Güzelyayla (Maçka-Trabzon) porfiri Cu-Mo cevherleşmesinin jeolojik yerleşimi ve jeokimyası

Abstract

ÖZET Bu çalışmada, Doğu Pontid Kuzey Zonu'nda yer alan Zigana-Hamsiköy (Trabzon) yöresindeki litolojik birimlerin stratigrafik konumları, petrografisi ve petrokimyasal özel likleri incelenmiştir. Ayrıca inceleme alanı içinde yer alan Güzelyayla porfiri Cu-Mo cevherleşmesinin mineralojik ve jeokimyasal verileri elde edilerek çeşitli yorumlara ve sonuçlara gidilmiştir. İnceleme alanında tabanı, Jura yaşlı bazalt, andezit, diyabaz ve bunların spilitleşmiş ürünlerinden oluşan Pontid Alt Bazik Karmaşığı oluşturmaktadır. Bu birimin üzerine Ber- diga Formasyonu olarak tanımlanan kristalize kireçtaşları gelmektedir. Bu kayaçları uyumsuz olarak üstlediği iddia edilen Senoniyen yaşlı Bekçiler Formasyonu, cevher minerali içeren Cevherli Dasit' lerle mineralleşme içermeyen Dikkaya Dasiti'nden oluşmuştur. Senoniyen yaşlı Hamsiköy Tortul-Vol- kanik Karmaşığı bazalt, andezit lav ve piroklastikleriyle, bu kayaçlar içinde ara seviye olarak izlenen volkano-tortul kayaçlardan ibarettir. Zigana Granitoyidi, üst Kretase sonra sında tüm bu birimleri keserek sokulum yapmıştır. Yörenin en genç birimleri dasit ve mikrogranit dayklarıyla, güncel ola rak oluşmaya devam eden travertenlerdir. Pontid Alt Bazik Karmaşığı' na ait kayaçlar genelde tole- yitik kalk-alkalen geçişli ve ada yayı ortamını belirtir karakterdedir, üst Kretase yaşlı dasitik ve bazaltik volkanik kayaçlar da yitim zonlarında oluşan kalk-alkalen nitelikteki kayaçlardır. Zigana granitoyidi, I tipinde ve kalk-alkalen özellikte olup, olgunlaşmakta olan bir adayayı ortamını ka- rakterize eder. Yöredeki granit sokulumuna bağlı olarak gelişen hidro- termal olaylar sonucunda porfiri tipteki Güzelyayla Cu-Mo cevherleşmesi oluşmuştur. Pontid Alt Bazik Karmaşığı ve Zi gana granitoyidi içindeki kuvarslı mikrodiyoritler içinde gelişen maden yatağı stokvörk ve saçınım şeklinde yerleşmiş tir. Potassik, fillik ve propilitik ayrışma zonları izlenen yatakta arjilik kuşak gelişmemiştir. Güzelyayla porfiri Cu- Mo yatağı mezotermal karakterde olup, 280-460 °C arasında oluşmuştur. Jeokimyasal arama ve sondaj verileri karşılaştırıldığın da topraktaki bakır anomalilerinin cevherli zonlar için veri taşımadığı, buna karşın molibden anomalilerinin yüksek tenör- lü zonları gösterdiği tesbit edilmiştir. Çalışma sonucunda Doğu Karadeniz Bölgesi porfiri tipteki Cu ve Mo cevherleşmeleri için bölgesel stratigrafik, petrog rafik, mineralojik, jeokimyasal ve petrojenetik özellikler belirlenmiştir. VGeological Setting and Geochemistry of the Güzelyayla (Maçka-Trabzon) Porphyry Cu-Mo Deposit, Pont id NE Turkey SUMMARY Within the framework of this investigation, the litholo- gic units exposed around the Zigana-Hamsiköy (Trabzon) area were investigated in relation to the stratigraphic locations, petrographical and petrochemical characteristics of the rock units. Furthermore, through obtaining data regarding the mi- neralogical and geochemical properties of the Güzelyayla por phyry Cu-Mo deposit, various interpretations have been drawn under the light of the data obtained. The basement of the study area consists of basalt, ande- site, diabase and their spilitized product which are Jurassic in age and are called Pontid Lower Basic Complex. This series is overlain by crystallized limestones commonly known as Berdiga Formation. The Bekçiler Formation, which is asserted to overlic discordantly these rocks, consists of ore-bearing dacite and the Dikkaya Dacite that lacks mineralization. This rock assemblage is of Cenomanian age, The Hamsiköy Sedimentary Volcanic Complex of Cenomanian age is composed of basalt, andesite and their pyroclastics, as well as the volcano-sedi mentary rocks which are observed as interbeds in these rocks. The Zigana Granitoid intruded, by crosscutting all the rocks already present, at the end of Cretaceous. The youngest units of the study area are dacite-microgranite dykes and traverti nes which are still being formed. The rocks belonging to the Pontid Lower Basic Complex are generally tholeiitic transiti onal to calc-alkaline in character and characterize an island-arc environment. Dacitic and basaltic volcanic rocks of Upper Cretaceous age, are also formed in a subduction zone and are calc-alkaline in affinity. The Zigana Granitoid is of I-type and calc-alkaline features and characterizes an island arc environment that is getting mature. The hydrothermal Güzelyayla porphypy copper-molydenum mineralization is porphyry copper in type formed as a conse quence of hydrothermal activity related to granitic intrusron in the area. The ore deposit is found in the Pontid Lower Ba sic Complex and the quartz microdiorites of the Zigana Grani toid and it is Stockwork and dissemineted in form. The argi- llic zone did not flourished in the deposit, while the potas- sic, phyllic and propylitic alteration zones were developed. The Güzelyayla porphyry Cu-Mo deposit is mesothermal in cha racter, and is formed between the temperatures of 280 and 460 °C. When the geochemical exploration data compared with those obtained from the drillings, it has been found Cu ano malies don't show the mineral-bearing zones, where as Mo anomalies indicate mineralization zones of high tenor values. In conclusion, the regional stratigraphic, petrographic, mineralogic, geochemical and petrogenetic properties for the porphyry type Cu-Mo mineralization are determined. VI

