长江中下游地区中生代成矿期花岗质岩石成因

Genesis of Granitic Rocks During the Mesozoic Metallogenic Epoch in the Middle and Lower Reaches of the Yangtze River

长江中下游成矿带是我国最重要的成矿带之一,其矿床类型多样,成矿岩浆岩多表现出埃达克岩的特征.长江中下游埃达克岩的Sr/Y和La/Yb比值较小,详细的锆石微量元素分析显示,长江中下游埃达克岩具有更高的Ce^(4+)/Ce^(3+)比值,表明具有高的氧逸度.综合这些特征,这些岩石被认为来源于洋壳部分熔融的产物.板片后撤模型,对于解释长江中下游岩浆活动从西南向东北逐渐变小的年龄时空分布,以及A型花岗岩和碱性火山岩的成因都较为合理.

The metallogenic belt in the middle and lower reaches of the Yangtze River is one of the most important metallogenic belts in China. Its deposit types are diverse, and the ore-forming magmatic rocks mostly show the characteristics of adakite. The Sr/Y and La/Yb ratios of adakite in the middle and lower reaches of the Yangtze River are relatively small. Detailed zircon trace element analysis shows that adakite in the middle and lower reaches of the Yangtze River have higher Ce4^+/Ce3^+ ratios, indicating that they have high oxygen fugacity. These rocks are believed to originate from partial melting of the oceanic crust. The sheet retreat model, which is more reasonable for explaining the age spatial-temporal distribution of magmatic activities in the middle and lower reaches of the Yangtze River gradually decreases from southwest to northeast, as well as the genesis of A-type granite and alkaline volcanic rocks.