SUMMARY
Results of study on ages and forming temperature of rubi formation in Quú Ch©u area
Phım V¨n Long, Virginie Garnier, Gaston Giuliani,
Hoµng Quang Vinh, Phan Träng TrÞnh,
Daniel Ohnenstetter, Dietmar Schwarz
Recent investigation in Quú Ch©u area has discovered corundum (ruby) in marble bed rock. It consists of white, small-grained calcite marble containing corundum, phlogopite, pargasite, graphite, and pyrite. By using the 40Ar/39Ar laser stepwise heating technique on purified syngenetic phlogopite and other mica minerals, the forming ages of corundum has been dated indirectly and giving the results between 22.1-21.6 Ma. The forming temperature of corundum is about 660oC that have been determined by using the carbon isotope of calcite-graphite pair.