宁夏卫宁北山地区伴生钴矿床地质特征、控矿因素及找矿方向

Geological characteristics, controlling factors and prospecting directions of associated cobalt deposits in the Weiningbeishan area, Ningxia

卫宁北山地区位于北祁连造山带东段,是宁夏境内钴矿成矿条件最好的地区之一。为详细了解该地区钴矿形成条件及矿化规律,在详细野外调查基础上,综合前人勘查成果,对卫宁北山地区典型伴生钴矿床地质特征、控矿因素及时空分布规律进行了总结,提出了下一步找矿方向。研究表明:大铜沟铜钴矿、茶梁子铁钴矿和土窑铁钴矿是该地区目前已发现的3个代表性伴生钴矿床,其中大铜沟铜钴矿共发现铜钴矿体3个,Co品位最高达0.06%,含钴矿物主要为辉砷钴矿、含钴黄铁矿和含钴褐铁矿;茶梁子铁钴矿分布有4条矿带共8个铁钴矿体,Co品位最高达0.03%,含钴矿物主要为含钴褐铁矿;土窑铁钴矿只发现1条铁钴矿体,Co品位最高为0.20%,含钴矿物与茶梁子相似。钴矿受断裂构造控制明显,其中西部主要受EW向断裂及其与NE向断裂联合控制,东部主要受SN向断裂控制。钴矿主要赋存于上石炭统土坡组中,为主要矿源层;岩性控矿主要表现在“硅钙面”和能干性不同的岩性组合界面,控制了矿质沉淀。钴矿化形成时间主要为印支期,Co成矿主要与Cu、Au、Fe和Mn关系密切,且与Cu、Au有关的钴矿主要分布于西部,而与Fe、Mn有关的钴矿分布于东部。多期构造叠加及热液改造可能是造成该地区矿种多样的主要原因。卫宁北山西部EW向断裂及其与NE向断裂交汇部位、东部SN向石炭系和泥盆系界面断裂、土坡组内“硅钙面”和能干性不同的岩性组合界面是寻找钴矿最有利部位,孔雀石化、褐铁矿化等围岩蚀变是铜钴矿、铁钴矿最重要的找矿标志。

Weiningbeishan is located in the eastern section of the North Qilian orogenic belt,which is one of the regions with the most favorable conditions for cobalt mineralization in Ningxia.[Objective]To understand the formation conditions and mineralization regularity of cobalt deposits in this area,[Methods]this paper summarizes the geological characteristics,controlling factors,and spatiotemporal distribution patterns of typical associated cobalt deposits in Weiningbeishan based on detailed field investigations and previous exploration results and proposes future exploration directions.[Results]Research has shown that the Datonggou copper cobalt deposit,Chaliangzi iron cobalt deposit,and Tuyao iron cobalt deposit are currently three representative associated cobalt deposits discovered in Weiningbeishan area.Among them,three copper cobalt ore bodies were discovered in Datonggou,with the highest Co grade of 0.06%.Cobalt-bearing minerals mainly include pyroxenite,cobalt-bearing pyrite and cobalt-bearing limonite.There are 4 ore belts and 8 iron cobalt ore bodies are distributed in Chaliangzi,with the highest Co grade of 0.03%.The cobalt-bearing minerals are mainly cobalt-bearing limonite.Only one iron cobalt ore body was found in Tuyao,with the highest Co grade of 0.20%.The cobalt-bearing minerals are similar to those of Chaliangzi.Cobalt mineralization is evidently controlled by faults,with the western cobalt deposit mainly controlled by east-west faults and their combined control with northeast faults,while the eastern cobalt deposits are mainly controlled by north-south faults.Cobalt ore are mainly found in the Upper Carboniferous Tupo Formation,which was the main source strata.Lithological control is mainly observed at the"silica-calcium interface"and the lithological combination interface with different competence,which controlled the mineral precipitation.The cobalt metallogenic era was the Indosinian.Cobalt was closely related to Cu,Au,Fe and Mn.Cobalt related to Cu and Au were mainly distributed in the west,while cobalt related to Fe and Mn were mainly distributed in the east.The diversity of mineral species in this region may be attributed to the multistage superimposition of structures and hydrothermal activity.[Conclusion]The most favourable locations for identifying cobalt deposits are the east-west faults and their intersections with the northeast faults in the western part,the north-south Carboniferous and Devonian interface faults in the eastern part,the"silica-calcium interface"within the Tupo Formation,and the lithological combination interfaces with different competence.Malachite alteration and ferritization are the most important prospecting indicators for copper cobalt deposits and iron cobalt deposits.