宁芜火山盆地梅山铁-金矿床的金矿化成因及与玢岩型铁矿床的关系

The Ningwu volcanic basin, the western portion of the Middle and Lower Yangtze River polymetallic metallogenic belt, is well endowed with numerous porphyry type iron deposits that are analogues of Kiruna-type iron deposits. Newly discovered gold ore bodies from the Meishan deposit, which has long been considered as product of crystallization of iron melts separated from iron rich magmas, provides an exceptionally excellent opportunity to better understand the ore genesis of both iron and gold mineralization and their potential link. In this proposal, we first conduct molybdenite Re-Os and sericitie 40Ar/39Ar dating to tightly constrain the age of gold mineralization. We further use textural characterization, trace element composition and fluid inclusions of main ore and gangue minerals, and in situ S isotope data of sulfides both from iron and gold ores in gold and iron ores to trace the source of gold and ore-forming fluids and understand the roles of Triassic gypsum-salt layer in the formation of iron and gold ores. When combined with independent studies, results from this study may also provide insights into the metallogenesis and potential links between gold and iron mineralization, information important for improving existing model of porphyry iron deposits and future exploration of Au resources in the Ningwu and Luzong basin. This study also has broad implications for classification of and genetic relationships between Kiruna and IOCG deposits worldwide.

宁芜火山盆地是国内玢岩型铁矿床最为集中发育的地区，也是我国玢岩铁矿床成矿模式的发源地。梅山铁矿床是宁芜盆地最典型的玢岩型铁矿床之一，近年来在矿区外围新发现了热液脉状金矿体，目前对于这种金矿体的成因及其与铁矿化之间的关系还缺少系统研究。本项目拟在详细的野外地质观察基础上，利用辉钼矿Re-Os定年和绢云母40Ar/39Ar定年准确限定金矿化的时代，进而开展主要矿石矿物和脉石矿物的显微结构及微区主-微量元素组成分析、流体包裹体显微测温和成分分析、黄铁矿原位S同位素和硬石膏Sr-O同位素组成分析，揭示金的来源和成矿流体的组成、性质、来源及演化，并通过与铁矿体中相应矿物的元素及同位素组成的对比分析，深入探讨金矿体的成因机制及与铁矿体可能存在的成因联系，完善玢岩型铁矿床的成矿模式，为玢岩型铁矿区的金矿找矿提供理论指导。