TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

tine. Data points near Fe-rich phases such as melt inclusions and alteration-filled
fractures were discarded.
3.4.4 Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-
MS)
Strontium, Y, Ba, La, Ce, Nd, Sm, and Eu were measured in plagioclase
crystals using a New Wave UP-213 UV laser ablation system interfaced with a
ThermoFinnigan Element 2 ICP-MS operated in fast magnet scanning mode at
the University of Notre Dame. I used a laser frequency of 5 Hz, pulse energy of
0.02-0.03 mJ pulse −1 , 15 µm or 30 µm diameter pits depending on crystal size
(40 µm diameter pits were used for analysis of Site 884 plagioclase crystals), and
helium as the carrier gas (∼ 0.7 l min −1 ) mixed with argon (∼ 1.0 l min −1 ) before
introduction to the plasma. Due to the transient nature of the laser ablation sig-
nal, analyses were conducted in peak jumping mode with one point quantified per
mass. The LA-ICP-MS spots were coincident with previous EPMA analyses, and
Ca measured by EPMA was used as an internal standard for each spot analysis,
because its fractionation behavior is similar to that of Sr, Ba, Y, and the REE
[52]. The trace element glass NIST 612 was used as a calibration standard for
all laser ablation analyses. Although heterogeneity for certain elements has been
documented in the widely used NIST 612 glass (i.e., [44]), Eggins et al. [44] consid-
ered it a reliable calibration standard for Sr, Ba, Y, and the REE. The analytical
protocols of Longerich et al. [88] were used for LA-ICP-MS data reduction.
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