Petrographical, geochemical and petrological characteristics of the Güre (Giresun, NE Turkey) Granitoid
Abstract
In the Güre (Giresun) area, Turonian-Coniacian basalt and pyroclastics, Coniacian-Santonian dacite-rhyodacite and pyroclastics, and Campanian-Maestrichtian (?) biotite-bearing andesite and pyroclastics crop out. Upper Cretaceous-Paleocene (?) Güre Granitoid intruded into dacite/rhyodacite and their pyroclastics. The Güre Granitoid shows xenomorphic granular, fine-grained porphyric, rarely graphic and micropegmatitic textures. The rocks contain mainly quartz, orthoclase, plagioclase, hornblende, biotite, accessory apatite and sphene, secondary chlorite, epidote and calcite. Mineral thermometer and barometer calculations indicate crystallization conditions of ~650-700oC and ~0.9-1.5 (χ–) kbar, respectively. The Güre Granitoid has I-type, calc-alkaline, metaluminous-peraluminous (A/CNK=0.9-1.2) characteristics, fractionated and alumino-cafemic (ALCAF) features. Major and trace element variations indicate that fractionation was significant in the evolution of the rocks. Trace element patterns of the rocks are similar to each other but some exhibit K, Rb, Ba and Th enrichments. The rocks have moderately enriched and spoon-shaped rare earth element patterns with (La/Lu)N =1-2, reflecting hornblende and plagioclase fractionations in the evolution. The Güre Granitoid evolved from a hybrid parental magma, possibly derived from arc crust and mantle sources. It was concluded that the crystallization of the granitic magma took place relatively at greather depth (~6 km) of the arc crust, and then completed in shallow level (~3 km) following magma uplift.
Abstract
Güre (Giresun) yöresinde Türoniyen-Koniyasiyen yafll› bazalt ve piroklastitleri, Koniyasiyen-Santoniyen yafll› dasit/riyodasit ve piroklastitleri ile Kampaniyen-Maestrihtiyen (?) yafll› biyotitli andezit ve piroklastitleri yüzeylenmektedir. Kretase-Paleosen (?) yafll› Güre Granitoyidi, dasit/riyodasit ve piroklastitlerini keserek yerleflmifltir. Güre Granitoyidi, genellikle özflekilsiz taneli, ince taneli porfirik, yer yer yaz› ve mikropegmatitik dokulu olup, kuvars, ortoklas, plajiyoklas, hornblend, biyotit, aksesuar apatit ve sfen, ikincil klorit, epidot ve kalsit içermektedir. Mineral termometre ve barometre hesaplamalar›, ~650-700oC ve ~0.9-1.5 (χ –) kbar’l›k kristallenme koflullar›n› göstermektedir. Güre Granitoyidi jeokimyasal olarak, I-tipi, kalkalkalin, metalümin peralümin (A/CNK=0.9-1.2) karakterli, fraksiyonlaflm›fl ve alümino-kafemik (ALCAF) özellikledir. Ana ve iz element de¤iflimleri kayaçlar›n gelifliminde ayr›mlaflman›n önemli oldu¤una iflaret etmektedir. Üz element da¤›l›mlar› birbirine benzemesine ra¤men, baz› örnekler K, Rb, Ba ve Th bak›m›ndan daha fazla zenginleflme gösterirler. Nadir toprak element da¤›l›mlar› orta derecede zenginleflmifl (LaN/LuN=1-2) ve kafl›k flekilli olup, muhtemel hornblend ve plajiyoklas ayr›mlaflmas›n› yans›tmaktad›r. Güre Granitoyidi, hibrid bir ana magmadan itibaren geliflmifl olup, bu ana magma muhtemelen yay kabu¤u ve manto kaynaklar›n› kapsamaktad›r. Granitik magman›n kristallenmesi, yay kabu¤unun nispeten derin kesimlerinde (~6 km) bafllam›fl ve magma yükselmesi ile s›¤ derinliklerde (~3 km) tamamlanm›flt›r.
Details
| Primary Language | Turkish |
|---|---|
| Subjects | Engineering |
| Journal Section | Articles |
| Authors | |
| Publication Date | April 1, 2004 |
| Submission Date | March 24, 2015 |
| Published in Issue | Year 2004 Issue: 30 |