摘要:
胶东地区是我国重要的金矿集中区, 区内大部分金矿床与煌斑岩具有密切的时空联系.本文以胶东地区牟乳成矿带北段邓格庄金矿煌斑岩为研究目标, 通过锆石 U-Pb 定年获得邓格庄煌斑岩主要形成时代在(120±2) Ma和(153±2) Ma两个阶段, 其中(120±2) Ma形成的脉岩与金矿形成时代高度吻合.在岩石化学组成上, 邓格庄煌斑岩SiO2=45.60%~49.20%, 属玄武质安山岩.岩石富集Th、U、Ba、K等大离子亲石元素和轻稀土, 亏损Nb、Ta、Ti等高场强元素, Mg#=50~53, δEu=0.71~0.59; 岩浆源区可能为与流体交代有关的富集地幔.此外, 煌斑岩与金矿脉空间上受控于同一构造体系, 相伴产出, 煌斑岩为金矿成矿提供热源, 是金矿成矿物质的重要载体.综合认为, 煌斑岩与金矿化关系密切, 可作为寻找金矿床的重要标志.
Abstract:
The Jiaodong area is an important gold ore concentration area in China. Most of the gold deposits in this area have a close spatial-temporal relationship with the lamprophyre. With the lamprophyre of the Denggezhuang gold deposit in northern Mouping–Rushan metallogenic belt of Jiaodong area as the study object, the authors detected that the zircon U-Pb ages of lamprophyre are mainly at (120±2) Ma and (153±2) Ma, and the lamprophyre formed at (120±2) Ma is highly consistent with the age of gold formation. In the rock chemical composition, the content of SiO2is 45.60%~49.20% in Denggezhuang lamprophyre, suggesting basaltic andesite. The lamprophyre is enriched in Th, U, Ba, K, large ion lithophile elements (LILE) and light rare earth elements (LREE), and depleted in Nb, Ta, Ti and other high field strength elements (HFSE), with Mg#being 50~53 and δEu being 0.71~0.59. The magma source area was probably the enriched mantle related to fluid metasomatism. In addition, the lamprophyre and gold veins were controlled by the same structural system in space and associated with each other. The lamprophyre provided the heat source for gold mineralization and was an important carrier of gold mineralization. It is considered that the lamprophyre is closely related to the gold mineralization, and can be used as an important indicator in search for gold deposits.
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