Mineral Chemistry and Whole-rock Geochemistry of Pillow lava from the Arangue Complex, Southeastern Hormozgan, Iran

Abstract

The Upper Cretaceous Arangue complex is located in the Makran zone at the SE of Iran. The complex consists of ultra-mafic rocks, microgabbro dykes, pillow lavas and lime stones that pillow lavas are mainly exposed to the northwest and southeast part of study area. There are oval and tubular basalt lavas with cracked bread crust surface. They predominantly have plagioclase, clinopyroxene with minor olivine and opaque minerals in a fine-grained groundmass along with glass. Mineral chemistry data show that plagioclases and clinopyroxene composition varies from An68.27-81.73 Ab18.27-31.57 Or0-0.41 and Wo38.1- 47.8Fs8.2-19.3 En38.6-48.7 respectively. In the geochemical diagrams, the Arangue complex pillow lavas fall in the basalt and sub-alkaline fields. Geochemical data indicate that the Arangue complex pillow lavas are tholeiitic. The absence of a distinct Eu anomaly (Eu/Eu*= 0.8-1.2), indicates that plagioclase fractionation is not notable, or that the magma is a little oxidized. The Arangue complex pillow lavas show properties similar to transitional basalts between enriched MORB and OIB and some BABB. However, their enrichment in incompatible elements and low Nb and La / Nb ratios (0.8-2.1) display that these have affinity of the BABB. These were produced by approximately 15-25% partial melting of plagioclase lherzolite where fractionation was controlled by removal of clinopyroxene, spinel, and olivine. Petrogenetic study indicates that the source of mantle lherzolite is subjected to enrichment variables in subduction components consisting of fluids for the Arangue Complex pillow lavas.