| Popis: |
As a part of the research pertaining to evaluation of the suitability of crystalline rocks for the disposal of nuclear fuel waste, a study of core samples from five boreholes in the Eye-Dashwa lakes pluton reveals several types and degrees of alteration. The different degrees of alteration are related to the intensity of pink coloration and the amounts of plagioclase and ferromagnesian minerals that are affected. The alteration process has reconstituted plagioclase to pure albite in highly altered rocks, whereas in unaltered and slightly altered rocks it occurs as oligoclase. The alteration products, chlorite and sericite, are relatively Fe-rich in the highly altered rocks. Unaltered to slightly altered, moderately altered, and highly altered samples each occupy a distinct field in a CaOMgOFeO variation diagram. A close association exists between alteration and fractures; a model relating fractures, alteration and fracture infillings is proposed. Distinct differences in chemical and some physical properties between altered and unaltered rocks indicate that significant changes have occurred. The distinct physical and chemical characteristics of the alteration, and its close association with faults and fractures, suggest the need to consider alteration as an important parameter in evaluating crystalline rocks for nuclear fuel waste disposal. |
