Abstract
Samples of natrocarbonatite showing various degrees of alteration are preserved in an older carbonatite platform that existed before and until the 1917 explosive eruption at Oldoinyo Lengai volcano, in Tanzania. The carbonatite samples contain two mineral assemblages: the first consists of relict primary magmatic minerals: nyerereite, fluorite, apatite-(CaF), barite, magnetite and khanneshite. The second consist of low-temperature subsolidus minerals: pirssonite, calcite, shortite, nahcolite, trona, thermonatrite, jacobsite and barytocalcite. Observed relationships between key primary and subsolidus minerals show the following sequence of formation: nyerereite → pirssonite → calcite → shortite. Three major processes, mineral dissolution, metasomatic replacement and crystallization from solution, alter the natrocarbonatite to pirssonite carbonatite, shortite carbonatite and calcite carbonatite. Nyerereite – pirssonite – calcite relationships depend on variations in P(H 2 O) and P(CO 2 ).
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.
