Thermal and geochemical footprints of low-temperature sedimentary rock-hosted hydrothermal Au-systems: identifying far-field vectors toward ore

在地球表面发现新的矿物是很罕见的。未来的发现将取决于地下勘探，这需要对此类矿床进行远场探测。沉积岩是加拿大乃至世界上Au、Pb、Zn、Cu等世界级矿床的重要赋矿围岩。它们形成于<4-6公里的深度，来自地壳较热层的热流体上涌。由于这些系统的温度低（<200-250 ℃），蚀变晕在空间上受限制和约束性差，因此确定其远场表达具有挑战性。本项目使用一套综合分析技术，推导出沉积岩型金矿中热液流体流动的热化学表达模型。具体来说，我们将应用详细的地质约束地球化学，矿物蚀变和稳定同位素研究（H，O和C），低温热年代学（磷灰石裂变径迹，磷灰石和锆石（U-Th）/He）。前一种技术提供了化学信息，可以追踪成矿流体通过岩石的通道。低温热年代学提供了一种追踪热液流体通过岩石时热效应的方法。总之，这两种方法将使我们能够以一种前所未有的方式了解沉积岩宿主系统的空间-热-化学演化。在建立了这种近端到远端表达的模型之后，我们将开发一种具有成本效益的方法和分析策略，使用热年代学的最佳组合，温度测量和地球化学/矿物学示踪剂，以提供可靠的远场向量的矿石。我们将重点研究在内华达州卡林型沉积岩容矿金矿床;世界上第三高的金矿产区。

New mineral occurrences at the earth's surface are rare. Future discoveries will depend on subsurface exploration and this requires the far-field detection of such ore deposits. Sedimentary rocks are important hosts for world-class deposits of Au, Pb, Zn & Cu in Canada and the world. They form at <4-6 km depth from the upwelling of hot fluids derived from hotter levels of the crust. Defining the far-field expression of these systems is challenging owing to their low temperature (<200-250 C) and subtle, spatially restricted and poorly constrained, alteration halos.This project uses an integrated set of analytical techniques to derive a model of the thermo-chemical expression of hydrothermal fluid flow in sedimentary rock-hosted Au-deposits. Specifically we will apply detailed and geologically constrained geochemistry, mineral alteration, and stable isotope studies (H, O & C), with low temperature thermochronology (apatite fission-track, apatite & zircon (U-Th)/He). The former techniques provide chemical information that tracks the passage of the mineralizing fluids through the rocks. The low-temperature thermochronology provides a means to track the thermal effect of the hydrothermal fluids as they pass through the rocks. Together, these two approaches will enable us to understand the spatial-thermal-chemical evolution of sedimentary rock-hosted systems in a way not previously possible.Having built such a model of the proximal to distal expression of such, we will develop a cost-effectivesampling and analysis strategy using the best combination of thermochronology, thermometry and geochemical/ mineralogical tracers to provide reliable far-field vectors toward ore.We will focus our study on Carlin-type sedimentary rock-hosted Au-deposits in Nevada; the third highestAu-producing area in the world.