The Taiping iron deposit is located in the Northeast part of the Zhonggu ore field in the Ning-Wu volcanic basin,as part of the Middle-Lower Yangtze River Valley metallogenic belt.The ore is hosted in the monzonite,which is different from regional porphyry iron deposits.LA-ICP-MS U-Pb dating of zircons from the monzonite yields 206pb/238U weighted average age ranging from 129.0±2.0 Ma to 132.8±1.8 Ma,which is consistent with the dioritic magmatic activities related to the porphyry iron deposits in the Ning-Wu volcanic basin.The Taiping monzonite is relatively enriched in Rb,Ba,Th,K and appreciably poor in P and Ti.It is also slightly low in Nb and Hf.Nb/La (＜1) and Nb/U (3.05-5.46) ratios are lower than those of the MORB and OIB,and that of the earth crust.The magma origin and evolution of the monzonite are similar to those of the diorite porphyries in the Ning-Wu volcanic basins,derived from enriched lithospheric mantle with crustal contamination.Formation of the monzonite and the associated Taipingshan iron deposit was possibly under the lithospheric thinning tectonic regime in East China,and the discovery of the deposit may hint a new ore prospecting possibility in the region.%太平山铁矿床位于长江中下游成矿带宁芜火山岩盆地南段的钟姑矿田北东部.与区域玢岩型铁矿赋矿岩石不同的是,太平山铁矿床赋存在二长岩中.对赋矿二长岩开展LA-ICP-MS锆石U-Pb定年和岩石地球化学特征分析,探讨其成岩成矿地质意义.研究显示,太平山铁矿床中二长岩的锆石206pb/238U加权平均年龄在129.0±2.0 Ma～132.8±1.8 Ma之间,属于早白垩世,与钟姑矿田内其他铁矿床的赋矿岩石年龄一致,与整个宁芜火山岩盆地内赋矿的闪长质岩浆活动时限也相吻合;二长岩总体具有大离子亲石元素Rb、Ba、Th、K相对富集,高场强元素Nb、Hf轻微亏损,P、Ti明显亏损的特征;微量元素对Nb/La比值＜1,Nb/U值介于3.05～5.46之间,低于全球MORB和OIB的平均值,也低于地壳的平均值,表明其起源于富集的交代岩石圈地幔并受到地壳物质混染,岩浆起源及演化与钟姑矿田、宁芜火山岩盆地内的赋矿闪长玢岩具有相似的特征.太平山铁矿床的成岩成矿作用应形成于中国东部整体岩石圈减薄的地球动力学背景,具有新的铁成矿指示意义.
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