410 Alexandre La Fontaine et al.


Figure 5. Pb and U detection limits. a: Mass spectra from 102–105Da and 126–136Da for the sample DN5. The first two mass spectra show Pb for the precipitate only and for the full data set. b: Mass spectra from 102–105Da and 126–136Da for the Krossey sample.


APT tip during TKD is its potential contamination by hydrocarbons that can affect the atom probe acquisition. The issue can be minimized by plasma cleaning.


Table 2. Detection Limits and Net Counts for 206Pb2+ and 207Pb2+ in the Krossey Sample.


Krossey Sample (~33M atoms) 206Pb2+


Net counts


Background counts LDL


7,710±88


Not detected 410±4 counts


13±1ppma 207Pb2+ 4,898±70


Not detected 325±3 counts


10±1ppma Figure 7 illustrates correlative TKD/APT microscopy


applied to the deformed zircon DN77. Figure 7a shows the reconstructed 3D volumes for Mg and Al. The dislocations are readily apparent with a strong segregation of Al and Y (Figs. 7a, 7c and 7d). Interestingly, there is also segregation of Mg around the dislocations, but it is much more spread out compared with Al. Figure 7b contains both the TKD defor- mation map and the APT 3D reconstructed volume with the misorientation profile obtained from the TKD data laid over both images. Here we show that high-resolution TKD orien- tation mapping provides essential structural information on the degree of deformation across the tip due to geometrically necessary dislocations. The use of APT on the same tip completes the nanoscale characterization of the sample deformation by revealing the elemental distribution within the dislocations that accommodate the observed deformation.


Table 3. Net Counts and Quantification Limits for 206Pb2+ and 207Pb2+ in the DN5 Sample (Full Volume and Pb-Rich Precipitate).


206Pb2+


(a) DN5 sample (full volume ~16M atoms) Net counts Net ppma


5,660±120


Ratio 207Pb/206Pb Background counts LQ


350±8ppma 0.054±0.025 3,890±62


880±6 counts 55±1ppma


1,425±30


Ratio 207Pb/206Pb Background counts LQ


207Pb2+ 300±110 19±7ppma 5,500±74


1,045±10 counts 65±1ppma


(b) DN5 sample (Pb-rich precipitate ~110.000 atoms) Net counts Net ppma


77±5 counts 310±17


13,000±270ppma 2,820±150ppma 0.217±0.006 30±5


277±16 235±6 counts 700±45ppma 2,100±55ppma CONCLUSION


The optimum acquisition parameters for the mineral zircon using UV-laser-assisted LEAP 400×SiTM were found to be ~400 pJ laser pulse energy, 250 kHz laser pulse frequency and ~60K base temperature. These parameters generate very limited thermal effects, a good mass resolving power, an acceptable rate of single events per pulse, and a good specimen yield. Themass spectra from different zircons were all similar and most of the peaks detected were identified. The detection and quantification limits of the key trace elements, U and Pb, were assessed using two different zircons and as expected they were found to be a function of the size of the data set, the initial U content, the age of the zircon as well as the potential clustering ofU or Pb. Finally, we demonstrate the necessity of correlative EBSD/TKD/APT microscopy for the study of the behavior of trace elements in deformed zircons.


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