AGES OF PEGMATITE AND VEIN MINERALS FROM RWANDA AND BURUNDI

Journal Article · Mon Jan 01 04:00:00 EST 1962 · Bull. Soc. Belge Geol., Paleontol., Hydrol.

OSTI ID:4680713

Cahen, L; Delwiche, R; Monteyne-Poulaert, G

BS>Presented is part of a program dealing with the ages of pegmatite and vein minerals from the Kibara-UrundiKaragwe Ankolean belt. Ages of sixteen pegmatite and vein minerals from Rwanda and Burundi were obtained by the strontium-- rubidium ( lambda = 1.47 x 10/sup -11/ yr/sup -1/), lead--uranium, and common lead methods. These ages fall into two groups. Eleven muscovites, one microcline, and one common lead, from tin and niobium-- tantalum-bearing pegmatites and veins (8 localities in Rwanda and 3 in Burundi), yield apparent and conventional ages between 870 and 1,000 m.y. Three Sr--Rb determinations on lepidolites from similar pegmatites from Northern Katanga, comprised in the expression 920 plus or minus 25 m.y., which lies in the range obtained in Rwanda and Burundi, are included for comparison. As the range from 870 to 1,000 m.y. is greater than the uncertainty of each measurement, it is probable that these pegmatites and veins do not represent one single event and that part of the scatier is real. The age range 870 to 1,000 m.y. characterizes pegmatites and veins which are post-tectonic events of the Urundian or Karagwe-Ankolean cycle. The occurrences from Northern Katanga are posttectonic events of the equivalent Kibara cycle. One, or two, much younger events are indicated by minerals found or thought to occur in quartz veins which are emplaced in the above-mentioned pegmatites. A mineral of the microlitepyrochlore group from Buranga is circa 555 m.y. old and a galena from Kababara has a common lead conventional age of 620 plus or minus 50 m.y. These figures occur in the range of Katangan and post- Katangan ages. The quartz veins therefore appear to be much younger than the host pegmatites. As this question is of interest to metallogeny it will be further investigated. A galena from Rushubi (Burundi) has a lead of anomalous isotopic constitution. (auth)

• Research Organization: Musee Royal de l'Afrique Centrale, Tervuren, Africa
• NSA Number: NSA-17-032268
• OSTI ID: 4680713
• Journal Information: Bull. Soc. Belge Geol., Paleontol., Hydrol., Journal Name: Bull. Soc. Belge Geol., Paleontol., Hydrol. Vol. Vol: 71: No. 2
• Country of Publication: Country unknown/Code not available
• Language: French

Related Subjects

AGE ESTIMATION
ALUMINUM SILICATES
CALCIUM OXIDES
DISTRIBUTION
FELDSPARS
GALENA
GEOCHEMISTRY
GEOLOGY
GEOLOGY, MINERALOGY, AND METEOROLOGY
LEAD ISOTOPES
LEAD SULFIDES
LEPIDOLITE
LITHIUM COMPOUNDS
MICA
MICROCLINE
MICROLITE
MINERALS
MUSCOVITE
NIOBIUM
NIOBIUM OXIDES
POTASSIUM SILICATES
PYROCHLORE
QUARTZ
ROCKS
RUBIDIUM ISOTOPES
SODIUM OXIDES
STRONTIUM ISOTOPES
TANTALUM
TANTALUM OXIDES
TIN
TITANIUM OXIDES
URANIUM ISOTOPES
URANIUM MINERALS