Determination of the formation conditions of carbonates in an alteration zone of the Soultz-sous-Forets granite (Rhine Graben): the fluid inclusion record.

A fluid inclusion study was carried out in quartz and ankerite veins (drill hole EPS-1, depth 1641 m) of the Soultz-sous-Forets granite (geothermal exc hanger). Homogenisation temperatures in quartz and ankerite lie in a narrow similar range and are consistent with the present-day in situ temperature measured in the well. Ankerite and quartz have precipitated in the same con ditions, which appear to be general at the site scale in all observed alter ation facies. Quartz and ankerite are likely to precipitate at present. The data suggest that the fluid probably has a pulsated mode of circulation. ( C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.