Vermeesch, P;
Rittner, M;
Petrou, E;
Omma, J;
Mattinson, C;
Garzanti, E;
(2017)
High Throughput Petrochronology and Sedimentary Provenance Analysis by Automated Phase Mapping and LAICPMS.
Geochemistry, Geophysics, Geosystems
, 18
(11)
pp. 4096-4109.
10.1002/2017GC007109.
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Abstract
The first step in most geochronological studies is to extract dateable minerals from the host rock, which is time consuming, removes textural context, and increases the chance for sample cross contamination. We here present a new method to rapidly perform in situ analyses by coupling a fast scanning electron microscope (SEM) with Energy Dispersive X-ray Spectrometer (EDS) to a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LAICPMS) instrument. Given a polished hand specimen, a petrographic thin section, or a grain mount, Automated Phase Mapping (APM) by SEM/EDS produces chemical and mineralogical maps from which the X-Y coordinates of the datable minerals are extracted. These coordinates are subsequently passed on to the laser ablation system for isotopic analysis. We apply the APM+LAICPMS method to three igneous, metamorphic, and sedimentary case studies. In the first case study, a polished slab of granite from Guernsey was scanned for zircon, producing a 609±8 Ma weighted mean age. The second case study investigates a paragneiss from an ultra high pressure terrane in the north Qaidam terrane (Qinghai, China). One hundred seven small (25 μm) metamorphic zircons were analyzed by LAICPMS to confirm a 419±4 Ma age of peak metamorphism. The third and final case study uses APM+LAICPMS to generate a large provenance data set and trace the provenance of 25 modern sediments from Angola, documenting longshore drift of Orange River sediments over a distance of 1,500 km. These examples demonstrate that APM+LAICPMS is an efficient and cost effective way to improve the quantity and quality of geochronological data.
| Type: | Article |
|---|---|
| Title: | High Throughput Petrochronology and Sedimentary Provenance Analysis by Automated Phase Mapping and LAICPMS |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1002/2017GC007109 |
| Publisher version: | https://doi.org/10.1002/2017GC007109 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| Keywords: | Geochronology; zircon; electron microscopy; LA-ICP-MS; EDS; provenance |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10040458 |
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