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

地球表面出现新矿物的情况很少见。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世界级金、铅、锌、铜矿床的重要赋存岩。它们形成于&lt；4-6千米深，是由较热的地壳产生的热流体上涌形成的。由于这些系统的低温(&lt；200-250℃)和微妙的、受空间限制和约束较差的蚀变晕，定义这些系统的远场表达是具有挑战性的。本项目使用一套综合的分析技术来推导沉积岩型金矿床中热液流动的热化学表达模型。具体地说，我们将应用详细的和地质限制的地球化学、矿物蚀变和稳定同位素研究(H，O&C)，以及低温热年代学(磷灰石裂变径迹，磷灰石和锆石(U-Th)/He)。以前的技术提供了追踪成矿流体通过岩石的化学信息。低温热年代学提供了一种追踪热液流体通过岩石时的热效应的方法。这两种方法将使我们能够以一种前所未有的方式理解沉积岩赋存系统的空间-热-化学演化。在建立了此类系统近端和远端表达的模型后，我们将开发一种经济高效的采样和分析策略，使用热年代学、测温学和地球化学/矿物学示踪剂的最佳组合来提供可靠的远场向量。我们将重点研究内华达州的卡林型沉积岩赋存金矿床。内华达州是世界上第三大金矿产区。

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.