鸭公塘铁铜矿床相关花岗闪长岩锆石U-Pb年龄、地球化学特征及地质意义

Zircon U-Pb Age, Principal and Trace Elements in the Whole Rock of Granodiorite Associated with Yagongtang Iron-Copper Deposit and Its Geological Significance

水口山地区岩浆作用的研究对于探讨鸭公塘深部铁铜矿床成因有十分重要的意义。水口山花岗闪长岩的LA-ICP-MS锆石U-Pb定年结果显示,其就位年龄为153.8±1.3Ma,燕山早期产物。地球化学分析结果表明:岩石高硅,高铝,高碱,属于钾玄岩系列准铝质花岗岩,稀土元素配分曲线为轻稀土元素富集的右倾型,富集大离子亲石元素Rb、Ba、K和强不相容元素U,相对亏损高场强元素Nb、Ta、Ti,轻、重稀土元素之间分馏相对明显,具有弱负Eu异常(δEu=0.77~0.83)。综合区域地质、地球化学特征,认为该岩体形成的构造环境为后造山阶段拉张减薄构造环境,岩浆为壳幔混源,为华南地壳与地幔物质混合形成。

The study of magmatism in Shuikoushan area is of great significance for exploring the genesis of the deep iron-copper deposit in Yagongtang. The LA-ICP-MS zircon U-Pb dating of Shuikoushan granodiorite shows that its emplacement age is 153.8 (+1.3 Ma) and the early Yanshanian product. Geochemical analysis results show that the rocks are high in silicon, aluminium and alkali,which belong to the potassium basalt series quasi-aluminous granite. The REE distribution curve is a right-leaning type enriched with light REE, enriched with large ion lithophile elements Rb, Ba, K and strong incompatible element U, and relatively depleted with high field strength elements Nb, Ta and Ti. The fractionation between light and heavy REE elements is relatively obvious, with weak negative Eu anomaly (delta Eu=0.77~0.83). Based on the regional geology and geochemical characteristics, it is considered that the tectonic environment for the formation of the pluton is post-orogenic extension and thinning tectonic environment, and the magma is crust-mantle mixed source, which is the mixture of crust and mantle materials in South China.