Analytical Dating in Geological Science (LA-ICP- MS)

摘要

The project samples are metasediments from the south of Spain, spanning late Proterozoic to Ordovician in age. The question being addressed is whether the provenance of zircons in these samples changed during this interval. There is evidence using Nd and O isotopes that there is a big shift in the middle of the sequence that reflects the availability ofAfrican zircons presumably following collision of Iberia with Africa. Patterns of zircon ages should confirm or disprove this hypothesis. The material, which I present, describes details of the preparation of rocks for use in LAICP-MS and the process of separating particulate mineral zircon from the mass of rock, mineral processing, as well as the process of laser ablation and the construction of geochronological profile using Concordia diagram. Firstly rocks were crushed with Jaw crusher.Using magnetic, density and liquid separation and microscope zircon was separated from the main mass of rock. Secondly zircons were ablated with LAICP-MS. With the resulting of ICP-MS analysis the age was calculated. Zircons were formed 600 mln years ago in Neoproterozoic Era, Ediacaran Period. This is the same age ofAfrican zircons. We propose that Spanish zircons were formed due to the same process-Iberia-Africa collision.