Single Shard Analysis of Volcanic Glass Shards by Timeof-Flight Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (TOF-LA-ICP-MS) Jeffrey R. Knott – Department of Geological Sciences, California State University-Fullerton, Fullerton, CA
100
Chondrite Normalizede
Goal: Determining minor and trace element composition of single shards from tephra layers using TOF-LA-ICP-MS for suitability in a large database. Need: Determination of minor and trace elements is limited to bulk samples.
10
1
250 0.77 Ma Bishop Ash Bed 3.35 Ma Zabriskie Wash 3.27 Ma Nomlaki >3.58 Ma Artists Drive
200 0
Rubidium (ppm
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Atomic Number
150
Typical Shards on Slide
Example Mean Rare-Earth element composition
100
50
0.77 Ma BISHOP 3.35 Ma ZABRISKIE WASH 3.28 Ma NOMLAKI >3.58 Ma ARTISTS DRIVE
0 0
100
200
300
400
500
600
700
Manganese (ppm)
Example Single Shard Analyses
800
Results: I have analyzed glass shards known to have similar major-element compositions. Single shard analyses using TOF-LAICP-MS are sufficiently precise and accurate to differentiate among tephra from the both different and the same volcanic source. The results from this project are sufficient that I am moving forward on completing analyses of the stratigraphically important and unresolved Wilson Creek ash beds of eastern California.
