赣南新安钼矿床花岗闪长岩岩石地球化学、锆石U-Pb测年、Hf同位素研究及其意义

Geochemical characteristics, U-Pb age and Hf isotope of zircons from granodiorite in Xin’an Mo deposit, southern Jiangxi Province and its significance

中文关键词:新安钼矿床  花岗闪长岩  岩石地球化学  锆石U-Pb年龄  Lu-Hf同位素  赣南

keywords:Xin’an Mo deposit  granodiorite  geochemical characteristics  zircon U-Pb age  Lu-Hf isotope  southern Jiangxi Province

中文摘要:赣南新安钼矿床位于南岭成矿带与武夷成矿带交汇部位，是新探明的中型钼矿床。钼矿体主要产于花岗闪长岩与围岩侵入接触界线附近，以浸染型和细脉-浸染型钼矿化为主，具有斑岩型钼矿床矿化特征。花岗闪长岩地球化学分析显示，岩石具有高碱、富Al及贫Ti、Mg、P特征，属弱过铝质钙碱性岩类；轻重稀土分馏明显，Eu无异常，稀土配分曲线为右倾型。文章利用LA-ICP-MS锆石U-Pb定年方法测得花岗闪长岩年龄为162.5~170.9 Ma，谐和年龄为(165.4±0.3)Ma(MSDW=0.6)，成岩时代属中侏罗世。锆石n(¹⁷⁶Lu)/n(¹⁷⁷Hf)=0.000 916~0.001 572，ε_Hf(t)=−10.9~−5.5，二阶段模式年龄（T_DM2）为1.56~1.90 Ga，显示其岩浆起源于古元古代地壳部分熔融，可能混有不同程度的幔源岩浆物质。综合分析认为，新安钼矿床成岩与成矿作用均发生于中侏罗世，是赣南新厘定的Mo成矿作用期，为区内钼矿找矿工作提出新方向。

Abstract:The Xin’an Mo deposit is a newly identified medium-sized Mo deposit in southern Jiangxi Province, which is located at the junction of the Nanling and Wuyi metallogenic belts. The disseminated and disseminated-veinlet Mo ore bodies are mainly distributed near the intrusive contact boundary between granodiorite and the surrounding rock, which has the mineralization characteristics of porphyry Mo deposit. The whole-rock geochemical analyses show that granodiorite has the features of week peraluminous, calc-alkali series, high Al₂O₃ and LREE contents, along with low TiO₂, MgO, and P₂O₅ Values. The REE distribution curve shows a typical right-skewed distribution pattern. LA-ICP-MS Zircon U-Pb dating of granodiorite yields emplacement age of 162.5~170.9 Ma, with a concordia age of (165.4±0.3)Ma (MSWD=0.6), indicating the magmatic intrusion diagenesis occurred in the Middle Jurassic. The n(¹⁷⁶Lu)/n(¹⁷⁷Hf) and ε_Hf(t) values are 0.000 916~0.001 572 and −10.9~−5.5, respectively, and T_DM2 are 1.59 Ga~1.90 Ga, indicating primary reworking of the Paleoproterozoic crust with different degrees of mantle-derived magma material. The comprehensive analysis shows that the diagenesis and Mo mineralization in Xin’an Mo deposit both occurred during the Middle Jurassic, representing a newly defined Mo mineralization phase in southern Jiangxi Province. This provides a new direction for Mo prospecting work in this region.