Characteristics and Assessment of the Geochemical Anomalies of Kawana Gold Deposit in Northwest Province,Zambia
|Course||Earth Exploration and Information Technology|
|Keywords||gold deposit geochemical anomaly gold metallogeneticdivision mathematical statistic analysis anomaly evaluation prognosis of resources Zambia|
Zambia is a country that is rich in mineral resources, with itsreserves of copper mine resources having a significant position in theworld. Its reserves of iron mines is also rich. As the exploration extentadvances continuously, many other kinds of minerals have been found.Copper used to be the key target of mineral exploration in Zambia, andthe exploration extent of gold deposits was relatively low. However, themineral exploration in recent years suggests that gold deposits in Zambiaare of favourable metallogenic geologic conditions and good prospectingpotential, and it may become a new direction of mineral exploration inZambia in future.Since the prospecting and mining of copper deposits were used to beemphasized, while the metallogenetic division was seldom to be payattention. The metallogenetic division of gold deposits in Zambia wasproposed in this paper, according to the known spatial distribution ofgold deposits, combined with occurring geological conditions and relatedtectonic-magmatic events. The gold deposits in Zambia are preliminarilydivided into3gold metallogenic belts and15gold mineralizedconcentrated districts. Metallogenic belt is the first-ordermetallogenic unit, relatively large. Mineralized concentrate districtis the second-order densely mineralized distribution area inside ofmetallogenic belts.Kawana gold field is affiliated to Northwest Province, Zambia,located in Lufilian orogen, obviously controlled by Lufilian arcuatetectonic belt. According to tectonic characteristics, predecessorsdivided Lufilian arcuate tectonic belt into3secondary tectonic units, which are external fold belt, dome belt and synclinorium belt from Northto South. Kawana gold field is located in the middle part of thesynclinorium belt in the secondary tectonic unit of the arcuate structure.This area is shallow covered region, most parts of which are covered byquaternary sediments, with little rocks exposed on the surface. In theregion, stratums contended with gold minerals are mainly Upper Roan Groupin Katanga Supergroup of late Proterozoic. The host rock of the gold orebody is siltstone in Upper Roan Group. Upper Roan Group trends nearlyEW, southward dipping, with a dip angle of10°－30°. Because of theeffect of Lufilian tectonic movement, open folds were occurred in thestratum, meanwhile, NE and NW trending faults formed. The NE trendingfault is the main ore-controlling fault.The1/25000soil geochemical survey in Kawana gold mine area wasinvestigated. The elements of Bi, Hg, Mo, W, Zn, Co, Sb, Ag, Pb, Cu, Asand Au in1120soil samples were analyzed. After the data processing ofthe analysis results, background values and anomaly thresholds of theelements in Kawana gold mine area were defined in this paper. Theanomalies of the Bi, Hg, Mo, W, Zn, Co, Sb, Ag, Pb, Cu, As and Au werealso defined and the features of these anomalies were analyzed. Afterthe analysis, it is concluded that Kawana area has obvious Au anomalies,associated with Cu and As anomalies, the Au anomalies are divided into3anomalies such as Au-1, Au-2and Au-3. Based on the study, theexploration methods of geochemistry prospecting are favored in thisarea.For better using Au and associated elements to synthetically reflectgeochemical anomalies in the metallogenic process, mathematicalstatistic analysis of the data was analyzed in this paper, whichincluding correlation analysis, cluster analysis and factor analysis ofeach elements. Au is main ore-forming element and associated with Cu, As, Zn, Co, Sb, Ag and Pb, which indicated that they are products of anidentical mineralization. Among these elements, Au is more closelyrelated to Cu and As, but Bi, Hg, Mo and W are not obviously related tothis period of mineralization. According to the correlation of Au withCu and As,4associated anomalies that are related with Au are defined,and they are ZAu-1, ZAu-2, ZAu-3and ZAu-4.The anomaly inspection for the defined Au anomalies and associatedanomalies were carry out, associated with the analysis of the geologicalconditions, the Au anomalies and associated anomalies were concluded asmineralized anomalies, and the ZAu-1, ZAu-2, ZAu-3associated anomalies areconfirmed as prospecting target areas. The ZAu-2target region was furtherverified in detail, and controlled by geological engineering.Ⅰgold orebody was found in ZAu-2target region after the verified in detail. Itis assessed that the intrinsic economic resources(334) of the Ⅰgold orebody is6.48ton. After observing and analysing of the Ⅰgold ore body,it is concluded that the host rock of the gold ore body is the siltstoneof Upper Roan Group in Katanga Supergroup. The Ⅰgold ore body wascontrolled by faults. The ore minerals in the Ⅰgold ore body are nativegold, pyrite, chalcopyrite, cubanite，covelline and limonite, while thegangue minerals are quartz and sericite. The formation of the gold orebody was the productions of the elements enrichment by the metallogenichydrotherm intruded along the faults in the mineralization.According to the verified result of ZAu-2associated anomalies andconsidering theⅠgold ore body as a known ore body, the Au anomalies inKawana area were evaluated. In this paper, evaluated method of the arealproductivity and elemental abundance are used respectively to prognosisof resources for Au geochemical anomalies(Au-1、Au-2、Au-3) in Kawanaarea. The similar results are appeared by the two quantitative evaluationmethods. As a result of the evaluation, the amounts of Au resource for the Au geochemical anomalies in Kawana area is11.74ton, which providesthe foundation for further mineral exploration in this area.