Abstract

The strata of the Linxi Formation (LXF) occupy an extensive area in eastern Inner Mongolia, NE China, and have close spatial and genetic relationship with some significant Mesozoic Sn-Cu-Pb-Zn-Ag veins and porphyry polymetallic deposits (ore occurrence). The rock types of the LXF mainly include sandstone, siltstone and shale. Major and trace element data (including REE) of rocks from the LXF in Hanmiao area indicate that these rocks have a greywacke protolith, derived from intermediate-acid arc igneous rocks and deposited during intensive tectonic activity. LA-ICP-MS U-Pb dating of detrital zircons from sandstone of the LXF yields ages of 985±10 Ma to 242±2 Ma. The youngest population of ages shows a peak at ca. 258 Ma, suggesting that the major deposition period of the LXF was in the late Permian. These ages, together with the youngest zircon age (ca. 242Ma), suggest that the deposition of the LXF mainly occurred during the late Permian and extended to the early Triassic. According to the results of analysis of 44 sandstone and siltstone samples, ore elements, e.g. W, Sn, Ag and Mo, are significantly enriched in the LXF of the study area. Combined with the fact that more and more polymetallic deposits have been discovered within the LXF strata in the southern Great Xing'an Range (GXR), it can be concluded that the strata of the LXF might be the ore source bed, and there is a large ore-prospecting potential for polymetallic deposits in the LXF of the GXR.

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