As technology becomes more sophisticated, the number and type
of tools available to the geochemist continue to grow and the
amount of data collected from a single sample is dramatically
increased. Micro-analytical techniques developed over the last
20--30 years allow the geochemist to obtain an almost overwhelming
wealth of data from single samples. Not only can bulk analysis be
routinely conducted, but detailed major- and trace-element
determinations, as well as isotopic analysis of individual
components from geological, metallic, ceramic, and plastic
materials are opening up a whole new avenue of research and
petrogenetic interpretation. In situ measurements have become an
important aspect of many geoscience applications, following the
realization that much of the information relating to the origin and
evolution of rock systems is retained at the scale of individual
mineral grains [e.g., Reed, 1989, 1990, 1993]. The new
generation of high resolution ion probes has furthered our ability
to perform trace element and isotope analyses at the micron (
m
= micron = 10
mm) scale. Laser ablation techniques, coupled
with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses
have opened up a parallel capacity for trace element analysis,
while laser fluorination oxygen extraction is fast becoming the
tool of choice for silicate oxygen isotope geochemistry. With
these analytical techniques available, a detailed data base on a
single sample or suite of samples can be quickly built up. For
major and minor element analyses, the electron microprobe is
normally used and as this has generally become a routine analytical
technique and has recently been extensively reviewed by Reed
[1993], it will not be discussed here.
This paper is concerned with the analysis of geologic materials on a sub-mm scale allowing the recognition of major and trace element, as well as isotopic zonation across individual mineral grains. The primary concentration is on work conducted in laboratories in the United States, although reference to work conducted in other countries is made where deemed appropriate. Three analytical techniques will be discussed: 1) In situ microsampling for isotopic analysis; 2) Secondary Ion Mass Spectrometry (SIMS); and 3) Laser Ablation Inductively Coupled Plasma---Mass Spectrometry (LA-ICP-MS). The object of the paper is to give the reader a current overview of the applications of each of the three analytical techniques as well as a detailed description of the newer LA-ICP-MS procedure.