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

重点：-设计和进行新的实验程序，以产生人造金脉，这是首次系统研究这类矿脉--在了解金的沉淀过程及其与黄金成分变化的关系方面开展一些开创性的工作--首次对来自不同矿床类型的金进行晶体成分表征，并利用实验和建模来研究沉积后的变化--综合所有实验途径的新数据，制定一种新的、全面的金粒子表征方法--应用新的认识来完善勘探地质方法，从而与行业密切接触--从热液系统中沉淀出来的自然金显示出多种矿物学特征。金颗粒内的不均匀程度直到最近才被认识到，包括合金带或轨迹，显示出其他金属的浓度升高，如银、铜、汞或钯。用TOF-LA-ICPMS对抛光金切片的新分析表明，由于其他矿物(通常为1-20微米)的包裹体以及Au-Ag合金中元素的局部微米级浓度(‘簇’)，微量元素的分布高度不均匀。初始的成分特征可以通过晶界迁移而改变，无论是在成矿的后期阶段，还是在深成环境中的后续停留。目前，我们对初始组成不均质性或随后的修饰的控制知之甚少。您将通过对在合成热液系统中沉淀的金的成分和结晶学表征，以及结果与对不同矿床类型的自然金的观察之间的关系来解决这些问题。项目内容一.金的合成将侧重于模拟造山和斑岩-浅成热液系统的典型热液系统。高温(&GT；200℃)流体含有低氯和低二氧化碳，并以二硫化物络合物和氯化物络合物的形式运移金和银。金的沉淀是与压裂有关的P和T的变化，或通过与流体-岩石相互作用有关的pH或FS2等化学参数的变化而产生的。人造黄金将根据成分、微观结构和结晶学进行表征。二、根据微量元素化学(TOF-LA-ICPMS和原子探针层析)和结晶学(EBSD)建立了第一个数据库，以确定不同矿床类型的金的特征。三、通过设计实验，利用光学和扫描电子显微镜技术实时观察变化，确定控制原有金的结晶修饰的参数。将实验数据与ELLE模拟模型相关联，以生成预测工具。综合所有项目成果，从形成过程的角度解释自然金的特征。V.应用项目成果改进现有方法，将碎屑金用作勘探中的指示矿物。专业经验和从项目中获得的机会通过设计新的实验方法和应用各种高端分析工具，您将获得基于实验室的研究经验。通过对各种矿床类型的金的研究，将大大提高矿床的地质专业知识。根据项目方向，可包括一个实地部分，涉及学习传统探矿技术，以收集更多的金矿样本。最后，该研究在矿产勘查中得到了实际应用，便于与行业专业人士进行对话。该项目为进一步的学术或应用矿床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.