Zircon U-Pb SHRIMP ages of sub-volcanic bodies related with porphyritic Fe-deposits in the Luzong and Ningwu basins, Middle and Lower Yangtze River Reaches, Central China
长江中下游地区庐(江)-枞(阳)和宁(南京)-芜(湖)盆地内与成矿有关潜火山岩体的SHRIMP锆石U-Pb年龄

Luzong basin and Ningwu basin, which are two largest basins among several Mesozoic volcanic basins distributed in the Middle and Lower Yangtze River Reaches, developed a suite of unique rock series (shoshonitic series ) and abundant iron- sulfur iron- and nonmetal ore deposits, especially porphyry Fe-deposits. The dominant metallogenic bodies are sub-volcanic rocks formed in second volcanic activity cycle, syenite-porphyry for the Luzong basin and augite diorite porphyrite for Ningwu basin. In this work, we used zircon SHRIMP U-Pb technique accurately dating their emplacement ages of the Bajiatan body and the Jiaochong body in the Luzong basin and the Yinshan body in the Ningwu basin. The results are as follows: The zircon grains from these three bodies yield an emplacement ages of 131.0±1.1Ma, 131.5±1.6Ma and 127.8±1.8Ma respectively. The volcanic-subvolcanic rocks in Luzong basin and Ningwu basin (as well as all Middle and Lower Yangtze River Reaches) formed in very short time, predicate that "suddenly" lithospheric thinning was dominant mechanism of magmatism and cosmically metallogenesis in the reaches.