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海南石碌铁矿床是我国最大的富铁矿矿床,其矿床成因一直存在着争论,其中争议之一是矿床成因除与火山-沉积变质有关外,是否还与后期构造-岩浆事件的改造富集作用有关。前人曾对石碌铁矿床铁矿石、主要赋矿围岩石碌群以及矿区周围出露的花岗岩类进行过多方法同位素地质定年,但迄今尚未对矿区内分布的花岗斑岩类进行相应的工作。本文采用激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)对矿区内花岗闪长斑岩进行了锆石U-Pb定年,获得了(93±2)Ma的年龄,表明该花岗斑岩侵入时代为燕山晚期晚白垩世。结合燕山晚期华南处于拉张构造环境的认识以及石碌矿区矿床地质特征,暗示晚白垩世拉张事件使石碌矿区内的断裂重新活动从而引起花岗斑岩侵位,而花岗斑岩后期演化的热液对石碌铁矿床的富化具有改造叠加作用。
The Shilu iron deposit in Hainan Province is the largest iron ore deposit in China. The origin of the deposit has been in dispute for some time. One of the controversies is whether the genesis of the deposit is related to alteration of the later tectono-magmatic events in addition to the volcanic-sedimentary metamorphism Set related effects. The predecessors have carried out a multi-method isotopic geologic dating of the iron ores in the Shusuo iron ore deposit, the major ore-bearing rock masses and the granites exposed in the vicinity of the mines, but so far no corresponding granite porphyry has been distributed in the mines work. In this paper, zircon U-Pb dating of granodiorite porphyry in the ore district was obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and the age of (93 ± 2) Ma was obtained, indicating that the granite plaque The rock intrusive age was Late Yanshanian Late Cretaceous. Combined with the understanding that the late Yanshanian southern China was in the extensional tectonic setting and the geological characteristics of the deposits in Shilu ore district, suggesting that the Late Cretaceous pull-out event reactivated the faults in Shilu mining area and caused the emplacement of granite porphyry, The hydrothermal fluid has a superposition effect on the enrichment of Shilu iron deposit.