Original paper

Carbon in igneous minerals of granulates from Rogaland (Norway): nuclear microanalysis and isotope geochemistry

Wilmart, Edith; Mosbah, Michelle; Pineau, Françοise

European Journal of Mineralogy Volume 5 Number 2 (1993), p. 269 - 280

27 references

published: Apr 27, 1993
manuscript accepted: Dec 2, 1992
manuscript received: Sep 25, 1992

DOI: 10.1127/ejm/5/2/0269

BibTeX file

ArtNo. ESP147050502005, Price: 29.00 €

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Abstract

Abstract The occurrence of carbon is reported in zircons (first occurrence), olivines and spinels from Rogaland (Norway). Minerals were separated from hypersthene granites (charnockites, granulite facies) which crystallized at fO2 close to FMQ buffer conditions. Up to 6600 ± 990 ppm of carbon were measured from the zircon sub-surface down to 5 μm deep (deep carbon) through the nuclear reaction 12C(d, po)13C. No carbon diffusion at depth or towards the surface was observed. In olivine and magnetite, deep carbon contents of several hundreds of ppm were detected. In an attempt to determine the carbon localization, speciation and origin we used several techniques: electron spectroscopy, scanning electron microscopy, transmission electron microscopy as well as isotopic analysis of carbon released by step-heating of zircon. The results obtained by these various techniques suggest that carbon in zircon is chiefly present in three forms: (1) as thin coating of carbonates on crystal surfaces and on late microfracture walls, (2) as minute graphite inclusions, and (3) as carbonaceous films. This last species accounts for 65 to 75% of the total amount of carbon extracted from zircon. It was probably formed by the reduction of pervasive fluids (magmatic?) on microcracks produced during cooling of the rocks. No evidence for dissolved carbon was found

Keywords

carboncarbon speciationzirconolivinemagnetitenuclear microprobeXPSSEMTEMisotope geochemistry