Writers : Heidari,Akbar;Mahboubi, Asadollah; Moussavi-Harami, Reza
Refference : The first international applied geological congress; Department of geology Islamic azad university- Mashhad
Publishing Year : 2010

Abstract :

Several diagenetic processes, which one prominent process is silicification, affected the Upper Paleocene carbonate rocks of Chehel-Kaman Formation in the Western Part of Kopet-Dagh basin (NE Iran and S Turkmenistan). The aim of this study is classification and interpretation of digenetic processes and environments for mentioned different silicification types. Five types of silicification are recognized in this study that formed in three diagenetic phases. Based on appearance and the place of silicification, two models (Immediate and late) for silicification interpreted. Silicification happened as three forms including micro and macro quartz as well chalcedonies. Micro types formed as solution voids filler and, do not follow any regular pattern. Macro types precipitated as four different forms, first type filled vacant voids between allochems in ooid grainstone facies that we have interpreted as oolithic shoals. This type is not fabric selective but can be commented facies selective. Second macrotype, formed in fractures and intersect the texture of the carbonate rocks. It is formed in a wide rang of facies. Third type of macrotype has seen as macroquartz that occurred in deepest facie. The Last feature of silicification is chalcedoic type that formed as fabric selective. This type precipitated in brachiopods and some bivalve shells with foliated fabric. Silicification of the carbonate rocks must have been taken place under acidic conditions (pH<7). In this conditions quartz precipitated and carbonate dissolved and provide appropriate space for next phase of silicification. Based on these diagenetic processes, formation of quartz and chalcedony infer as mixed (Eogenes phase that precipitated some of microquartz type), burial (mesogenes that deposited some micro-macro quartz and chalcedonic types) and uplifting zones (telogenes phase that some macroquartz type spatially fracture type formed in it).

Subject List : Silicification