| The Heilongshan area is located in the Hebei province bordering Beijing,and under jurisdiction of Chicheng County and Fengning County.The working region belongs to the middle part of the North China Platform,which is one of the key planning areas of national geological prospecting.It is also a part of the Chicheng-Fengning Ag-Pb-Zn-Mo polymetallic exploration area.The exposure strata from old to new are as followed: the upper section of Qianxi formation of middle and lower Archaean;the Dantazi formation and Ciyushan formation of Shuangshanzi group of the upper Archean;the Ch group and Jx group of the middle and upper Proterozoic;Houcheng formation,Baiqi formation and Zhangjiakou formation of Jurassic;the Quaternary of Cenozoic.The exposed intrusive rocks are mostly Archaean ultrabasic rocks and diorite;granite and granodiorite of late Paleozoic;granite and orthophyre of early Yanshanian.We collect 11500 samples of stream sediment in the Heilongshan area,coverd 2233 km2.And the sampling density is 5.15 piece/ km2.Each sample is consists of multipoint acquisition from a stream-lined line in a range of 20~30 m.Most samples are acquired in the bottom of riverbeds,regions with slow-flowing stream and the inner part of watercourse.The samples with sizes of-10~+80 meshes are sieved and weighted more than 300 g.Sample analysis is undertaken by Hebei Central Laboratory of Geology and mineral resource.With a monitoring of sample tests,it proves that the analysis methods and analysis quality meet the standards of related rules and criterion.We select 16 elements to analyze,including Cu?Pb?Zn?Ag?Au?W?Sn?Mo?Bi?As?Sb?Hg?Ni?Cr?Cd?Co.The data show the characteristics of the distribution,enrichment and impoverishment of these elements.Through the analysis of geochemistry field characteristics,we consider the high content of Au,Cu,Pb,Ag,Zn and Cd are control by the geological structure and related to the strong siliconization and ferritization caused by the rich hydrothermal process.The high content of Mo?W?Sn are control by the intermediate acidic granite of early Yanshanian.As for Cr,Co and Ni,they are strictly controlled by the geological structure,which spread along NW and NE direction.Besides,they have a close relationship with super basite,basite and the archaean stratum.After a cluster analysis of the raw data in the area,the regularity of distribution and grouping for the elements are determined.Taking the catchment and geological conditions in the anomalous points into consideration,element anomaly thresholds are delineated.The area are divided into 3 concentration zones by 1,2 and 4 times the anomaly thresholds.Based on the combination of elements and geological metallogenic conditions,we analysis the single element anomaly and delineate 65 comprehensive anomaly,which provides a great deal of prospecting information.Finally,the Heilongshan area is partitioned into 7 metallogenic prospective areas after the comprehensive anomaly is verified and evaluated,and 8 prospecting targets areas are outlined,which provide a direction and foundation for further exploration. |
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