Geological and geochemical characteristics of basalts from Hardat Tolgoi Mine,Inner Mongolia,China

Basalts from Hardat Tolgoi Mine were studied systematically by using petrochemical and isotope geochemical methods in order to discuss their chemical properties, diagenetic material sources and tectonic environment. The analysis results indicate that the alkali basalts are characterized by low silica and high alkalinic (Na>K) and iron-titanium contents. The distribution patterns of the rare earth elements (REE) are the “rightist” type, which typically show evident fractionation between light REEs and heavy REEs with (La/Yb)_N ratios from 8.04 to 10.4, but no significant negative Eu anomalies were observed (δEu=1.01 to 1.04). The basalts are relatively enriched in large ion lithophile elements (LILE, Ba, Sr) and high field strength elements (HFSE, Nb, Ta, Hf). Ratios of ²⁰⁶Pb/²⁰⁴Pb vary between 18.434 and 18.550, ratios of ²⁰⁷Pb/²⁰⁴Pb are between 15.541 and 15.569, and ratios of ²⁰⁸Pb/²⁰⁴Pb are between 38.331 and 38.536. The diagenetic substance is believed from the asthenospheric mantle and in intraplate environment, which was constructed during continent stretch, without being significantly contaminated by crustal materials.