金矿立体地球化学探测模型与深部钻探验证

深部资源地球化学探测科学问题的的焦点是元素大深度垂向迁移机理和立体地球化学探测模型的建立。本文以胶东蚀变岩型金矿和贵州水银洞卡林型金矿钻孔岩芯和地表联合取样获得的数据, 建立千米深度立体地球化学探测模型。蚀变岩型金矿立体地球化学模型显示, Au、S和Hg与金矿密切相关, 分布模式既有相似性又有差异性, Au的立体几何分布模式兼具矿化剂元素S和远程指示元素Hg的双重特征, 金异常和矿化剂元素硫与矿体倾斜方向一致, 反映了成矿过程中流体沿控矿构造的轴向运移; 金异常与类气体元素汞在垂向上一致, 而且出现从矿体到地表的连续贯通式异常, 反映了流体沿微裂隙和纳米孔的垂向迁移。卡林型金矿立体地球化学模型显示, Au、As、Sb、Hg、Tl和S在不整合面都显示高含量特征, 与深部层状主矿体分布一致; 在矿体上覆地层中都存在弱异常, 显示了明显的成矿流体沿隐伏微小断裂垂向迁移特点; 所不同的是Sb和Tl元素在不整合面附近显示了最高的元素含量, 而Sb和Hg在近地表均显示了明显高的异常特征。立体几何模型清晰地显示了矿体的展布特征和范围, 而且金及其伴生元素垂向迁移在地表形成清晰异常, 为利用金及伴生元素和矿化剂元素进行深部矿体三维预测提供了重要依据, 对指导深部金矿勘查发挥了重要作用。针对胶东蚀变岩型金矿地表完全被土壤覆盖区的穿透性地球化学微细粒级土壤采样, 金属活动态提取分析圈定的异常, 经深部钻探验证, 胶东焦家成矿带五一村3200 m钻探, 在2428.00~3234.16 m深度发现6层矿化体, 其中高品位矿体位于2854 m深度; 上宫金矿地表基岩出露, 采集断层泥或裂隙岩石样品, 可以清晰探测深部异常, 经2000 m钻探, 在1312 m处发现高品位金铅锌银矿体; 贵州水银洞采集地表细粒级土壤, 能够直接有效地揭示深部金矿体, 经500~1500 m钻探验证, 在300~1500 m深度新增金资源量203 t。

Three-dimension Geochemical Patterns of Gold Deposits:Implications for the Discovery of Deep-seated Orebodies

The research on geochemical exploration for deep-seated ore deposits in covered terrains is centralized on understanding of long-distance vertical migration of mineralization and associated elements and 3D geochemical patterns. This paper provides an insight into 3D metal dispersion patterns of the buried gold ore deposits by sampling drill core rocks and surface soils. The 3D geometric pattern of the alteration type gold deposit in Jiaodong shows that the highest values of Au, S and Hg are in good correlation with the gold orebody, suggesting that the fluids migrated during the process of gold minerlization formation along the hosting fault channels, whereas Au and Hg exhibit vertical anomalies from the deep-seated orebody to the surface, implying that the elements with vertical dispersion of fluids were permeable upwards through the microfractures or rock pores, as supported by finding nanometer-sized particles of gold in wall rock microfractures. The 3D geometric pattern of the Carlin-type gold deposits in Guizhou shows that high values of Au, As, Sb, Hg, Tl and S are enriched in unconformity, which controls the distribution of deep-seated layer-bedded gold orebody, whereas anomalies of Sb, Hg and Au occur at the surface, implying vertical migration through the microfractures of the wall rocks. The geochemical patterns provide predicting methodology for the deep-seated orebody. A deep-seated orebody was discovered in the depths of 2428~3234 m by followup drilling exploration in the soil covered locations of gold anomalies delineated by fine-fraction soil sampling at Wujiazhuang of Jiaodong. An orebody of Au-Ag-Pb-Zn at a depth of 1312 m was discovered by drilling exploration based on fault gouge sampling at Shanggong, Henan. A reserve of 203 tones of gold in the depths of 300~1500 m was discovered according to the targets delineated by geochemical sampling of fine-fraction soils at Shuiyindong of Guizhou Province.