measurement and analysis of zircon crystals is used for
the following objectives.
Classification of geological formation
it is difficult to confirm the original rock in cores
and cuttings due to strong alteration. Zircon (ZrSiO4,
Fig.5-1) is a general sub-component mineral in all kinds
of igneous and metamorphic rocks and is one of main heavy
minerals in sedimentary rocks. And due to its chemical
stability it remains unchanged even after the rock is
altered. On the other hand, the form and quantity of Zircon
crystals differs from rock type to type. Therefore,
it is possible to classify geological formations and rock
types by classifying the type of Zircon crystal and by
the quantity of its occurrence.
utilizing this technique (Fig.5-2), West JEC found a small-scale
subsidence zone (Fig.5-3) in a geothermal field under
development. This interpretation integrated to the results
of gravity survey resulted in the disclosure of a geothermal
reservoir around the faults conforming this subsidence
Zircon is often used together with the Fission Track method
(F.T.) for age determination to study thermal histories
by analyzing the contraction of spontaneous track lengths.
Recently, the thermo-luminescence method for age determination
(T.L.) using Zircon became possible as mentioned in section
the geological and thermal structures of a geothermal
field can be disclosed by a comprehensive analysis including
not only Zircon crystal forms but also by determining
the age of the rocks using this mineral.