Comparative Studies of the Properties of Synthetic Hydroxylated Zircons and Natural Metamict Zircons: Hypothesis of the Genesis of Malacons

摘要

The particular experimental conditions which led to the hydrothermal synthesis of hydroxylated zircon of general formula Zr(SiO sub 4 )/sub 1 - x/(OH) sub 4 /sub x/, and the properties which result from replacement of (SiO sub 4 ) exp 4- by (OH) sub 4- make it possible to compare this synthetic compound with natural metamict zircons (malacons). In fact, because of the common characteristics, it can be postulated that, at least in some cases, the metamict zircons are derived from hydroxylated zircons formed in a hydrated and fluorinated medium which is rich in radioactive elements. Fluorine induces the substitution of (SiO sub 4 ) exp 4- by (OH) sub 4- ; this replacement leads to formation of weaker bonds, and makes the lattice vulnerable to bombardment by particles emitted by disintegration of radioactive elements, whose presence is favored by the known fixing action of fluorine, particularly in the case of uranium. (ERA citation 02:060545)