Abstract
In the Upper Proterozoic rift sediments of the Damara Orogen (Namibia) up to 1000-m-thick metaplaya sequences of partly evaporitic origin occur. The playa evaporites include thick layers of scapolite, albite pseudomorphs after Na-carbonates, K-spar pseudomorphs after Ca-sulfate, and other mineralogical and structural features of playa environments. During metamorphism, large quantities of highly saline fluids were mobilized, which were of major importance for the structural development and the mineralization of Cu, Ti, U and Au in this region. Within this sequence stratiform tourmalinites of several meters thickness occur, which can be traced over several tens of kilometers. The sedimentary origin of these tourmalinites is substantiated by well-preserved fine-laminated primary bedding features, which indicate a hot-spring activity during the time of deposition. Correlation of F/Cl and FeO ( MgO + FeO) ratios with tourmalines from various strata-bound massive sulfide deposits also indicates a sedimentary origin of the tourmalinites. The meta-evaporite sequence also contains megaquartz bodies some of which are built of single crystals up to 50 m in size, intergrown with large crystals of dolomite (ф 1 m). In one locality this quartz-dolomite mineralization shows a high content of native sulfur. Thermometric measurements, verified by Raman probing indicated native sulfur as a daughter mineral and dissolved HS − is suspected to be present in the fluid inclusions in this quartz. Further microthermometric measurements on fluid inclusions in the tourmalinites, the sulfurous quartz and several other related quartz-dolomite mineralizations (Duruchaus, Tsumeb) confirm the hitherto existing results and strongly suggest a derivation of the mineralizing fluids from the metaplaya sequence. The detailed analyses of fluid inclusions and their various daughter phases within the inclusions allow the estimation of the chemical composition of the mineralizing fluids.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
