Dear Mr. Aminov,

you expect too much from a single set of trace elements normalized to a standard and overstretch the possibilities of such analyses. You have to take a more diversified approach also including REE (see first response of Dr. Towe), isotopes and last but not least carefully examine the lithology of the volcanic rock to see which processes affected this magmatic rock. It is not only the source that counts. On the way up a magma can also be contaminated.

Best regards

H.G.Dill

 Dear Dr. Dill, 

thank you very much for your suggestions. I  understand that consideration of  only trace element data normalized to a standard will not give any valuable information. For addressing the questions about source and evolution of magma all of those features of rocks that you mentioned should be considered together.  Asking this question I just want to know whether theoretically  it is possible to get such  pattern as a result of fractionation of primary magma. 

Best regards.

 Hi Jovid,

Perhaps the best examples of highly fractionated basaltic melts are layered intrusions. You might check the literature there. It is also useful to consider trace element evolution in a crystallizing lunar magma ocean. From some experimental work I did on trace element partitioning in Fe-rich systems, I have a model which calculates REE variations in a crystallizing lunar magma ocean. You can find a complete description in Dygert et al., 2014, GCA.

I am attaching a quick calculation I did using a global average N-MORB as my starting melt composition. The lines show liquid compositions during the final 14% of crystallization.

You can see that on a PM normalized plot, the slope of the REE pattern is much shallower than in your granites. There is also a Eu anomaly that develops due to plagioclase fractionation.

Thanks for your interesting question.

Nick

Well, interesting, LILE enrichment, Pb behaves incompatibly, REE strongly fractioned, HFSE depleted (in residue), Ba depleted (K-feldspar fractionation) but no plagioclase fractionation.. definitely no mafic magma fractional crystallization, instead source enriched by hydrous fluids.. It is very important to know in what context do these rocks appear.

 Are these subduction-related samples? Maybe andesite?

It showed Nb, Ta and Ti negative anormalies

Although the article were about lower crust,

but I think it might help if you want to connect the crust and the rocks if it were subduction related samples

http://www.sciencedirect.com/science/article/pii/B9780080959757003235

"Can fractional crystallization of the primitive mafic magma (or andesitic; mantle derived) give such pattern?"

The simply answers is no.

If you crystalize olivine, plagioclase, clinopyroxene from a MORB you will never attain the trace element patterns of your samples without significant crustal assimilation. However, if you are looking at a primary mantle-derived andesite, which formed from a heavily metasomatized mantle-wedge, then the answer is maybe.

I would recommend that you have a look at this instructive paper:

Ersoy, Y., & Helvacı, C. (2010). FC–AFC–FCA and mixing modeler: A Microsoft® Excel© spreadsheet program for modeling geochemical differentiation of magma by crystal fractionation, crustal assimilation and mixing. Computers & Geosciences, 36(3), 383-390.

They present a simply Excel spread sheet that allows you to easily explore different options for your data with different starting magmas.

Harald G. Dill is correct in answering that you must take into account the setting, petrograpy and lithogeochemistry of the rock suite as well as radiogenic isotopic data if it is available. Nevertheless, it is important to note that low and perhaps moderate degree partial melts of a previously metasomatised lithospheric mantle (see Gallagher and Hawkesworth, 1992 - below), may also generate relatively primitive basaltic to ultrapotassic melts with prominent negative HFSE anomalies.

K. Gallagher, C.J. Hawkesworth, Dehydration melting and the

generation of continental flood basalts, Nature 358 (1992) 57–59.