Abstract

• The research area is situated about 170 km north-east of Yangon and about 96 km north-west of Mawlamyine. Lamprophyres are melanocratic, porphyritic and hypabyssal rocks. Lamprophyre is mainly composed of hornblende, plagioclase, orthoclase and opaques. Under the microscopic study, this lamprophyre may be classified as spessartite; it has medium-grained porphyritic and panidiomorphic texture, dominantly comprising euhedral to subhedral forms of hornblende phenocrysts, groundmass of plagioclase and minor amount of K-feldspar and quartz. According to the chemical analysis data, MgO-K2O-Al2 O3 and Fe2O3-Al2O3-MgO ternary diagrams show that the samples fall in the lamprophyre field. MgO-Al2O3-CaO triangular diagram indicates that the samples fall in the field of alkaline lamprophyre. These lamprophyres have high K2O and Na2O concentration and show alkaline characters. Due to the alkaline characters, lamprophyres are porphyritic, volatile-rich igneous rocks, which are emplaced as dykes. Lamprophyre is observed as dyke intruding into the pyroxenite at Winpyan quarry. This dyke is a very late phase of large igneous intrusion. By the field investigation and petrographic analysis, the petrogenesis of lamprophyre may be considered as magmatic origin. Lamprophyre in the research area are generally thought to be derived from low degree partial melting of a lithospheric mantle that has been previously metasomatised by subduction-related fluids. Absolute age of the lamprophyre is still unknown, due to lack of radiometric dating of the rock. In the research area, the age of the biotite granite is 51.9±0.7 Ma (Eocene) in age. Therefore, the age of lamprophyre may be younger than Eocene age. Specular hematite ore minerals found near the lamprophyre dyke. Specular hematite has been used as jewellery; such as necklaces, rings and bracelets. By wearing specular hematite, it makes to treat disorders of the blood, to heal broken bones, to help the effects of electromagnetic fields and to protect toxic energy from computers.