鄂东南地区金井咀斑岩型金矿成矿机理

Porphyry gold deposit had been recognized as a new type metallic deposit since 1990s, but many studies on the origin have not been undertaken in the past, and it provide the best sample for studies of gold-enrich mechanism in porphyry deposits. Plenty of magmatic hydrothermal gold deposits have discovered during the past 20 years in the Middle-Lower Yangtze River Valley metallogenic belt, including Au skarn deposits and stock-hosted gold-only deposits. Compared with Cu-Fe deposits, few studies of these gold deposits, especially gold-only deposits, have been undertaken to understand their ore-forming mechanism. The Jinjingzui gold deposit is one of typical representative gold-only deposits hosted into stocks in the Middle-Lower Yangtze River Valley metallogenic belt. Primary study shows mineralized-related stock in the Jinjingzui is oxidized dioritic rock, different from reduced intrusions-related gold deposits. The types of ores, and vein, and hydrothermal alteration, and fluid inclusions are consistent with porphyry gold-only deposits worldwide, distinguishing from gold-rich porphyry copper deposits. What is the ore-forming mechanism of these gold-rich deposits in this belt? The Jinjingzui gold deposit has been chosen in this application, and considered to case study. This application will constrain the origin of the ore-bearing porphyry and its relationship with gold mineralization, and identify the occurrence of gold, and estimate characteristics and zonation of hydrothermal alteration and vein, and establish ore-forming fluid evolution, and discuss the ore-forming mechanism of the Jinjingzui porphyry gold deposit. The implementation of the project may contribute to understanding ore-forming mechanism of gold mineralization in the Middle-Lower Yangtze River Valley metallogenic belt, and extend knowledge of gold deposit theory, and help to gold exploration.

斑岩型金矿是上世纪90年代确定的新类型矿床，研究程度较低，它是破解斑岩型矿床金富集机制的最佳对象。长江中下游成矿带近20年岩浆热液型金矿找矿取得重大突破，探明了一批矽卡岩型金矿和产于小岩体内的独立金矿。相比铜铁矿来说，对该带金矿，特别是独立金矿成矿机理的研究较少。 鄂东南金井咀金矿是长江中下游产于小岩体内的独立金矿的典型代表。初步研究显示，其含矿岩体为氧化型斑状闪长岩，不同于与侵入岩(还原性)有关的金矿，该矿的矿石类型、脉体、热液蚀变、流体包裹体特征与斑岩型独立金矿类似，不同于富金斑岩型铜矿。这一类斑岩型金矿的成矿机理如何？ 本申请以金井咀金矿为研究对象，开展解剖研究，厘定含矿岩体的成因及其与金矿化的关系；查明金的赋存状态，厘定蚀变和脉体特征及分带规律；刻画成矿流体演化过程，探讨成矿机理。本项目实施有助于进一步认识长江中下游金矿的成矿机理，丰富金矿成矿理论，为该带金矿找矿提供理论基础。

斑岩型金矿是上世纪90年代确定的新类型矿床，研究程度较低，它是破解斑岩型矿床金富集机制的最佳对象。长江中下游成矿带近20年岩浆热液型金矿找矿取得重大突破，探明了一批矽卡岩型金矿和产于小岩体内的独立金矿。相比铜铁矿来说，对该带金矿，特别是独立金矿成矿机理的研究较少。鄂东南金井咀金矿是长江中下游产于小岩体内的独立金矿的典型代表。本项目以金井咀金矿为研究对象，开展解剖研究，厘定含矿岩体的成因及其与金矿化的关系，查明金的赋存状态，厘定蚀变和脉体特征，刻画成矿流体演化过程，探讨成矿机理。. 通过本项研究，确定含矿岩体为闪长岩，它形成于晚侏罗世至早白垩世(139Ma)，具有高钾钙碱性特征，岩浆源区是富集地幔部分熔融混染部分下地壳的混合产物，与全球较少的钙碱性岩有关的富金斑岩型矿床类似，不同于传统的碱性岩有关的富金斑岩铜矿。确认高品位金矿石是网脉状和石英硫化物脉叠加的部位，发现自然金与丰富的Bi-Te化物共生，成矿流体存在高温高盐的岩浆流体，以岩浆硫为主。矿石类型、热液蚀变、流体包裹体、H-O-S同位素证据均表明金井咀金矿是全球为数较少的斑岩型金矿。初步提出富金幔源岩浆和高Bi-Te岩浆流体是斑岩型矿床金富集机制的关键因素。到目前为止，发表了10篇标注科学论文，其中SCI论文6篇。培养了2名硕士和1名博士研究生。本项目的成果丰富了金矿成矿理论，为长江中下游成矿带金矿找矿提供理论基础。