Partial Melting of Pelites and Semi-Pelites in the Kalaybar Thermal Aureole, NW Iran

Moazzen, M.; Hajialioghli, R.

doi:10.22071/gsj.2008.58207

Document Type : Original Research Paper

Authors

Department of Geology, Faculty of Natural Sciences, Tabriz University, Iran.

https://doi.org/10.22071/gsj.2008.58207

Abstract

Intrusion of the Kalaybar nepheline syenite and nepheline gabbro into the Cretaceous pelitic and calcareous rocks during Eocene-Oligocene has caused the development of a thermal aureole up to 1 km thick. The contact between igneous and country rocks is sharp. The protholite rocks in the study area had not been metamorphsed prior to contact metamorphism. Pelitic and calcareous rocks in the northern and eastern parts of the aureole and basic rocks in the southern part of the aureole were thermally metamorphsed and formed different types of hornfelses. High-grade metamorphic rocks with chemically suitable compositions were melted adjacent to the contact (within 100m from the contact) due to the heat from the pluton. Migmatites with small-scale leucosomes are produced. Scale of partial melting and volume of produced melt are very small. Main minerals in the light coloured parts of the migmatites (leucosomes) include quartz and K-feldspar with an igneous texture specially euhedral to subhedral texture of K-feldspar, graphic texture of quartz-K-feldspar and interstitial texture of quartz. Textural differences between light leucosomes and dark mesosomes, mineralogical composition of the leucosomes, existence of igneous textures within the leucosomes and restriction of the leucosome formation to the pelitic rocks all are distinct evidence for occurrence of partial melting in the Kalaybar aureole. The liable reactions for melting include fluid-present reactions and fluid-absent reactions. High-grade metamorphic assemblages such as orthopyroxene-bearing assemblages have been accomplished by dehydration of hydrous minerals such as biotite via fluid-absent melting reactions. Mineralogical compositions of leucosomes resemble leucogranites to granites. This indicates crystallisation of the leucosomes from a silicate melt.

Keywords

20.1001.1.10237429.1386.16.64.2.0

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Scientific Quarterly Journal of Geosciences

Partial Melting of Pelites and Semi-Pelites in the Kalaybar Thermal Aureole, NW Iran

References

References

Volume 16, Issue 64
March 2007
Pages 2-13

Partial Melting of Pelites and Semi-Pelites in the Kalaybar Thermal Aureole, NW Iran

References

References

Volume 16, Issue 64March 2007Pages 2-13

Volume 16, Issue 64
March 2007
Pages 2-13