For a good primer on oxygen isotopes in meteorites, see:
http://www.psrd.hawaii.edu/Dec01/Oisotopes.html
The formula for the "del" notation is given in a footnote
on p. 116 of Clayton's paper, and is difficult to read. The formula
for del 18O is:
where SMOW stands for Standard Mean Ocean Water (a reference standard for oxygen isotopes). This formula describes the 18O/16O ratio of a sample compared to the SMOW standard. A similar formula can be written for the proportion of oxygen-17 to oxygen-16 (del 17O).
Mass-dependent (or chemical) fractionation - This is the kind of variation between the three oxygen isotopes that is caused by differences in mass between the three isotopes. Oxygen-18 is 18/16 times heavier than oxygen-16, and 18/17 times heavier than oxygen-17. Processes such as evaporation or condensation of water will cause a mass fractionation of oxygen isotopes.
Non-mass dependent fractionation - This is the kind of variation between the three oxygen isotopes that cannot be explained by differences in mass between the three isotopes. Processes such as nuclear fusion reactions in stars, or the rapid formation of ozone in the laboratory, will cause such a fractionation.
Pre-solar grain - This is a grain that has been identified as having existed before the birth of the solar system, based on unusual isotopic compositions.
Nucleosynthesis - This is the formation of chemical elements. Most elements are formed during the life cycle of a massive star and during supernova explosions. Examples of nuclear processes that occur during a star's life cycle and during supernova explosions include r-process, s-process, and p-process. You don't need to understand these processes.
Interstellar medium - This is the material (gas and dust) that resides between stars.
Anneal/annealing - This means to heat a solid without melting it.
Equilibrated ordinary chondrites (EOCs) vs. Unequilibrated ordinary chondrites (UOCs) - UOCs are petrographic type 3 chondrites; EOCs are petrographic type 4, 5, 6 chondrites. Compared to a type 3 chondrite, types 4-6 were annealed during metamorphism.
Xenolith - This is an inclusion (object) in a rock which is not genetically related to other components of the rock.
In situ - This means "in the original location".