Aluminous granulites from the Pulur complex, NE Turkey: a case of partial melting, efficient melt extraction and crystallisation


Topuz G. , ALTHERR R., KALT A., SATIR M., WERNER O., SCHWARZ W.

LITHOS, cilt.72, ss.183-207, 2004 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

In the Pulur complex, NE Turkey, a heterogeneous rock sequence ranging from quartz-rich mesocratic gneisses to silica- and alkali-deficient, Fe-, Mg- and Al-rich melanocratic rocks is characterized by granulite-facies assemblages involving garnet, cordierite, sillimanite, ilmenite, +/- spinel, +/- plagioclase, +/- quartz, +/- biotite, +/- corundum, rutile and monazite. Textural evidence for partial melting in the aluminous granulites, particularly leucosomes, is largely absent or strongly obliterated by a late-stage hydrothermal overprint. However, inclusion relations, high peak P-T conditions, the refractory modes, bulk and biotite compositions of the melanocratic rocks strongly support a model of partial melting. The melt was almost completely removed from the melanocratic rocks and crystallised within the adjacent mesocratic gneisses which are silica-rich, bear evidence of former feldspar and show a large range in major element concentrations as well as a negative correlation of most elements with SiO2. Peak conditions are estimated to be greater than or equal to 800degreesC and 0.7-0.8 GPa. Subsequent near-isothermal decompression to similar to 0.4-0.5 CiPa at 800-730degreesC is suggested by the formation of cordierite coronas and cordierite-spinel symplectites around garnet and in the matrix. Sm-Nd, Rb-Sr and Ar-40/Ar-39 isotope data indicate peak conditions at similar to 330 Ma and cooling below 300degreesC at similar to 310 Ma. (C) 2003 Elsevier B.V. All rights reserved.