WOLFRAMITE-REPLACING PROCESSES

Abstract

Processes that alter wolframite already begin under endogene conditions, almost immediately after its crystallization from hydrothermal solutions, and lead to its total breakdown or replacement at that time or later in the oxidation zone. We give the results of our study of wolframite and its replacement products in specimens from various deposits of quartz-wolframite type. In wolframite that has been replaced, as shown by X-ray spectroscopic microanalysis, there are zones within the crystal, or in contact with the replacing mineral, which range in width from tens to hundreds of micrometers and, in their reflected-electron images, look darker than normal wolframite. In composition, these zones are similar to so-called 'altered wolframite'. The replacement of wolframite by secondary minerals develops in its 'altered' zones. Newly formed minerals thereby inherit certain features of the chemical composition of wolframite.