Rodingite from Ailaoshan ophiolite zone, Yunnan Province, China

Abstract

Massive- and vein-type rodingites occurring in serpentinized peridotite of the Jinchan ultramafic body in the Ailaoshan ophiolite zone, S.W. China, have been investigated mineralogically and chemically. Rodingites of the massive-type consist of garnet, chlorite and diopside in rims, and garnet, diopside and subordinary chlorite in cores, while rodingites of the vein-type consist of garnet, chlorite and subordinary diopside. The garnet of the massive rodingites belongs essentially to the grandite-hydrograndite series, but extremely rich in TiO₂: (Ca_5.92Mg_0.07)_Σ5.99(Ti_1.11Al_0.44Fe_1.11²⁺Fe_1.32³⁺Cr_0.02)_Σ4.00(SiO₄)_5.78(O₄H₄)_0.22. The petrography suggests that the rodingites were originally formed by metasomatism between titanium- and iron-rich and aluminum-poor rock and calcium-rich solution, and that they were deformed by the Ailaoshan metamorphism after the formation.