Geological Setting and Geochemistry of the Güzelyayla (Maçka-Trabzon) Porphyry Cu-Mo Deposit, Pont id NE Turkey SUMMARY Within the framework of this investigation, the litholo- gic units exposed around the Zigana-Hamsiköy (Trabzon) area were investigated in relation to the stratigraphic locations, petrographical and petrochemical characteristics of the rock units. Furthermore, through obtaining data regarding the mi- neralogical and geochemical properties of the Güzelyayla por phyry Cu-Mo deposit, various interpretations have been drawn under the light of the data obtained. The basement of the study area consists of basalt, ande- site, diabase and their spilitized product which are Jurassic in age and are called Pontid Lower Basic Complex. This series is overlain by crystallized limestones commonly known as Berdiga Formation. The Bekçiler Formation, which is asserted to overlic discordantly these rocks, consists of ore-bearing dacite and the Dikkaya Dacite that lacks mineralization. This rock assemblage is of Cenomanian age, The Hamsiköy Sedimentary Volcanic Complex of Cenomanian age is composed of basalt, andesite and their pyroclastics, as well as the volcano-sedi mentary rocks which are observed as interbeds in these rocks. The Zigana Granitoid intruded, by crosscutting all the rocks already present, at the end of Cretaceous. The youngest units of the study area are dacite-microgranite dykes and traverti nes which are still being formed. The rocks belonging to the Pontid Lower Basic Complex are generally tholeiitic transiti onal to calc-alkaline in character and characterize an island-arc environment. Dacitic and basaltic volcanic rocks of Upper Cretaceous age, are also formed in a subduction zone and are calc-alkaline in affinity. The Zigana Granitoid is of I-type and calc-alkaline features and characterizes an island arc environment that is getting mature. The hydrothermal Güzelyayla porphypy copper-molydenum mineralization is porphyry copper in type formed as a conse quence of hydrothermal activity related to granitic intrusron in the area. The ore deposit is found in the Pontid Lower Ba sic Complex and the quartz microdiorites of the Zigana Grani toid and it is Stockwork and dissemineted in form. The argi- llic zone did not flourished in the deposit, while the potas- sic, phyllic and propylitic alteration zones were developed. The Güzelyayla porphyry Cu-Mo deposit is mesothermal in cha racter, and is formed between the temperatures of 280 and 460 °C. When the geochemical exploration data compared with those obtained from the drillings, it has been found Cu ano malies don't show the mineral-bearing zones, where as Mo anomalies indicate mineralization zones of high tenor values. In conclusion, the regional stratigraphic, petrographic, mineralogic, geochemical and petrogenetic properties for the porphyry type Cu-Mo mineralization are determined. VI