新疆索尔库都克铜钼矿床稀土元素地球化学特征及成矿作用示踪

索尔库都克矽卡岩型铜钼矿床位于新疆东准噶尔北缘,矿区发育早、晚两期矽卡岩并分别伴有成矿作用。两期矽卡岩在产出特征、矿物组合及成矿过程方面均有明显区别,其中与早期矽卡岩有关的成矿金属元素为Fe-Cu-Mo组合,与晚期矽卡岩有关的成矿金属元素为Cu-Mo-Zn组合。本文对索尔库都克铜钼矿床的矽卡岩单矿物、安山质围岩、矿石及与成矿有关的脉岩进行了稀土元素测试分析。结果表明早期矽卡岩成矿过程与安山质围岩关系密切,成矿环境经历了由进化变质阶段的弱还原-弱氧化条件→氧化物阶段的弱还原环境→退化变质早阶段氧化环境→退化变质中晚阶段弱氧化-还原环境的变化过程,铁质可能主要来自于围岩;晚期矽卡岩成矿过程中成矿环境经历了由进化变质阶段的氧化环境→退化变质阶段的弱氧化-弱还原环境→石英-硫化物阶段的弱还原-还原环境→石英-方解石阶段还原环境的变化过程。虽然在具体的成矿过程方面有明显的区别,但在早、晚两期矽卡岩各自的主成矿阶段均经历了由氧化环境向还原环境转变的过程,这种转变为大量金属硫化物的形成创造了良好的条件,是导致矿质沉淀的重要机制。

REE Geochemistry of the Suoerkuduke Cu-Mo Deposit and its Metallogenic Implications

The Suoerkuduke Cu-Mo deposit is a skarn-type deposit located in the northeastern margin of East Junggar. The deposit is characterized by two stages of skarn mineralization. The skarns of the two stages have strikingly different outcrop characteristics, mineral assemblages and mineralization processes. For instance, the Fe-Cu-Mo assemblage is associated with the early skarn mineralization, while the Cu-Mo-Zn assemblage is associated with the late skarn mineralization. This study analyzed the rare earth element concentrations of the skarn minerals, surrounding andesitic rocks, ore minerals, and the dykes in the mining area. The results indicated that the early stage skarn mineralization is intimately related to the surrounding andesitic rock, and the redox status varied from weak reducing to weak oxidizing in the prograde stage→ weak reducing in the oxide stage→ oxidizing in the early retrograde stage→ weak oxidizing to reducing in the late retrograde stage of the skarnization. On the contrast, the mineralization processes of late stage skarnization experienced the following redox status changes: oxidizing in the prograde stage→ weak oxidizing to weak reducing in the retrograde stage→ weak reducing to reducing in the quartz-sulfide stage→ reducing in the quartz-calcite stage of the skarnization. Although ore-forming processes may differ, these two skarn episodes experienced similar oxidizing to reducing environment conversion in their main metallogenic stage. The redox shifts may have created ideal conditions for the precipitation of metal sulfides and contributed to the ore mineralization.