胶西北巨量金堆积成矿系统时空结构与演化

A booming event of gold accumulation occurred in the northwestern Jiaodong terrain during a short period of the Early Cretaceous. This spectacular Au metallogeny displays strong peculiarity in several aspects including tectonic-magmatic setting, ore-related thermal anomaly, sources of gold and ore-forming fluids, and mineralizing mechanism. These particular features cannot be readily explained by traditional genetic model of gold deposits. This research project will be centered on understanding the spatio-temporal evolution of the ore-forming systems within the Jiaodong gold province, which will be integrated with analysis of regional geology and metallogenic background. We also seek to constrain the correlation between the multi-phase evolutions of stress fields and gold mineralization during Late Mesozoic by investigating ultimate shapes of the roots of the ore-controlling faults and orebodies. Besides, special attention will be devoted to unraveling potential links between the magmatic-hydrothermal evolution and mechanism of Au accumulation, transportation and deposition. Through detailed characterization of the ore-forming systems, we will reveal the genetic relation between tectonic-magmatic-hydrothermal activities and Au booming event within the geologic context of decratonization. Combining the above endeavor, we will be capable of delineating the underlying patterns of gold metallogeny and improving the genetic model for the northwestern Jiaodong (or even the entire Jiaodong) Au province, which will definitely assist in gold exploration in this region and other similar areas as well.

胶西北在早白垩世发生了爆发式金堆积成矿事件，金矿形成的构造－岩浆背景、成矿热事件及流体来源及成矿机制等显示出明显的地域特色，难以用传统金矿成因模型来诠释。本项目以成矿系统演化为主线，系统剖析胶西北金矿集区区域成矿特征，厘定成矿背景与金矿产出环境；查明胶西北金矿床控矿断裂与矿体浅、深部空间形态特征及其配合关系，建立晚中生代多期应力场构造演化格架及对金成矿的制约；厘清胶西北晚中生代岩浆系统和流体系统演化对金聚集、运移和沉淀的制约机制；确定胶西北金矿床成矿系统的性质、发育、演化，揭示克拉通破坏环境下构造－岩浆－热液作用与巨量金堆积之间的成因联系，揭示成矿规律、完善胶西北(胶东)金矿床成矿模型，为在胶东和类似地区发现新的金矿资源提供理论依据。

四年的研究工作表明，控制胶西北金沉淀的两个重要机制，硫化和流体不混溶作用，均消耗成矿流体中的硫，H2S从主成矿流体中逃逸，总硫浓度降低，不仅可导致金的高效沉淀，还能引起还原性矿物磁黄铁矿和氧化性矿物磁铁矿等矿物的沉淀。胶西北金矿主成矿期内的黄铁矿在单颗粒尺度显示出复杂的显微结构特征，微量元素（主要为富As环带与金的耦合）和硫同位素组成同样有一定规律性变化，富As流体可能是由于初始成矿流体流经富As的变沉积岩地层所导致，黄铁矿边部As-Au振荡环带的产生则与断层活动导致的压力波动和流体发生局部相分离有关；胶西北三山岛金矿床中存在金成色的时空演化，水/岩反应（硫化作用）是早期金矿化的成矿机制，形成相对高成色金，而后期在浅部显著降压并伴随流体相分离是晚期金矿化的成矿机制，形成低成色金；胶西北金矿的成矿流体为克拉通破坏背景下，新生下地壳发生角闪岩相-麻粒岩相的变质脱水，形成富含Au和CO2的成矿流体，流体沿深大断裂及其次生构造上升，形成区内大规模断裂控制的金矿床。已发表标注资助论文15篇（其中SCI论文13篇），国际会议论文1篇；培养博后3名、博士生4名；获得山东省科技进步奖一等奖，中国黄金协会科学技术奖一等奖；举办亚洲流体包裹体国际会议1次，参加国际学术会议3次。课题成果将为在胶西北及邻区发现新的金矿研究与资源探查提供理论依据。