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ANR-funded project

WarHol

Glaciers in a warming world:

Lessons from Holocene records based on the novel cosmogenic nuclide dating tool “in situ carbon-14”

Glacier Blanc, Massif des Ecrins

This extraction technique relies on quartz diffusion at high temperature (1650°C) and cleaning of the released gas using cryogenic traps.


This extraction line, originally designed by ETH in Zurich, was started for implementation in CEREGE in march 2016. Implementation phase is at its end and soon (beginning of 2018) we will proceed to blank tests and firsts sample extraction/purification.

Construction status in 2016

CO2 minican installation. It is used to realize carbon yield test through the line.

 

Starting from geological samples, rock sample are crushed then chemically purified from sample matrice in order to extract quartz where in situ 14C is produced. 

Construction status in the end of 2017

 

Protocol main steps : 

- 5g of purified quartz is placed in a platinum crucible and hanged to an alumina rod inside the vertical extraction furnace.

- Heating up to 500°C in order to release the gas diffused which is composed with 14C atmospheric contaminant.

- Then heating up to 1650°C and holding for several hours to release gas containing in situ carbon molecules and other componants. With an O2 flux, carbon is transformed to CO2 gas form. A second furnace at 1100°C with quartz beads in a quart tube complete carbon transformation to CO2.

- Gathering condensable gas with liquid nitrogen trap (-196°C) in a hellicoidal trap

- Series of gas separation to eliminate water vapor (-80°C cryogenic trap), halide and sulfide oxydes (furnace with Ag/Cu whool 610°C) and nitrogen oxydes (-145°C cryogenic trap).

-We finally gather our purified carbon dioxyde gas which will be kept in a sealed glass vessel.

 

CO2 sample is finally measured in AMS (Aix-Micadas)  to determine its exposure age.

 

In the firsts experiments, baths slush were used to reach and maintain a cryogenic temperature. To improve the temperature trap stability  and precision, we are using variable temperature traps which are monitored by a PID controller. 

Platinum crucible hanged to an alumina rod (around 50cm length).