Petrology and geochemistry of mantle peridotites from the Kalaymyo and Myitkyina ophiolites (Myanmar): Implications for tectonic settings

摘要: Abstract Ophiolites within Myanmar have been commonly divided into two belts, i.e., the Eastern Belt and Western Belt. The Kalaymyo ophiolite from crops out at eastern margin of Indo-Burma Range was formed during Early Cretaceous, whereas Myitkyina Middle Jurassic. Both ophiolites are characterized by occurrence big massifs mantle peridotites. Mantle peridotites mainly composed spinel lherzolites harzburgites, with minor plagioclase consist dunites. Spinel relatively fertile compositions, 40.12–45.19 wt.% MgO, 1.1–2.74 wt.% Al 2 O 3 0.67–2.67 wt.% CaO. Their spinels Cr# values 0.12–0.4, yielding fractional melting degrees 3–15%. In comparison, harzburgites more refractory, 42.08–48.73 wt.% 0.09–0.99 wt.% 0.07–0.8 wt.% 0.3–0.73, giving 12–21% melting. Plagioclase compositions intermediate between harzburgites. Compared to peridotites, in higher TiO contents. Harzburgites ophiolite, containing 40.88–48.16 wt.% 0.13–1.65 wt.% 0.1–1.68 wt.% CaO, refractory similar Spinels low contents (i.e.,