis II Other microbeam and surface analysis techniques 15.1 Introduction 486 ll.l Introduction 383 15.2 Fire assay procedures 487 11.2 The ion probe 383 15.3 Acid extraction of noble metals 492 11.3 The laser microprobe 391 15.4 Other metho.Js of noble metal analysis 492 11.4 Particle-induced x-ray emission (PIXE) 392 15.5 Noble metal analysis--{;omparisons of data 493 11.5 Electron spectroscopy for chemical analysis 15.6 A note on the distribution of noble metals 494 (ESC.<\) 395 15.7 Graphical presentation of PGE data 496 VI COl"TEi'<TS 16 Mass spectrometry: principles and instrumentation 18.4 Hydrogen isotope analysis 552 16.1 Introduction 497 18.5 Carbon isotope analysis 554 16.2 Mass spectrometric techniques in geology 497 18.6 Nitrogen isotope analysis 555 16.3 The ion source 498 18.7 Oxygen isotope analysis 556 16.4 The mass analyser 498 !8.8 Sulphur isotope analysis 558 16.5 Resolution 500 18.9 Noble gas analysis 559 !6.6 Double-focusing mass spectrometer 502 18.10 Potassium-argon geochronometry 560 16.7 Quadrupole mass spectrometer 503 16.8 Ion detectors 505 19 Spark source mass spectrometry !6.9 Vacuum requirements 508 19.1 Introduction 566 !6.!0 Abundance sensitivity 508 19.2 Instrumentation and ion production 566 !6.!! Beam switching v. multiple collection 509 19.3 Internal standardization 568 !6.!2 Isotopes and mass spectra: the structure of 19.4 Routine data acquisition 568 atoms and nuclear stability 5!0 !9.5 Photoplate calibration and element sensitivities 569 !6.!3 Mass defect phenomena 5!2 !9.6 Applications and results 57! !6.!4 Radioactive isotopes in nature 512 19.7 Future developments 573 !6.!5 Geochronology 514 !6.!6 Geochronometers of geological importance 516 20 Inductively coupled plasma-mass spectrometry 20.! Introduction 575 17 Thermal ionization mass spectrometry 20.2 Development of ICP-MS instrumentation: the !7.! Introduction 523 plasma-mass spectrometer interface 575 !7 .2 Ion production 523 20.3 The inductively coupled plasma as ion source 578 !7.3 Rubidium-strontium isotope analysis 525 20.4 ICP-mass spectrometry instrumentation 582 !7.4 Neodymium-samarium isotope analysis 528 20.5 Performance and applications 583 17.5 Lead, uranium and thorium isotope analysis 53! 20.6 Internal standardization 583 !7.6 Isotope dilution 536 20.7 Isotope dilution 584 18 Gas source mass spectrometry !8.1 Geological applications 546 References 587 18.2 Instrumentation 546 18.3 The delta convention for reporting isotope data 552 Index 611 VII Analytical Instrumentation for the Geochemist • AN 10 000 Energy Dispersive X-Ray Microanalysis System • Fast accurate quantitative analysis • Automation packages for combined EDIWD analysis • Comprehensive range of application software with user programmability • Range of systems to suit analytical and budgetary requirements • XR200/300 Energy Dispersive X-Ray Fluorescence Spectrometers e Simultaneous multi element capability e Superb quantitative analysis from Na-U in periodic table e Fully automatic analysis using computer controlled automation e Powerful on-line processing using dedicated computer I L. LINK SYSTEMS LIMITED, LINK SYSTEMS (FRANCE), LINK ANALYTICAL, LINK NOADISKA, AB Ii 5iJ 7H ALIFAX ROAD, LEMAZIERE, 240 TWIN DOLPHIN DRIVE, BOX 153, HIGH WYCOMBE. RUE DES MAZIE RES, SUITE B. 181 22 LINDINGOE, BUCKS HP12 3SE. 91033 EVRY CEDEX, REDWOOD CITY, SWEDEN. sYSTEMS ENGLAND. TEL:(1)60781020 CALIFORNIA 94065 USA TEL: 08-767 9170 TEL: 0494 442255 TELEX: 691884F TEL: (415) 595-5465 TELEX: 12645SPECTAB TELEX: 837542UNK HWG FAX: (415)595 5589 FAX: 0494 24129 Preface The techniques available for the chemical analysis of silicate without an appreciation of what happens in between. rocks have undergone a revolution over the last 30 years. However, to use an analytical technique most effectively, No longer is the analytical balance the only instrument used it is essential to understand its analytical characteristics, in for quantitative measurement, as it was in the days of classi particular the excitation mechanism and the response of the cal gravimetric procedures. A wide variety of instrumental signal detection system. In this book, these characteristics techniques is now commonly used for silicate rock analysis, have been described within a framework of practical ana including some that incorporate excitation sources and detec lytical aplications, especially for the routine multi-element tion systems that have been developed only in the last few analysis of silicate rocks. All analytical techniques available years. These instrumental developments now permit a wide for routine silicate rock analysis are discussed, including range of trace elements to be determined on a routine basis. some more specialized procedures. Sufficient detail is In parallel with these exciting advances, users have tended included to provide practitioners of geochemistry with a firm to become more remote from the data production process. base from which to assess current performance, and in some This is, in part, an inevitable result of the widespread intro cases, future developments. duction of microcomputers for instrument control, and in This manuscript could not have been completed without part a consequence of the logistics of organizing a modern the constant help of my wife Barbara, the assistance of many laboratory for rapid and efficient routine analysis. The friends and colleagues at the Open University and the patient resultant lack of interaction between user and machine leads encouragement of the publishers. to the danger of a 'black-box' attitude towards analytical chemistry-samples in at one end, result out at the other- P.J.P. lX