Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany

Chemical Geology
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Abstract

The KTB pilot borehole in northeast Bavaria, Germany, penetrates 4000 m of gneiss, amphibolite, and subordinate calc-silicate, lamprophyre and metagabbro. There are three types of calcite in the drilled section: 1) metamorphic calcite in calc-silicate and marble; 2) crack-filling calcite in all lithologies; and 3) replacement calcite in altered minerals. Crack-filling and replacement calcite postdate metamorphic calcite. Multiple calcite generations in individual cracks suggest that different generations of water repeatedly flowed through the same cracks. Crack-filling mineral assemblages that include calcite originally formed at temperatures of 150-350??C. Presently, crack-filling calcite is in chemical and isotopic equilibrium with saline to brackish water in the borehole at temperatures of ???120??C. The saline to brackish water contains a significant proportion of meteoric water. Re-equilibration of crack-filling calcite to lower temperatures means that calcite chemistry tells us little about water-rock interactions in the crystal section of temperatures higher than ~120??C. -from Author

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany
Series title Chemical Geology
DOI 10.1016/0009-2541(95)00063-R
Volume 124
Issue 3-4
Year Published 1995
Language English
Publisher Elsevier
Contributing office(s) Minnesota Water Science Center
Description 17 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Chemical Geology
First page 199
Last page 215