首页|Distribution of mantle-melt interaction zone: A petrological exploration tool for podiform chromitite deposits in the Kalaymyo ophiolite, Myanmar
Distribution of mantle-melt interaction zone: A petrological exploration tool for podiform chromitite deposits in the Kalaymyo ophiolite, Myanmar
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NSTL
Elsevier
? 2021 Elsevier B.V.Podiform chromitite deposits in the Kalaymyo ophiolite, Myanmar, are hosted by replacive dunites and harzburgites with varying degrees of mantle-melt interaction. Combining petrography and spinel and whole-rock compositions of harzburgites from the Bophi-Vum area, one of the ultramafic massifs of the Kalaymyo ophiolite, we investigated petrological and geochemical indicators of the mantle-melt interaction in the harzburgites and their spatial relationship with the location of chromitites. Two end-member types of mantle harzburgites with distinct textures and compositions are recognized in the study area. Low-Cr# (Cr-spinel Cr# < 30; Cr# = molar Cr/(Cr + Al) × 100) harzburgites represent residual mantle peridotites after low degree of partial melting. They are characterized by high whole-rock Al2O3, CaO, and TiO2 contents with a negative correlation between spinel Cr# and TiO2 contents, following the partial melting model trend of the depleted mid-ocean ridge basalt (MORB) mantle. The Cr-spinels from the low-Cr# harzburgites are lobate and vermicular and occur in association with orthopyroxenes, which is typical features of residual harzburgites. On the other hand, the high-Cr# (Cr-spinel Cr# > 30) harzburgites mostly have lower whole-rock Al2O3 (< ~1.4 wt%), CaO (< ~1.3 wt%), and TiO2 (< ~0.04 wt%) contents than the low-Cr# harzburgites, indicating lower modal abundances of pyroxenes. The positive correlation between spinel Cr# and TiO2 contents in the high-Cr# harzburgites suggests their metasomatic origin from the interaction between the low-Cr# harzburgite and island-arc tholeiitic or boninitic melts. The Cr-spinels from the high-Cr# harzburgites, recrystallized during the mantle-melt interaction, are mostly euhedral and associated with olivine. Geochemical maps of the spinel Cr#, whole-rock Al2O3, and CaO contents for the mantle harzburgites show that the distribution of the high-Cr# harzburgites, i.e., the mantle-melt interaction zone, is closely associated with the locations of the dunite and chromitite outcrops. This spatial relationship suggests the potential use of the distribution of mantle-melt interaction zone for podiform chromitite exploration in the study area.
NSTL
Elsevier
