Test of a Model for Formation and Preservation of an Ancient Late Stage Epithermal Precious Metal Deposit

9909359 Hall/Kesler该项目测试了大安的列斯群岛一个不寻常的低温贵金属存款的形成和保存模型。使古巴岛上的卡马圭区与众不同的特征包括：1）在主岛弧历史晚期形成的矿床; 2）矿化发生在深度侵蚀的弧基上; 3）矿床相对古老（晚白垩世），表明它们在历史早期被保存下来，此后未受干扰。我们提出的模型的核心是Camaguey岩石，相关的拉谢拉组的韵律等特征的年龄，以及矿化本身的年龄。除了Jacinto存款的冰长石-绢云母相关矿化外，现有的地质年代学约束较差。为了解决这一问题，我们提出了迄今为止所有相关单位的建议。具体而言，激光40 Ar/39 Ar将用于测定Camaguey岩基的角闪石和黑云母、拉谢拉组流纹岩的长石，以及贵金属矿床的冰长石和明矾石。此外，我们将使用真空封装辐射来测定绢云母样品从冰长石绢云母和酸性硫酸盐矿床。该项目涉及经济地质学和加勒比历史的重要问题。特别是，如果卡马圭区的形成模式能够得到证实，它将为在通常被认为没有希望的矿床中勘探浅成热液矿床开辟新的战略。此外，我们将能够限制这个岛弧的岩石学演化，以及估计卡马圭岩侵位和金、银矿床形成之间的侵蚀速率。

9909359Hall/KeslerThis project tests a model for the formation and preservation of an unusual epithermal precious metal deposit in the Greater Antilles. Features which make the Camaguey District on the island of Cuba distinct include: 1) the deposits formed late in the history of the host island arc; 2) mineralization took place on a deeply eroded arc batholith; 3) the deposits are relatively old (late Cretaceous) indicating that they were preserved early in their history and left undisturbed since. Central to the model we propose are the ages of such features as the Camaguey Batholith, the rhyolites of the associated La Sierra Formation, and the age of mineralization itself. Existing geochronological constraints are poor, with the exception of adularia-sericite related mineralization at the Jacinto deposit. We address this issue by proposing to date all of the relevant units. Specifically, laser 40Ar/39Ar will be used to date hornblendes and biotites of the Camaguey batholith, feldspars from La Sierra Formation rhyolites, plus adularia and alunite from precious metal deposits. In addition, we will use vacuum encapsulated irradiation to date sericite samples from both adularia-sericite and acid sulfate deposits. The project addresses important issues, both for economic geology and for the history of the Caribbean. In particular, if the model for formation of the Camaguey District can be confirmed, it opens up new exploration strategies for epithermal deposits in what would normally be considered unpromising terranes. In addition, we will be able to constrain the petrological evolution of this island arc, as well as estimate the rate of erosion between the emplacement of the Camaguey Batholith and formation of the gold and silver deposits.