Abstract

The Tarim large igneous province (TLIP) comprises a complex suite of lithologies including voluminous ferrobasalts, although the petrogenetic relation of these rocks is still poorly understood. In this study, we report the chemical compositions of olivine in two types of olivine pyroxenites (porphyritic and coarse-grained) from the Wajilitag mafic-ultramafic intrusion in the northwestern TLIP, aiming to characterize the mantle sources of magmas. Olivine in the porphyritic olivine pyroxenites shows low 100 * Mn/Fe (∼1.3) and Mn/Zn (<13) ratios, whereas that in the coarse-grained olivine pyroxenites is characterized by markedly higher ratios of 100 * Mn/Fe (>1.9) and Mn/Zn (>14), suggesting a heterogeneous mantle source beneath the Wajilitag area. The low olivine V/Sc values (<1.5) in the two types of olivine pyroxenites reflect high oxygen fugacity conditions during magma crystallization. The maximum temperatures of crystallization of porphyritic olivine pyroxenites and olivine pyroxenites estimated based on the Al-in-olivine thermometer are 1350 °C and 1190 °C, respectively. A comparison of the results from our study in terms of mantle source and oxygen fugacity suggests less potential for metallogeny in this region, as against the Panxi area in the Emeishan Large Igneous Province.

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