STUDY OF THE ORIENTED MICROSTRUCTURE IN APATITE FROM ULTRABASIC ROCK OF THE DABIE - SULU ULTRA-HIGH PRESSURE TERRANE

The apatite are one of the most common accessory minerals in sedimentary, metamorphic, and igneous rocks.Microstructure exist obvious differences in apatite under different environment. For example ,fluorapatite which associated with UHP eclogites occurred pyrrhotite, anhydrite and dolomite crystal rods in silicate-bearing carbonate rocks in Norway , a specific orientation exsolution formation under ultra-high pressure metamorphism such as abundant exsolutions (monazite, iron oxide and barite etc) in apatite aggregates from eclogitic drillhole samples of CCSD project like Research and compare apatite orientation microstructure has a more important meaning in apaite which formation on different environment and pressure conditions .

The Dabie–Sulu belt is the eastern part of the Qinling–Dabie orogenic belt in central China, which was formed by subduction and consequent collisions between different microplates followed by final continental collisions between the South and North China Blocks in the Triassic period. Ultrabasic rock was collected form the eastern limb of the Su-Lu ultrahigh-pressure metamorphic terrain in chijiadian of Shandong Peninsula of china , some rock mass in these area has experienced UHP metamorphism at 820 to 900℃ that the body was derived from depths of >300km. Using Optical microscope find right apatite area which was preparation thin slices, and SEM and Raman spectra analyzed the structure and composition of microinculusion,than drilling the region for more careful microstructure analysis on TEM .

Both mineral and fluid inclusions occur in the investigated apatite . The main prominent mineral inclusion is acicular pyrrhotite, which forms an opaque, rutile , plagioclase , and some fluid inclusionsetc . It occurs as needle-shaped inclusions oriented parallel to the crystallographic c-axis of apatite. The size of the needles ranges between 5–300 μm in length and 1–6μm . Irregular magnetite and hematite intergrowths, which occur as massive opaque blebs with length of 30–150 μm and widths of 10–50μm. The textural appearance of the pyrrhotite lamellae in apatite may suggest that pyrrhotite formed due to exsolution from apatite, similar to exsolved monazite from apatite in the UHP Dabie-Sulu eclogites .

keywords: Apatite, UHP, Exsolution, Microstructure