Award Abstract #0215953
Acquisition and Development of an Ultra Violet Laser Sulfur Isotope Microprobe for the Analysis 32S, 33S, 34S, and 36S in Sulfide Minerals

NSF Org:	EAR Division of Earth Sciences
Initial Amendment Date:	July 16, 2002
Latest Amendment Date:	July 16, 2002
Award Number:	0215953
Award Instrument:	Standard Grant
Program Manager:	David Lambert EAR Division of Earth Sciences GEO Directorate for Geosciences
Start Date:	August 1, 2002
Expires:	July 31, 2004 (Estimated)
Awarded Amount to Date:	$211783
Investigator(s):	Douglas Rumble rumble@gl.ciw.edu (Principal Investigator)
Sponsor:	Carnegie Institution of Washington 1530 P ST NW WASHINGTON, DC 20005 202/387-6400
NSF Program(s):	MAJOR RESEARCH INSTRUMENTATION
Field Application(s):	0000099 Other Applications NEC
Program Reference Code(s):	OTHR, 1189, 0000
Program Element Code(s):	1189

ABSTRACT

0215953

Rumble

The acquisition of a new isotope-ratio-monitoring, gas chromatograph inlet mass spectrometer (IRMS-GC MS) equipped with four collectors and four channel output for simultaneous analysis of the ion beams of SF6 will make it possible to develop a new ultraviolet (UV) laser fluorination microprobe for the analysis of 32S, 33S, 34S, and 36S in sulfide minerals. Based on previous experience with the successful in situ microanalysis of oxygen isotopes in silicate minerals, it should be possible to measure 50-micrometer diameter spots on sulfide minerals with a precision of 0.1 to 0.2 per mil in d33S and d34S and 0.05 per mil in ?33S. Analysis for d36S will be at a lower level of precision owing to the rarity of the isotope 36S. A new UV laser macroprobe and GC purification system has already been built and validated for 400 micrometer diameter spot measurements of sulfur isotopes using an existing mass spectrometer that is incapable of GC-continuous flow operation. The new IRMS-GC MS requested from NSF-MRI is needed to improve analytical spatial resolution from 400 to 50 micrometers. The new sulfur isotope microprobe will be used to test the validity of the discovery of mass-independent sulfur isotope anomalies in Archean rocks by direct fluorination of sulfide minerals. The proposed relationship between the anomalies and the oxygenation of Earth's atmosphere will be tested by detailed measurements of drill cores spanning the Archean-Proterozoic transition. The mechanisms responsible for fixing mass-independent signatures in rocks will be investigated through spatially resolved analyses of inter-mineral fractionations and intra-mineral isotopic heterogeneity. The new microprobe's capacity to analyze microgram samples will be put to use in a laboratory study of the fractionation of sulfur isotopes by microbes. Use of the new sulfur isotope microprobe will be open to qualified users from throughout the research community.

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