Mineralogy and mineral chemistry of andesites in comparison with their magmatic enclaves from the Ghikhlar area (East Azarbaidjan)

The Ghikhlar area is located at the NW Marand town, East Azarbaidjan. The wide range of Plio-Quaternary volcanic activites with volcanic and associated volcano-clastic rocks having compositions mainly as andesite to silica-undersaturated rocks (leucite basanite, leucite-tephrite and tephrite) have been covered mostly the rock units prior to the Cenozoic. The phenocrysts in andesites are amphibole, plagioclase and clinopyroxene which occurred in microcrystalline and microlithic matrix. The main characteristic of these rocks is bearing various enclaves as autholiths and xenoliths. The clinopyroxenes in the host andesite and cumulative enclaves are diopside to augite. The autholithic andesitic and dioritic enclaves indicates compositions as augite and dipside, respectively. Investigation of mineral chemistry and magmatic features for the host andesitic rocks and their enclaves are the main goal of this research. Variety of magmatic enclaves are including homogenic, cumulative and gabbroic ones. They all show similar mineralogy with host andesitic rocks whereas they are different texturally. Homogenic and gabbroic enclaves are more fine and coarse grained than host andesite, respectively. Cumulative enclave has been formed as aggregation of coarse grained ferromagnesian crystals similar with phenocrysts of andesite. On the basis of mineral chemistry data, composition of the host andesite as well as homogenic and cumulative enclaves are subalkaline with arc magmatic tectonic setting feature. However gabbroic enclave with alkaline characteristic corresponds to interior plate tectonic setting. Considering mineralogy, textural evidence and mineral chemistry data from the host andesite and their magmatic enclaves it can be concluded that the homogenic and cumulative enclaves are autoliths. The homogenic enclave corresponds to chilled margin of magma reservoir which disjoined during upward ascending of andesitic magma and their falling into magma chamber. Cumulative enclave resulted from aggregation of magmatic minerals in the magma chamber. About genesis of the gabbroic enclave it seems that gabbroic enclave has exotic genesis. Gabbroic rocks fall into andesitic magma during magma passing upward.