Provenance of Sediments in the Faroe-Shetland Basin: Characterisation of Source Components in Southeast Greenland
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DANMARKS OG GRØNLANDS GEOLOGISKE UNDERSØGELSE RAPPORT 2012/62 Provenance of sediments in the Faroe-Shetland basin: characterisation of source components in Southeast Greenland Final report prepared for SINDRI C46-50-01 Kristine Thrane & Nynke Keulen GEOLOGICAL SURVEY OF DENMARK AND GREENLAND DANISH MINISTRY OF CLIMATE, ENERGY AND BUILDING DANMARKS OG GRØNLANDS GEOLOGISKE UNDERSØGELSE RAPPORT 2012/62 Provenance of sediments in the Faroe-Shetland basin: characterisation of source components in Southeast Greenland Final report prepared for SINDRI C46-50-01 Kristine Thrane & Nynke Keulen Confidential report Copy No. To be released 01.07.2017 GEOLOGICAL SURVEY OF DENMARK AND GREENLAND DANISH MINISTRY OF CLIMATE, ENERGY AND BUILDING Contents Abstract 5 Introduction 7 Previous Sindri Projects ................................................................................................... 8 Aim of new project .......................................................................................................... 10 Database ........................................................................................................................ 11 Publications .................................................................................................................... 11 Sample preparation and analytical techniques 12 Introduction to Computer-Controlled Scanning Electron Microscopy (CCSEM) ............. 12 Sample preparation ................................................................................................... 12 CCSEM analysis ....................................................................................................... 12 CCSEM output files and parameters ......................................................................... 13 Heavy Mineral Analysis ............................................................................................. 15 Limitation to the mineral classification based on CCSEM ......................................... 15 Garnet classification .................................................................................................. 16 Zircon provenance by LA-SF-ICPMS ............................................................................. 17 Methods .................................................................................................................... 18 Discordance .............................................................................................................. 19 TIMS analyses of Baddeleyites ...................................................................................... 20 Project A: Provenance of sediments in the Faroe-Shetland basin: Characterisation of source components in Southeast Greenland. 21 Samples ......................................................................................................................... 22 CCSEM Results ............................................................................................................. 25 U-Pb results ................................................................................................................... 31 Discussion ...................................................................................................................... 41 Provenance characteristics of the Eastern Greenlandic basement between 62° and 68° N. ........................................................................................................................ 41 CCSEM ................................................................................................................ 41 U-Pb data ............................................................................................................. 44 Comparison of the Faroe-Shetland Basin with the Kangerlussuaq region and other source regions ........................................................................................................... 45 CCSEM ................................................................................................................ 45 U-Pb zircons ......................................................................................................... 46 Summary and Conclusions of Project A ......................................................................... 49 G E U S 3 Project B: Testing baddeleyite and zircon U-Pb age dating as a tool for the establishment of a robust geochronological framework for Palaeocene volcanic rocks in the Palaeocene interval T36 to T50 50 Samples ......................................................................................................................... 51 Results ........................................................................................................................... 53 Tuff samples from cuttings ........................................................................................ 53 Kangerlussuaq .......................................................................................................... 55 Summary and Conclusions of Project B ........................................................................ 56 Tuff samples from cuttings ........................................................................................ 56 Kangerlussuaq .......................................................................................................... 56 Possible Future Plans 57 Acknowledgements 58 References 59 Appendix A: Modal mineral distributions, Garnet compositions, and Titanium concentrations in Titanium minerals 66 Appendix B: Chemistry and mineralogy of pyroxenes and amphiboles 78 Appendix C: Background information on CCSEM and Garnet classification 85 Computer-Controlled Scanning Electron Microscopy .................................................... 85 Range of application for the CCSEM technique ........................................................ 85 Grain morphology analysis ....................................................................................... 85 Cost and efficiency compared to complementing methods ....................................... 86 Validity of the CCSEM measurements ........................................................................... 86 Accuracy of the CCSEM in comparison to the electron microprobe .......................... 86 Precision of the CCSEM analyses ............................................................................ 87 Repetitive analysis test ............................................................................................. 88 Garnet classification ...................................................................................................... 89 Background ............................................................................................................... 89 Method ...................................................................................................................... 90 Visualisation of the results ............................................................................................. 91 4 G E U S Abstract The aim of this Sindri project, C46-50-01, was to broaden our understanding of the timing of pulsing observed between sedimentary and volcanic Palaeogene deposition across the Faroe-Shetland region to better understand the sub-, syn- and early post-basaltic sedimen- tary succession offshore the Faroe Islands. The project is based on A) a detailed study of the provenance sensitive features of the possible source areas for sediment supply to the Faroe-Shetland basin in Southeast Greenland; and B) exploring the possibilities offered by baddeleyite and zircon for high precision U-Pb dating of the Palaeocene basalts and mafic igneous rocks exposed in the Faroe-Shetland basin. The two projects are both described in this report. In project A, geochemical analyses and U-Pb ages from detrital zircons have been carried out for a total of four tillite samples and 19 stream sediment samples collected along the South-East Greenland shore between 62-68N. The main conclusions are: • The age pattern and the geochemical data for samples from Southeast Greenland are markedly different from the drill core samples from the Faroe-Shetland Basin and, therefore, an unlikely source. • There are several potential source areas for the Faroe-Shetland sediments, e.g. Scotland, Central East Greenland, Svalbard (Scandinavia), which all share a com- mon signature. It is not possible to discriminate the sources based only on U-Pb de- trital zircon ages, or geochemical data. • Central East Greenland is the most likely source when combined with other studies, e.g. pollen studies and flow patterns. • The Kangerlussuaq sediments show characteristics from both Southeast and Cen- tral East Greenland and must, therefore, have been fed from both the north and the south. In project B, the main aim was to recover baddeleyite crystals from Palaeogene mafic ba- saltic rocks and tuffs from the lower lava sequence exposed at Sudoroy, to obtain precise crystallization ages from the rocks. Unfortunately, we were not able to find any baddeleyites in any of the samples, because they were too fine grained. To prove that we are able to recover baddeleyites from mafic samples, three mafic dykes collected in the Skaergaard area were also processed, only one of the dykes had baddeley- ite. The grains were analysed and yielded a U-Pb age of 55.87 ± 0.06 Ma. The samples are part of another Sindri project C46-53-02, carried out by Pierpaolo Guarnieri. G E U S 5 6 G E U S Introduction Palaeogeographic reconstructions of the North Atlantic