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Carbonates at extreme conditions

Speaker: Prof. Dr. Monika Koch-Müller (GFZ Potsdam) -------- ab 16 Uhr MGC Generalversammlung)
Most carbonates are sediments - why should we study them at extreme conditions? There is evidence for the presence of carbonantes in the Earth's mantle. Two out of many other examples illustrate this: Kaminsky et al. (2013) report on magnesite and dolomite inclusions in a diamond from the deep mantle and Korsakov and Herrmann (2006) found carbonate inclusions in deeply subducted rocks from Kazakhstan. Thus carbonates are present in the deep Earth. Carbon can be transferred into the mantle through subduction processes and it can return to the surface through volcanism. But not all carbon returns to the surface - parts of it can be carried mostly as carbonates into the deep mantle. The quantity of C carried into the deep mantle compared to the quantity of C released to the surface is highly under debate. It is clear, that the petrology of the deep carbon storage is responsible for the long-term evolution and the distribution of carbon on and in the earth (Manning 2014). Thus, the stability of carbonates under extreme conditions is an important issue in experimental petrology. The scientific community is talking about the Deep Carbon Cycle. And nowadays many groups worldwide are working on carbonates within the frame of the Deep Carbon Observatory. In this presentation I will focuse on two subjects: A) the melt relations in the system CaCO3-MgCO3 at 6 GPa under anhydrous and hydrous conditions. I will show how we can improve our knocklegde about the formation of carbonate melts by doing experiments; how with the help of a rotating multi-anvil press the reported quenching problems in carbonate systems can be overcome; how the presence of water influences the melting temperature. B) Siderite (FeCO3) and magnesite (MgCO3) form a complete solid solutions series. It is known from recent literature that Fe-bearing minerals may undergo a high-spin to low-spin transtion at high pressures. I will show that Fe-bearing carbonates also undergo a HS-LS transition and how the transition pressure changes with composition and temperature. Although directly applicable to the Earth's mantle - this study has been performed mainly to mimic the spin state within the Earth's mantle using siderite as an analogue material. Kaminsky et al. (2013) Canadian Min., 51, 669-688 Korsakov and Hermann (2006) EPSL, 241, 104-118 Manning C. (2014) Nature Geoscience, 7, 333 - 334
by last modified 31. Oct 2018 08:20
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Printed 27. May 2019 14:00