IMPLICATIONS OF THE GEOLOGICAL CHARACTERISTICS AND GENESIS OF THE ALLCHAR DEPOSIT FOR THE LOREX PROJECT

Abstract

The polychronous and polygenetic Sb-As-Tl-Au Allchar deposit was formed in complex physicochemical processes occurring in a heterogeneous geological environment, in interaction of polyphase hydrothermal fluids with the surrounding magmatic, sediment and metamorphic rocks. The genesis of ore mineralization is related to the products of polyphase magmatic activity of Pliocene age (~6.5 to ~1.8 My), whereas it spatial location was controlled by magmatic, structural and lithological factors. The Allchar deposit comprises several orebodies of various shapes, textural-structural characteristics and element associations. Thallium mineralization, which is of significance for the LOREX project, has been proved in the northern (Crven Dol) and the central parts of the Allchar deposit. The present depth of ore mineralization from the present soil surface is 40–120 m, whereas the paleodepth of its formation is considerably bigger. Using the method of quantitative geomorphological analysis, the erosion rate has been established to be 30–35 m/My at the broader area of the Crven Dol locality and 27–50 m/My in the central part of the deposit. Using the AMS-measurement of 26Al in quartz from the southeastern part of the Allchar deposit, the erosion rate was established to be 50 to 70 m/My. Geological and mineralogical investigations to date, regarding lorandite, its trace elements – Pb, U and Th being the first and foremost, the quantities of lorandite in orebodies, and the geological age of Tl-mineralization, have provided positive results and indicate the feasibility of the LOREX project.  

Key words: Allchar deposit; LOREX; thallium; age of mineralization; erosion