Main and trace elements in KTB-VB fluid: composition and hints to its origin

The pilot hole (VB) of the German Continental Deep Drilling Program (KTB) was drilled to a depth of 4000 m, where large amounts of free fluids were met. The KTB-VB 4000 m fluid can be related to either Mesozoic seawater or formation water from Permo-Carboniferous sedimentary rocks of the Weiden embayment. During the Upper Cretaceous uplift of the Bohemian Massif both fluids could have passed organic-rich Triassic to Carboniferous formations of the Weiden embayment before invading the uplifted and fractured basement rocks of Devonian amphibolites and metagabbros, where the chemical composition of the fluids was changed by albitization, adularization, and chloritization. Results of chemical mass balances for both sources are presented. In order to concentrate the formation water from the Weiden embayment significant amphibolitization has to be assumed. During a 1-year pumping test the chemical composition of the 4000 m fluids remained constant. The accuracy of chemical analyses is critically reviewed. An improved preconcentration method of rare earth elements and yttrium in high-Ca-bearing saline fluids is described.