铜陵地区胶状黄铁矿矿石的成因矿物学研究

It has long been recognized that colloform pyrite ore plays a key role in elucidating genesis of the stratabound Cu-Au pyrite-dominant sulfide orebodies in Tongling region, which precipitation processes and mechanisms of the orebodies are not yet fully understood. In order to better constrain their genesis and evaluate their implications for Cu-Au mineralization, researches on genetic mineralogy, morphology and microstructure of colloform pyrite ore should be carried out at nanometer scale. On the base of the discovery of pyrite’s precursor “nano-pyrrhotite”, we will focus on the morphological characteristics, microtextures of pyrite, minor minerals (siderite, quartz, illite and other clay mineral et al.) in colloform pyrite ores, and their interface relationship. It is expected that the study at the nanometer scale will help us to understand mineral characteristics, mineral formation mechanisms in the colloform pyrite ores. The occurrence of pyrrohotite nanopaticles in the colloform pyrite ores from other stratabound Cu-Au sulfide orebodies in Tongling region must be well known. A detailed investigation on morphological characteristics of microbial residues and biomarkers, as well as relationship between pyrite’s precursor and organic material with the experiments of iron sulfide and microbial interaction will be undertaken to illustrate the formation process and mechanism of colloform pyrite and its ores. The study will help us to understand mineralization of the stratiform Cu-Au iron sulfide orebodies in the Tongling Cu-Au polymetallic deposits, and promote the development of nanomineralogy and its application in the field of economic geology.

铜陵地区层状含铜硫化物矿体成因认识上一直存在很大争议，而主要由纳米矿物组成的胶状黄铁矿矿石的成因又是该类矿体争论的焦点，也是解决争议的重要切入点，迫切需要从微观尺度提取其成因信息，为该类矿体的研究提供纳米矿物学支撑。本项目在前期发现形成黄铁矿前驱体纳米磁黄铁矿存在的基础上，研究胶状黄铁矿矿石中黄铁矿、次要矿物（菱铁矿、石英、粘土矿物等）形貌、微结构、相互之间的界面关系，从纳米矿物学角度提取矿石成因信息；进一步在胶状黄铁矿矿石中寻找前驱体纳米磁黄铁矿，并确认其在铜陵地区同类矿床中是否普遍存在；借助矿石中有机生物残体分离、形貌观察及生物标志物分析、黄铁矿前驱体及其与有机质界面关系研究、铁硫化物与微生物交互作用实验模拟，揭示胶状黄铁矿形成过程和机制。研究成果对铜陵地区层状含铜硫化物矿体和铜金多金属矿床的成矿作用认识具有重要价值，有助于推动纳米矿物学发展及其在矿床地质研究领域的应用。

本项目以铜陵矿集区层状硫化物矿体中胶状黄铁矿矿石为主要研究载体，在广泛地质调查、分析测试研究和合成模拟实验基础上，探讨该特殊矿石的矿物组合、微结构形貌及矿物界面关系和化学组成对其成因指示，并剖析其潜在成矿价值。结果显示：铜陵地区胶状黄铁矿矿石主要由黄铁矿、白铁矿、菱铁矿、方解石、白云石、石英、有机质、高岭石或伊利石等粘组成的矿物组合；纳米-亚微米粒径的黄铁矿、表面多孔且具纳米黄铁矿硬模或亚微米自形石英的微结构和形貌特征是胶状黄铁矿沉积成因重要标志；层状矿体中广泛存在的胶状、同心环状结构主要由黄铁矿、白铁矿、有机质组成的沉积结构；胶状黄铁矿矿石中浸染状分布的菱铁矿为纳米黄铁矿沉积成岩过程中有机降解产物，沉积-成岩过程的重要标志；矿石中有机质生物标志物揭示胶状黄铁矿中有机质主要来自陆源，其次为海源，暗示矿石为半封闭海盆环境或类泻湖环境下直接生物化学沉淀，该沉积纳米铁硫化物层可能为中生代铜金成矿的矿化剂。研究成果为揭示铜陵矿集区层状硫化物矿体成因和成矿作用提供系统纳米矿物学资料，同时对剖析区域中生代铜金矿床成矿机制具有重要价值。在本项目资助下发表学术论文14篇，SCI检索论文8篇，EI收录论文1篇，培养毕业硕士研究生2名，在读硕、博士研究生7名，参加国际国内学术会议23人次.