Sonia Sánchez Martínez
Universidad Complutense de Madrid
Project Title: U-Pb dating of the ophiolites involved in the Variscan suture of Galicia (NW Iberian Massif)
GB-TAF Host: Dr Teresa Jeffries, Department of Mineralogy
Project Objectives:
The objective of this project is to resolve the geochronology of Galician
ophiolitic units, for which little data exists. Ages determined will be used to
develop a model to assemble the oceanic terranes in the Paleozoic paleogeography
of the peri-Gondwanan realm. Seven samples of metabasites and metasediments have
been collected and prepared for LA-ICP-MS U-Pb dating. From these samples I aim
to
a) Constrain the age of the igneous protoliths (zircons from the metabasites)
b) Obtain metamorphic ages (using the higher grade samples)
c) Determine the maximum depositional ages and provenance constraints (using age spectra derived from detrital zircon populations in the metasediments).
Project Achievements:
I've been trained in the use of LA-ICP-MS for U-Pb dating of zircons in
metabasites and metasedimentary rocks.
We have succesfully dated 9 samples from 5 different ophiolitic units of the Variscan Belt that have never been dated before. The model that we have proposed in recent contributions for the origin of the oceanic domains in the peri-Gondwanan realm during Paleozoic times will be improved with this data. It could mean an important step forward in the knowledge about European Geology.
Training received:
Collection of CL images using analytical SEM with CL attachment.
Preparation and mounting of samples for zircon dating by LA-ICP-MS.
Collection and processing of U-Pb data by laser ablation ICP-MS.
Use of SEM microscope for taking images of laser ablated zircons.
One-to-one with Sonia Sánchez Martínez
1. Why did you apply for access to GB TAF under SYNTHESYS?
The PhD project I have been developing during the past four years deals with the geochronological and geochemical study of the ophiolites in the NW Iberian Massif (Allochthonous Complexes of Galicia) that are lithological assemblages of oceanic affinity. A fundamental part of this project entails determining their age by the U-Pb analytical method in zircons. To perform this kind of analysis it is necessary to resort to highly sophisticated analytical techniques by using equipments that supply data of proven quality. We don’t have laboratories with facilities that fulfil such characteristics in our country and that is why I had to apply to the SYNTHESYS programme to carry out the geochronological study using the LA-ICP-MS facility at the NHM laboratories, supervised by Dr. Teresa Jeffries, the first worldwide expert in this technique.
2. What direct benefits to your personal research did you gain from the visit?
Firstly, it would not be possible for me to finish the PhD project without the funding of the SYNTHESYS programme and the stay at the NHM to obtain the geochronological data. On the other hand, these data have proved to be very novel and unexpected, changing radically the knowledge about the basement geology of Spain. The ophiolitic units that have been studied have ages ranging from Mesoproterozoic to Lower Devonian, which implies that part of the terranes with oceanic affinity in the NW Iberian Massif have been involved in two supercontinental clycles, participating in the Rodinia and Pangea assemblies. These data have also let us discover the existence of 1160 Ma-old igneous rocks, the oldest in the Iberian Peninsula, that duplicate its age known until now. This discovery had a widespread repercussion in national and local media of our country and even of the neighboring country, Portugal. Besides, part of the obtained results have been already published in an international scientific journal, The Journal of the Geological Society of London, and we have planned to write new articles that we expect will be published shortly.
3. How will the outputs from the visit benefit the following:
a) Environment and/or Conservation
b) Biodiversity
c) Improved Industrial Processes/products
d) Health/medicine or related issues
The output from my visit benefit the Environment (a) because they lead to a better understanding of the natural environment and the reconstruction of the geological history of Spain and Western Europe.
4. Have you passed on your knowledge/training to fellow researchers in your home Institution and/or home Country?
As I said, in our country there are no laboratories available with analytical facilities similar to those I used at the NHM, but I hope this situation will change in the future and then I will try to help other scientists in using and obtaining isotopic data by LA-ICP-MS.
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