Making wealth: precipitating synthetic gold from hydrothermal solutions to understand gold deposition processes

亮点：- 设计和进行新的实验程序，在首次系统研究中生成合成金矿脉-在理解金沉淀过程及其与金成分变化的关系方面开展一些开创性工作-首次对不同存款类型的金进行晶体学-成分表征，并使用实验和建模来研究沉积后的变化-综合来自所有实验途径的新数据，开发一种新颖的、全面的金颗粒表征方法--应用新的理解来完善勘探地质学方法，从而与工业密切联系从热液系统中沉淀出来的天然金具有广泛的矿物学特征。金颗粒内的不均匀程度最近才被认识到，并且包括合金的区域或轨迹，其显示出其他金属（例如Ag、Cu、Hg或Pd）的浓度升高。通过ToF-LA-ICP-MS对抛光金切片进行的新分析表明，由于其他矿物（通常为1- 20 μ m）的夹杂物以及Au-Ag合金中元素的局部微米级浓度（“簇”），微量元素分布高度不均匀。最初的成分特征可能会被修改的晶界迁移，无论是在后期阶段的矿化或随后居住在深成环境。目前，我们对初始成分不均匀性或随后的修改的控制了解甚少。您将通过在合成热液系统中沉淀的金的成分和晶体学特征以及结果与不同矿石存款类型的天然金观察的关系来解决这些问题。项目构成部分金的合成将集中于模拟典型的造山热液系统和斑岩-浅成热液系统。高温（> 200 ℃）流体含低Cl和低CO2，金以二硫化物络合物形式迁移，银以氯化物络合物形式迁移。金沉淀是由于与断裂有关的P和T的变化或通过与流体-岩石相互作用有关的化学参数如pH或fS 2的变化而产生的。合成金将根据成分、显微结构和晶体学进行表征。二.根据微量元素化学（ToF-LA-ICP-MS和原子探针层析成像）和晶体学（EBSD），建立第一个数据库，以表征不同存款类型的金。三.通过设计实验来定义控制预先存在的金的晶体学改性的参数，以使用光学和SEM技术观察真实的时间变化。实验数据与Elle模拟模型的相关性，以生成预测工具。综合所有项目结果，从形成过程的角度解释天然金的特征。v.应用项目成果改进现有的方法，在勘探过程中使用碎屑金作为指示矿物。从项目中获得的专业知识和机会您将通过设计新的实验方法和应用各种高端分析工具获得实验室研究的经验。通过对各种存款类型的金的研究，将大大提高矿床的地质专门知识。视项目方向而定，可包括实地部分，包括学习传统探矿技术，以收集更多的黄金样本。最后，该研究在矿产勘探中有实际应用，促进了与行业专业人士的对话。该项目为今后的存款理论和应用研究提供了良好的基础。

Highlights: -Design and undertake new experimental procedures to generate synthetic gold veins in the first systematic study of its kind-Produce some seminal work on understanding the process of gold precipitation and its relationship to gold compositional variations-Produce the first crystallographic-compositional characterization of gold from different deposit styles and use experimentation and modelling to investigate post- depositional changes -Synthesize new data from all experimental avenues to develop a novel and holistic approach to gold particle characterization -Apply new understanding to refine methodologies for exploration geology leading to close contact with industry Natural gold, precipitated from hydrothermal systems exhibits a wide range of mineralogical features. The degree of heterogeneity within gold particles has only recently been recognised and comprises zones or tracks of alloy exhibiting elevated concentrations of other metals such as Ag, Cu, Hg or Pd. New analyses of polished gold sections by ToF-LA-ICP-MS show that trace element distribution is highly heterogeneous because of inclusions of other minerals (typically 1-20um) and as a consequence of localised micron scale concentrations ('clusters') of elements in the Au-Ag alloy. The initial compositional features may be modified by grain boundary migration, either in late stages of mineralization or subsequent residence in the hypogene setting. At present we have little understanding of the controls of initial compositional heterogeneity or subsequent modification. You will address these questions through compositional and crystallographic characterization of gold precipitated in a synthetic hydrothermal system, and the relation of outcomes to observations of natural gold from different ore deposit styles. Project elements i. Gold synthesis will focus on simulating hydrothermal systems typical of orogenic and porphyry- epithermal systems. The high temperature (>200C) fluids contain low Cl and low CO2 and transport gold as a bisulphide complex, and silver as a chloride complex. Gold precipitation results from changes in P and T associated with fracturing or through change in chemical parameters such as pH or fS2 associated with fluid-rock interaction. Synthetic gold will be characterized according to composition, microtextures and crystallography. ii. Generation of the first data base to characterize gold from different deposit styles according to trace element chemistry (ToF-LA-ICP-MS and atom probe tomography) and crystallography (EBSD). iii. Definition of parameters which control crystallographic modification of pre - existing gold through design of experiments to observe changes in real time using optical and SEM techniques. Correlation of experimental data with Elle simulation models to generate a predictive tool.iv. Synthesis of all project results to interpret characteristics of natural gold in terms of processes of formation. v. Application of project outcomes to refine existing approaches to the use of detrital gold as an indicator mineral during exploration.Expertise gained and opportunities flowing from the projectYou will gain experience of laboratory based research through design of new experimental approaches, and application of various high- end analytical tools. Geological expertise in ore deposits will be greatly enhanced through study of gold from a range of deposit styles. Depending on project direction a field component could be included involving learning traditional prospecting techniques to collect further gold samples. Finally the research has a practical application in mineral exploration facilitating dialogue with industry professional. The project provides an excellent foundation for further academic or applied ore deposit studies.