Petrology and Geochemistry of the Nipissing Gabbro: Exploration Strategies for Nickel, Copper, and Platinum Group Elements in a Large Igneous Province Ontario Geological Survey Study 58 1996 Petrology and Geochemistry of the Nipissing Gabbro: Exploration Strategies for Nickel, Copper, and Platinum Group Elements in a Large Igneous Province Ontario Geological Survey Study 58 by P.C. Lightfoot and A.J. Naldrett 1996 Queen’s Printer for Ontario, 1996 ISSN 0704-2590 ISBN 0-778-4804-X All publications of the Ontario Geological Survey and the Ministry of Northern Development and Mines are available for viewing and purchase at the following locations: Mines and Minerals Information Centre (MMIC) Macdonald Block, Room M2-17 900 Bay Street Toronto, Ontario M7A 1C3 Telephone: 1-800-665-4480 (within Ontario) (416) 314-3800 Fax: (416) 314-3797 Publication Sales 933 Ramsey Lake Road, Level B2 Sudbury, Ontario P3E 6B5 Telephone: (705) 670-5691 Fax: (705) 670-5770 E-mail: [email protected] Use of Visa or Mastercard ensures the fastest possible service. Cheques or money orders should be made payable to the Minister of Finance. Canadian Cataloguing in Publication Data Lightfoot, Peter C. (Peter Charles) Petrology and Geochemistry of the Nipissing gabbro: exploration strategies for nickel, copper, and platinum group elements in a large igneous province (Ontario Geological Survey report, ISSN 0704-2590; 58) Includes bibliographical references. ISBN 0-7778-4804-X 1. Gabbro---Ontario---Nipissing Region. I. Naldrett, A.J. II. Ontario Ministry of Northern Development and Mines III. Ontario Geological Survey. IV. Series. QE462.G3L53 1995 552’.3 C95-964107-6 Every possible effort is made to ensure the accuracy of the information contained in this report, but the Ministry of Northern Development and Mines does not assume any liability for errors that may occur. Source references are included in the report and users may wish to verify critical information. If you wish to reproduce any of the text, tables or illustrations in this report, please write for permission to the Manager, Publication Services Section, Ministry of Northern Development and Mines, 933 Ramsey Lake Road, Level B4, Sudbury, Ontario P3E 6B5. Cette publication est disponible en anglais seulement. Parts of this report may be quoted if credit is given. It is recommended that reference be made in the following form: Lightfoot, P.C. and Naldrett, A.J., 1996. Petrology and geochemistry of the Nipissing Gabbro: Exploration strategies for nickel, copper, and platinum group elements in a large igneous province; Ontario Geological Survey, Study 58, 81p. Critical Reader: J.A. Fyon Editor: T. Ayalew ii Contents Objective and Approach of the Present Study.................................................. 3 Acknowledgements ..................................................................... 6 Introduction and General Geology........................................................ 6 Empirical Metallogeny of the Nipissing Gabbro................................................ 9 Sampling and Analysis .................................................................. 11 Effects of the Textural Variations in the Gabbro on the Analytical Data........................ 11 Geochemical Evidence for the Emplacement and In-situ Differentiation of Nipissing Intrusions.... 12 Duration of Nipissing Magmatic Activity and Associated Compositional Variation............... 24 Compositional Variation in the Parental Nipissing Magma Type............................... 26 Empirical Observations Related to Mineral Potential, Land Use Planning and Exploration........ 37 Further Work .......................................................................... 48 Conclusions ........................................................................... 48 Appendix 1: Sampling, Analysis, Geology, Petrography and Mineralogy of the Nipissing Intrusions..... 49 1.1 Sampling and Analysis ............................................................. 49 1.2 Age and Distribution: .............................................................. 49 1.2.1 Differentiation ................................................................ 49 1.2.2 Thickness .................................................................... 49 1.2.3 Emplacement sites ............................................................. 49 1.2.4 Deformation .................................................................. 50 1.3.1 Geology of the Nipissing sills and dykes around Lake Temagami...................... 50 1.4 Geology of the Kerns Sill........................................................... 50 1.5 Petrography and Mineralogy of the Nipissing Gabbro................................... 56 1.6 Metamorphism of the Nipissing Gabbro.............................................. 65 Appendix 2 ............................................................................... 66 2.1 Assimilation and Fractional Crystallisation in the Kerns Intrusion - a Case Study of the Physical Process ............................................................. 66 References ............................................................................... 76 Conversion Factors for Measurements in Ontario Geological Survey Publications.................... 80 FIGURES 1a. Distribution of Nipissing gabbro across the Southern Province................................... 4 1b. Sketch diagram showing the relationship between the petrology of the undulatory sills and the associated mineralisation ................................................................ 5 1c. Typical sequence of lithologies seen in a well-differentiated intrusion of Nipissing gabbro showing the relationship between silicate rocks and sulphide mineralization....................... 6 1d. Location of samples and results from U-Pb geochronology work................................. 7 2. Regional tectonic setting of the Nipissing gabbro and the location of the 2.2 Ga Preissac Dyke Swarm ........................................................................... 7 3a. Ni versus forsterite relationships in olivines from the Cross Lake Sill.............................. 12 3b. PGE distribution patterns for the Rathbun Lake showing (after Lightfoot et al., 1993 and Rowell and Edgar, 1986) ................................................................. 12 4. Geological relationships between Nipissing intrusions, mineralisation, and geophysical anomalies, Paleoproterozoic mineralisation, and the Sudbury Igneous Complex..................... 13 5a. Comparison of primitive mantle normalised spidergrams on vari-textured gabbronorite patches and gabbronorite host; Emerald Lake gabbro........................................... 18 5b. Comparison of primitive mantle normalised spidergrams on vari-textured gabbronorite patches and gabbronorite host; Basswood Lake Intrusion.............................................. 19 iii 6. Location of individual intrusive bodies and detailed study areas referenced in this report.............. 20 7a. Chemostratigraphy of the High Rock Intrusion, Lake Temagami................................. 21 7b. Primitive mantle normalised spidergrams of the High Rock Intrusion samples, Lake Temagami......... 21 7c. Primitive mantle normalised spidergrams of the High Rock Intrusion samples....................... 22 8. Geochemical stratigraphy of the Miller Lake Intrusion, Gowganda................................ 22 9a. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Chilled basal quartz diabase, quartz diabase .......................................................................... 23 9b. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Hypersthene gabbro.......................... 24 9c. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Vari--textured gabbro......................... 25 9d. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Granophyric gabbro.......................... 26 9e. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Aplites.................................... 27 9f. Primitive-mantle normalised trace element spidergrams for representative samples from the Kerns Intrusion, northwest of New Liskeard Hornfelsed sediment rafts within the granophyric gabbro, and roof sediments. See text and Appendix 1 and Lightfoot et al. (1987) for detailed sample locations and descriptions...................................... 28 10. Geochemical variations in samples from the Kerns Intrusion, where elemental and oxide abundances are plotted against Zr concentration............................................... 29 11. a) VariationinThversusNb,b) Variation in Cu versus Zr in Nipissing gabbros, c) Variation in Cu/Zr versus SiO2 for all Nipissing gabbro samples.......................................... 35 12. a) Variation in 143Nd/144Nd versus 147Sm/144Nd in samples from the Kerns Intrusion and local country rocks. b) Relationship of the array of the Kerns Intrusion to isochron lines based on U - Pb geochronology for magmas with a range in initial 143Nd/144Nd isotopic composition............ 37 13. A model for the evolution of the Kerns Intrusion.............................................