Search

The Shaolang River metallogenic belt in Inner Mongolia is one of the main lead‐zinc polymetallic belt on the northern margin of the North China Plate. The granodiorites, which are closely coexisting with lead‐zinc veins in deposit, are extensively developed. Previous geochronological research results show that the dikes and veins in the metallogenic belt belong to the products of magmatic hydrothermal activity in the middle Yanshanian, so the genesis of the metallogenic belt deposit is generally considered to be a hydrothermal vein type deposit related to sub‐volcanic dikes. We obtained zircon LA‐ICP‐MS U–Pb ages and Hf isotopic compositions of granodiorites, which are widely distributed in the deposit and were considered to be closely connected with the genesis of the deposits. The zircon U–Pb ages are 419.4 ± 1.4 Ma and 424.5 ± 4.1 Ma for the granodiorites, respectively, and they formed in the late Silurian. The geological and geochemical data indicate that the granodiorites are consistent with the geochemical characteristics of typical adakite. All εHf(t) values of the granodiorites are minus, on the zircon Hf isotope age diagram, εHf(t) are below the evolution curve of chondrite. The two‐stage model ages (tDM2) are 2.45 ~ 2.79 Ga and 1.87 ~ 2.29 Ga, respectively, showing rock‐forming materials mainly derived from the Paleoproterozoic and earlier crustal partial melting, and there may have been mantle‐derived magma underplating of the lower crust. Combining with the previous regional research, it is concluded that the granodiorites were formed during the extinction of the island arc under the background of subduction of the Paleo‐Asian Ocean and North China Craton. Because of the 125 ~ 170 Ma metallogenic age, we concluded that the granodiorites in the ore areas have no obvious relationship with the deposit genesis. However, it provided the advantageous space for the formation of the lead‐zinc veins, it can be regarded as an important prospecting indicator in metallogenic belt. [ABSTRACT FROM AUTHOR]

Abstract: Research on the causes of grassland degradation in the Inner Mongolia has mostly focused on anthropogenic activities. Few studies examined plant interactions during the processes of grassland degradation. In this study, we found that the major constituents of the VOCs from undamaged Artemisia frigida were eucalyptol, camphene, (E)-3-hexen-1-ol acetate, α-terpineol, β-terpineol, (R)-(–)-p-menth-1-en-4-ol, p-cymene and camphor. The content and amount of these VOCs increased when A. frigida was damaged. The VOCs from A. frigida significantly decreased the seedling growth of three common grass species (Elymus dahuricus, Agropyron cristatum and Leymus chinensis) in the Inner Mongolia pastures. The inhibition effect of the VOCs on the tested grass species was significantly greater from damaged than from undamaged plants of A. frigida. Findings from this study suggest that the dominance of A. frigida in degraded grasslands may affect the recovery of other native plant species through mechanisms of allelopathic effect of VOCs emission, especially when under severe disturbance by overgrazing. [Copyright &y& Elsevier]