Experiments on various word segmentation approaches for the Burmese language are conducted and discussed in this note. Specifically, dictionary-based, statistical, and machine learning approaches are tested. Experimental results demonstrate that statistical and machine learning approaches perform significantly better than dictionary-based approaches. We believe that this note, based on an annotated corpus of relatively considerable size (containing approximately a half million words), is the first systematic comparison of word segmentation approaches for Burmese. This work aims to discover the properties and proper approaches to Burmese textual processing and to promote further researches on this understudied language.

The Paleogene Mogok metamorphic belt in central Myanmar is composed mainly of high-grade metamorphic rocks from upper-amphibolite to granulite facies and younger intrusions. Ti-rich biotite grains (up to 6.9 wt% TiO 2 ) from the Onzon and Shwe Myin Tin areas were systematically analyzed to examine the mechanisms of Ti-bearing substitutions. The Onzon and Shwe Myin Tin paragneisses are composed mainly of garnet, biotite, plagioclase, K-feldspar, quartz, ilmenite, and graphite. One of these contains cordierite porphyroblasts, which contain a spinel [Al/(Al + Fe 3+ + Cr + V) = 0.97-0.99, Mg/(Mg + Fe 2+ ) = 0.34-0.35, Zn = 0.04-0.05 atoms per formula unit (apfu) for O = 4], quartz, sillimanite, biotite, plagioclase, and ilmenite assemblage as inclusions. The Shwe Myin Tin paragneiss contains sillimanite as an inclusion in garnet. Using the garnet-biotite geothermometer and the garnet-biotite-plagioclase-quartz (GBPQ) geobarometer, the matrix assemblage indicates pressures (P) and temperatures (T ) of 0.77-0.84 GPa and 780-850°C, respectively. The coexisting spinel and quartz and the estimated P/T conditions imply a wide distribution of granulite facies metamorphic rocks in the northern part of the Mogok metamorphic belt. The high Ti content of biotite in the sillimanite-free Onzon samples is probably progressed result of the TiÃR −2 substitution, where R is the sum of divalent cations and à represents vacancy in the octahedral sites. The biotite grains in the sillimanite-bearing Shwe Myin Tin sample showed a combination of TiÃR −2 and TiRAl −2 substitutions.

The Mogok metamorphic belt in central Myanmar is composed mainly of high-temperature paragneisses, marbles, calc-silicate rocks, and granitoids. The garnet-biotite-plagioclase-sillimanite-quartz and garnet-cordieritesillimanite-biotite-quartz assemblages and their partial systems suggest pressure-temperature (P-T ) conditions of 0.60-0.79 GPa/800-860°C and 0.65 GPa/820°C, respectively, for the peak metamorphic stage, and 0.40 GPa/620°C for the exhumation stage. Ti-in-biotite and Zr-in-rutile geothermometers also indicate metamorphic equilibrium under upper amphibolite-and granulite facies conditions. Comparison of these estimates with previously described P-T conditions suggests that (1) the metamorphic conditions of the Mogok metamorphic belt vary from the lower amphibolite-to granulite facies, (2) metamorphic grade seems to increase from east to west perpendicular to the north-trending extensional direction of the Mogok belt, (3) granulite facies rocks are widespread in the middle segment of the Mogok belt, and (4) the granulite facies rocks were locally re-equilibrated at lower amphibolite facies conditions during the exhumation.

Rutile grains occur extensively in host phases of biotite and quartz-feldspar aggregate in high-temperature paragneisses of the Mogok metamorphic belt of Myanmar. They occur as an isolated phase and sometimes show intergrowth texture with ilmenite. Most rutile grains contain up to 3.7 wt.% Nb2O5, which shows positive correlations with Fe and trivalent elements. Niobium substitutes for Ti by a coupled substitution with the trivalent cations (M3+) of Nb5+M3+Ti4+-2. Fine-grained rutile grains included in ilmenite are distinctly poor in Nb (<0.1 wt.% as Nb2O5) and contain Fe of 1.7–3.2 wt.% as Fe2O3, suggesting vacancybearing substitution of Fe3+4 Ti4+-3□–1, where □ indicates a vacancy. The rutile grains in the felsic phases contain high Zr contents of up to 4200 ppm, suggesting equilibrium temperatures over 800°C using the Ti-in-rutile geothermometer. These high-temperature conditions are consistent with those estimated by conventional methods reported in the literature and suggest widespread occurrences of the upperamphibolite and granulite facies metamorphic rocks in the middle segment of the Mogok metamorphic belt. In contrast, the Zr contents of rutile grains in biotite are usually <1000 ppm, implying equilibrium temperatures lower than 750°C. Most of the rutile grains poorer in Zr might have been included in biotite and were isolated from the zircon-bearing system during an early stage of prograde metamorphism. Some other rutile grains poorer in Zr might have been an exsolved phase from Ti-rich biotite during retrograde metamorphism, which was furthered by the infiltration of metamorphic fluid under lower-amphibolite facies conditions.

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