HIGH RESOLUTION MASS SPECTROMETRY FOR 40AR/39AR GEOCHRONOLOGY: A DESIRE OR NEED? (Invited Presentation)

The ⁴⁰Ar/³⁹Ar community is moving from a single collector to multi-collector beam detection approach with the Noblesse and Argus VI mass spectrometers as the main proponents of this transition. In addition, new approaches for the detection of individual ion beams have already been introduced such as Faraday collectors with 10¹² and 10¹³ Ohm resistor amplifiers. Here, we report our findings on a  relatively new branch on the tree: the high resolution Helix MC. The Helix is fitted with 5 Faraday collectors with 10¹² and 10¹³ Ohm amplifiers and 5 compact discrete dynode secondary electron multipliers for pulse counting detection on each channel. The design of the instrument includes a 120 degrees deflection magnet with a measured standard resolution of ca 900, allowing full resolution of hydrocarbon at all relevant masses. The high resolution mode on channel L2 has a resolution of ca 1700 used for the detection of ³⁶Ar. Here, we will explain some of our newly developed analytical protocols. We will present data on Mount Etna, Italy and compare that with data previously published in our lab. Implications of these data for Earthtime targets will be discussed.