黑龙江五道岭钼铁矿床地质地球化学特征及成因

Geological and geochemical characteristics and genesis of ferromolybdenum deposit in Wudaoling,Heilongjiang Province

五道岭钼铁矿床是小兴安岭—张广才岭成矿带内典型的矽卡岩型矿床。矿体赋存于碱长花岗岩的蚀变产物--黄铁矿化石英斑岩与五道岭组凝灰质砂岩、酸性凝灰岩接触的矽卡岩带内。矽卡岩矿物组合为石榴子石、透辉石、阳起石和绿帘石等组成,矿体呈不规则脉状,具分枝复合形态特征,矿石类型包括钼矿石、铁矿石和黄铁矿矿石。与成矿密切相关的碱长花岗岩和石英斑岩为准铝质-过铝质、高钾钙碱性系列的I型花岗岩;富集Rb、K、U等大离子亲石元素,亏损P、Ti等高场强元素,具有与俯冲带花岗岩相似的地球化学特征。锆石LA-ICP-MS U-Pb测年结果表明,石英斑岩和碱长花岗岩的形成时代分别为193.6±1.1 Ma和193.9±1.3 Ma。结合区域地质演化特征,认为五道岭钼铁矿床的形成与古太平洋板块俯冲挤压造山后期的伸展环境有关,成矿时代为早侏罗世(186±2 Ma),矿床属于矽卡岩型成因。

Wudaoling ferromolybdenum deposit is a typical skam deposit in Lesser Xing＇an range-Zhangguangcai range metallogenic belt. Orebodies are hosted in skarn zone between pyritized quartz porphyry, alterated product of alkali-feldspar granite, with tuffaceous sandstone and acid tuff of Wudaoling Formation. The mineral assemblage of skarn was composed of garnet, diopside, actinolite and epidote, etc. The orebodies are irregular in shape, and characterized by branch and composite form. The types of ores included molybdenum, iron and pyrite ores. The alkali-feldspar granite and quartz porphyry closely related to mineralization, are metaluminous-peraluminous in nature, belonging high potassium calc-alkaline I-type granties. The granties were enriched in LILE （such as Rb, K, U） and depleted in HFSE （ such as P, Ti） , which was compatible with the geochemical characteristics of subduction granites. LA-ICP-MS U-Pb zircon dating showed that the formation age of quartz porphyry and alkali feldspar granites were 193.6 ± 1.1 Ma and 193.9± 1.3 Ma, respectively. Combining with regional geological evolution characteristics, the authors suggested of that the formation of Wudaoling ferromolybdenum deposit was related to the extended environment after subduction of the ancient Pacific Hate. The metallogenic epoch was Early Jurassic （186± 2 Ma） and genesis belonged to skarn type.