Carbonatites in Phong Tho, Lai Chau Province, Northwest Vietnam: Their petrogenesis and relationship with Cenozoic Potassic Alkaline magmatism

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Nguyen Trung, Chi۱; Martin J.F., Flower۲; Duong The, Hung۲
Holding Date 28 September 2008

Carbonatites in Phong Tho area, Lai Chau Province are mainly distributed in 4 localities namely South Nam Xe, Ban Mo, North Nam Xe, Then Thau-Ban Mao and in some other places of Phong Tho district. They are calcite carbonatite(sovite), aegirine carbonatite and RE- carbonatites which are appeared in the form of intrusive massif and bodies; volcanic pyroclast or agglomerate and tuff lavas; hydrothermo-metasomatic replacement dykes and veins. These carbonatites of Phong Tho is closely related with rich and very rich- in - K alkaline-silicate magmatism belong to PuTra - PuSamCap volcanic - intrusive assemblage and lamproite - lamprophyres of NW Vietnam having absolute age of 44 , 28 Ma corresponding to Late- Middle Paleogene(E2-3). The physic-chemical data and petrological models have proved that Phong Tho carbonatites have been differentially crystalized from a silicate- carbonate immiscibility liquids which was derived from upper mantle in conditions of 1-15Kb and 725-1250 C - degree. Potassic alkaline silicate magmatic assemblages and carbonatites of Phong Tho were formed in the spreading geodynamic tectonic regime caused by collision between India and The Tibet, directly related to the closing of Tethys Ocean on Cenozoic.