Two centimeter resection margins are just as safe and effective as 5 cm margins for 0.8–2 mm thick cutaneous melanoma tumor surgery

Abstract

The mineralogical composition of the 2–20 μm silt fraction from two soil profiles, developed upon loessial sediments in the southern Chaco region of Argentina, was studied by means of X-ray diffractometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These fine silts from the Chaco region contained more quartz and less feldspar and glass than those pointed oit for fine silts of loessial materials from the Pampa region. Microscopic analyses in particular evidenced some complexity with regard to both the composition and the condition of constituents of this fraction. Even though a considerable quantity of silt-size grains are quite fresh, different processes of weathering, transformation, and formation of mineral constituents have also been evidenced.Cation exchange capacities of these fine silts ranged from 8 to 23 cmolc kg−1 and accounted for approximately 1/6 to 1/3 of the CEC values of the soil samples. The high CEC of the silt may be due mainly to mica and mica grains undergoing a transformation process, but “contaminating” clay particles, clay aggregates, weathered feldspars, silt grains with neoformed fibrous clays and weathered biological silica particles would also contribute.