鄂东南程潮铁矿床花岗质岩和闪长岩的岩体时代、成因及地质意义——锆石年龄、地球化学和Hf同位素新证据

利用LA-ICP-MS锆石U-Pb法测得程潮矿区花岗岩成岩年龄为（128.8±0.5） Ma，石英二长斑岩成岩年龄为（128.3±0.5） Ma，闪长岩成岩年龄为（140.0±0.3） Ma，辉绿玢岩成岩年龄为(125.5±0.5) Ma，皆形成于早白垩世。地球化学分析结果显示：花岗质岩为高钾准铝质I型系列；闪长岩和辉绿玢岩为高钾钙碱性系列。各岩体的稀土元素总量较高，轻稀土强烈富集，轻、重稀土元素分异明显，无明显的负铕异常。花岗质岩的微量元素以富集Rb、Th、U、La等元素，贫Ba、Nb、Sr等元素为特点。闪长岩和辉绿玢岩具有相似的微量元素特征，表现为K、La、Nd富集和Ta、Nb、Sr、P、Ti亏损的特点。根据岩体的锆石Hf同位素组成和地球化学特征可知，程潮矿区各岩体可能是岩石圈地幔在部分熔融过程中，混入了不同数量古老下地壳物质的产物。矿区花岗质岩的成岩年龄与程潮Fe矿床的成矿年龄相近，暗示其与矿体有着密切的联系。

Zircon U-Pb Ages,Geochemistry and Hf Isotopes of Granitoids and Diorite in the Chengchao Fe Deposit in Southeastern Hubei Ore Cluster and Its Significance

This contribution has carried out LA-ICP-MS zircon U-Pb dating, geochemistry and Hf isotopes. The ages of the granite, porphyritic quartz monzonite, diorite and porphyritic diabase in the Chengchao Fe deposit are dated at (128.8±0.5) Ma, (128.3±0.5) Ma, (140.0±0.3) Ma and (125.5±0.5) Ma, respectively, showing that granitoids and diorite of the Chengchao Fe deposit formed in Early Cretaceous. Geochemical analysis indicates that the granitoids in the deposit belong to metaluminous and I type series; the diorite and porphyritic diabase are of nature of high K calc alkalic series. These igneous rocks in the Chengchao Fe deposit have high REE contents, characteristics of LREE enrichment, obvious LREE and HREE fractionation, and weakly negative Eu anomaly. The granitoids are all rich in Rb, Th, U and La, but considerably depleted in Ba, Nb and Sr; the diorite and porphyritic diabase are rich in K, La, Nd and poor in Ta, Nb, Sr, P, Ti. The Hf isotope compositions and geochemical characteristics indicate that these igneous rocks in the Chengchao Fe deposit formed from a magma source with lower, Neoproterozoic and Paleoproterozoic crustal derived contribution. Consistence between the metallogenic age of the Chengchao Fe deposit and the intrusion age of granitoids shows their close relations.