Petrographical and geochemical features of the syn-plutonic mafic dikes and enclaves in the baskil granitoids

ABSTRACT (Masters Thesis) PETROGRAPHICAL AND GEOCHEMICAL FEATURES OF THE SYN-PLUTONIC MAFIC DIKES AND ENCLAVES IN THE BASKIL GRANITOIDS Mehtap TATU Fırat University Instutute of Sciences Geological Engineering Department 2005, Page 49 The Baskil Granitoid is exposed as a large intrusive body at the vicinity of Baskil (Elazığ), which displays a great variety of magmatic products. It has been subdivided into two subunits which are named as the Hacı Mustafa Granodiorite/Tonalite and the Şahaplı Granite in this study. Syn- plutonic mafic and felsic dikes cut both the Hacı Mustafa granodioritc/toiialite and the Şahaplı Granite. Mafic dikes graduate to the dike like swarms at the their ends at some localities. Karahidrbaba Gabro/Diorite is the largest of these syn-plutonic mafic intrusions. Petrographic and mineralogical features of the Karahidirbaba Gabro/Diorite highlight the importance of magma mixing in their genessis. In particular, quartz ocelli texture and resorbed plagioclase ksenocrysts are common in the Karahidirbaba Gabro/Diorite, which suggest that mixing between mantle and crustal derived magmas occured relatively late in the crystallisation history of the pluton. The Mafic microgranular enclaves (MME) are common in the Baskil Granitoid and display variable size, texture and composition. They are diorite, quartz diorite and monzodiorite in composition, and are marked by sharp contacts next to their host granitoid rocks. The characteristic petrographical features of the MMEs are presence of corroded plagioclase and quartz ksenocrysts, acicular apatite, biotite poiklitically enclosing plagioclase lathas, K-feldspar and quartz poiklitically enclosing mafic minerals. Petrographical and geochemical observations suggest that the MMEs are derived from a hybrid magma formed as a result of the mafic magma injected into the felsic host magma. VI