High-resolution LA-ICP-MS trace element mapping of igneous minerals: In search of magma histories Teresa Ubide ⁎, Cora A. McKenna, David M. Chew, Balz S. Kamber School of Natural Sciences, Department of Geology, Trinity College Dublin, Dublin 2, Ireland abstract article info Article history: Received 19 December 2014 Received in revised form 20 May 2015 Accepted 28 May 2015 Available online 3 June 2015 Editor: Prof. K. Mezger Keywords: Microanalysis Laser ablation ICP-MS Geochemical mapping Mineral zoning Antecryst Magma history We report experiments on optimisation of LA-ICP-MS mapping as a tool for visualising and quantifying internal structure of trace element concentration in igneous minerals. The experimental design was refined with maps on clinopyroxene and amphibole macrocrysts (mainly antecrysts) from a porphyritic lamprophyre in NE Spain, as well as on a high precision metal wire grid. In terms of spatial resolution, we demonstrate with scanning electron microscope and white light interferometry that a full ablation removes between 0.4 and 0.7 μm of material, de- pending on ablation parameters. Maps were produced with square laser beam spots of 12 and 24 μm. It was found that complexities can be resolved in the sample even though they are smaller than the beam diameter (e.g., 7–10 μm discontinuities using 12 μm laser beam). Resolution in x and y was found to be identical, probably reflecting the fast washout of the two-volume ablation cell and the short total dwell time of the analyte menu selected. Due to the excellent stage reproducibility and the limited ablation depth, it is feasible to re-ablate the identical map area many times employing different instrument parameters or analyte menus. On the magmatic crystals, LA-ICP-MS maps define very sharp compositional zoning in trace elements, highlight- ing complex crystallisation histories where ‘normal’ magmatic fractionation is not the only process. Events of mafic recharge are easily recognised as zones enriched in compatible metals such as Cr, Ni or Sc. Further, trace element maps reveal complexities in mineral zoning previously undetectable with petrography or major element data. These include resorbed primitive cores and oscillatory zoning within apparently homogeneous mineral zones. Therefore, LA-ICP-MS mapping opens a new window of opportunity for analysis of magmatic histories. The wide combination of instrumental parameters, such as laser beam size, scan speed and repetition rate, make it possible to carry out experiments at different levels of detail. We recommend a two-step approach to mapping. The initial step involves rapid maps to gain an overview of potential complexities in the sample; this enhances representativeness of the analysed materials, as a large number of crystals and trace elements can be tested in little time. Subsequently, detailed maps can be carried out on areas of interest. An additional function- ality is to create 1D-profiles from 2D-maps. The potential of the technique to unveil compositional complexities efficiently and at greater detail than traditional microanalysis will help to improve our understanding of process- es in the magmatic environment and beyond. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Compositional variations in geological materials at the microscopic scale can contain a record of geological processes and the evolution of environments. The rich compositional archive has particularly been exploited in igneous petrology, where chemical zoning of individual crystals can be directly related to changes in magmatic environment (Bussweiler et al., 2015; Streck, 2008). Trace element variations during crystal growth bear important information on magma compositions and conditions during crystallisation, complementing petrography and major element studies (Ginibre et al., 2007). Technological improvements in microanalysis have led to the reali- sation that magmatic mineral phases are often not in equilibrium with their enclosing groundmass (e.g., Davidson et al., 2007). This has informed the premise that many large crystals, rather than being phe- nocrysts, should be regarded as antecrysts that formed prior to em- placement at depth (Charlier et al., 2005; Davidson et al., 2007; Gill et al., 2006; Hildreth and Wilson, 2007; Jerram and Martin, 2008; Larrea et al., 2013). The complexity within antecrysts implies the exis- tence of complex magma plumbing systems with episodes of contami- nation, recharge and magma mixing (Francalanci et al., 2012; Sakyi et al., 2012; Ubide et al., 2014a, 2014b). Events of recharge into deep magma chambers with a more primitive (often fluid-rich) batch of magma have been studied with particular interest as they are consid- ered the main cause for triggering volcanic eruptions (e.g., Kent, 2013; Chemical Geology 409 (2015) 157–168 ⁎ Corresponding author. E-mail address: teresaubide@gmail.com (T. Ubide). http://dx.doi.org/10.1016/j.chemgeo.2015.05.020 0009-2541/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo