Argillizite "Hats" of Kompleksnoe Ore Occurrence in Kayenmyvaam Volcanic Uplift (Central Chukotka)

The article is devoted to the results of mineralogical and geochemical studies of argillizites at Compleksnoe Au-Ag ore occurrence, localized on the southern flank of the Kajenmyvaam volcanic uplift in the inner zone of the Late Cretaceous marginal-continental Okhotsk-Chukchi volcanic belt (OChVB). At the ore occurrence, a series of isometric (oval) in plan view argillizite "hats" with diameters of 200 to 900 m are described. They are composed of red and light gray clay formations and accompanied by complex (Au-Ag-Mo-Cu-Pb-Zn-Bi-Sn) anomalies. In the recent relief, argillizite "hats" are characterized by gently sloping domes and crown subvolcanic bodies of granitoids and explosive breccias. A series of argillizite "hats" is surrounded by elongated lenticular bodies of secondary quartzites, which form the outer boundary of a large annular volcanostructure. The argillizites are composed of the following minerals: illite-smectite (mixed-layered formation), kaolinite, muscovite, jarosite, quartz, and rutile. The average content of Au and Ag in bulk samples are 0.06 and 0.075 g/t, respectively. Au is found in invisible form. According to the geological and geochemical data, argillizite "hats" record a near-surface (up to 300 m), slightly eroded, level of a large porphyry-epithermal mineral-forming system.