Dear Dr. Latha,

zircon is an end-member of the zircon-hafnon s.s.s. It is a continuous solid solution series. Neither Hf-free zircon nor Zr-free hafnon are very widespread. The mean Hf contents stand at 1.7 wt. % Hf (Ahrens and Erlank 1969). The common range is 0.6 to 3.0 wt. % Hf  of all zircons. It is a mirror image of their abundance in the earth. The Hf content increases from basic to felsic igneous rocks. Size and morphology do not correlate with the Hf contents. The interaction of Zr-Hf with other elements is not yet very well studied. I used these values for provenance studies since zircon ranks second to none in terms of resistance to weathering and is one of the most common heavy minerals. Extraction of zirconium and last but not least Hf is carried out from placer deposits, mainly in the coastal environments.

With kind regards

H.G.Dill

Hafnium (density 13.09 g/cm3, melting point 2222oC) is geochemically very similar to zirconium but  less abundant, with a crustal average of 4.9 ppm. Natural hafnium consists of 6 isotopes of which 176Hf is a useful petrogenetic indicator. 176Hf is a radiogenic decay daughter of REE 176Lu (decay constant 1.865×10−11 per year), which is enriched in the mantle. Therefore, the ratio 176Hf/177Hf (εHf = 0 when normalised to bulk Earth: Allègre 2008)  in zircon allows to differentiate between mantle, mixed  and crustal melts, and helps to spot specific melt sources (e.g. Shaw et al. 2011, van Dongen et al. 2010).  Hafnium tenors in zircon are about 2 wt. %. Recovery is a coupled product of zirconium metallurgy. Its separation from zirconium is expensive, however. Hafnium uses are in superalloys for gas turbines, control rods for nuclear reactors and, although in small quantities, manufacturing microprocessors for the latest generation of computer chips.  

There are not limits for hafnium contents in the zircon. When a share of HfSiO4 is more 50% it is the hafnon. Hf-rich zircons with HfO2 contents>3% have been numerously found in rare-metal granites and pegmatites, alkali granites and syenites.

hofnium concentration in zircon is temperature n chemistry of megma dependent ,some of the indian beach zircon have analysed 1500 to 5000 ppm,as suggested provinance wise study will give the effect of temperature and chemical activity of liquid on its concentration in zircon,how ever zircons associated with carbonatite contains less.