'Sampling the carbon of the deep Earth: what can kimberlite carbonates tell us about the SCLM and the deep C cycle?', by Montgarri Castillo i Oliver
- May 31, 2023 | 12:00 h CET
- online and in-person GEO3BCN-CSIC
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The deep source of the kimberlite parental melts (>250 km), combined with their high CO2 contents, render them unique probes for carbon in the subcontintental lithospheric mantle (SCLM). Primary carbonates in kimberlites are particularly good traps for the CO2 in kimberlite magmas and thus could be used to constrain the original carbon and oxygen isotope composition of parental melts, including their deep mantle source.
Early studies have shown that carbonate petrogenesis in kimberlites can be very complex and their composition can be influenced by a wide variety of processes, such as crustal contamination, degassing and hydrothermal or meteoric alteration. However, the contribution of these syn- and post-emplacement processes to the modification of the C-O isotope composition of kimberlites is yet to be fully constrained. In this talk, a multi-technique approach, including petrographic examination, major-, minor-element analysis, and both bulk and in situ, carbonate C-O-Sr isotope analysis, will be presented as a succesful methodology to accurately describe the different generations of carbonates in kimerlites.
In this sense, our recent work on the Benfointein kimberlite sills will be used as an excellent example to demonstrate the complexity of kimberlite carbonates. Moreover, this case study also shows that our in situ C-O-Sr isotope approach allows identification of primary pristine carbonates in the Benfontein kimberlite sills, and thus correctly constrains the C-O isotopic compostion of their parental melts. Following the same methodology, carbonates from fresh hypabyssal kimberlites worldwide have recently been characterised. Our preliminary results, as well as new publications on kimberlite carbonates, are used to shed new light on our the deep Earth carbon and its evolution through time.
Montgarri Castillo i Oliver studied Geology at the University of Barcelona (UB), completing her studies in 2009. The following year, she began her career in research, focusing on kimberlites. For her master's work, she conducted research on mineral indicators of diamonds in fertile and sterile kimberlites of Angola. Her doctoral thesis continued in this line, with a special emphasis on the characterization of the mantle lithospheric NE of Angola using Mantel.lic xenoliths.
Following a research stay at Macquarie University (MQUni, Sydney), she completed her doctoral thesis as a cotutelle between UB and the Australian University, earning a double degree in late 2016. Since then, she has been employed as research staff at MQUni, where she combines her postdoc project on the isotopic characterization of carbonates in kimberlites with other research lines. These include the study of superreduced phases of the mantle and the development of new methodologies for in situ analysis of S isotopes in sulfides. She has now returned to Barcelona, thanks to a postdoctoral contract awarded by María Zambrano.