Age and Lithogeochemistry of Volcanic-hosted Massive Sulfide Deposits of the Ambler District, Southern Brooks Range, Alaska

火山块状硫化物(VMS)矿床的现代实例表明，与这些矿床形成相关的热液活动是一个稳定的过程。相比之下，古代的例子通常定义了不同的年龄组，而最近的成因模型将VMS成矿与特定的构造事件联系起来，例如早期的弧内裂谷作用。VMS成矿的稳态模型和准时模型的区分需要高精度的地质年代学数据，以确定单个矿床规模的岩浆作用持续时间，并建立区域尺度上观察到的岩浆作用的对比、区分或迁移。北美科迪勒拉北部广泛分布的泥盆纪至密西西比期VMS矿床为研究这一问题提供了理想的环境。结合与矿化和热液蚀变有关的长英质岩石和镁铁质岩石的主要、微量和稀土元素地球化学，U-Pb年代学和Ndsr同位素地球化学将建立阿拉斯加南部Brooks山脉Ambler地区VMS矿化的时代和构造背景。由此产生的数据库将作为比较和评估育空-塔纳纳地体中相当于广泛年龄的VMS矿床以及邻近地体和科迪勒伦微地斜中的沉积物托管矿床的基础。该项目的结果将对整个科迪勒拉北部VMS成矿的时间和构造背景提供有价值的洞察。这一洞察可能会导致在其他环境中产生新的VMS矿床演化和保存的遗传模型。该项目还将解决科迪勒拉地区中古生代岩浆活动的构造背景这一长期存在的问题。

McClellandEAR-0208162Modern examples of volcanic-hosted massive sulfide (VMS) deposits suggest that hydrothermal activity associated with formation of these deposits is a steady-state process. In contrast, ancient examples typically define distinct age groups and recent genetic models relate VMS mineralization to specific tectonic events such as incipient intra-arc rifting. Distinction between steady state and punctual models for VMS mineralization requires high precision geochronologic data to establish the duration of magmatism at the scale of individual deposits and to establish correlation, distinction, or migration of magmatism observed at the regional scale. The widespread occurrence of Devonian to Mississippian VMS deposits in the northern North American Cordillera provides an ideal setting to examine this issue. U-Pb geochronology and Nd-Sr isotope geochemistry combined with major, trace, and REE geochemistry of felsic and mafic rocks associated with mineralization and hydrothermal alteration will establish the age and tectonic setting of VMS mineralization in the Ambler district, southern Brooks Range, Alaska. The resulting database will serve as a basis for comparison with and evaluation of broadly age equivalent VMS deposits in the Yukon-Tanana terrane as well as sediment-hosted deposits within adjacent terranes and the Cordilleran miogeocline. The results of this project will provide valuable insight into the temporal and tectonic setting of VMS mineralization throughout the northern Cordillera. This insight will potentially lead to the generation of new genetic models for the evolution and preservation of VMS deposits in additional settings. The project will also address the long-standing question of the tectonic setting of mid-Paleozoic magmatism in the Cordillera.