PETROCHEMICAL CHARACTERISTICS AND GEOCHRONOLOGY OF THE IGNEOUS ROCKS IN BILIN AND ITS ENVIRONS, BILIN TOWNSHIP, MON STATE
Abstract
- The research area is located in Bilin Township and its vicinity, Mon State. It lies between Lattitude 17˚12΄45˝N to 17˚21΄45˝N and Longitude 97˚09΄00˝E to 97˚14΄45˝E. The total area coverage is about 116.5 km2 . Four samples were sent to ALS laboratory of Geological Survey of Japan and analysed by XRF and LA-ICPMS. Eight samples were analyzed at DSSTRC (Defence Service Science and Technology Research Centre) in Pyin-Oo-Lwin Township and seven samples were sent to Geology Department, Mandalay University for XRF analysis. Geochemically, biotite granite, biotite-muscovite granite and biotite microgranite show chemical composition (weight percent) of SiO2 (69.4 - 75.96), Al2O3 (13.34-16.8), TiO2 (0.154-0.284), Na2O+K2O (7.765- 10.31), Fe2O3+MgO (1.149-2.64), MnO (0.039-0.151), CaO (0.897-3.14) and P2O5 (0.027-0.159), suggesting calc-alkaline series and are predominantly peraluminous. Diorites and microdiorite exhibit SiO2 (52.3-55.95), Al2O3 (17.69-22.3), TiO2 (0.738-0.973), Na2O+K2O (4.95-6.364), Fe2O3+MgO (9.211-13.35), MnO (0.121-0.359), CaO (5.435-7.51) and P2O5 (0.285-0.602); proposing calc- alkaline series and are metaluminous. According to Harker’s variation diagrams, TiO2, Al2O3, Fe2O3, MnO, CaO, MgO and P2O5 are negatively correlated with SiO2 and then Na2O, K2O are positively correlated with SiO2. Result from geochemical analysis, biotitemuscovite granite and some biotite granites have high sodium content, normatic corundum ranges from 0.831 to 0.974 and biotite microgranite is low in sodium content, NaO2 Vs K2O diagram shows that the granitic rocks involve both I and S-types, Chappell and White (1994). Based on the tectonic discrimination diagram of Maniar and Piccoli (1989), the granitic rocks fall within the IAG+CAG+CCG field. In Y Vs Nb diagram; all the granitic rocks fall in the field of Syn-COLG and VAG. Y+Nb Vs Rb diagram indicates that all granites fall in the VAG field. U-Pb zircon dating of the biotite granite from the northern part of Lakhin pogoda gives the age of 51.9 0.7 Ma and suggests that the biotite granite was emplaced in Eocene.
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Year
- 2020
Author
-
Mya Moe Khaing
Subject
- Geology
Publisher
- Myanmar Academy of Arts and Science (MAAS)