Journals / Turkish Journal of Earth Sciences / 2002 / Cilt: 11 - Sayı: 3
The Silistar Intrusive, Eastern Srednogorie Zone, Bulgaria: Structural Data and Potential for Porphyry Copper and Epithermal Systems
- Pages
- 217–229
- DOI
- —
Abstract
The Late Cretaceous Silistar intrusion comprises of gabbros, gabbro-diorites to quartz-diorites and aplites, that were emplaced into a volcano-sedimentary succession of similar age. Structural data suggest that this intrusion is part of a larger, partially exposed body. A dense network of primary and secondary joints, in many places filled with various ore and gangue minerals, is a conspicuous feature of the intrusion. Hydrothermal alteration affecting the intrusion and the wall rocks includes: uralitization (amphibole±epidote), secondary biotitization and propylitization. Propylitic alteration occurred in two stages: high temperature (epidote-actinolite-chlorite) and middle to low temperature (sericite-chlorite-carbonate-epidote and chlorite-sericite-carbonate). Products of later alteration events include quartz-adularia, quartz-carbonate, carbonate, quartz-zeolites and zeolites. Apart from previously recognized contact-metasomatic mineralization, the presence of stockwork-type and disseminated pyrite and chalcopyrite mineralization, hosted by both the intrusion and the host rocks, is documented here. Two types of magnetite and pyrite (magmatic and metasomatic) are recognized. Based upon the alteration products and ore minerals, the presence of two differing zones is suggested. The first zone, which closely coincides with the intrusion, is potassic and hosts py-ma-cpy-hm-(ilm). The second zone is propylitic with py-ma-cpy-hm-(ilm)+(sph+ga)+(bo+hz). Cu is the main ore element; Mo contents are very low or nil. The types of ore mineralization and alteration products, along with structural data, show elements of both porphyry copper and epithermal systems and suggest their occurrence of such (and the first recognition of such) in the incipient rift zone of the Eastern Srednogorie Zone.
Özet
Gabro, gabro-diyorit, kuvars diyorit ve aplitlerden oluflan Geç Kratese yafll› Silistar Sokulumu ayn› yafll› volkano-sedimanter bir istif içine yerleflmifltir. Yap›sal veriler, Silistar sokulumunun genifl bir sokulumun k›smen yüzeylemifl bir parças› oldu¤una iflaret eder. Ço¤unlukla cevher ve gank mineralleri ile doldurulan ve yo¤un bir a¤ oluflturan birincil ve ikincil eklemler busokulumun önemli yap›sal unsurlar›d›r. Gerek sokulumu gerekse kenar kayaçlar› etkileyen hidrotermal alterasyonlar uralitleflme (amfibol±epidot), ikincil biyotitleflme ve profilitleflmedir. Profilitik alterasyon, yüksek s›cakl›k (epidot-aktinolit-klorit) ve orta-düflük s›cakl›k (serizit-klorit-karbonat-epidot ve klorit-serizit-karbonat) koflullar›nda olmak üzere iki aflamada geliflmifltir. Daha sonraki alterasyon olaylar›n›n ürünleri aras›nda kuvarsadularya, kuvars-karbonat, karbonat, kuvars-zeolit ve zeolitler say›labilir. Daha önceleri tan›mlanan kontak-metasomatik mineralleflmenin yan› s›ra, sokulum ve yan kayaçda geliflen stokwork-tipli (a¤s›) ve dissemine pirit ve kalkopirit mineralleflmesi bu çal›flmada tan›mlanm›flt›r. Magmatik ve metasomatik olmak üzere iki tip manyetit ve pirit belirlenmifltir. Alterasyon ürünleri ve cevher minerallerine göre birbirinden farkl› iki kufla¤›n varl›¤› ileri sürülmüfltür. Sokulum içinde geliflen birinci kuflak daha çok potasik olup, py-ma-cpy-hm-(ilm) mineralleflmesi ile tan›mlan›rken; ikinci kuflak propilitik py-ma-cpy-km-(ilm)+(sph+ga)+(bo+hz) parajenezi ile karakterize olur. Cu ana cevherelementi iken, Mo içeri¤i ya çok azd›r ya da hiç yoktur. Cevherleflme ve alterasyon ürün tipleri ile yap›sal veriler porfiri bak›r ve epitermal sistem elamanlar›n› iflaret eder ve oluflumlar›n›n Do¤u Srednogorie Kufla¤› riftleflmesinin ilk aflamalar›nda gerçekleflti¤ini gösterir.