成矿深度研究及其对深部找矿的指示意义——以胶东典型焦家式金矿为例

Study on Metallogenic Depth and Its Significance for Deep Prospecting——Taking Jiaojia Type Gold Deposits in Jiaodong Peninsula as an Example

近年来,焦家式金矿在500~3000 m深部不断取得重大找矿突破,显示出深部巨大的找矿潜力。然而,该类型金矿深部是否仍具有找矿空间,赋矿空间在哪是目前制约深部找矿亟需解决的关键科学问题。本文以三山岛、焦家、台上水旺庄等3个千吨级超巨型金矿床为研究对象,在分析前人定量计算成矿深度方法的基础上,综合利用构造特征、岩浆作用及地温梯度约束该类型金矿成矿深度,构造特征分析结果表明,焦家式金矿成矿作用发生于韧脆性转换空间至脆性空间内,成矿深度范围大约在<5~10 km。岩浆作用研究表明,与金成矿密切相关的玲珑花岗岩和郭家岭花岗闪长岩侵位深度分别为10~15 km,6~13 km。岩浆热液出溶深度<12 km,成矿深度<10 km。成矿温度及地温梯度计算结果表明成矿深度范围约2.5~9.5 km。焦家式金矿成矿后至今虽略有剥蚀,但整体剥蚀量不大,深部矿体保存良好,深浅部金矿体沿同一控矿断裂构造倾斜方向分布,具有明显的侧伏规律,沿侧伏方向厚度×品位高值区具有似等间距分布规律,焦家式金矿深部仍具有2~4 km的找矿空间,沿侧伏方向按照厚度×品位高值区的间距向深部具有良好的找矿前景。

Jiaojia type gold deposithas have made great breakthroughs in the depth of 500~2000m underground prospecting in recent years.It has great prospecting potential in the deep.However,whether there is still ore prospecting space in the deep,where is the ore prospecting space are key scientific problems that restrict the deep ore prospecting at present.Choosing three super giant gold deposits of 1000t as the research objects,they are Sanshandao gold deposit,Jiaojia gold deposit and Taishang-Shuiwangzhuang gold deposit,basing on the analysis of previous methods of quantitatively calculation,using structural characteristics,magmatism and geothermal gradient to constrain the metallogenic depth,structural characterisiics have been analyzed.It is showed that the mineralization of Jiaojia type gold deposit occurred in the ductile and brittle transition space to the brittle space,and the metallogenic depth is about less than 5~10km.As showed by the study of magmatism,the emplacement depth of Linglong granite is 10~15km,and Guojialing granodiorite is 6~13km.The magmatic hydrothermal dissolution depth is less than 12km,and the metallogenic depth is less than 10km.As showed by the calculation results of ore-forming temperature and geothermal gradient,the metallogenic depth is about 2.5~9.5km.Although there has been slight denudation after the mineralization,the overall denudation is not large,and the deep ore bodies are well preserved.The deep ore bodies and the shallow ore bodies are distributed along the same ore- controlling fault,withing obvious lateral trending.The high value area with thickness times grade along the lateral direction has the distribution law of similar equal distance.It still has a prospecting space of 2~4km in deep.It has a good prospecting prospect along the lateral direction and according to the interval of high thickness times grade value zone to deep part in Jiaojia type gold deposits.