Dear Mr. Bute,

the Ce anomaly is a response to the redox conditions and Eu anomaly  is controlled by the accompanying tectosilicates. A more precise answer can only be given on a more detailed database provided for the sheared and altered granite with respect to the mineral assemblage and the tectono-mineralogical evolution of the post-granitic stage. I myself studied hydrothermal alterations which involved the system ZrSiO4-USiO4 in the wall rocks of granites. It is not as easy as it looks like and needs a very careful and thorough description of the mineralogical and structural processes before a profound answer can be given.

Best regards

H.G.Dill

Dear Saleh,

Based on some literature, zircons from altered rocks are characterized by REE patterns with a steep slope from La to Lu and a significantly positive Ce-anomaly and relatively negative Eu-anomaly, similar to magmatic zircons for some igneous rocks. Zircons from altered rocks are indistinguishable from magmatic zircons in regards to morphology, CL patterns, and chemical and isotopic signatures. Therefore, in many cases zircons do not provide unequivocal evidence of a hydrothermal origin.

But you got very interesting results from your analysis!

As Prof. Dill mentioned it is not as easy as it looks like and needs a very careful study.

Let me to say, In contrast, based on some literature intensive hydrothermal alteration of the granite occurred along brittle structures that are mostly filled by dikes and quartz veins. Hydrothermal alteration is indicated by depletion of both light and heavy REE and Eu-enrichment. Eu-enrichment is due largely to chemical contribution from hydrothermal fluids. Ground gamma-ray spectrometry measurements indicate that radioactive element concentrations are generally low in the altered granite.

I followed your question to see convincing answers.

Best wishes,

Shahrokh.

Hoskin 2005,and some other works discriminated hydrothermal zircons from magmatic zircons based on morphology and REE patterns. I plotted my results on the plot of Ce/Ce* against (Sm/La)N and (Sm/La)N.the samples majority cluster at the boundary and some few in the field of magmatic zircons. Though some interpreted this scenario as hydrothermally altered magmatic zicrons, Which could also be the case to my studies. HREE patterns is hardly distinguishable between the end members, but hyrothermal zircons have more flat Enriched LREE most especially La.