安徽庐枞盆地泥河铁矿床年代学研究及其意义  

Geochronology of the Nihe deposit and in the Lu-Zong basin and its metallogenic significances

作　　者：范裕[1] 刘一男[1] 周涛发[1] 张乐骏[1,2] 袁峰[1] 王文财[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]Centre of Excellence in Ore Deposit (CODES),University of Tasmania

出　　处：《岩石学报》2014年第5期1369-1381,共13页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划"973"项目(2012CB416802);国家自然科学基金项目(41172084;41172086);中国地质调查局地质调查工作项目(1212011121115);国家"深部探测技术与实验研究"专项课题(SinoProbe-03-02-05)联合资助

摘　　要：庐枞盆地位于长江中下游断陷带内,地处扬子板块北缘,是长江中下游成矿带中重要的铁铜多金属成矿区。庐枞盆地内火山岩和侵入岩分布广泛,包括龙门院、砖桥、双庙和浮山4组火山岩以及34个出露地表的侵入岩体。泥河铁矿床是盆地西北部新勘探发现的大型铁矿床,其精确的成岩成矿时代及其形成构造背景研究仍十分薄弱。本次工作在详细野外地质工作的基础上,系统开展了泥河铁矿床成岩成矿年代学研究,通过对岩浆岩锆石LA ICP-MS和金云母40Ar-39Ar定年方法,确定矿区中的辉石闪长玢岩、正长斑岩和粗安斑岩的成岩时代分别为132.4±1.5Ma、129.4±2.0Ma和134.3±1.2Ma,成矿时代为130.9±2.6Ma。矿床地质特征表明辉石闪长玢岩是成矿母岩,粗安斑岩形成于成矿作用之前,正长斑岩为成矿期后形成的脉岩,穿切火山岩地层和矿体。上述定年结果与地质事实吻合,表明泥河铁矿床的成岩成矿作用几乎同时发生。通过与庐枞盆地和区域成岩成矿时代对比,认为盆地内玢岩型铁矿床集中形成于130Ma左右,是长江中下游成矿第二期成矿作用活动的产物,庐枞盆地内130Ma左右的辉石闪长玢岩侵入体是寻找泥河式玢岩型铁矿床的勘探靶区。The Lu-Zong basin is one of the important parts of the Middle-Lower Yangtze River Valley metallogenic belt, where there are widespread iron deposits. The volcanic and intrusive plutons occur widely in Lu-Zong basin, including four formations of volcanic rocks, such as Longmenyuan Formation, Zhuanqiao Formation, Shuangmiao Formation and Fushan Formation and 34 intrusive plutons. Nihe deposit located in the northwest part of Lu-Zong basin, which is a new found large iron deposit. However, the precise ore-forming and magmatic activity epoch study about Nihe deposit are still very weak. Based on detailed field geological work, we carried out systematic geochronological study of Nihe iron deposits. LA ICP-MS U-Pb zircon dating of pyroxene diorite porphyrite, syenite porphyry and trachyandensite is 132.4 ± 1.5Ma, 129.4±2. 0Ma and 134. 3 ± 1.2Ma, respectively; 40Ar/39Ar dating of phlogopite is 130. 9 ± 2. 6Ma. Geological characteristics of ore deposit indicate that syenite porphyry formed after the deposit and trachyandensite formed before the mineralization, coinciding with the dating result. The Nihe deposit are formed in early stage of Early Cretaceous about 130Ma, which can nearly represent the metallogenetic epoch of the porphyry-like type iron deposits in the basin. The Nihe deposit in the Lu-Zong basin were the product of the second period magmatic activity and obviously later than high-K calc-alkaline intrusions related to skam-porphyry Cu-Au deposits in uplift areas in the Middle-Lower Yangtze River Valley metallogenic belt. The pyroxene diorite porphyrite in Lu-Zong volcanic basin were thought to be important metallogenetic potentiality.

关 键 词：成岩成矿时代 泥河铁矿床 庐枞盆地 长江中下游成矿带 

分 类 号：P597.3[天文地球—地球化学] P681.31[天文地球—地质学]