内蒙古自治区大型金矿地球化学标志与预测

The Geochemical Indicator and Prognosis of Large Gold Ore Districts in Inner Mongolia

利用1:20万区域化探扫面数据和中蒙边界1:100万地球化学填图数据编制了内蒙古自治区1:100万金地球化学图,发现内蒙古已知大型金矿与地球化学异常具有良好的对应关系。以内蒙古四个典型大型金矿为例,建立了1:100万尺度大型金矿地球化学预测指标:(1)异常具有3层套合结构,即局部异常被区域异常所包裹,区域异常被地球化学省所包裹;(2)异常面积通常大于1000 km^2;(3)地球化学块体的异常衬度大于2.2;(4)常伴生有Ag、As、Sb、Bi等元素的异常;(5)异常区或周边常具有区域性深大断裂及其次级断裂等构造;(6)异常区或周边一般发育有火成岩。根据建立的大型金矿预测指标,圈定了大型金矿集区14个,为下一步在内蒙古选择重点地区开展大型金矿勘查提供了远景区。

The 1:1000000 gold geochemical map in Inner Mongolia was compiled,based on the datasets of 1:200000 Regional Geochemistry-National Reconnaissance Program(RGNR)and 1:1000000 China–Mongolia Geochemical Mapping Project which was carried out across the boundary regions.The large gold ore deposits have a good relationship with gold geochemical anomalies.Geochemical indicators based on the four large gold ore deposits in Inner Mongolia show the following features:(1)3-level nested geochemical anomalies occur around the large deposits,i.e.,a geochemical province containing regional anomalies and local concentration centers;(2)The gold anomaly area is usually larger than 1000 km^2;(3)The gold anomaly contrast is higher than 2.2;(4)There are Ag,As,Sb,Bi,Hg geochemical anomalies in general;(5)There are regional deep faults and secondary faults in the gold anomaly area or its periphery;(6)There are generally igneous rocks in the gold anomaly area or its periphery.Finally,14 large-size gold metallogenic prospective areas were delineated based on the geochemical indicators,regional geology and tectonic setting.