Chronostratigraphy and geochemical characterization of volcanic rocks from the Hormuz Complex: Constraints from the Halul Island, The State of Qatar

Geochemical and Sr-Nd isotopic data are reported for volcanic rocks in the Hormuz Complex, Halul Island, Eastern Qatar. Two groups of volcanic rocks are distinct in their geochemical characteristics. Group 1 samples have chemical compositions of transitional and alkali basalts, show LREE-enriched patterns and plot mainly in the field of within-plate basalt on a number of trace element discrimination diagrams. Group 2 rocks have tholeiitic compositions and are characterized by LREE-enriched patterns and fall into the MORB field. The Halul volcanics were most likely formed in an environment similar to an ensialic rift developing into a proto-oceanic basin (e. g. Proto-Tethys) during the Cambrian. Group 1 samples are characterized by high present-day ⁸⁷ Sr/ ⁸⁶ Sr ratios (0.709678 to 0.718711) and low present-day ¹⁴³ND/¹⁴⁴Nd (0.512152 to 0.512842). εNd(0) values range between 3.98 to -9.84. Rock chemistry and the high present-day ⁸⁷ Sr/ ⁸⁶ Sr, and low present-day ¹⁴³Nd/ ¹⁴⁴Nd indicate that crustal contamination, sea water interaction and alteration were significant in the genesis of these volcanics.